US20110125158A1

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Publication number: US20110125158A1
Application number: US12/920,453
Authority: US
Inventors: Ashish Dhar Diwan; Johnathon Choi; Zoran Milijasevic
Original assignee: Individual
Current assignee: Kunovus Pty Ltd; Columna Pty Ltd
Priority date: 2008-05-01
Filing date: 2008-05-01
Publication date: 2011-05-26
Also published as: WO2008131498A1; US20140257417A1; KR20120068656A; KR101464983B1; US9492291B2; US10010427B2; EP2285312A1; US20170049577A1; EP2285312A4; US20180271670A1; US20200229937A1

Abstract

A tissue prosthesis insertion system includes a first assembly comprising a plurality of nested tubes, one of the tubes being a carrier tube which, in use, receives a component of a tissue prosthesis at a distal end of the carrier tube. A magnetic mount is carried at a proximal end of the first assembly. A second assembly is removably attachable to the first assembly. An attachment device is carried at a distal end of the second assembly, the attachment device being responsive to the magnetic mount of the first assembly, the magnetic mount and the attachment device carrying complementary engaging formations to facilitate hermetic sealing between the magnetic mount and the attachment device.

Description

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Application No. 60/915,410, filed on May 1, 2007.

Additionally, each of the following applications are herein incorporated by reference, in its entirety:

International Application No. PCT/AU2003/001289, filed on Sep. 30, 2003;

Australian Provisional Application No. 2002951762, filed on Oct. 1, 2002;

International Application No. PCT/AU2006/000267, filed on Mar. 1, 2006;

Australian Provisional Application No. 2005900952, filed on Mar. 1, 2005;

International Application No. PCT/AU2006/001176, filed on Aug. 15, 2006;

U.S. Provisional Application No. 60/708,687, filed on Aug. 15, 2005;

International Application No. PCT/AU2007/001601 filed on Oct. 22, 2007;

U.S. Provisional Application No. 60/867,574, filed on Nov. 28, 2006;

International Application No. PCT/AU2007/001657, filed on Oct. 31, 2007;

U.S. Provisional Application No. 60/915,410, filed on May 1, 2007; and

U.S. Provisional Application No. 60/971,633 filed on Sep. 12, 2007.

FIELD OF THE DISCLOSURE

The present disclosure generally relates to tissue prostheses and more particularly, the present disclosure relates to systems, methods, and apparatuses for formation and insertion of tissue prostheses.

BACKGROUND INFORMATION

Joints of the musculoskeletal system of the human or animal body rely on the presence of healthy cartilaginous tissue for proper operation. Cartilaginous tissue can degenerate due to a number of causes, e.g., age or injury. Degradation of the tissue can reach a point where movement can cause severe discomfort and pain.

Degradation of tissue can occur in the spinal column. The spinal column comprises a series of 26 mobile vertebral bones, or vertebrae, connected by 75 stable articulations that control motion. The vertebrae are generally divided into posterior and anterior elements by thick pillows of bone called pedicles. The anterior element of the vertebra is a kidney shaped prism of bone with a concavity directed posteriorly and has flat superior and inferior surfaces called end plates. An intervertebral disc is sandwiched between adjacent pairs of vertebrae forming a joint between the adjacent pair of vertebrae. These discs are viscoelastic structures comprising a layer of strong, deformable, soft tissue. The intervertebral discs are subjected to a considerable variety of forces and moments resulting from the movements and loads of the spinal column. Each intervertebral disc has two components, being the annulus fibrosis surrounding a nucleus pulposus. The intervertebral disc cooperates with end plates of the vertebrae between which it is sandwiched.

The primary function of the nucleus pulposus of the disc is to give the disc its elasticity and compressibility characteristics to assist in sustaining and transmitting weight. The annulus fibrosis contains and limits the expansion of the nucleus pulposus during compression and also holds together successive vertebrae, resisting tension and torsion in the spine. The end plates of the vertebrae are responsible for the influx of nutrients into the disc and the efflux of waste products from within the disc.

With age or injury, a degenerative process of the disc may occur whereby its structures undergo morphological and biological changes affecting the efficiency with which the disc operates. Thus, the nucleus pulposus may reduce in volume and dehydrate resulting in a load reduction on the nucleus pulposus, a loss in intradiscal pressure and, hence, additional loading on the annulus fibrosis. In a normally functioning disc, the intradiscal pressure generated results in deformation of the end plates of the adjacent vertebrae generating the natural pumping action which assists in the influx of the nutrients and the efflux of waste products as stated above. A drop in intradiscal pressure therefore results in less end plate deformation. The nutrients supplied to the discal tissue are reduced and metabolic wastes are not removed with the same efficiency. This contributes to a degenerative cascade.

Radial and circumferential tears, cracks and fissures may begin to appear within the annulus fibrosis. If these defects do not heal, some of the nuclear material may begin to migrate into the defects in the annulus fibrosis. Migration of the nuclear material into the annulus fibrosis may cause stretching and delamination of layers of the annulus fibrosis resulting in back pain due to stimulation of the sinu-vertebral nerve. An intervertebral disc without a competent nucleus is unable to function properly. Further, since the spine is a cooperative system of elements, altering the structure and mechanics at one location of the spinal column may significantly increase stresses experienced at adjacent locations thereby further contributing to the degenerative cascade.

In the past, operative intervention has occurred to relieve lower back pain arising from intervertebral disc degeneration. Most of this operative intervention has been by way of a discectomy where leaking nuclear material is removed or, alternatively, fusion. The primary purpose of a discectomy is to excise any disc material that is impinging on the spinal nerve causing pain or sensory changes. Fusion means eliminating a motion segment between two vertebrae by use of a bone graft and sometimes internal fixation. Biomechanical studies show that fusion alters the biomechanics of the spine and causes increased stresses to be experienced at the junction between the fused and unfused segments. This promotes degeneration and begins the degenerative cycle anew. Clearly, being an invasive operative procedure, fusion is a risky procedure with no guarantee of success.

Due to the minimal success rate of these previous procedures, as well as their inability to restore complete function to the spinal column, alternative treatments have been sought in the form of artificial disc replacements. Theoretical advantages of artificial disc replacement over a fusion procedure include preservation or restoration of segmental motion in the spine, restoration of intervertebral architecture and foraminal height, sparing of adjacent segments of the spine from abnormal stresses and restoration of normal biomechanics across the lumbar spine. The established artificial disc replacement procedure consists of techniques that require a surgical incision on the abdomen, retraction of large blood vessels, a total excision of the anterior longitudinal ligament, anterior and posterior annulus along with the nucleus and near total removal of the lateral annulus and implantation of an articulated prosthesis. This is a major spinal column reconstruction operation carried out by a very invasive technique.

Accordingly, the present inventors has observed that there is a need for surgical procedures, methods, and/or systems which, as far as possible, restore the biomechanics of joints such as those between adjacent vertebrae of the spine by the provision of a tissue prosthesis mimicking natural, healthy cartilaginous tissue as well as a means of carrying out the surgical procedure in a minimally invasive manner and/or percutaneous manner.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1-8 show schematic illustrations of various steps of a method, in accordance with certain exemplary embodiments disclosed herein, for forming a tissue prosthesis in situ at a site in a patient's body;

FIG. 9 shows a schematic illustration of a delivery device for use in accordance with certain exemplary embodiments disclosed herein;

FIG. 10 shows a schematic, sectional side view of part of equipment, in accordance with certain exemplary embodiments disclosed herein, for forming a tissue prosthesis, in situ at a site in a patient's body;

FIG. 11 shows a schematic, sectional side view of the equipment in accordance with certain exemplary embodiments disclosed herein;

FIG. 12 shows a schematic, side view and end view of part of the equipment in accordance with certain exemplary embodiments disclosed herein;

FIG. 13 shows a sectional side view of an envelope, attached to a delivery device, the envelope forming part of a tissue prosthesis, in accordance with certain exemplary embodiments disclosed herein;

FIG. 14 shows a sectional side view of another mounting of the envelope on the delivery device in accordance with certain exemplary embodiments disclosed herein;

FIGS. 15-17 show different shapes of envelopes for use in the tissue prosthesis in accordance with certain exemplary embodiments disclosed herein;

FIG. 18 shows a plan view of another embodiment of equipment for forming a tissue prosthesis, in situ, at a site in a patient's body in accordance with certain exemplary embodiments disclosed herein;

FIG. 19 shows a sectional side view taken along line XIX-XIX inFIG. 18 in accordance with certain exemplary embodiments disclosed herein;

FIG. 20 shows, on an enlarged scale, a sectional side view of the part of the equipment encircled by circle ‘A’ inFIG. 19 in accordance with certain exemplary embodiments disclosed herein;

FIG. 21 shows, on an enlarged scale, a sectional side view of the part of the equipment encircled by circle ‘B’ inFIG. 19 in accordance with certain exemplary embodiments disclosed herein;

FIG. 22 shows a sectional side view of yet a further embodiment of equipment for forming a tissue prosthesis, in situ, at a site in a patient's body in accordance with certain exemplary embodiments disclosed herein;

FIG. 23 shows on an enlarged scale, a sectional side view of the part of the equipment encircled by circle ‘C’ inFIG. 22 in accordance with certain exemplary embodiments disclosed herein;

FIG. 24 shows on an enlarged scale, a sectional side view of the part of the equipment encircled by circle ‘D’ inFIG. 22 in accordance with certain exemplary embodiments disclosed herein;

FIG. 25 shows a plan view of a first assembly of a tissue prosthesis insertion system in accordance with certain exemplary embodiments disclosed herein;

FIG. 26 shows a sectional side view of the first assembly of the system ofFIG. 25 taken along line II-II inFIG. 25 in accordance with certain exemplary embodiments disclosed herein;

FIG. 27 shows a sectional side view, on an enlarged scale, of the part of the first assembly surrounded by circle ‘A’ inFIG. 26 in accordance with certain exemplary embodiments disclosed herein;

FIG. 28 shows a sectional side view, on an enlarged scale, of the part of the first assembly surrounded by circle ‘B’ inFIG. 26 in accordance with certain exemplary embodiments disclosed herein;

FIG. 29 shows a plan view of an assembly of the tissue prosthesis insertion system in accordance with certain exemplary embodiments disclosed herein;

FIG. 30 shows a sectional side view of the assembly of the system taken along line VI-VI inFIG. 29 in accordance with certain exemplary embodiments disclosed herein;

FIG. 31 shows a sectional side view, on an enlarged scale, of the part of the assembly surrounded by circle ‘C’ inFIG. 30 in accordance with certain exemplary embodiments disclosed herein;

FIG. 32 shows a sectional side view, on an enlarged scale, of the part of the assembly surrounded by circle ‘D’ inFIG. 30 in accordance with certain exemplary embodiments disclosed herein;

FIG. 33 shows a plan view of a valve member forming part of a tissue prosthesis of the system in accordance with certain exemplary embodiments disclosed herein;

FIG. 34 shows an end view of the valve member in accordance with certain exemplary embodiments disclosed herein;

FIG. 35 shows a sectional side view of the valve member taken along line XI-XI inFIG. 34 in accordance with certain exemplary embodiments disclosed herein;

FIG. 36 shows a schematic side view of a working cannula of the assembly in position after formation of the tissue prosthesis in accordance with certain exemplary embodiments disclosed herein;

FIG. 37 shows a schematic side view of a further part of the system inserted into the cannula to complete formation of the tissue prosthesis in accordance with certain exemplary embodiments disclosed herein;

FIGS. 38A and B shows a sectional side view of a prosthesis delivery system in accordance with certain exemplary embodiments disclosed herein;

FIG. 39 shows, on an enlarged scale, a sectional side view of the encircled portion of the system marked ‘A’ inFIG. 38 of the drawings in accordance with certain exemplary embodiments disclosed herein;

FIG. 40 shows a component of a prosthesis delivery system in accordance with certain exemplary embodiments disclosed herein;

FIG. 41 shows a sectional side view of a part a prosthesis delivery system including the component ofFIG. 40 in accordance with certain exemplary embodiments disclosed herein;

FIG. 42 shows a sectional side view of a part of a further embodiment of a prosthesis delivery system including the component ofFIG. 40 in accordance with certain exemplary embodiments disclosed herein;

FIGS. 43a,43band43cshow, respectively, front, side and plan views of an intervertebral disc implant, in accordance with certain exemplary embodiments disclosed herein;

FIGS. 44a,44band44cshow, respectively, front, side and plan views of an intervertebral disc implant, in accordance with certain exemplary embodiments disclosed herein;

FIGS. 45a,45band45cshow, respectively, front, side and plan views of an intervertebral disc implant, in accordance with certain exemplary embodiments disclosed herein;

FIGS. 46a,46band46cshow, respectively, front, side and plan views of an intervertebral disc implant, in accordance with certain exemplary embodiments disclosed herein;

FIGS. 47a,47band47cshow, respectively, front, side and plan views of an intervertebral disc implant, in accordance with certain exemplary embodiments disclosed herein;

FIGS. 48a,48band48cshow, respectively, front, side and plan views of an intervertebral disc implant, in accordance with certain exemplary embodiments disclosed herein;

FIGS. 49a,49band49cshow, respectively, front, side and plan views of an intervertebral disc implant, in accordance with certain exemplary embodiments disclosed herein;

FIGS. 50a,50band50cshow, respectively, front, side and plan views of an intervertebral disc implant, in accordance with certain exemplary embodiments disclosed herein;

FIGS. 51a,51band51cshow, respectively, front, side and plan views of an intervertebral disc implant, in accordance with certain exemplary embodiments disclosed herein;

FIGS. 52a,52band52cshow, respectively, front, side and plan views of an intervertebral disc implant, in accordance with certain exemplary embodiments disclosed herein;

FIGS. 53a,53band53cshow, respectively, front, side and plan views of an intervertebral disc implant, in accordance with certain exemplary embodiments disclosed herein;

FIG. 54 shows a schematic side view of an intervertebral disc implant in a first configuration, in accordance with certain exemplary embodiments disclosed herein;

FIG. 55 shows a schematic plan view of the implant ofFIG. 54 in a second configuration in accordance with certain exemplary embodiments disclosed herein;

FIG. 56 shows a schematic side view of an intervertebral disc implant in first configuration, in accordance with certain exemplary embodiments disclosed herein;

FIG. 57 shows a schematic plan view of the implant ofFIG. 56 in a second configuration in accordance with certain exemplary embodiments disclosed herein;

FIG. 58 shows a schematic side view of an intervertebral disc implant in a first configuration, in accordance with certain exemplary embodiments disclosed herein;

FIG. 59 shows a schematic plan view of the implant ofFIG. 58, in use, in a second configuration in accordance with certain exemplary embodiments disclosed herein;

FIG. 60 shows a schematic plan view of an intervertebral disc implant, in accordance with certain exemplary embodiments disclosed herein;

FIG. 61 shows a schematic plan view of an intervertebral disc implant, in accordance with certain exemplary embodiments of the inventions disclosed herein:

FIG. 62 shows a schematic three dimensional view of the implant ofFIG. 61 in accordance with certain exemplary embodiments disclosed herein;

FIG. 63 shows a schematic three dimensional view of an intervertebral disc implant, in accordance with certain exemplary embodiments disclosed herein;

FIG. 64 shows a schematic three dimensional view of an intervertebral disc implant, in accordance with certain exemplary embodiments disclosed herein;

FIG. 65 shows a three dimensional view of an intervertebral disc implant, in accordance with certain exemplary embodiments disclosed herein;

FIG. 66 shows a sectional side view of the implant ofFIG. 65 in accordance with certain exemplary embodiments disclosed herein;

FIG. 67 shows a three dimensional view of the implant ofFIG. 65, in accordance with certain exemplary embodiments disclosed herein;

FIG. 68 shows a schematic three dimensional view of an intervertebral disc implant, in accordance with certain exemplary embodiments disclosed herein;

FIG. 69 shows a schematic, sectional plan view of an intervertebral disc implant, in accordance with certain exemplary embodiments disclosed herein;

FIG. 70 shows sectional end view taken along line A-A inFIG. 69 in accordance with certain exemplary embodiments disclosed herein;

FIG. 71 shows a schematic, sectional three dimensional view of an intervertebral disc implant, in accordance with certain exemplary embodiments disclosed herein;

FIG. 72 shows, on an enlarged scale, the detail encircled by “A” inFIG. 71 in accordance with certain exemplary embodiments disclosed herein;

FIG. 73 shows the detail ofFIG. 72 in a collapsed configuration in accordance with certain exemplary embodiments disclosed herein;

FIG. 74 shows a three dimensional view of a system, in accordance with certain exemplary embodiments disclosed herein, for implanting an intervertebral disc implant;

FIG. 75 shows, on an enlarged scale, a three dimensional view of the system ofFIG. 74 in accordance with certain exemplary embodiments disclosed herein;

FIG. 76 shows a schematic, sectional side view of an introducer for a system, in accordance with certain exemplary embodiments disclosed herein, for implanting an intervertebral disc implant.

FIGS. 77-79 illustrate, schematically, various stages of the use of an embodiment of equipment, in accordance with certain exemplary embodiments disclosed herein, for preparing a site for the implantation of a tissue prosthesis;

FIGS. 80-85 illustrate, schematically, various stages of the use of another exemplary embodiment of equipment, in accordance with certain exemplary embodiments disclosed herein, for preparing a site for the implantation of a tissue prosthesis;

FIG. 86 illustrates spinal disk load vs. displacement as determined in accordance with a finite element analysis of an exemplary implant;

FIG. 87 illustrates a sectional view of a ball valve inside an envelope in an open position in accordance with certain exemplary embodiments disclosed herein;

FIG. 88 illustrates a sectional view of a ball valve inside an envelope in a closed position in accordance with certain exemplary embodiments disclosed herein;

FIG. 89 illustrates a sectional view of a umbrella valve inside an envelope in an open position in accordance with certain exemplary embodiments disclosed herein;

FIG. 90 illustrates a sectional view of a umbrella valve inside an envelope in a closed position in accordance with certain exemplary embodiments disclosed herein;

FIG. 91 illustrates an exemplary valve-like configuration where the diameter gradually decreases to limit backflow in accordance with certain exemplary embodiments disclosed herein;

FIG. 92 illustrates a means of sealing through an O-ring (the cross section of the O-ring can be seen in the close up view) in accordance with certain exemplary embodiments disclosed herein;

FIG. 93 illustrates a means of sealing through a luer lock in accordance with certain exemplary embodiments disclosed herein;

FIG. 94 illustrates a means of sealing through a luer slip or luer fitting (taper fit) in accordance with certain exemplary embodiments disclosed herein;

FIG. 95 illustrates an exemplary priming means in which air is vented through a slit as the biomaterial primes the tube in accordance with certain exemplary embodiments disclosed herein;

FIG. 96 illustrates a single lumen delivery means where the air vents around the space between the filler tube and the valve-like structure in accordance with certain exemplary embodiments disclosed herein; and

FIG. 97 illustrates an end on view of the space around the tube when it has been pushed into the valve in accordance with certain exemplary embodiments disclosed herein.

DETAILED DESCRIPTION

In certain exemplary embodiments disclosed herein, there may be provided methods of forming a tissue prosthesis in situ at a site in a patient's body, that comprise accessing the site in the patient's body; if necessary, removing tissue from the site to form a cavity; inserting an envelope of a biologically inert, elastically deformable material into the cavity; charging a filler material, in a fluent state, into the envelope to cause the envelope to expand and, if necessary, stretch and conform to the shape of the cavity; and allowing the filler material to cure, the filler material being of the same class of material as the envelope so that, when the filler material has cured, a unified prosthesis is formed. In some aspects, these methods may be carried out using minimally invasive techniques. In some aspects, these methods may be carried out using percutaneous techniques. In some aspects, these methods may be carried out using a combination of minimally invasive and percutaneous techniques.

In certain exemplary embodiments disclosed herein, there may be provided methods of forming a tissue prosthesis in situ at a site in a patient's body, that comprise means for accessing the site in the patient's body; if necessary, means for removing tissue from the site to form a cavity; means for inserting an envelope of a biologically inert, elastically deformable material into the cavity; means for charging a filler material, in a fluent state, into the envelope to cause the envelope to expand and or stretch, if necessary and conform to the shape of the cavity; and means for allowing the filler material to cure, the filler material being of the same class of material as the envelope so that, when the filler material has cured, a unified prosthesis is formed. In some aspects, these methods may be carried out using minimally invasive techniques. In some aspects, these methods may be carried out using percutaneous techniques. In some aspects, these methods may be carried out using a combination of minimally invasive and percutaneous techniques.

In certain exemplary embodiments disclosed herein, the methods may include accessing the site percutaneously in a surgical procedure that is less invasive than conventional procedures. Hence, the method may be used to perform less invasive intervertebral disc nucleus replacement and the method may comprise forming an aperture in an annulus fibrosis of the disc percutaneously; extracting a nucleus pulposus of the disc to form a disc cavity bounded by the annulus fibrosis of the disc and end plates of vertebrae between which the disc is located; inserting the envelope, in a first state, into the cavity through the aperture; charging the filler material into the envelope to cause the envelope to expand and conform to the shape of the disc cavity; allowing the filler material to cure to form, together with the envelope, the substantially unified prosthesis; and occluding the aperture.

In certain exemplary embodiments disclosed herein, there may be provided methods of preparing a first assembly of a tissue prosthesis system for insertion into a patient's body, the methods comprising providing a first assembly which comprises a plurality of nested tubes, one of the tubes being a carrier tube; mounting a component of the prosthesis on a distal end of the carrier tube, the component being of an elastically deformable material; inserting a stiffening member into the first assembly so that the stiffening member extends into an interior of the component and causing a proximal end of the stiffening member to engage a proximal end of the first assembly; attaching a withdrawing device to the first assembly so that the withdrawing device is in fluid communication, at least with the interior of the component; and operating the withdrawing device to reduce the pressure, at least in the interior of the component to cause the component to collapse about the stiffening member.

In certain embodiments disclosed herein, there may be provided methods of preparing a first assembly of a tissue prosthesis system for insertion into a patient's body, the methods comprising means for providing a first assembly which comprises a plurality of nested tubes, one of the tubes being a carrier tube; means for mounting a component of the prosthesis on a distal end of the carrier tube, the component being of an elastically deformable material; means for inserting a stiffening member into the first assembly so that the stiffening member extends into an interior of the component and causing a proximal end of the stiffening member to engage a proximal end of the first assembly; means for attaching a withdrawing device to the first assembly so that the withdrawing device is in fluid communication with the interior of the component; and means for operating the withdrawing device to reduce the pressure in the interior of the component to cause the component to collapse about the stiffening member.

In certain exemplary embodiments of the disclosed herein, there may be provided methods of forming a tissue prosthesis at a site in a patient's body, the methods comprising providing a first assembly comprising a plurality of nested tubes, one of the tubes being a carrier tube with a component of the prosthesis carried at a distal end of the carrier tube; inserting the first assembly into a cannula placed in the patient's body, whereby the working cannula or cannula provides percutaneous access to the disc; engaging (e.g., magnetically attaching) a second assembly to a proximal end of the first assembly; and charging a filler material from the second assembly into the component and allowing the filler material to set.

In certain exemplary embodiments disclosed herein, there may be provided methods of implanting an intervertebral disc implant into an intervertebral disc, the methods comprising percutaneously performing a nucleotomy on the disc to remove a at least a portion of the nucleus pulposus of the disc to create a volume; inserting an envelope of the implant into the volume; charging an interior of the envelope with filler material in a manner to allow the envelope to expand to conform substantially to the volume; and causing the interior of the envelope to be closed off to retain the filler material within the envelope. The filler material may be selected to mimic, enhance or at least restore as much as possible the natural biomechanical characteristics of the nucleus pulposus of the disc. In certain embodiments, the filler material (e.g., the implant) may cooperate with the annulus to restore at least a portion of the natural biomechanical characteristics of the disc.

In certain exemplary embodiments disclosed herein, there may be provided methods of implanting an intervertebral disc implant into an intervertebral disc, the methods comprising means for accessing the disc percutaneouslty using for example a working cannula; means for percutaneously performing a nucleotomy on the disc to remove at least a portion of the nucleus pulposus of the disc to create a volume; means for inserting an envelope of the implant into the volume; means for charging an interior of the envelope with filler material in a manner to allow the envelope to expand to conform substantially to the volume; and means for causing the interior of the envelope to be closed off to retain the filler material within the envelope, the filler material being selected to mimic natural biomechanical characteristics of the nucleus pulposus of the disc.

In certain exemplary embodiments disclosed herein, there is provided methods of implanting an intervertebral disc implant into an intervertebral disc, the methods including a method of accessing the disc percutaneously using for example a working cannula, a method for removing at least a portion of the nucleus pulposus of the disc to create a volume; inserting at least one envelope into the volume; charging an interior of the at least one envelope with material in a manner to allow the at least one envelope to expand to substantially fill the volume, or partially fill the volume; and causing the interior of the envelope to be closed off to retain the material, the filler material being selected to at least partially mimic characteristics of the nucleus pulposus of the disc.

In certain exemplary embodiments disclosed herein, there is provided methods of implanting an intervertebral disc implant into an intervertebral disc, the methods including means for performing a nucleotomy on the disc to remove a nucleus pulposus of the disc to create a volume; means for inserting an envelope of the implant into the volume; means for charging an interior of the envelope with filler material in a manner to allow the envelope to expand to conform substantially to the volume; and means for causing the interior of the envelope to be closed off to retain the filler material within the envelope, the filler material being selected to mimic natural biomechanical characteristics of the nucleus pulposus of the disc.

In certain exemplary embodiments disclosed herein, there is provided methods of implanting an intervertebral disc implant into an intervertebral disc, the methods including percutaneously performing a nucleotomy on the disc to remove a nucleus pulposus of the disc to create a volume; inserting an introducer into an opening formed in an annulus of the disc; and introducing into the volume, via the introducer, at least one element which changes from a first configuration, in which the at least one element is able to be inserted into the introducer, to a second configuration in which the at least one element conforms substantially to the volume.

In certain exemplary embodiments disclosed herein, devices may be provided for forming a tissue prosthesis in situ at a site in a patient's body, the devices may comprise a delivery device displaceably receivable in a lumen of an introducer, the delivery device defining a passageway; an envelope carried at a distal end of the delivery device, the envelope being of a biologically inert, elastically deformable material capable of being expanded to conform to an interior surface of a cavity formed at the site; and a supply of a filler material chargeable in a fluent state into the envelope through the passageway of the delivery device, the filler material being of the same class of material as the envelope to form, when cured, together with the envelope, a unified prosthesis.

In certain exemplary embodiments disclosed herein, devices may be provided for forming a tissue prosthesis in situ at a site in a patient's body, the devices may comprise a tubular delivery device, the delivery device defining a passageway, an envelope of the prosthesis being mountable to a distal end of the delivery device to be received in a cavity at the site; a filler member receivable in the passageway of the delivery device, the filler member being receivable with clearance in the passageway to define a gap to enable fluid to be manipulated, displaced, or evacuated at least from the envelope; and a removal mechanism carried by the delivery device for enabling the envelope to be removed from the delivery device after the envelope has been charged with filler material via the filler member.

In certain exemplary embodiments disclosed herein, devices may be provided for forming a tissue prosthesis in situ at a site in a patient's body, the devices may comprise a means for tubular delivery device, the delivery device defining a passageway, an envelope of the prosthesis being mountable to a distal end of the delivery device to be received in a cavity at the site; a filler member receivable in the passageway of the delivery device, the filler member being receivable with clearance in the passageway to define a gap to enable fluid to be evacuated at least from the envelope; and a means for a removal mechanism carried by the delivery device for enabling the envelope to be removed from the delivery device after the envelope has been charged with filler material via the filler member.

In certain exemplary embodiment disclosed herein, devices may be provided for forming a tissue prosthesis in situ at a site in a patient's body, the devices may comprise a tubular delivery device, the delivery device defining a passageway, an envelope of the prosthesis being mountable to a distal end of the delivery device to be received in a cavity at the site; a stiffening element arranged, or means for providing a stiffening element, to project from a distal end of the delivery device with the envelope, in use, being received over the stiffening element to be supported by the stiffening element; and a removal mechanism carried by the delivery device for enabling the envelope to be removed from the delivery device after the envelope has been charged with filler material via the filler member.

In certain exemplary embodiment disclosed herein, tissue prosthesis insertion systems may be provided which include a first assembly comprising a plurality of nested tubes, one of the tubes being a carrier tube which, in use, receives a component of a tissue prosthesis at a distal end of the carrier tube; a magnetic mount carried at a proximal end of the first assembly; a second assembly removably attachable to the first assembly; and an attachment device carried at a distal end of the second assembly, the attachment device being responsive to the magnetic mount of the first assembly, the magnetic mount and the attachment device carrying complementary engaging formations to facilitate sealing between the magnetic mount and the attachment device. In certain embodiments, the second assembly may have the magnetic mount where the first assembly has the engaging member which is sealingly responsive to the magnetic mount of the second assembly.

In certain exemplary embodiment disclosed herein, tissue prosthesis insertion systems may be provided which include an assembly comprising a plurality of nested tubes, one of which is a carrier tube for carrying a component of a tissue prosthesis at its distal end and another of which is a filler tube received with clearance in the carrier tube to define a passage between the filler tube and the carrier tube, the proximal end of the filler tube and the proximal end of the carrier tube being in sealing engagement; and a withdrawing device attachable to the assembly so that, when the withdrawing device and material dispenser is attached and the component of the tissue prosthesis is mounted on the distal end of the carrier tube, a closed system is formed which allows the withdrawing device to be used to increase the volume of the closed system to form a low pressure region at least in the component.

In certain exemplary embodiment disclosed herein, tissue prosthesis insertion systems may be provided which include a working cannula for accessing a site in a patient's body percutaneously, in a less invasive manner for carrying out a tissue prosthesis insertion procedure at the site; and an obturating device receivable in the cannula for tamping a part of a tissue prosthesis into position after formation of the tissue prosthesis.

The obturating device may comprise a blunt-ended rod slidably receivable in the working cannula.

In certain exemplary embodiment disclosed herein, tissue prosthesis components may be provided which include an envelope of an elastically deformable material, the envelope defining an access opening; and a flow control member arranged in the access opening, the flow control member being configured to permit withdrawal of fluid from an interior of the envelope prior to filling the envelope with a filler material.

In certain exemplary embodiment disclosed herein, prosthesis delivery systems may be provide which includes a plurality of nested tubes, an outermost tube of which functions as a cannula in which the remaining tubes are received, the remaining tubes forming part of a prosthesis delivery apparatus, a wall portion of at least one of the tubes having a change in diameter along its length to mate with a corresponding part of a dispensing arrangement for use with the prosthesis delivery apparatus.

In certain exemplary embodiments disclosed herein, systems are provided which include a plurality of tubes, wherein an outermost tube functions as a cannula in which the remaining tubes are received, the remaining tubes forming part of a prosthesis delivery apparatus, a wall portion of at least one of the tubes having a change in diameter along its length to mate with a corresponding part of a dispensing arrangement for use with the prosthesis delivery apparatus.

In some exemplary embodiments, the prosthesis delivery devices may include at least one carry tube which may carry at least one component of the prosthesis on its distal end and at least one filler tube receivable in the carrier tube for charging a filler material into the component when the component is located at the desired location. The prosthesis delivery apparatus may include a connector for connection to a withdrawal device to enable fluid (e.g., air or gas) to be manipulated (e.g., withdrawn) from the component during formation of the prosthesis in situ, the connector being arranged, in use, at a proximal end of the prosthesis delivery apparatus.

In some exemplary embodiments, the prosthesis delivery apparatus may include a displacement device for displacing the component of the prosthesis after it has been charged with the filler material. The displacement device may be a further tube mounted about the carrier tube.

In some exemplary embodiments, the prosthesis delivery apparatus may include at least one cover tube to cover the component of the prosthesis, the at least one cover tube fitting over the at least one carrier tube. The at least one cover tube may include a resiliently flexible distal portion to accommodate the component of the prosthesis. In certain embodiments, the at least one cover tube may be received over the displacement device/tube which is mounted about the carrier tube.

In some exemplary embodiments, a wall portion of each of the tubes has a change in diameter along its length. In some exemplary embodiments, the change in diameter along the length of each tube may be provided by a flared wall portion of each tube.

In some exemplary embodiments, the systems may include a manipulating arrangement for effecting manipulation of the tubes located within the cannula. The manipulating arrangement may include a rupturing mechanism for rupturing the cannula for removal. The rupturing mechanism may comprise a plurality of spaced zones of weakness in a wall of the tube of the cannula and a gripping device arranged at a proximal end of the tube of the cannula. The gripping device may comprise a plurality of outwardly extending tabs which are pulled outwardly to cause rupturing of the zones of weakness of the cannula to facilitate withdrawal of the cannula after placement and positioning of the component of the prosthesis in the cavity or after formation and/or setting of the prosthesis.

In some exemplary embodiments, the systems may include the dispensing mechanism, the dispensing mechanism including a tubular element having a distal end which corresponds with and mates with that part of the wall portion of the at least one tube having the change in diameter. The nested tubes may be configured to extend proximally of the distal end of the element to overlie the element. With this arrangement, the length of the unsupported ends of the tubes is shortened thereby improving the rigidity of the tubes and the stability of the system. In addition, the balance of the system is improved rendering it easier for the clinician to control the system. This overall reduction in the length of the delivery system may also result in a reduction in the pressure required to deliver the filler material to the envelope component of the prosthesis.

The dispensing mechanism may include a dispenser to which the element is attachable. The element may be a static mixer.

In certain exemplary embodiment disclosed herein, prosthesis delivery systems are provided which include a plurality of nested tubes, one tube being a carrier tube which carries at least a component of a prosthesis at its distal end and another tube constituting a delivery tube for delivering the nested tubes to a site at a patient's body; and a cover tube forming part of the nested tubes, the cover tube being arranged outwardly of the carrier tube to cover the component when the carrier tube is inserted into the delivery tube to protect the component.

In certain exemplary embodiments disclosed herein, there is provided an introducer for introducing an intervertebral disc implant into a disc that has undergone a nucleotomy, the introducer including at least two sleeves arranged telescopically with respect to each other; and a displacement mechanism arranged on an operatively inner surface of an innermost one of the sleeves for assisting in displacing filler material along the sleeves into an interior of the disc, in use.

The displacement mechanism may comprise a ratchet arrangement for urging the filler material along the sleeve.

In certain embodiments disclosed herein, equipment may be provided for preparing a site for the implantation of tissue prosthesis. The equipment may include, for example a conduit assembly; an elastically stretchable and/or an inflatable member receivable on a distal end of the conduit assembly, the inflatable member being positioned, in use, at a site in a patient's body at which a tissue prosthesis is to be implanted; and a plurality of fluid dispensers connectable to the conduit assembly to communicate with the inflatable member, operation of the fluid dispensers manipulating the inflatable member to facilitate formation of the tissue prosthesis at the site.

Manipulating the inflatable member may comprise priming the inflatable member to receive a volume of fluid (e.g., a liquid or gas) to determine a size of the site. Still further, manipulating the inflatable member may comprise cyclically inflating and deflating the inflatable member to condition tissue surrounding the site.

The equipment may include a monitoring mechanism for monitoring a volume of fluid dispensed by a selected one or more of the fluid dispensers into the inflatable member to determine a size of a cavity at the site to be filled by the tissue prosthesis. In this manner, the inflatable member may act as a mock implant and may also determine the relative position of the implant as well. In certain exemplary embodiments, the monitoring device may be a pressure transducer. It will, however, be appreciated that other transducers such as force transducers, strain gauges, or the like could be employed to function as an end-point monitor. Alternatively, in embodiments where at least the volume of nucleus removed, or the volume created by the nucleotomy procedure, is replaced. Accordingly, the device may allow the volume to be measured which allows the surgeon to gauge the required volume of biomaterial to be dispensed into the envelope component of the implant.

In certain embodiments, the conduit assembly may comprise at least one tube on which the inflatable member is mountable with a branched connector being carried at a proximal end of the at least one tube, one of the fluid dispensers being connectable to each branch of the connector. The branched connector may be for example, a Y connector or a T connector.

In certain exemplary embodiments, the conduit assembly may comprise a pair (e.g., at least 2, 3, 4, 5, 6, 7, 8, etc.) of nested tubes, an outer tube being a carrier tube on which the inflatable member is carried and an inner tube being a fluid delivery tube for dispensing a volume of fluid from one of the dispensers into the interior of the tube. In certain embodiments, at least one of the tubes may extend, in use, to a distal end of the inflatable member and the tube may have an aperture defined in it which facilitates fluid communication between an interior of the inflatable member and an interior of the tube or tubes. The at least one tube extending into the inflatable member may, in certain embodiments, serve to allow the inflatable member to be collapsible about the tube and more easily introduced percutaneously or minimally invasively through the working cannula.

In another exemplary embodiment, the conduit assembly may comprise a single tube on a distal end of which the inflatable member is carried. A flow control member may be received in communication with an interior of the tube for placing a selected one of the fluid dispensers in fluid communication with the interior of the tube and hence the interior of the inflatable member as desired. Similar to other exemplary embodiments, the tube may extend, in use, to a distal end of the inflatable member and have an aperture defined in it which facilitates fluid communication between an interior of the inflatable member and an interior of the tube.

In certain embodiments, the flow control member may be a device which controls the direction and flow of fluid. This can be, for example, a 3-way stopcock, or it can be a valve which opens up when the fluid dispenser is engaged, and shuts off when the fluid dispenser is disengaged (e.g., a duck bill valve). For example, with a duck bill valve, when the fluid dispenser is engaged, the tip of the fluid dispenser pushes open the leaflets of the valve, placing the interior of the tubes and inflatable component in fluid communication with the fluid dispenser. When the fluid dispenser is disengaged, the leaflets of the valve. Such an apparatus using this form of valve system can omit the need for the dual syringe system because a single syringe can be used to prime the system and any air or gas or other unwanted fluids which are displaced from within the system and into the syringe can be purged by removing the syringe from the rest of the apparatus and purged by manipulating the piston of the syringe. In the meantime, the fluid within the system is maintained within the system because of the valve which has closed off to substantially seal in the fluid which has been used to displace the unwanted air, gas or other fluid which was originally within the system.

At least one of the fluid dispensers may be a reciprocally operable device such as for example, a syringe.

In certain exemplary embodiments disclosed herein, there may be provided methods of preparing a site for the implantation of tissue prosthesis. The methods may include inserting a member into a cavity at a tissue site to be prepared; priming the member; and inflating the member at least once with a volume of fluid to determine a size of the cavity.

In certain exemplary embodiments disclosed herein, there may be provided methods of preparing a site for the implantation of tissue prosthesis. The methods may include means for inserting an inflatable member into a cavity at a tissue site to be prepared; means for priming the inflatable member; and means for inflating the inflatable member at least once with a volume of fluid to determine a size and/or position of the cavity.

The method may include priming the inflatable member prior to inserting into the cavity which may entail priming the inflatable member prior to inserting the inflatable member into the patient's body. In certain exemplary embodiments, the method may include inflating and deflating the inflatable member a number of times to condition tissue surrounding the cavity. In certain exemplary embodiment, the method may include monitoring a predetermined parameter to determine the quantity of fluid dispensed into the inflatable member to fill the cavity.

The method may include means for priming the inflatable member prior to inserting into the cavity which may entail priming the inflatable member prior to inserting the inflatable member into the patient's body. In certain exemplary embodiments, the method may include means for inflating and deflating the inflatable member a number of times to condition tissue surrounding the cavity. In certain exemplary embodiments the method may include means for monitoring a predetermined parameter to determine the quantity of fluid dispensed into the inflatable member to fill the cavity.

In certain exemplary embodiments disclosed herein, tissue prostheses are provided which comprise at least one envelope of a biologically inert, elastically deformable material capable of being expanded to conform to an interior surface of a cavity formed at a site in a patient's body; and a filler material received in a fluent state in the at least one envelope, the filler material being of the same class of material as the at least one envelope to form, when cured, together with the envelope, a unified, or substantially unified, structure.

In certain exemplary embodiments disclosed herein, tissue prostheses are provided which comprise an envelope of a foraminous, chemically inert material shaped to conform to an interior surface of a cavity formed at a site in a patient's body in which the envelope is to be placed; and a filler material received in a fluent state in the envelope, the filler material being of an elastomeric material which, prior to being cured, is urged into foramens of the envelope to form an integrated structure which inhibits relative movement between the envelope and the filler material, in use, and once the filler material has cured.

In certain exemplary embodiments, there is provided an intervertebral disc implants which includes an envelope constructed of at least one stretchable and/or elastically deformable elastomeric material, the envelope including an attaching formation for attachment to an introducer to enable the envelope, in a first state, to be introduced into a volume of an intervertebral disc that has undergone a nucleotomy; and a filler material receivable in the envelope via the introducer to cause the envelope to expand elastically to conform substantially to the volume in which the envelope is received, in use.

According to certain exemplary embodiments, there is provided an intervertebral disc implant which includes a first object constructed of at least one stretchable and/or elastically deformable elastomeric material, the first object being in communication with second object for attachment to a third object to enable the first object, in a first state, to be introduced into a volume of an intervertebral disc that has undergone a nucleotomy; and a material receivable in the first object via the second object which results in expansion, or partial expansion of the first object such that the first object substantially conforms to the volume in which the first object is received, in use.

According to certain exemplary embodiments, there is provided an intervertebral disc implant which includes an envelope constructed of at least one stretchable and/or elastically deformable elastomeric material, the envelope including means for attaching an introducer to enable the envelope, in a collapsed state, to be introduced into a volume of an intervertebral disc that has undergone a nucleotomy; and means for introducing a filler material into the envelope via the introducer to cause the envelope to expand elastically to conform substantially to the volume in which the envelope is received, in use.

In certain exemplary embodiments, there is provided an intervertebral disc implant which includes an envelope, the envelope including an attaching formation for attachment to an introducer to enable the envelope, in a collapsed state, to be introduced into a volume of an intervertebral disc that has undergone a nucleotomy; and a filler material receivable in the envelope after placement of the envelope in the volume of the disc, in use, to cause expansion of the envelope to conform to the volume, the filler material comprising a plurality of discrete, elongate elements introducible, via the introducer, into an interior of the envelope.

In certain exemplary embodiments, there is provided an intervertebral disc implant which comprises an envelope receivable in a volume of an intervertebral disc that has undergone a nucleotomy, the envelope defining a plurality of chambers, the chambers being configured so that, when at least certain of the chambers contain a filler material, the envelope conforms substantially to the volume of the disc; a filler material receivable in the at least certain of the chambers; and at least one of the chambers having a filler mechanism associated with it.

One advantage of certain disclosed methods and equipments are that they facilitate minimally invasive formation of tissue prosthesis in situ. Another advantage of certain disclosed methods and equipments are that they facilitate percutaneous formation of tissue prosthesis in situ. In addition tissue prosthesis is provided which are resistant to delamination. In particular, in the case where the tissue prosthesis has an envelope and filler material of the same class of material, a substantially unified, integrated structure may be provided which is resistant to delamination and relative movement between the envelope and the filler material. The unified structure and the fact that the envelope is elastically deformed and is retained under tension also renders the envelope resistant to creasing increasing the operational efficiency of the prosthesis by being better able to distribute forces to the annulus fibrosis of the disc.

In addition, the use of a silicone rubber envelope in certain embodiments is particularly advantageous due to the fact that, when a nucleotomy has been performed, residue remains behind which is irregular in shape. It is beneficial to have a prosthesis which expands and conforms as closely as possible to the shape (micro and macrostructure) of the cavity in order that compressive, tensile, bending and torsional forces can be accommodated by the disc. In addition, the provision of a tissue prosthesis expanding and closely conforming to the shape of the cavity results in an improvement in stimulation and deformation of the end plates of the vertebrae and thereby aiding in restoration of the natural pumping action which assists in the influx of nutrients and the efflux of waste products from within the disc.

It is yet a further advantage of certain embodiments that the tissue prosthesis can be formed in situ in a minimally invasive manner. The need for invasive surgical procedures is therefore obviated and there is the added advantage of more rapid post-operative recovery and the reduced need for a prolonged period in hospital.

In certain embodiments, the equipment further provides an efficient, easy to use manner of forming the tissue prosthesis. By having the tubes etc nested, a clinician is more easily able to manipulate the equipment to place and form the tissue prosthesis. With the added use of a working cannula, the access to the disc and hence the nucleus pulposus need only to be established once. All the remaining tubular apparatus for positioning and forming the tissue prosthesis are slideably receivable within the protected confines of the working cannula. Therefore, there is no repeated movement of having to go in and out of the tissue which could increase the risk of damage to muscle, subcutaneous tissue and particularly nerves. Further, the use of a barrelled dispensing device connected to a static mixer and tube which delivers the mixed biomaterial directly into the envelope avoids the use of complex systems (for example, ones with pressure feedback etc) for injecting the material which may be used to overcome the changes in pressures while injecting into confined tissue spaces.

It is yet a further advantage that the procedure is not restricted to large hospitals requiring costly operating tools in the hand of professionals like spinal surgeons, neurosurgeons and orthopaedic surgeons; but can be performed by numerous physician including pain physicians, radiologists, anaesthesiologists, sports physicians and any other professional confident of using a fluoroscope imaging device and placing needles into intervertebral discs. The larger community and societal benefit of such superiority of the present inventions are great as it improves access and affordability to a large population of chronic back pain sufferers. Other advantages include a non heat generating catalytic interaction(or in certain embodiments, the reaction may be slightly endothermic or slightly exothermic) for polymerisation of the flowable material, obviating the risk of thermal damage to adjacent tissues. More advantages include, prevention of leakage of flowable material into undesirable confines in the event the prepared tissues walls have fissures and or breaches that communicate to areas where there may be organs at risk.

While the inventions described herein are described with reference to certain exemplary embodiments related to intervertebral disc nucleus replacement, it will readily be appreciated by persons of ordinary skill in the art, in view of this disclosure, that the inventions disclosed herein are not limited to such embodiments and that the inventions described herein are more generally related to tissue prostheses.

In certain exemplary embodiments, the filler material may be any natural, synthetic or biological polymer. The materials may be polymers or copolymers. The material should preferably present with biocompatible characteristics. The material may at least closely mimic and or at least closely restore the function of the joint or tissue it is replacing. In the case of the intervertebral disc, the material may restore the biomechanics of the joint by restoring the intradiscal pressure and hence the hoop stresses to the annulus fibrosis. Should it be required, the material may also be able to supply sufficient pressure to the disc to restore any loss in disc height or at least maintain the disc height. The material may also have some load bearing capabilities. Patients undergoing nucleus prosthesis treatment may have a mildly compromised annulus fibrosis (small tears and or fissures), hence the prosthesis may bear some of the axial load, whilst still sharing and distributing some of the incident load to the annulus to keep it in tension (i.e., be both load bearing and load sharing). Also, the material should preferably not inhibit the flow of nutrients and other such fluids through the disc, as the residual (remaining) nucleus and annulus still requires hydration and nutrients to at least slow down or halt the degeneration of the disc. The material may also possess resilience, viscoelasticity and fatigue resistance (as the disc is loaded cyclically during everyday activities, the disc needs to be able to retain or at least restore its height under cyclic fatigue). The class of materials which suits these features are elastomers, in particular silicones. Silicones have an established history of use. They are extremely stable (mechanically and biologically) in its cured form and even when they are cured in situ, the catalysts used to cure the material are not harmful to the surrounding tissue and the curing process is harmless to the surrounding tissue. Silicones are resilient, elastic and have excellent shock absorbing capabilities.

Although the range of hardness for the silicones (or elastomer in general) which are suitable for this application are between about 5-90 A (e.g., 5-15 A, 20, 20-40 A, 40-60 A, 50-70 A, 70-90 A, etc.), the preferred hardness range is about 20-40 A and more specifically about 30 A (e.g., about 27, 28, 29, 30, 31, 32, 33, etc.). Since silicones deform elastically under a given load, it spreads the load evenly across the endplates and minimizes stress concentration and or stress shielding which could all lead to subsidence of the implant into the endplate.

Additionally, the filler material may have varying degrees of porosity (such as silicone foams). Porosity may allow for tissue to grow into it, it may not affect the flow of nutrients across the disc, and by adjusting the porosity, the mechanical characteristics of the material may also be varied (such as deformation under load, creep, fatigue properties etc.).

The filler material may be selected to at least partially mimic natural biomechanical characteristics of the nucleus pulposus of the disc.

The at least one envelope may be made from an elastomeric material, preferably a silicone, which is biologically inert and which can elastically deform up to 3, 5, 7, 10, 30, 50, 80, 100, 120, or 150 times the size of the at least one envelope in its relaxed state. In some embodiments, the at least one envelope may be made from the silicone rubber material which is substantially biologically inert and which can elastically deform in the ranges of 3 to 5, 5 to 7, 7 to 10, 10 to 50, 10 to 100, 20 to 150, 30 to 100, 20 to 120, 70 to 100, or 50 to 150 times the size of the at least one envelope in its relaxed state. In other embodiments, the envelope may be compliant (e.g., with or without be elastic) which may allow the envelope to conform or substantially conform to the cavity.

The at least one envelope may also be made of other materials. For example, the at least one envelope made from less expansible material such as a biological or a synthetic polymeric material. A suitable synthetic polymeric material may, for example, be polyester such as polyethylene terephthalate (PET). The at least one envelope may also be constructed of a knitted PET material so that, when the filler material is charged into the at least one envelope, the filler material fills foramens or interstices in the at least one envelope to form an integrated structure which resists relative movement between the filler material and the at least one envelope. Alternatively, the knitted PET material may be coated with silicone allowing the filler material to integrate with the coating.

The materials which the envelope may be made from may be any natural, synthetic or biological polymer or copolymer which possesses biocompatibility. The envelope may be a porous material which allows for the surrounding tissue to grow into the implant and anchor or stabilize the implant within the disc space (or in general at the tissue site which it is being implanted into). The porosity may also allow for the filler material to seep through the envelope and bond to the envelope to form a substantially unified structure. Should the envelope be made of a non porous material, the advantage is that it prevents filler material from seeping into unwanted fissures, cracks and tears in the annulus. Even if the envelope is non porous, having filler and envelope of the same class of materials can also achieve the same substantial unification. Having a unified structure means that there is no relative movement between the filler and envelope, thus reducing the wear and hence the wear particles being produced. An advantage of having an envelope of an elastic, resilient material such as silicone is that the envelope may be capable of expanding and conforming to the macro and micro structures of the interior of the disc. This also increases the contact area of the implant across the endplates reducing stress concentrations and thus reducing the chances of implant subsidence.

As used in the specification the performance of a nucleotomy on the disc involves the removal of a certain amount of the nuclear tissue constituting the nucleus pulposus. The methods, devices, and/or systems disclosed herein often refer to the removal of the nuclear tissue. The amount of nuclear material removed may vary from procedure to procedure and this will be understood by those skilled in the art in view of the present disclosure. Using the devices, methods, and/or systems disclosed herein, it may be desirable to completely remove the nuclear tissue, in other instances it may be sufficient to substantially remove the nuclear tissue, or in other instances it may be sufficient to partially remove the nuclear tissue.

Depending on the degree of nucleus pulposus removal, the prosthesis may be classed as a total nucleus replacement or a partial nucleus replacement. Regardless of the degree of tissue removal, the one or more implants may completely or at least partially fill the cavity which remains. Completely filling the cavity will allow the transfer of load onto the annulus and restore the hoop stresses which are necessary to minimise the shear stresses on the annular layers and hence, at least slow further degeneration of the disc. If the implant were to partially fill the space, it allows the implant to reposition itself in a manner which prevents further migration and minimise the chances of extrusion. It may also reposition itself to a position which is of least resistance and hence minimise the stresses on the implant and surrounding tissue. The kangaroo data detailed later demonstrates the restoration of the kinematics of the spine even after the partial filling of the nucleus cavity.

One of the advantages of the implant is that multiple units can be implanted from various directions to achieve a partial, near complete or complete filling of the nuclear space. For example one device can be implanted on the right side from the right posterolateral corner or the right lateral corner or anteriorly. The other one can be implanted from the opposite side as well.

In certain embodiments, a percutaneous approach as opposed to open or minimally invasive surgery may be used. With a percutaneous approach, a needle is usually used for intravenous injections, intramuscular injections or intradiscal injections. For minimally invasive surgery, some operations have been described and defined as requiring 1. visualisation; which may be magnified by using optical loops, endoscopic cameras, microscopes etc. 2. illumination which is obtained either via cold light sources, optical cables orother means 3. retraction; retraction of tissues is an important components of minimally invasive surgery as a lot of resources and effort have gone into developing this third and final component of minimally invasive surgery. It is understandable that a small incision may be required for minimally invasive surgery (e.g., about 5 cm, about 6 cm, about 7 cm, etc.) and such incisions can be multiple in nature. The present inventors propose the percutaneous surgery which is carried out without the aid of optical visualisation, illumination, or the use of any specialised retractors as is required for minimally invasive surgery. In certain embodiments the method may be performed as a micro-invasive surgery. For example, in certain embodiments, the opening used may be less than 4 cm. For example, the opening (e.g., the incision, puncture, or other means of accessing the body) may be up to 200 microns, or up to 400 microns, or up to 800 microns (e.g., about 200, 250, 300, 350, 400, 450, 500, 550, 600, 650, 700, 750, or 800) or alternatively of the order of about 2 cm to about 4 cm (e.g., about 2, 2.5, 3, 3.5, 4) or alternatively, of the order of up to 1 cm or up to 6 cm.

The methods and apparatus defined for formation and insertion of tissue prosthesis can be used in many clinical scenarios in varying fashions. In the area of degenerative disc of the spine, advanced stage disc diseases requires the application of posterior spinal fusion with or without decompression with the fusion either being static or dynamic. In situations where the fusion is dynamic and performed with the use of pedicle screws there is a risk that the lordosis of the motion segment may be compromised. In static fusions, the lordosis is recreated by use of a interbody cage or interbody fusion device and the operation is called posterior interbody lumbar fusion. In dynamic fusions, the CPDRD can be implanted in an interbody manner within the nucleus to recreate the lumbar lordosis, to share load bearing anteriorly and thereby prevent loosening of the pedicle screws. This method may be a preferable method of performing posterior dynamic fusion of the spine, using existing systems like Dynesis, N-Flexrod (Spine next).

Further, in more advanced disc disease, the clinical condition of spinal stenosis exists where the gap between the spinous processes decreases. In these patients, the classical older operation has been laminectomy, foraminolaminectomy, posterior spinal decompression. More modern operations include implantation of the Wallis device, X-Stop, or In Space, Diam. However, these interspinous distraction devices have numerous disadvantages including incisions to expose the area (minimally invasive spinal surgery), and/or being hard and not allowing for shock absorption. The device disclosed herein can be implanted in the interspinous area in a percutaneous manner after clearing the interspinous area with the patient in a flexed position. The distraction of the interspinous area leads to effective improvement in the spinal stenosis. The same interspinous implant can be used after discectomies performed for herniated nucleus pulposus fragments either by small incision or endoscopically.

In certain embodiments, an apparatus for forming a tissue prosthesis (e.g., a disk prosthesis) in situ in a patient's body may be provided. The apparatus may comprise, an inflatable component and a delivery mechanism for delivering a filler material into the inflatable component so that when the filler material is cured, a unified prosthesis is formed. In certain embodiments, the delivery mechanism may comprise at least one priming mechanism (e.g., a hole, valve, or opening) proximate to the area where the inflatable component is coupled to the delivery mechanism (see, for example,FIG. 38B for an example of ahole1010 on either side of the delivery mechanism and proximate to an end of the delivery mechanism). The at least one hole may be large enough for gas to pass through but small enough so that the filler material can not pass through. In this manner, it may be possible to prime the apparatus to remove a substantial amount of the gas from within the system so that the gas does not need to be purged when the delivery system is in the body.

Certain embodiments may provide a method system or apparatus that comprises any of the details disclosed throughout this specification exclusive of, for example, a bone grafting, stabilization, or fastening and/or holding devices such as screws (e.g., facet screws, and/or pedicle screws), staples, etc. For example, in certain embodiments, a method may be provided that consists only of accessing the site in the body of a patient (e.g., a vertebral disk), removing tissue from the site to form a cavity, if necessary, inserting an inflatable component into the cavity, and delivering, via a delivery mechanism, a filler material into the inflatable component so that when the filler material is cured, a unified prosthesis is formed. The exemplary method may optionally include some of the additional steps disclosed throughout the specification. In certain embodiments, a method for completing the implantation of a tissue prosthesis in situ in a patient's body may be provided and the method may consist exclusively of accessing the site in the body of a patient; optionally, removing tissue from the site to form a cavity; optionally, priming a delivery mechanism with filler material to remove gas from within the delivery system; optionally, sizing the cavity; inserting an inflatable component into the cavity; delivering a filler material into the inflatable component so that when the filler material is cured, a unified prosthesis is formed; and completing the procedure by removing the delivery mechanism from the site in the patients body and optionally, applying a bandage to the site. In certain embodiments, the method may not require a bandage but may merely be completed without the use of any mechanical closing means such as for example, sutchers or stitches.

Certain embodiments may provide a method for forming a tissue prosthesis in situ in a patient's body. The method may comprise accessing the site in the body of a patient (e.g., a vertebral disk), removing tissue from the site to form a cavity, if necessary, and priming a delivery mechanism with filler material to remove gas from within the delivery system. The method may further comprise inserting an inflatable component into the cavity, and delivering, via a delivery mechanism, a filler material into the inflatable component so that when the filler material is cured, a unified prosthesis is formed.

In certain embodiments, the delivery mechanism may be configured to be primed prior to forming the tissue prosthesis and the inflatable component may be deflated during the priming so that after the delivery mechanism is primed, there is an acceptable amount of gas (e.g., substantially no gas or a minimal amount of gas) in the inflatable component, thereby further eliminating the need for a gas removal system during delivery of the filler material (e.g., a two lumen system such as discussed elsewhere herein). In certain embodiments, the opening discussed above may be used to remove the gas. In particular, as the filler material fills the delivery mechanism, the gas within the system may be pushed out through the hole. In this manner, only a desirable amount of gas may remain in the delivery mechanism. In certain embodiments, the inflatable component may be at least partially primed with filler material. Partially priming the inflatable component may include partially filling the inflatable component in a manner such that the inflatable component remains in a relaxed state or alternatively in a state where it may still be inserted into the site of the body without substantially more difficultly than if the inflatable component was not primed (e.g., readily inserted into the working cannula after priming).

In certain embodiments, delivery mechanism and inflatable component may form a closed system or in certain embodiments, the delivery mechanism and inflatable component may form an open system. An open system is one where matter and or energy can flow into and or out of the system. A system that receives inputs of energy and or matter and then outputs material into surrounding environments is termed an open system. In contrast, a closed system is where energy can enter or leave but matter may not. A system that is shut off from the surrounding environment and is self contained is termed a closed system. More specifically, a closed system may be enclosed by barriers which prevent the influx of material and also efflux of material. The volume, pressure and or temperature are still able to change, but, fluid and or other matter are not in direct fluid communication with the surrounds external to the bounds of the closed system.

In certain embodiments, the site within the body of the patient may be accessed in a minimally invasive manner, percutaneously, or in a micro-invasive manner. Additionally, the diameter of the access point for accessing the site within the patient's body may less than 6 cm, less than 5 cm, less than 4 cm or less than 3 cm, less than 2 cm, less than 1 cm, less than 0.75 cm, less than 0.6 cm, less than 0.5 cm, or less than 0.4 cm. In certain embodiments, the access point through the skin for accessing the site within the patient's body may be sufficiently small so as not to require anything more than a bandage. In certain embodiments, the access point may be sufficiently small so as not to require any closing device such as for example, stiches, sutures, or a fastening bandage upon termination of the surgical procedure.

In certain embodiments, the filler material may have a shore hardness of less than about 10 A, between 10 to 20 A, between 20 to 30 A, between 30 to 50 A, between 50 to 70 A or greater than 70 A, but preferably about 30 A. In certain embodiments the filler material may be CSM-2186-14, manufactured by Nusil Technologies or MED5-4230, manufactured by Nusil Technologies. In certain embodiments, the inflatable component may be made from liquid silicone rubbers. Examples include, but are not limited to, MED-4805, MED-4810, MED-4820, MED-4830, MED-4840 manufactured by Nusil Technologies. In certain embodiments, the inflatable component may be made from high consistency elastomers. Examples include, but are not limited to MED-2174, MED4-4515, MED-4520, MED-4535 manufactured by Nusil Technologies. In certain embodiments, the inflatable component may be made from dispersions. Examples include, but are not limited to MED-2214, MED-6400, MED-6600, MED1-6604, MED-6605 manufactured by Nusil Technologies.

Certain embodiments may provide a tissue prosthesis comprising: an inflatable component; and a filler material received in a fluent state in the inflatable component, the filler material being of an elastomeric material with a shore hardness of less than 90 A and preferably about 30 A. In certain embodiments the filler material may be CSM-2186-14, manufactured by Nusil Technologies or MED5-4230, manufactured by Nusil Technologies. In certain embodiments, the inflatable component may be MED-4830, manufactured by Nusil Technologies.

The filler material is a two-part pourable silicone elastomer that cures at room temperature. It contains about 5% BaSO₄(e.g., about 3%, 4%, 5%, 6%, or 7%) in both parts and mixes at about a ratio of 3:1 to 1:3 (e.g., 0.5:1 to 1.5:1, 1:1). The viscosity of part A may be about 105,000 cP (e.g., about 100,000 cp, 101,000 cp, 102,000 cp, 103,000 cp, 104,000 cp, 105,000 cp, 106,000 cp, 107,000 cp, 108,000 cp, 109,000 cp, or 110,000 cp) while the viscosity of part B may be about 71,000 cp (e.g., about 65,000 cp, 67,000 cp, 69,000 cp, 71,000 cp, 73000 cp, or 75,000 cp). Additionally, the filler material may have a durometer of about 22-35 D2240 (e.g., about 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33 or 34), a tensile strength or between 850 to 1200 psi (e.g., about 900 psi, 950 psi, 1000 psi, 1050 psi, or 1100 psi), an elongation of between 500% -1200% (e.g., about 500%, 550%, 600%, 650%, 700%, 750%, 800%, 850%, 900% or 1000%), and a tear strength of between 80-120 (e.g., about 90 ppi, 95 ppi, 100 ppi, 105 ppi, or 110 ppi). The filler material may typically be filled with inorganic material for example silica, titanium dioxide, fly ash or other bio-acceptable fillers (e.g. amorphous silica). These fillers can optionally be surface treated with hydrophilic agents and/or hydrophobic agents. The inorganic fill material may be present in the filler material in amounts between 5 and 50 wt. %, (e.g., 10-40 wt. % including 15 wt. %, 20 wt. % up to 30 wt. %, 35 wt. %, 40 wt. %). The inorganic fill material may be present in either part A or B or both A and B.

The envelope material may typically be a two-pan translucent silicone system that cures rapidly with no required post-cure. It mixes at about a 3:1 to 1:3 ratio (e.g., 0.5:1 to 1.5:1 and 1:1). The composition may have a durometer of about 25-35 D2240 (e.g., about 26, 27, 28, 29, 30, 31, 32, 33, or 34), a tensile strength of between 1100 and 1500 psi (e.g., about 1250 psi, 1300 psi, 1350 psi, 1400 psi, or 1450 psi), an elongation of between 500% and 1100% (e.g., about 550%, 600%, 650%, 700%, 750%, 800%, 8505, 900%, 950% or 1000%), a tear strength of between 140 175 ppi (e.g., about 140 ppi, 145 ppi, 150 ppi, 155 ppi, or 160 ppi), and a stress at 200% strain of between 150 and 200 psi (e.g., about 160 psi, 165 psi, 170 psi, 175 psi, 180 psi, 185 psi, or 190 psi).

The silicone used for the filler material or envelope material may include any one of a variety of silicones generally referred to bio-compatible elastomers formed from polysiloxanes or polyorganosiloxanes which are polymers having the general chemical formula [R₂SiO]_n, where R is any suitable organic group and n is any integer. Such polysiloxanes suitable for these purposes may also include abroad family of more complex synthetic polymers containing a repeating silicon-oxygen backbone with organic side groups attached via carbon-silicon bonds. Such complex silicones, or polymeric siloxanes, may be linear, branched or cross-linked, and can be represented by the formula [R_pSiO_(4-p/2)]_m, where p is 1-3, m>1, and R is any suitable organic group such as alkyl, alkenyl, Iluoroalkyl, phenyl, vinyl, hydroxyl, alkoxy, amino or alkylamino or combination of one or more of these organic groups, e.g., -phenylvinyl. The term silicone as used herein is also meant to include elastomers that are hetero- or copolymers of the above-described polysiloxanes. The polysiloxanes suitable for the present invention may also have their terminal ends such as alkyl, alkenyl, fluoroalkyl, phenyl, hydride, vinyl, hydroxyl, alkoxy, amino or alkylamino group or combinations of one or more of these organic groups, e.g., -alkylvinyl (this could be part A of a two-part system). The polysiloxanes suitable for example as a counter part polysiloxane (e.g., part B) can be modified to include functional, active or inactive organic groups for various purposes, such as to promote crosslinking (for example hydrides or other terminal groups functional groups suitable for treating with ethylenically unsaturated functional groups) or for copolymerization or other reactions. The two groups undergoing an addition reaction during curing. Such addition reaction can be aided by a Group VIII metal (e.g., platinum, rhodium, or palladium).

Non-limiting examples of some polysiloxanes include: polydiorganosiloxanes, polyaklysiloxanes, polydialkylsiloxanes, polydimethylsiloxanes, polyaminoalyklsiloxanes, polyaminoalklsiloxanes, polyethyleneglycol-polydimethyl siloxane co-polymers, silicone polyesters, polysiloxane-polylactone copolymers, polydimethyldiphenylsiloxane, polyalkylsiloxane-polyurethane copolymers with one or more terminal groups such as alkyl, alkenyl, fluoroalkyl, phenyl, vinyl, hydroxyl, alkoxy, amino or alkylamino group or combination of two, three or more of these groups (e.g., -alkylvinyl).

In certain embodiments, the priming may occur after the inflatable component is inserted into the cavity. In either of these cases, the priming may be achieved by having a small opening or several small perforations at some point near the distal end of the delivery mechanism, preferably just proximal to the inflatable member. This opening may allow for gases or certain fluids within the delivery mechanism to escape through the opening, but will substantially limit the flow of the filler material through this opening. The opening may allow less viscous fluids to pass through the opening easily, but substantially limit more viscous fluids from passing through this opening. Therefore, as the filler material primes the delivery mechanism, the gases or certain fluids within the delivery mechanism may be pushed out through this opening and limit the entrapment of gas or certain fluids within the inflatable member. The opening may be a slit or a hole (see, for example,FIG. 95 for an example of a slit1008 on a side of the delivery mechanism and proximate to an end of the delivery mechanism). In the case of a slit, the width of the slit may be less than 0.1 mm, between 0.1 to 0.5 mm, between 0.5 to 1 mm, between 1 to 5mm or greater than 5 mm. In the case of a hole, the diameter may be less than 0.1 mm, between 0.1 to 0.5 mm, between 0.5 to 1 mm, between 1 to 5 mm or greater than 5 mm. In certain embodiments, the inflatable component is deflated during the priming and preferably maintained deflated until at least the delivery mechanism is substantially primed. In either of these situations, after priming; there may be substantially minimal quantities of gas or certain fluids in the inflatable component, thereby eliminating the need for a gas removal system (e.g., a second lumen) during delivery of the filler material. Additionally, in certain embodiments, the inflatable component may be primed during the priming.

In certain embodiments, the body of the patient may be accessed in a minimally invasive manner, percutaneously, or in a micro-invasive manner. Additionally, the diameter of the incision for accessing the patient's body may less than 6 cm, less than 5 cm, less than 3 cm or less than 2 cm. In some embodiments, the incision may be less than 1 cm. In certain embodiments, no external stitches would be required to close the incision or puncture created when the site is accessed.

In certain embodiments, the delivery apparatus may comprise a carrier tube for carrying a component of the prosthesis at its distal end. There is also a filler tube which is slideably receivable within the lumen of the carrier tube with clearance. At some point near the distal end of the carrier tube is at least one slit or several small perforations which may allow for gases or certain fluids within the delivery mechanism to escape through the opening, but will substantially limit the flow of the filler material through this opening. The opening may allow less viscous fluids to pass through the opening easily, but substantially limit more viscous fluids, such as the biomaterial, from passing through this opening. The method of forming the implant in situ may comprise positioning the carrier tube at the desired location within the patient's body. Then the filler tube (which may be attached to a material dispenser apparatus) is primed substantially with the biomaterial prior to being inserted into the carrier tube. As the filler tube is inserted into the carrier tube, the volume of gas, or air, or other fluids within the delivery apparatus, are displaced by the volume occupied by the introduction of the filler tube. This volumous gas is displaced through the perforations at the distal end of the carrier tube. The gas within the delivery apparatus may preferably be displaced through the perforations at the distal end of the carrier tube than the annular space between the carrier tube and filler tube for a couple of reasons. First, the biomaterial may have overflowed from the distal tip of the filler tube (substantially enough), to form a plug at the tip of the filler tube as it is introduced through the carrier tube, thereby not allowing gas to flow around and between the carrier tube and filler tube. Second, the resistance to the flow of gas or air is significantly less through the perforations than through the annular space between the filler tube and carrier tube.

Whatever the case may be, substantial volumes of the gas, air or certain fluids within the delivery apparatus would have been displaced and only a small quantity of air entrapment is likely to occur within the implant. Additionally, if the component of the implant were to be maintained collapsed (either through a clamping mechanism, or the sheath) throughout the procedure whilst the filler tube is being introduced, then removal of the sheath or clamping mechanism from around the component of the implant would result in an even further reduction of air entrapment into the component.

Using the apparatus described in above, a similar method may be used to form the tissue prosthesis. If the filler tube were to terminate proximally to the perforation within the carrier tube, when nested and assembled as it would be in use, the filler tube may not need to be primed before being introduced into the lumen of the carrier tube. If the resistance to the flow of gas or air at the perforations is significantly less than that of the annular space between the carrier tube and the filler tube, then as the filler material is charged through the filler tube, the air or gas may be displaced through the perforations, minimizing air entrapment into the envelope.

In certain embodiments, the means for maintaining the envelope collapsed may be a sheath which has built in weaknesses in its walls at its distal end. Rather than having to retract the sheath, by delivering the biomaterial into the envelope, causes a rise in the internal pressure, breaking the sheath open (in the form of e.g., an orange peel opening) and filling the envelope can commence with minimal introduction of air or gases into the envelope. This form of a sheath may be used to allow for easy delivery of the envelope through the introducer (working cannula) and rather than having to retract the sheath, any form of pressure (such as that by inflating the envelope with air) will break the sheath open, thereby exposing the envelope within the disc cavity. Preferably however, the sheath will be maintained over the envelope until such time the biomaterial has reached the envelope and as the pressure builds up within the envelope, the sheath breaks open and the expansion and filling of the envelope can commence (with minimal air entrapment). This apparatus may be applicable in combination with the apparatus and method disclosed in 1 and 2 (above).

The preferred number of mixing elements for the static mixer, to achieve an optimal mix and hence an optimal cure characteristics of the biomaterial, are 12. However, the mixing elements may range up to about 5, 10, 15, 20, 25, 30, 35.

Exemplary elements of percutaneous surgery is the development of a series of nested tubes that may or may not interlock with each other by various means which enables the device in its preformed or fully formed stage to be delivered to the tissue site being treated to achieve an implantable status. A component of these nested tubes is a working cannula which has the advantages of docking and can have elements which lock the other tubes or the unlocking and unsheathing of a component of the prosthesis.

Advantages of the system may include: (1) that it is capable of achieving compactness with the system and fit lots of components and elements into a small confinement; (2) the compactness of the system provides the means for conducting percutaneous, minimally invasive procedures; and the working cannula is docked relative to the patient and the tubes which go through the working cannula are locked or lockable or reversibly lockable to the working cannula. This means that during the implant positioning, deployment or filling process, the procedure can be performed in a stable manner and there is no unnecessary or unintentional relative movement during the implantation which can damage the tissue and the tissue prosthesis. Additionally, this may help avoid repeated trauma to tissue as instruments go in and out—preventing the crowding of muscles into the path and isolating structures like nerves etc—thereby not only protects outer structures—but internally protects our device. It may also maintain the deployment of a disc device or prosthesis) in the desired position. Additionally, in certain embodiments, the device and or components of the device may be substantially frictionless. If more force is required ratchets can be built into the wall to crawl the progress of the device and or components of the device and or components of the system.

Implant detachment means may include, screw in and screw off of the implant, chemically dissolve the interface which holds the implant, vibrational detachment, RF (Radio-frequency) or infrared cutter. Other means of implant removal include, sliding the implant off the carrier tube by utilization of slideably displaceable nested tubes. These can be tubular structures. Also, external or internal cutting mechanism on the tubes which can sever the implant from the delivery apparatus. Also, means of twisting and or crimping the neck of the implant. This can both seal and detach the implant. Also if the means in which the envelope is held onto the carrier tube is purely an interference fit or friction fit, or just tight fit, then pulling on the carrier tube can result in detachment of the envelope. Also, the tube can be rotated to detach. Also, another means for detachment of the implant can include lubrication of the interface which holds the implant. There may be a preformed opening or multiple preformed perforations at the distal end of the carrier tube and or filler tube. The perforations on the carrier tube may be at or near the implant interface. Once the implant has been substantially filled to capacity, the pressure of filling forces the filler material to seep through these perforations and lubricate the interface of the implant allowing it to be removed easily. Other suitable, biocompatible lubricating media may be used in this way or similar way to lubricate the interface which holds the implant.

In certain embodiments, a pressure generating apparatus may prevent outer bulging of the barrels, counterbalances the thrust force. Alternatively, the barrel may be integrated into the base of the pressure generating apparatus.

Referring toFIG. 1, anintervertebral disc10 is generally arranged between

adjacent vertebrae

12 and14. Thedisc10 comprises anannulus fibrosis16 made up of concentric layers of fibrous tissue. Theannulus fibrosis16 circumscribes anucleus pulposus18 of thedisc10, thenucleus pulposus18 being of soft tissue. Thedisc10 is sandwiched betweenend plates20 of the

vertebrae

12 and14. Relative movement between the

vertebrae

12 and14 causes compression of thenucleus pulposus18 by theend plates20. This serves to assist in the influx of nutrients into thedisc10 and the efflux of waste products from within thedisc10.

Certain exemplary embodiments disclosed herein provide methods for implanting an intervertebral disc implant into an intervertebral disk by percutaneously performing a nucleotomy on the disc, if necessary, to remove a nucleus pulposus of the disc to create a volume. Once the volume is created, at least one envelope of the implant is inserted into the volume and an interior of the envelope is charged with at least one filler material in a manner to allow the at least one envelope to expand to conform substantially, or partially to the volume. Additionally, the interior of the at least one envelope is closed off, or substantially close off, to retain the at least one filler material within the envelope. As discussed herein, the filler material may be selected to at least partially mimic natural biomechanical characteristics of the nucleus pulposus of the disc.

As will be discussed in more detail elsewhere herein, the methods may further include inserting the envelope into the volume using an introducer by placing the envelope in a collapsed state on a distal end of the introducer and inserted percutaneously through an opening in an annulus of the disc. Further, the opening may be the same opening via which the nucleotomy had been performed. The methods may also include charging the filler material into the interior of the envelope through the introducer. Further, the methods may include closing off the interior of the envelope by sealing a wall of the envelope. In certain exemplary embodiments, the methods may include closing off the interior of the envelope by the action of withdrawing the introducer from the envelope. In certain embodiments, the methods may use a minimally invasive technique or the percutaneously technique may be combined with the minimally invasive technique.

In certain exemplary embodiments the methods for implanting an intervertebral disc implant into an intervertebral disc may include percutaneously performing a nucleotomy on the disc to remove a nucleus pulposus of the disc to create a volume; inserting an introducer into an opening formed in an annulus of the disc; and introducing into the volume, via the introducer, at least one element which changes from a first configuration, in which the at least one element is able to be inserted into the introducer, to a second configuration in Which the at least one element conforms substantially to the volume.

The methods may further include using a single element which, in its second configuration, conforms substantially or at least partially to the volume of the disc. Alternatively, the methods may include using a plurality of elements which together, when each such element is in its second configuration, conform substantially or at least partially to the volume of the disc. In the latter case, the methods may include, prior to insertion of the elements in the volume, introducing at least one envelope, in a collapsed state, into the volume and introducing the elements into the at least one envelope to cause the at least one envelope to expand to conform substantially or sufficiently to the volume of the disc. The methods may include, after introduction of the elements into the at least one envelope, closing off a filler opening of the at least one envelope. Preferably, the methods includes closing off the filler opening of the at least one envelope by withdrawal of the introducer from the filler opening of the envelope.

In certain exemplary embodiments, there is provided an introducer for introducing an intervertebral disc implant into a disc that has undergone a nucleotomy, the introducer including at least two sleeves arranged telescopically with respect to each other; and a displacement mechanism arranged on an operatively inner surface of an innermost one of the sleeves'for assisting in displacing filler material along the sleeves into an interior of the disc, in use.

In certain exemplary embodiments, there may be provided methods of preparing a first assembly of a tissue prosthesis system for insertion into a patient's body, the method, or methods, comprising providing the first assembly which comprises a plurality of nested, or partially nested, tubes, one of the tubes being a carrier tube; mounting a component of the prosthesis on a distal end of the carrier tube, the component being of an elastically deformable material or a sufficiently elastically deformable material; inserting a stiffening member into the first assembly so that the stiffening member extends into an interior of the component and causing a proximal end of the stiffening member to sealingly engage a proximal end of the first assembly; attaching a withdrawing device to the first assembly so that the withdrawing device is in fluid communication with at least the interior of the component; and operating the withdrawing device to reduce the pressure in the interior of the component to cause the component to collapse about the stiffening member. The stiffening member may allow the retraction of the outer sleeve, which covers the component of the prosthesis, without the component buckling or prevent the total retraction into the carrier tube when the syringe is withdrawn to collapse the component.

The method, or methods, may include attaching the withdrawing device to a fluid port of the first assembly in a sealing manner. The withdrawing device may be a syringe which is attached by a Luer lock mechanism to the fluid port of the first assembly. Other withdrawing devices may be a vacuum pump, a pre-evacuated container (such as vacutainer), or a container with a preformed low pressure environment, or any apparatus (e.g., which has moveable walls allowing for the volume of the system to be alterable).

After the component has been collapsed, or sufficiently collapsed, about the stiffening member, the method, or methods, may include placing a protective sheath about the component. The method, or methods, may include placing the protective sheath about the component by sliding the protective sheath over the component, the protective sheath constituting one of the tubes of the nested tubes of the first assembly.

Further, the method, or methods, may include treating one of the protective sheath and the component with a lubricating medium to facilitate relative displacement between the protective sheath and the component.

Exemplary lubricants may include, but not limited to, media such as water for injections, 0.9% salines solution, albumin, fat, mineral oil, lipids, silicone oils, etc.

The method, or methods, may include using the withdrawing device to test the integrity of the combination of the first assembly and the component and the stiffening member attached to the first assembly. Testing the integrity may include determining whether the interior of the envelope is in fluid communication with fluid external to the walls of the envelope, and/or inspecting whether the system still remains a closed system or substantially closed system, or whether it is an open system. The feedback mechanism may have an associated pressure, force or volume monitor which is capable of indicating whether or not there is a breach of the seal. These monitors may indicate whether there is a loss in pressure, force, volume associated with the applied pressure, force or volume.

In certain exemplary embodiments, there may be provided methods of forming a tissue prosthesis at a site in a patient's body, the methods may comprise providing a first assembly comprising a plurality of nested tubes, one of the tubes being a carrier tube with a component of the prosthesis carried at a distal end of the carrier tube; inserting the first assembly into a cannula placed in the patient's body; magnetically attaching or engaging a second assembly to a proximal end of the first assembly; and charging a filler material from the second assembly into the component and allowing the filler material to set.

The methods may include, initially, preparing the first assembly as described elsewhere herein.

The methods may include, once the distal end of the first assembly is at the desired location at the site in the patient's body, withdrawing the protective sheath to expose the component, the component being an envelope of an elastically deformable material. The methods may also include activating the withdrawing device as the sheath is withdrawn to substantially collapse the envelope, minimising the contact area between the envelope and the sheath, minimise the friction between the envelope and the sheath and hence facilitate sliding between the envelope and the sheath.

The methods may include removing a stiffening rod prior to magnetically attaching the second assembly to the first assembly. Further, the methods may include causing the second assembly to engage sealingly with the first assembly so that, together with the component and the withdrawing device, a closed system is formed.

After the second assembly has been attached to the first assembly, the methods may include operating the withdrawing device to create a low pressure in the component. Further, the methods may include using the withdrawing device to test the integrity of the system comprising the two assemblies and the component attached to the first assembly. This may be performed by either withdrawing or pushing forward on the piston of the withdrawing device and it should also be noted that the integrity of the system can be tested at the stage once the first assembly has been introduced to the desired location in the patients body (as described above)

The methods may include dispensing the filler material from a dispenser of the second assembly. The methods may also include purging filler material from the dispenser prior to attaching the dispenser to a static mixer constituting a part of the second assembly. The methods may include, during filling of the component via a filler tube extending from the static mixer, operating the withdrawing device at least to maintain, or increase, the volume of the closed system. Mixing may also be performed dynamically. Also, the parts may be premixed and delivered rather than being mixed during the delivery (or charging) process. In certain aspects, the mixing may not be necessary if it is a single part filler material. The filler material may be a single part, or at least a 2 part mixture (i.e., may have 3 parts, etc.). For example, the 3^rdcomponent of the mixture may be the initiating catalyst. Alternatively, these initiators for the curing reaction may be coated onto the inner surfaces of the lumen which the material comes into contact. For example, the lining of the static mixer, mixing elements, and the lumen of the filler tube may be treated with a platinum catalyst. Certain primers may contain the catalyst. Therefore the inner lining of the envelope may be coated/treated with the primer and when the 2 part filler material enters and fills the envelope, it comes into contact with the inner lining of the envelope, thereby initiating or accelerating the cure. Additionally, because it is also a primer, it may enhance the adhesion between the envelope and the filler material.

The methods may include, after filling the component, detaching the carrier tube from the tissue prosthesis formed by the combination of the component and the filler material contained in the component. The carrier tube may be detached prior to the filler material having cured or set or after the filler material has at least partially set. In some aspects, the carrier tube may be detached prior to the filler material having been partially or substantially cured. The methods may include detaching the carrier tube from the tissue prosthesis when the required pressure has been reached in the component. In the case of intervertebral disc nucleus prosthesis, the required pressure may be that which restores the height of the disc to that of pre-surgery, or that which substantially fills the volume of the disc. However in certain embodiments, pressure may not be a determinant. Another method may include the filling of the component being determined by the volume. The volume to be replaced can be determined by visual or mathematical calculation of the nuclear area from patients own images, amount of nuclear material removed, use of a sizing tool, progressive surgeon experience, use of a software or self learning algorithm that may determine the volume of nucleus that either exists or is removed or may be required to be replaced. The method of determining the nuclear volume could also use a disc mapping strategy. Additional methods may include the methods described in International Application No. PCT/AU03/001289, filed on Sep. 30, 2003 entitled “Mapping and Viewing Device for an Intervertebral Disc”, which claimed priority from Australian Provisional Application No. 2002951762 filed on Oct. 1, 2002. The entire contents of which are herein incorporated by reference in its entirety

In certain exemplary embodiments, the methods may include detaching the tissue prosthesis by relative axial motion between the carrier tube and a displacement device of the first assembly. The displacement device may be a further tube arranged about the carrier tube and the relative axial motion may be affected by withdrawing the carrier tube relative to the displacement device. In certain exemplary embodiments, the methods may include detaching the tissue prosthesis by filling the component with filler material to the extent that the component is released from the carrier tube. In a further exemplary embodiment, the methods may include detaching the tissue prosthesis by manipulating the carrier tube relative to the component to cause separation of a part of the component attached to the carrier tube from a remainder of the component, the separation occurring at a zone of weakness in the component. The manipulation may involve rotating the carrier tube with respect to the component.

The methods may further include, after formation of the tissue prosthesis, tamping a part of the tissue prosthesis into position.

In certain exemplary embodiments, the methods may also include, before placing the component in position at the site, preparing the site. The methods may include preparing the site by removing degenerative tissue from the site prior to placing the component at the site.

In certain exemplary embodiments, there may be provided methods of forming a tissue prosthesis in situ at a site in a patient's body, the methods may comprise accessing the site in the patient's body; if necessary, removing tissue from the site to form a cavity; inserting at least one envelope of a biologically inert, elastically deformable material into the cavity; charging a filler material, in a fluent state, into the envelope to cause the envelope to expand and conform to the shape of the cavity; and allowing the filler material to cure, the filler material being of the same class of material as the envelope so that, when the filler material has cured, a unified, or substantially unified, prosthesis is formed.

The methods may further include accessing the site by inserting an introducer through an aperture formed in tissue associated with the site and removing nuclear tissue, if required, from the site. The nuclear material may be removed by mechanical, ultrasonic, laser, Argon gas or radio frequency ablation, or the like, in combination with suction and irrigation. For example, mechanical removal may be effected by using a reaming-type tool. Additional methods may include the methods described in U.S. Provisional Application No. 60/971,633, filed on Sep. 12, 2007, entitled “Equipment for, and a method of, removing tissue from a site in a patient's body”. The entire contents of which are herein incorporated by reference in its entirety.

Once the nuclear tissue has been removed, the methods may include checking dimensions of the cavity so formed. Thus, the methods may include using the at least one envelope, containing suitable markers, to check the dimensions and or position of the cavity. This may be effected by inflating the at least one envelope using a suitable fluid such as a water/saline solution. Instead of using the at least one envelope with markers, the method may include using a flexible wire fed down the introducer and checking the position of the wire using a fluoroscopic x-ray technique once the wire is in position. In a further way of checking the dimensions of the cavity, the methods may include deploying at least one jacket of similar dimensions to the at least one envelope in the cavity, inflating the jacket with the water/saline solution and, using a fluoroscope, detecting the periphery of the jacket by radio opaque markers on an outer surface of the jacket.

Once the at least one envelope has been placed in position, the methods may include checking the integrity of the at least one envelope, i.e. to ensure that the at least one envelope does not have any leaks or other defects. This may be effected and affected by filling the at least one envelope with the water/saline or radioopaque solution.

The methods may include evacuating an interior of the envelope to inhibit the formation or entrapment of fluid bubbles in the filler material. Instead, the methods may include commencing filling of the envelope from a distal end of the envelope and progressively filling the envelope towards a proximal end of the envelope (by withdrawing a filler tube or allowing the material buoyancy to lift the filler tube) to inhibit the formation or entrapment of fluid bubbles in the filler material. In the latter case, either a delivery device by which the envelope is introduced into the cavity or the envelope may define a formation allowing the escape of air, or gas, or certain fluids, as the envelope is charged with the filler material. It may be desirable, in certain embodiments, to limit the formation or entrapment of bubbles, or to eliminate substantially the formation or entrapment of bubbles, in the filler material. An advantage of minimising air or gas or certain fluid bubbles is that it maximises the volume occupied by the biomaterial and the less voids (air bubbles) the implant has, it may maximise the mechanical performance and stability from a fatigue and creep resistance perspective. Any trapped air may be compressed inside the envelope.

The methods may include, once filling of the at least one envelope has been completed and a filler element withdrawn, occluding the aperture in the tissue of the site. Occluding the aperture may comprise closing it off by a non-return valve or by crimping closed a neck portion of the envelope. A removable tube may be nested over the delivery device and may be propelled distally to remove the at least one envelope and valve from the delivery device.

The methods may include attaching the at least one envelope to a distal end of a tubular delivery device and everting the at least one envelope on the distal end prior to insertion of the delivery device into the introducer for delivery of the envelope into the cavity of the site.

In certain exemplary embodiments, the method, or methods, may include accessing the site using an appropriate percutaneous surgical procedure. Hence, the method, or methods, may be used to perform less invasive (as compared with minimally invasive and/or other surgical procedures) intervertebral disc nucleus replacement and may comprise forming an aperture in an annulus fibrosis of the disc percutaneously; extracting a nucleus pulposus of the disc to form a disc cavity bounded by the annulus fibrosis of the disc and end plates of vertebrae between which the disc is located; inserting the at least one envelope, in a substantially relaxed state (or first state), into the cavity through the aperture; charging the filler material into the at least one envelope to cause (or resulting in) the at least one envelope to expand (or second state) and conform, or substantially conform, to the shape of the disc cavity; allowing the filler material to cure to form, together with the at least one envelope, the unified, or substantially unified, prosthesis; and occluding the aperture.

In certain exemplary embodiments, the method, may include accessing the site using a percutaneous surgical procedure. Hence, the method may be used to perform less invasive intervertebral disc nucleus replacement and may comprise forming an aperture in an annulus fibrosis of the disc percutaneously; extracting a nucleus pulposus of the disc to form a disc cavity bounded by the annulus fibrosis of the disc and end plates of vertebrae between which the disc is located; inserting the envelope, in a first state, into the cavity through the aperture; charging the filler material into the envelope to cause the envelope to expand and conform to the shape of the disc cavity; allowing the filler material to cure to form, together with the envelope, the unified prosthesis; and occluding the aperture.

In certain exemplary embodiments, the methods include expanding and stretching the walls of the envelope and retaining the envelope under tension after charging it with filler material. In other embodiments where the cavity is relatively small, it may not be necessary for the envelope to expand.

In an exemplary embodiment disclosed herein a method of forming tissue prosthesis, in situ is provided. In the exemplary method, a damaged nucleus pulposus18 of thedisc10 is removed and is replaced by an artificial prosthesis. Thus, as shown inFIG. 1 of the drawings, anintroducer22 is inserted percutaneously into abutment with thedisc10. An aperture forming element in the form of atrocar24 is inserted into alumen26 of theintroducer22. Apoint28 of the trocar pierces theannulus fibrosis16 of thedisc10 forming an aperture30 (FIG. 2) in theannulus fibrosis16 of thedisc10.

After the formation of theaperture30, thetrocar24 is removed from theintroducer22. Once thetrocar24 has been removed, a nucleotomy is performed on thedisc10. The nucleotomy involves the removal of sufficient nuclear tissue constituting thenucleus pulposus18. While various methods of removing the nucleus pulposus can be used (examples of which are discussed throughout the specification), the example herein shows the use of amechanical device32. Themechanical device32 comprises a reamingtool34. Themechanical device32 is inserted through thelumen26 of the introducer and theaperture30 in theannulus fibrosis16 of thedisc10 into thenucleus pulposus18. The reaming tool34 (FIG. 3) is operated to remove the nucleus pulposus as shown inFIG. 4 of the drawings so that acavity36 remains. Thecavity36 is bounded by theannulus fibrosis16 and theend plates20 of the

vertebrae

12 and14.Residue64 of thenucleus pulposus18 remains resulting in thecavity36 having irregular walls.

In certain embodiments, anenvelope38 of an elastomeric material, more particularly, a silicone rubber material is mounted on a distal end of atubular delivery device40. Thetubular delivery device40 defines a passageway42 (FIG. 5). Theenvelope38 may be made from the silicone rubber material which is biologically inert and which can elastically deform up to for example 3, 5, 7, 10, 20, 30, 40, 50, 60, 80, 100, 120, 140, or 150 times the size of theenvelope38 in its relaxed state.

In an exemplary embodiment, as shown in greater detail inFIG. 10, theenvelope38, in its relaxed, or deflated, state, is a snug fit over adistal end44 of thedelivery device40. Afirst sleeve46 is arranged coaxially over thedelivery device40 adjacent thedistal end44 of thedelivery device40. Thissleeve46 may have a plurality ofopenings48 defined in it. Theseopenings48 cooperate withopenings50 at thedistal end44 of thedelivery device40. Afurther sleeve52 is mounted coaxially about thesleeve46 and communicates with an evacuation device (not shown) via an evacuatingtube54. Proximal ends of the

sleeves

46 and52 are sealed against an outer surface of thedelivery device40 via seals56. Afurther seal58 is arranged between a distal end of thesleeve52 and thesleeve46.

When filler material, referenced generally by the reference numeral60 (and discussed in more detail elsewhere herein), is injected into theenvelope38, a low (e.g., lower than ambient) pressure may be, simultaneously, prior to injection, or a combination thereof imparted to thedelivery device40 and orenvelope38 to manipulate (e.g., evacuate) fluid, more particularly, gases, from within theenvelope38. This assists in substantially airless mixing and helps ensure that the formation of gas bubbles in thefiller material60 is substantially inhibited. Evacuation of gases also helps inhibit entrapment of gases within theenvelope38 by theincoming filler material60 and facilitates the flow of thefiller material60 into theenvelope38. As thefiller material60 is charged into theenvelope38 through the fillingopenings50, gas is drawn out of theenvelope38 by operation of the evacuation device via theevacuation tube54. The gas is received between the outer surface of thedelivery device40 and thesleeve46. This gas passes through theopenings48 in thesleeve46 and through theevacuation tube54.

In alternative embodiments (e.g., open and/or closed multi lumen systems), gas can be removed in other manners as well. For example, the filler tube could be primed before it is inserted it into the envelope (or carrier) tube and deliver the biomaterial into the envelope. Alternatively, the envelope could be maintained in a collapsed state so that the envelope does not need to be actively evacuated during any stages of the filling. In other embodiments, a first and second lumen may be used to deliver fluid (one of course delivers low pressure fluid). The term deliver is not specifically directional towards the envelope or away from the envelope. In a closed or open system scenario, the filling tube may extend (perhaps half way or all the way to the end) into the envelope and as the envelope is filled, the fluid in the envelope may be pushed out through a second lumen. In certain embodiments, the filling tube terminates at a point substantially in alignment with the proximal end of the envelope or just proximal to the envelope. The filling tube may terminate substantially in line with the distal end of the carrier tube, or just proximal to the distal end of the carrier tube. As the filler material is charged into the envelope, evacuation, or manipulation of fluid, or withdrawal of fluid, at least from within the envelope may no longer be active, as the annular space between the first and second lumen, which was in fluid communication with the interior of the envelope has been substantially occluded. In a single lumen filling system, the envelope may be carried by the filling tube (thereby the filling tube being both the filling tube and carrier tube) and the fluid in the envelope may be vented around thespace1016 between the fillingtube1014 and avalve1012 on the envelope (see, e.g.,FIGS. 96 and 97). In certain embodiments, a valve may not be necessary, so long as there is some clearance between the envelope and the outside of the filling tube, fluid will be able to be pushed out from the envelope as the envelope fills with a biomaterial.

It may also be useful to monitor the shape and size of thecavity36 taking theresidue64 into account. This can be achieved in a number of ways. One of the ways in which this can be achieved is by having radioopaque markers70 arranged on theenvelope38. Prior to charging theenvelope38 with thefiller material60, theenvelope38 can be expanded to conform to the shape of thecavity36 by means of a water/saline solution or a radio opaque solution. Themarkers70, being radio opaque, are monitored under a fluoroscope to determine the shape and size of thecavity36.

Other methods of assessing the size of thecavity36 include the use of a flexible wire inserted down thelumen26 of theintroducer22, the wire being monitored by a fluoroscope. Yet a further way of monitoring the shape and size of thecavity36 is by use of a dedicated jacket, of similar dimensions to thecavity36, which is inserted into thecavity36 and inflated using the water/saline solution or the radio opaque solution. The jacket carries radio opaque markers which are monitored by a fluoroscope.

FIGS. 77-79 illustrate an embodiment of equipment for preparing a site for implantation of tissue prosthesis. Theequipment10 comprises aconduit assembly12 carrying amember14 at a distal end of theconduit12

assembly

12. Theequipment10 further may also include a plurality offluid dispensers16 connectable to a proximal end of theconduit assembly12 to communicate with themember14. In certain aspects, the member may be sufficiently inflatable, resiliently flexible, able to be elastically deformed, or combinations thereof of these properties.

This equipment may be used to determine, or approximate, the size of acavity18 formed in anintervertebral disc20. Thedisc20 has anannulus22 surrounding anucleus24. Degeneration of thedisc20 may result in herniation of nuclear material of thenucleus24 through theannulus22. To repair a damageddisc20, thenucleus24 may replaced by an intervertebral disc prosthesis as described in the embodiments disclosed in this specification.

In addition, the equipment may also measure the position of the cavity. The position of the cavity as well as the position of the prosthesis may be checked under the fluoroscope or other imaging means to check the cavity position laterally and in the anterior-posterior view (AP view). In other words, the sizing device can be viewed as a mock implant. An advantage of sizing the cavity and the position is that the remainder of the implant can actually be performed blind without the need of any imaging assistance. This is because the working cannula will position the implant and the sizing device has determined for the surgeon the volume required to fill the implant.

To prepare the site for implantation of the prosthesis, it may be desirable to conduct a nucleotomy to remove portions, or substantial portions, of the nuclear material from thedisc20. However, in certain circumstances, thenuclear material24 may have either degenerated or herniated through theannulus22 to a sufficient extent that acavity18 is formed with can receive the tissue prosthesis to reconstruct theintervertebral disc20. The amount of nuclear material that needs to be removed may be expected to vary from situation to situation.

Themember14 may be made from a number of different materials. In certain preferred embodiments, it is desirable that the member be inflatable, resiliently flexible and/or able to be elastically deformed. In certain embodiments, themember14 could be of a silicone material and may have similar or substantially the same characteristics of the envelope of the applicant's tissue prosthesis described herein.

In the exemplary embodiment illustrated, theequipment10 comprises a pair offluid dispensers16 each in the form of a

syringe

26,28. Thesyringe26 has abarrel30 and aplunger32 slidably displaceable in thebarrel30. Similarly, thesyringe28 has abarrel34 and aplunger36 slidably displaceable in thebarrel34. Further, in this embodiment, theconduit assembly12 comprises a first, outer conduit, or tube,38. Theelement14 is mounted on a distal end of theouter tube38. An inner, filler conduit, or tube,40 is co-axially arranged within theouter tube38. Thefiller tube40 projects from thesyringe26 through abranched connector42 arranged at a proximal end of thetube38. The branchedconnector42 may be a Y connector defining aprimary lumen44 through which thetube40 extends and a secondary, branchedlumen46. Thesyringe28 is connected to apart48 of theconnector42 defining thesecondary lumen46.

In use, in this exemplary embodiment, theequipment10 is inserted percutaneously via a working cannula (not shown in these figures but described elsewhere) so that themember14 is received in thecavity18 of thedisc20. Theequipment10 is inserted percutaneously.

Initially, theequipment10 may be primed. The priming of theequipment10 is effected and affected by drawing on theplunger36 of thesyringe28 in the direction ofarrow50. This may result in themember14 collapsing. Because theequipment10 defines a closed system, or substantially closed system, it also results in theplunger32 of thesyringe26 being drawn in the direction ofarrow52. Thesyringe26 contains a volume measuring fluid. In certain embodiments, the volume measuring fluid may comprise non-compressible fluid, and/or fluids, such as a liquid (e.g., but not limited to, a radioopaque dye (such as urografin), or water or a saline solution). In some aspects, the fluid may be substantially non-compressible fluid and/or fluids. Theequipment10 is regarded as being fully or substantially primed when the liquid from thesyringe26 begins to flow into thesyringe28.

The position of theplunger36 of thesyringe28 may be fixed in position as shown inFIG. 78. Theplunger32 of thesyringe26 is then further pushed in the direction ofarrow52 to inflate theinflatable member14 fully. Instead of fixing the position of theplunger36 in thesyringe28, can be removed and a sealing cap (not shown) can be placed over the branch of the Y connector to maintain the closed or substantially closed system.

Referring toFIG. 79, theplunger32 of thesyringe26 may be drawn in the direction ofarrow54 to deflate themember14. Inflation and deflation of themember14 using thesyringe26 is then repeated for a number of cycles to condition thedisc20. The cyclical inflation/deflation of thedisc20 increases the laxity of thedisc20 and is generally referred to as “mobilising the joint”. By cycling the member14 a number of times, surrounding residual nuclear material55 in thedisc20 may be compressed or compacted and is less likely to interfere with the subsequently implanted nuclear prosthesis.

Once thedisc20 has been cycled a number of times, theplunger32 of thesyringe26 may be drawn to a start position in which themember14 is, once again, substantially collapsed. It will be appreciated that, because the system is a closed system, and theplunger36 of thesyringe28 is locked in position, theplunger32 of thesyringe26 will only be able to be withdrawn to a certain fixed, start position in thebarrel30 of thesyringe26. In this position, themember14 is substantially collapsed and the

conduits

38 and40 are filled with gas and/or liquid, respectively, it being appreciated that there will also be some liquid in theconduit38. Depending on the degree of withdrawal of thepiston36,conduit38 may be composed completely or substantially of fluid (liquid) also. In this position, theequipment10 is substantially primed.

Theplunger32 of thesyringe26 is urged in the direction ofarrow52 to displace the volume measuring liquid from thesyringe26 into theinflatable member14. This fully inflates themember14 so that it conforms to the shape of thecavity18 in thedisc20. When themember14 fully conforms to thedisc18, any attempt to further displace theplunger32 in the direction of thearrow52 will result in a substantial increase in pressure. This is therefore the end point indicating that themember14 fully conforms to thecavity18 of thedisc20 and the amount of liquid dispensed from thesyringe26 after priming of theequipment10 is an accurate indication of the volume of thecavity18.

As will be described in the embodiments described below with reference toFIGS. 80-85, theplunger32 may carry a transducer (not shown in this embodiment). The transducer may, for example, be a pressure transducer and, when the sudden increase in pressure occurs, an enunciator may be activated to indicate the end point.

Referring now toFIGS. 80-85, additional embodiments of equipment for preparing a site for implantation of tissue prosthesis is described. In these embodiments, theconduit assembly12 comprises asingle tube38 to which theconnector42 is connected at a proximal end of thetube38. A distal end of thetube38 carries themember14.

In this embodiment, theconnector42 may be a T-connector defining theprimary lumen44 and thesecondary lumen46. It will, however, be appreciated that theconnector42 could, as in the previous embodiments, be a Y-connector.

Theconduit assembly12 further includes a fluid control arrangement in the form of a threeway stopcock56. The stopcock56 is operable to place either thelumen44 of theconnector42 in fluid communication with an interior of thetube38 or thelumen46 of theconnector42 in communication with the interior of thetube38.

As in the case of the previous embodiments, thesyringe26 is connected to theconnector42 to be in communication with thelumen44 of theconnector42. Thesyringe28 is connected to theconnector42 to be in communication with thelumen46 of theconnector42. In use, in these embodiments, theequipment10 may be inserted percutaneously via a working cannula (not shown).

To prime theequipment10, the

syringes

26 and28 are operated. More particularly, thestopcock56 is positioned so that thelumen46 is occluded while thelumen44 of theconnector42 is open. Theplunger32 of thesyringe26 is urged in the direction ofarrow58. This causes inflation of themember14. Some liquid from thesyringe26 will enter themember14 and so will gas which was present in theequipment10. The fluid from thesyringe26, being heavier than the gas, will sink to the distal end of themember14. The gas in theequipment10 will be displaced to be arranged near the distal end of thetube38.

Withdrawal of thepiston32 of thesyringe26 in a direction of arrow59 will draw out the gas from thetube38 and, subsequently, fluid from themember14 as well. These steps may be repeated a number of times to ensure that theequipment10 is fully primed. Theequipment10 is regarded as being fully primed when thepiston32 of thesyringe26 is drawn to the position shown inFIG. 82 in which themember14 is substantially collapsed.

It should be appreciated that the priming method described above is applicable when the inflating member is pointing down (i.e., as it would be the case if the device were positioned in the disc) and the filling tube/member stops at the proximal junction to the inflation member. For the case where the filling tube extends into the distal part of the inflating member, the priming should occur with the inflating member pointing up (i.e., or as the case may be, primed before being positioned into the disc). This is because when the fluid is ejected from the syringe to prime the system, the buoyancy of the gas may force the gas towards the distal part of the inflatable member where the lumen of the tube is.

With thepiston32 of thesyringe26 in the position shown inFIG. 82, thestopcock56 is switched to occlude thelumen44 of theconnector42 and to open thelumen46 of the connector42 (seeFIG. 83). This places thesyringe28 in communication with the interior of thetube38 and the interior of themember14. Thesyringe34 contains a volume measuring liquid (e.g., water or a saline solution).

Theplunger36 of thesyringe28 is urged in the direction of arrow60 (FIG. 84) to inflate themember14 fully so that it substantially conforms, or at least partially conforms to the shape of thecavity18 of thedisc20. Theplunger36 of thesyringe28 is then drawn in the direction of arrow62 (FIG. 85) to cause deflation of themember14. Theplunger36 is cycled a number of times to inflate and deflate themember14 to condition thedisc20 as described in this specification.

After conditioning thedisc20, theplunger26 is drawn to a zeroing position in thesyringe28. It will be appreciated that, because theequipment10 defines a closed system, or substantially closed system, theplunger36 can only be withdrawn to a certain, fixed position in thesyringe28. This position occurs when themember14 is sufficiently collapsed. In this zeroing position, theplunger38 is, once again, urged in the direction ofarrow60 to inflate themember14 fully so that it conforms, or substantially conforms to thecavity18 of thedisc20. It will be appreciate that, when themember14 has been fully or appropriately inflated, further attempts to displace theplunger36 in the direction ofarrow60 will typically result in a sudden or steep increase in pressure. The pressure is recorded by apressure transducer64 carried on theplunger36 of thesyringe28. Thetransducer64 is connected to atransducer readout66 which contains an enunciator. The enunciator may be an audible and/or visual enunciator to alert an operator that the end point has been reached and that themember14 is fully, or appropriately, inflated. The volume of liquid displaced from thesyringe28 represents the volume of thecavity18 of thedisc20. Since the radioopque dye being injected is significantly incompressible, there is a significant difference (steep pressure rise) in the resistance to further displacement of thesyringe piston36 when themember14 has been inflated to capacity, thus the tactile feedback is a sensitive enough indication in being able to gauge the endpoint of filling. The feedback which the surgeon receives from the resistance of thesyringe piston36 is significantly sensitive for the surgeon to be able to gauge the endpoint of filling.

In certain embodiments disclosed herein, theconduit assembly12 may act as a stiffening member for themember14. Thus, in certain embodiments, thefiller tube40 may extend to a distal end of themember14 as indicated bydotted lines68 inFIGS. 78 and 80 of the drawings. Theextension68 of thefiller tube40 has aslot70 defined in it to place the interior of themember14 in communication with the interior of thefiller tube40 to allow inflation and deflation of themember14. In these embodiments, when themember14 is substantially collapsed, it is collapsed about theextension68 of thefiller tube38. Similarly, in the embodiments described with reference toFIGS. 80-85, thetube38 of theconduit assembly12 may have theextension68 with theslots70 defined in theextension68. In these embodiments, it may be desirable to prime theequipment10 externally of the patient as gas needs to move to a top of themember14 with theequipment10 being held vertically so that themember14 is at the top of theequipment10. In certain embodiments, theequipment10, whether with theextension68 of thefiller tube40 or not, can be primed when theequipment10 is positioned within the patient. In general, theequipment10 should be able to be primed so that an accurate measure of the volume of a cavity to receive tissue prosthesis can be determined. In addition, by cycling the inflatable member, the surrounding tissue can be conditioned for receiving the tissue prosthesis.

After the shape and size of thecavity36 have been determined, thefiller material60 is dispensed from thedispenser62 and is monitored via the

sensing arrangements

66 or68, as the case may be. As illustrated inFIG. 7 of the drawings, thefiller material60 causes elastic expansion or inflation of theenvelope38 so that theenvelope38 conforms to the shape of thecavity36 and bears against theresidue64 of the nucleus pulposus remaining in thecavity36. Theenvelope38, having been elastically expanded by thefiller material60, remains under tension around thefiller material60 while conforming to the shape of thecavity36.

Backflow filler material

60 from the interior of theenvelope38 may be controlled either by avalve72 as shown inFIG. 13 of the drawings or by aclamping device74 as shown inFIG. 7 of the drawings. Thevalve72 is a duckbill valve and acts as a one way valve so that backflow offiller material60 from theenvelope38 is substantially restricted or inhibited.

Once theenvelope38 has been filled and has expanded so that it conforms closely, sufficiently, and/or substantially to the shape of thecavity36 and is received snugly in thecavity36, thefiller material60 is allowed to cure for a predetermined period of time of, for example, about 5, 10, 15, 20, 25 or 30 minutes. After substantial curing of thefiller material60, thedelivery device40 is removed (alternatively, as described elsewhere herein, thedelivery device40 may be removed after delivery of thefiller material60 but before curing) leaving theaperture30 occluded as shown at76 inFIG. 8 of the drawings. Theunified tissue prosthesis100 so formed is preferably, substantially cured after about 15 minutes.

To facilitate removal of thedelivery device40 from theenvelope38, theenvelope38 may incorporate a zone of weakness in the form of a circumferential groove78 (FIG. 14) formed at a proximal end. The zone or area of weakness may be achieved in a number of different manners as well, for example, but not limited to, being built in during the manufacturing process. As thedelivery device40 is withdrawn, when its distal end comes into register with thegroove78, thedelivery device40 is twisted relative to the envelope to cause a break at thegroove78 to form theocclusion76 in theaperture30 of theannulus fibrosis16 of thedisc10. In certain embodiments, theocclusion76 may be formed as a result of the annular fibers closing over the aperture after the delivery device has been removed.

FIG. 12 shows another way of delivering theenvelope38 into thecavity36 in accordance with certain embodiments. In.FIG. 12, theenvelope38 is everted to lie within the distal end of thedelivery device40 to facilitate its insertion into thecavity36. A similar arrangement is shown inFIG. 9 andFIG. 14.

InFIG. 11, another embodiment of equipment for forming thetissue prosthesis100 is shown. In this embodiment, afiller tube80 is used. Thetube80 is received in thepassageway42 of thedelivery device40. Asleeve82 is arranged coaxially about thedelivery device40. A first displacement device, such as a trigger,84 is provided for controlling relative movement between thedelivery device40 and thetube80. A second displacement device, which may also be in the form of a trigger,86 controls relative movement between thedelivery device40 and thesleeve82.

The equipment, as shown inFIG. 11, is for use where an evacuating device is not used. Thus, to fill theenvelope38, thetube80 is urged towards the distal end of theenvelope38 and charging of thefiller material60 into theenvelope38 commences at the distal end of theenvelope38. Filling of theenvelope38 progresses from its distal end towards its proximal end. Thus, asfiller material60 is charged into theenvelope38, thetube80 is slid proximally relative to thetube40 by manipulating thetrigger84 or slides back through buoyancy of the filler material. Once theenvelope38 is in its fully inflated state, theenvelope38 is urged off the distal end of thedelivery device40 by manipulating thetrigger86. As thetube80 is withdrawn from thevalve72 and theenvelope38 is removed from the distal end of thedelivery device40, thevalve72 closes to form theocclusion76. To facilitate expulsion of gas when an evacuating system is not being used, theenvelope38 has a bead88 (FIG. 12) formed along that portion which seats on the distal end of thedelivery device40 to createpassages90 through which air or gas or certain fluids can be discharged as theenvelope38 is charged with thefiller material60.

Theenvelope38 may be constructed of a silicone rubber material which can be inflated up to about 5, 10, 15, 25, 50, 75, 100, or 150 times its relaxed size without rupturing. In certain embodiments, theenvelope38 may be made of less expansible material such as a biological or a synthetic polymeric material. A suitable synthetic polymeric material may, for example, be a polyester such as polyethylene terephthalate (PET). Theenvelope38 may be constructed of a knitted PET material so that, when thefiller material60 is charged into theenvelope38, the filler material fills foramens or interstices in theenvelope38 to form an integrated structure which resists relative movement between thefiller material60 and theenvelope38. Alternatively, the knitted PET material may be coated with silicone allowing thefiller material60 to integrate with the coating.

FIGS. 15 to 17 show different shapes ofenvelopes38 which can be used depending on whichintervertebral disc10 is to have its nucleus pulposus18 replaced. Additional detail regarding the envelopes is provided elsewhere herein.

FIGS. 18 to 21, show further embodiments of equipment for forming a tissue prosthesis, in situ, at a site in a patient's body is illustrated. In these embodiments, theequipment110 comprises a delivery device in the form of anenvelope tube112. Theenvelope tube112 carries theenvelope38 at its distal end.

A filler member in the form of afiller tube114 is slidably received within a passage116 of theenvelope tube112. As illustrated inFIG. 21, thefiller tube114 has a smaller outer diameter than an inner diameter of theenvelope tube112 to form anannular gap118 between thefiller tube114 and theenvelope tube112.

A removal mechanism in the form of a push-offtube120 is a snug fit on the outer surface of theenvelope tube112.

In certain embodiments, theenvelope38 is of a two part construction comprising a sleeve122 (FIG. 21) to which anenvelope defining member124 is adhesively bonded as shown by an annularadhesive layer126. The sleeve (and hence the valve) may be molded into the envelope defining member via insert molding or alternatively, the molded envelope may include a valvular member. Thesleeve122 defines thevalve72. For materials other than silicone, the sleeve may be welded (hot or cold), insert molded (or overmolded), onto the envelope defining member. Alternatively, the sleeve and the envelope defining member may be held together by a friction fit. Combinations of all of the above may also be applicable.

A distal end of thefiller tube114 carries an engagingmember128 which engages and opens thevalve72 so that theannular gap118 is in flow communication with an interior130 of theenvelope38. A distal end of the push-offtube120 terminates short of a proximal end of thesleeve122 of theenvelope38. However, it is also to be noted, that theenvelope tube112 is displaceable relative to the push-offtube120 in the direction ofarrow132. Instead of the engagingmember128, thevalve72 could have a small opening (not shown) in it. The size of the opening in thevalve72 is selected to allow the passage of air, gas and certain other fluids through it in a particular direction or directions, but is sufficiently small that the viscosity of the filler material will substantially restrict or inhibit the passage of the filler material through it in a particular directions or directions.

Yet a further way of evacuating theinterior130 of theenvelope38 is to insert thefiller tube112 into theinterior130 of theenvelope38 and to have a slit (not shown) in thefiller tube114 upstream of thevalve72. Thus, if thevalve72 seals about thefiller tube112, air can still be drawn from theinterior130 of theenvelope38 into the gap116 via the slit when the evacuation device is operated.

A proximal end of theenvelope tube112 carries aconnector134. Theconnector134 is a Y-connector having aprimary member136 and asecondary member138 projecting from theprimary member136. Theenvelope tube112 is fast with theprimary member136 of theconnector134. Thesecondary member138 of theconnector134 is in flow communication with the passage116 of theenvelope tube112 and, hence, in use with thegap118 between theenvelope tube112 and thefiller tube114. Thesecondary member138 is connectable to an evacuation device (not shown) such as an evacuation pump for creating a low pressure in thegap118 and, via the engagingmember128 opening thevalve72, theinterior130 of theenvelope38 prior to filler material being charged into theinterior130 of theenvelope38.

As shown inFIG. 20, theconnector134 includes aretaining mechanism140 for retaining theenvelope tube112 in position relative to theintroducer22. Theretaining mechanism140 comprises a receivingformation142 carried at a proximal end of theintroducer22. Theretaining mechanism140 further includes aclip portion144 forming the distal end of theconnector134 which clips into the receivingformation142 to retain theenvelope tube112 in position relative to theintroducer22.

A proximal end of the push-offtube120 carries agripping formation146 which is accessible externally of theretaining mechanism140 for enabling the push-offtube120 to be held while theenvelope tube112 is moved in the direction of thearrow132 after charging of theenvelope38 with the filler material.

Theequipment110 may further include adispensing device148 for dispensing filler material. Thedispensing device148 includes adispenser150 feeding into a mixing device in the form of astatic mixer152. A distal end of thestatic mixer152 carries thefiller tube114. ALuer lock arrangement154 is arranged at the distal end of the static mixer.152 and connects the dispensingarrangement148 to theconnector134.

In certain embodiments, the filler material is of a silicone rubber. To inhibit curing of the filler material prior to its being charged into theenvelope38, the filler material is retained in two, separate parts. Thus, thedispenser150 includes tworeservoirs156 in each of which a part of the filler material is initially received. Eachreservoir156 has aplunger158 associated with it for dispensing the parts from thereservoirs156 into thestatic mixer152 where the parts are mixed prior to being charged into theenvelope38. It is to be noted that theplungers158 are displaceable together with each other via a suitable displacing device (not shown) such as a pneumatic gun.

Thus, in use, the filler material to be charged into theenvelope38 is provided in the dispensingarrangement148. The dispensingarrangement148 is connected to theconnector134 via theLuer lock154. Anenvelope38, in a deflated condition, is mounted on theenvelope tube112. After the nucleotomy has been performed on thedisc10, theenvelope tube112 with theenvelope38 on its distal end is inserted through theintroducer22 so that theenvelope38, in its deflated condition, is received within thecavity36 of thedisc10. Thefiller tube114 is inserted into the interior of theenvelope tube112 so that the engagingmember128 engages thevalve72 and opens thevalve72. By opening thevalve72, theinterior130 of theenvelope38 is placed in fluid communication with thegap118 between theenvelope tube112 and thefiller tube114.

An evacuation device (not shown) is attached to thesecondary member138 of theconnector134 and a vacuum is drawn. This creates a lower pressure within thegap118 and theinterior130 of theenvelope38 and inhibits the formation of gas bubbles in theprosthesis100 as the filler material is charged into theenvelope38.

The filler material is dispensed from thedispensing device148 into thefiller tube114 and into theinterior130 of theenvelope38. This causes theenvelope38 to expand elastically to conform to the shape of thecavity36 of thedisc10 with theenvelope38 being retained under tension by the filler material.

After charging of the filler material into theinterior130 of theenvelope38, thefiller tube114 is withdrawn. Withdrawal of thefiller tube114 causes withdrawal of the engagingmember128 allowing thevalve72 to close to inhibit leakage of filler material from theinterior130 of theenvelope38.

After curing, theenvelope tube112 is moved relative to the push offtube120 in the direction of thearrow132 by holding the push offtube120 using thegripping device146. This urges thesleeve122 of theenvelope38 off the end of theenvelope tube112 as theenvelope tube112 is withdrawn relative to the push offtube120. Thevalve72 occludes the opening to theenvelope38. Theequipment110, including theintroducer22, is then withdrawn from the patient's body, allowing theaperture30 to occlude as the fibres of theannulus fibrosis16 close over and the procedure is complete.

FIGS. 22 to 24, illustrate further embodiments of equipment for forming a tissue prosthesis, in situ, at a site in a patient's body is illustrated. Theequipment110 includes a stiffening element in the form of a stiffening rod ortube160. Prior to insertion of thefiller tube114 into theenvelope tube112, the stiffeningrod160 is inserted into the passage116 of theenvelope tube112. Adistal end162 of the stiffeningrod160 projects beyond a distal end of theenvelope tube112 and terminates at a distal wall in theinterior130 of theenvelope38. Agap161 is created between theenvelope tube112 and thestiffening rod160. Thegap161 and theinterior130 of theenvelope38 are evacuated by operation of the evacuation device to cause theenvelope38 to collapse on to thedistal end162 of the stiffeningrod160. This facilitates insertion of theenvelope38 into theintroducer22 and into thecavity36 of thedisc10.

Once theenvelope38 has been located within thecavity36, the evacuation device is turned off to release theenvelope38 from thedistal end162 of the stiffeningrod160 and this allows the stiffeningrod160 to be withdrawn. Thefiller tube114 can then be inserted into theenvelope tube112, as described above, to enablefiller material60 to be charged into theenvelope38.

In certain embodiments (not illustrated), the stiffeningrod160 is dimensioned to fit in the interior of thefiller tube114. With this arrangement, thegap118 between theenvelope tube112 and thefiller tube114 is evacuated, as described above, with the stiffeningrod160 projecting through the distal end of theenvelope tube112 and theenvelope38 being collapsed over thedistal end162 of the stiffeningrod160.

Aproximal end164 of the stiffening rod carries acap connector166 which connects to theY connector134 to retain thestiffening rod160 in position relative to theenvelope tube112 and/or thefiller tube118, as the case may be. Thecap connector166 seals against a proximal end of the Y connector to enable the fluid and or the fluid pressure in thegap161 and theinterior130 of theenvelope38 to be manipulated through operation of the withdrawal device, connected to the Y connector134 (the port which does not have thecap connector166 attached to it). Such a withdrawal device may be a syringe.

In additional exemplary embodiments, there may be provided a prosthesis delivery system which includes a plurality of nested tubes, an outermost tube of which functions as a cannula in which the remaining tubes are received, the remaining tubes forming part of a prosthesis delivery apparatus, a wall portion of at least one of the tubes having a change in diameter along its length to mate with a corresponding part of a dispensing arrangement for use with the prosthesis delivery apparatus.

The prosthesis delivery devices may include a carrier tube which carries a component of the prosthesis on its distal end and a filler tube received in the carrier tube for charging a filler material into the component when the component is located at the desired location at a site in a patient's body. The prosthesis delivery apparatus may include a connector for connection to a withdrawal device to enable gas to be withdrawn from the component during formation of the prosthesis in situ, the connector being arranged, in use, at a proximal end of the prosthesis delivery apparatus. Further, the prosthesis delivery apparatus may include a displacement device for displacing the component of the prosthesis after it has been charged with the filler material. The displacement device may be a further tube mounted about the carrier tube. In addition, the prosthesis delivery apparatus may include a cover tube to cover the component of the prosthesis, the cover tube fitting over the carrier tube. The cover tube may include a resiliently flexible distal portion to accommodate the component of the prosthesis. In certain embodiments, the prosthesis delivery apparatus may include a connector for connection to a withdrawal device to enable gas to be withdrawn, or manipulated, or evacuated from at least the component during formation of the prosthesis in situ. More specifically and preferably, the withdrawal device may manipulate the fluid and or fluid pressure at least within the delivery apparatus and or the envelope; when in use. Although the fluid and or the fluid pressure manipulation remains active whilst the filler material is being charged down the filler tube, once the material reaches the distal end of the filler tube (i.e., The proximal end of the component/envelope), the annular space/gap between the filler tube and the carrier tube is occluded by the filler material. Hence during the formation and filling of the envelope, the fluid and or fluid pressure manipulation of at least the interior of the envelope is no longer active

In certain embodiments, a wall portion of each of the tubes may have a change in diameter along its length. The change in diameter along the length of each tube may be provided by a flared wall portion of each tube.

The disclosed systems may include a manipulating arrangement carried at a proximal end of at least the cannula for effecting manipulation of the nested tubes. The manipulating arrangement of the cannula may include a rupturing mechanism for rupturing the cannula for removal. The rupturing mechanism may include a plurality of circumferentially spaced, longitudinally extending zones of weakness in a wall of the tube of the cannula and a gripping device arranged at a proximal end of the tube of the cannula. The gripping device may comprise a plurality of circumferentially spaced radially outwardly extending tabs which are pulled outwardly to cause rupturing of the zones of weakness of the cannula to facilitate withdrawal of the cannula after placement and setting of the prosthesis.

The systems may include the dispensing mechanism, the dispensing mechanism including a tubular element having a distal end which corresponds with and mates with that part of the wall portion of the at least one tube having the change in diameter. The nested tubes may be configured to extend proximally of the distal end of the element to overlie the element. With this arrangement, the length of the unsupported ends of the tubes is considerably shortened thereby improving the rigidity of the tubes and the stability of the system. In addition, the balance of the system is improved rendering it easier for the clinician to control system.

In certain embodiments, there are provided systems which includes a plurality of tubes, wherein an outermost tube functions as a cannula in which the remaining tubes are received, the remaining tubes forming part of a prosthesis delivery apparatus, a wall portion of at least one of the tubes having a change in diameter along its length to mate with a corresponding part of a dispensing arrangement for use with the prosthesis delivery apparatus.

In certain embodiments, the prosthesis delivery devices may include at least one carrier tube which may carry at least one component of the prosthesis on its distal end and at least one filler tube received in the carrier tube for charging a filler material into the component when the component is located at the desired location. The prosthesis delivery apparatus may include a connector for connection to a withdrawal device to enable gas and or certain fluids to be withdrawn from the component during formation of the prosthesis in situ, the connector being arranged, in use, at a proximal end of the prosthesis delivery apparatus.

In certain embodiments, the prosthesis delivery apparatus may include a displacement device for displacing the component of the prosthesis after it has been charged with the filler material. The displacement device may be a further tube mounted about the carrier tube.

In certain embodiments, the prosthesis delivery apparatus may include at least one cover tube to cover the component of the prosthesis, the at least one cover tube fitting over the at least one carrier tube. The at least one cover tube may include a resiliently flexible distal portion to accommodate the component of the prosthesis.

In certain embodiments, a wall portion of each of the tubes has a change in diameter along its length. In some aspects, the change in diameter along the length of each tube may be provided by a flared wall portion of each tube.

In certain embodiments, the system may include a manipulating arrangement for effecting manipulation of the tubes located within the cannula. The manipulating arrangement may include a rupturing mechanism for rupturing the cannula for removal. The rupturing mechanism may include a plurality of spaced zones of weakness in a wall of the tube of the cannula and a gripping device arranged at a proximal end of the tube of the cannula. The gripping device may comprise a plurality of outwardly extending tabs which are pulled outwardly to cause rupturing of the zones of weakness of the cannula to facilitate withdrawal of the cannula after placement and setting of the prosthesis.

In certain embodiments, the system may include the dispensing mechanism, the dispensing mechanism including a tubular element having a distal end which corresponds with and mates with that part of the wall portion of the at least one tube having the change in diameter. The nested tubes may be configured to extend proximally of the distal end of the element to overlie the element. With this arrangement, the length of the unsupported ends of the tubes is shortened thereby improving the rigidity of the tubes and the stability of the system. In addition, the balance of the system is improved rendering it easier for the clinician to control system.

In certain embodiments, the dispensing mechanism may include a dispenser to which the element is attachable and/or the element may be a static mixer.

In certain exemplary embodiments, there may be provided a prosthesis delivery system which includes a plurality of nested tubes, one tube being a carrier tube which carries at least a component of a prosthesis at its distal end and another tube constituting a delivery tube for delivering the nested tubes to a site at a patient's body; and a cover tube forming part of the nested tubes, the cover tube being arranged outwardly of the carrier tube to cover the component when the carrier tube is inserted into the delivery tube to protect the component. The cover tube may have a length approximating a length of the delivery tube with the carrier tube being dimensioned so that the component protrudes beyond a distal end of the delivery tube in an uncovered condition.

In certain exemplary embodiments, the system may include a displacement device arranged outwardly of the carrier tube with the cover tube being arranged outwardly of the displacement device. The displacement device may be a further tube mounted about the carrier tube. The cover tube may have a resiliently flexible distal end to accommodate the component of the prosthesis. The resilient flexibility of the distal end of the cover tube may be affected and effected by slotting the distal end to provide a plurality of leaves able to flex radially outwardly.

The equipment may include at least one sensing arrangement configured to sense a parameter of the filler material charged into the at least one envelope. The at least one sensing arrangement may comprise a pressure sensor for sensing the pressure of filler material charged into the at least one envelope, a temperature sensor for sensing the temperature of the filler material charged into the at least one envelope, be configured to sense the quantity of filler material charged into the envelope and/or comprise a flow rate sensor for sensing the rate of flow of the filler material into the at least one envelope. Further, the at least one sensing arrangement may be configured to sense the presence of gas bubbles in the filler material charged into the at least one envelope. Further, the sensing arrangement may be configured to sense the displacement of the pistons of the dispenser mechanism. Further, the sensing arrangement may be configured to sense the force applied to the pistons to displace the pistons of the dispenser mechanism.

In certain embodiments, there may be provided equipment for forming a tissue prosthesis in situ at a site in a patient's body, the equipment comprising a tubular delivery device, the delivery device defining a passageway, and at least one envelope of the prosthesis being mountable to a distal end of the delivery device to be received in a cavity at the site; a stiffening element arranged to project from a distal end of the delivery device with the envelope, in use, being received over the stiffening element to be supported by the stiffening element; and a removal mechanism carried by the delivery device for enabling the at least one envelope to be removed from the delivery device after the at least one envelope has been charged with filler material via the filler member.

In certain embodiments, the stiffening element may be an elongate element, such as a rod or tube, receivable with clearance in the passageway of the delivery device to define a gap to enable at least some fluid to be withdrawn from the at least one envelope to collapse the envelope on to a distal end of the elongate element projecting from the distal end of the delivery device.

The equipment may include a filler member receivable in the passageway of the delivery device after removal of the stiffening element, the filler member being receivable, after removal of the stiffening element, with clearance in the passageway to define a gap to enable fluid to be evacuated at least from the at least one envelope.

In certain embodiments, the equipment may include a tubular filler member receivable in the passageway of the delivery device, the filler member being receivable with clearance in the passageway to define a gap to enable fluid to be evacuated at least from the envelope and the stiffening element being an elongate element receivable through the passage of the filler member.

In certain embodiments, there may be provided a tissue prosthesis insertion system which includes a first assembly comprising a plurality of nested tubes, one of the tubes being a carrier tube which, in use, receives a component of ;tissue prosthesis at a distal end of the carrier tube; a magnetic mount carried at a proximal end of the first assembly; a second assembly removably attachable to the first assembly; and an attachment device carried at a distal end of the second assembly, the attachment device being responsive to the magnetic mount of the first assembly, the magnetic mount and the attachment device carrying complementary engaging formations to facilitate sealing between the magnetic mount and the attachment device.

The use of a plurality of nested tubes, as described herein, may have several advantages. For example, the device may be more compact than other devices which allow the device and all of its components to fit into a smaller confinement. This may, in certain embodiments, provide a means for conducting percutaneous and/or minimally invasive procedures. The nested tubes also reduce trauma to the tissue that can result from repeatedly moving instruments in and out of the body. The nested tubes also provide additional protection for the instruments inside of the outermost tube. Additionally, the device can be more easily maintained in its desired location and the system may operate with less frictional resistance. Since the working cannula is fixed and docked relative to the patient, and all the other nested tubes lock to the working cannula, the positioning and deployment of the envelope within the disc space is consistent and repeatable. Also, since all the tubes are fixed relative to each other, during any process of the implant procedure, the risk of damage to the envelope is minimised because movement (laterally and or axially) of the envelope is minimised. Excessive movement of the envelope during any part of the implant procedure increases its chances of being damaged by either the surrounding tissue or other tubes (in particular the working cannula).

The complementary engaging formations of the magnetic mount and the attachment device may comprise a Luer slip fitting (see, e.g., the luer slipfitting mechanism1006 ofFIG. 94). By “Luer slip fitting” is meant that one of the engaging formations comprises a tapered socket and the other of the engaging formations comprises a tapered fitting receivable in the tapered socket to form a sufficient or substantial seal between the fitting and the socket.

In certain embodiments, instead of a luer slip fit formation, sealing can be achieved through the use of an O-ring or a gasket between the surfaces of the mounts such that a substantial seal if formed.

Also, one engaging end can have a protruding member, in the form of a tapered fitting, and the receiving end may comprise an engaging formation (not necessarily tapered) which is substantially parallel, but of a softer material than the protruding member such that it deforms to accommodate the protruding member and form a seal. Two surfaces of dissimilar materials (dissimilar hardness) engaging with mechanical interference may provide a substantial seal. For two surfaces of similar materials engaging with mechanical interference, to improve the seal, a dissimilar material (e.g., Silicone) can be used between the two surfaces to provide a substantial seal. Also the applicant of a sealant between the two similar surfaces can provide the necessary seal.FIG. 92 illustrates the use of an O-ring1000 between the two surfaces. Although not illustrated, the seal could also be formed at theinterface1002 of the two surfaces.

The magnetic mount of the first assembly may be a first magnetic mount and the attachment device may comprise a second magnetic mount which magnetically attaches to the first magnetic mount.

In certain embodiments, both mounts do not necessarily have to be magnetic, as long as one is magnetic, the other can be of a material which is attracted to a magnet.

Alternatively, another means of engaging two surfaces is through the application of an adhesive on one or more of the surfaces and using the tackiness of the surfaces as a means for engaging the two surfaces.

Other means of coupling can include a luer lock connection (see, e.g., theluer locking mechanism1004 ofFIG. 93), bayonet connection, ball seal connection and any other connection which allow the two engaging components to be reversibly attachable. To achieve the closed system status, any of the listed engaging means can be used in conjunction with any or all of the above mentioned sealing mechanisms either singly or in combination.

The second assembly may include a stiffening member received within the first assembly, the stiffening member, in use, projecting into an interior of the component of the prosthesis, the stiffening member having a securing formation at its proximal end which engages the engaging formation of the magnetic mount in a sealing manner.

Further, the system may include a withdrawing device attachable to the first assembly, the withdrawing device, in use, being in communication with the interior of the component of the prosthesis and, with the stiffening member in position, creating a closed system, contained system, or hermetically sealed system so that operating the withdrawing device causes an increase in the volume of the closed system with a corresponding reduction in the pressure in the interior of the component, resulting in the component collapsing about the stiffening member.

The withdrawing device may be operable to test the integrity of the first assembly with the component mounted on the first assembly.

The protective sheath may have a distal end configured to facilitate sliding displacement of the protective sheath relative to the component of the prosthesis. In some aspects, the distal end of the protective sheath may be configured by being bifurcated. The protective sheath may include an operating member arranged at its proximal end to facilitate manipulation of the protective sheath.

The systems may include the component, the component comprising at least one envelope of an elastically deformable material, the at least one envelope defining an access opening with a flow control member being arranged in the access opening, the flow control member being configured to permit withdrawal of fluid from an interior of the at least one envelope prior to filling the at least one envelope with a filler material. The flow control member may be a flow control valve which, in a rest condition, defines a withdrawal opening to allow withdrawal of the fluid from the interior of the at least one envelope. In certain aspects, the valve may be a duckbill valve having a pair of opposed operating flaps, the flaps being shaped so that, in their rest condition, they are spaced from each other to define the withdrawal opening The flaps may be skewed or staggered so that when the flaps come together, a small opening is defined. Other types of valves include umbrella valves, star valves, valves which have at least 1 flap (preferably 2), ball valve, dome shaped (e.g., umbrella shaped) valve with a slit(s) cut into the very tip of the dome. For example,FIGS. 87 and 88 illustrate an exemplary ball valve in an open and closed position, respectively andFIGS. 89 and 90 illustrate an exemplary umbrella valve in an open and closed position, respectively. The valve may be pressure sensitive whereby it prevents flow in a particular direction at a certain pressure. When that certain pressure is exceeded; it allows for fluid to flow in that particular direction.

In certain embodiments, the flow control member may not necessarily have to be a valve. If the neck of the envelope were inverted, once the envelope has been filled, the inverted neck would form a flap which seals to prevent the backflow of material. The inverted neck may be parallel (tubular), tapered or stepped (i.e., the diameter changes). Also, another alternative to a valve (which is built into the envelope) is a tubular section which has a gradual reduction in diameter (See, for example,FIG. 91). This functions like a valve but may not necessarily be referred to as a valve. Various cross sections are possible for this form of flow restricting mechanism. It still has an opening in its relaxed state but once the envelope is filled, the significantly more viscous biomaterial cannot flow back out. All of the above mentioned design features can be applicable for a valve or a valve like structure which does not have an opening defined in its relaxed state. It could require an extending member (either an extension of the carrier tube or other) to open up the valvular member in order to define this opening, which may be necessary to operate the envelope (e.g., collapse). Alternate to a valve, the delivery apparatus can be twisted (or rotated) once the filling is completed and this twisting crimps and seals the neck of the implant.

In certain embodiments, the flow control member in its resting condition may be configured to define at least one withdrawal opening and in its non resting condition may be configured to allow less viscous fluids to flow in at least two directions and more viscous fluids to flow in at least one direction. Less viscous materials are those materials that require less energy to flow. Less viscous fluids include, but not limited to, air, water, certain oils. (The term “less viscous” can be seen as a relative term where it defines a material which is less viscous than the material being introduced into the envelope as the biomaterial, or less viscous than the material which is limited to flow in at least one direction by the flow control member.)

In certain embodiments, the flow control member in its first condition may be configured to define at least one withdrawal opening and in its second condition may be configured to allow less viscous fluids to flow in at least two directions and more viscous fluids to flow in one direction.

In some aspects, other flow control mechanisms or means for flow control may be used. For example star valves, multi cuspid valves, umbrella valves. In some aspects, other flow control mechanisms may be used as long as that mechanism controls the flow of certain fluids in at least one direction. In certain aspects, the flow control mechanism may be configured to allow less viscous fluids to flow in at least two directions and more viscous fluids to flow in at least one direction. For example, using certain flow control mechanisms fluids such as gas, water, solutions or combinations thereof, will be permitted to substantially flow in at least two directions through the flow control mechanism and viscous filler material will be permitted to substantially flow through the control mechanism into the envelope.

In certain aspects, the means for flow control may be configured to allow less viscous fluids to flow in either direction or more viscous fluids to flow in at least one direction.

In certain embodiments, the flow control member may be configured to allow less viscous filler material to flow into the envelope where the filler material becomes more viscous, thereby preventing it from flowing back through the flow control member.

One advantage of certain flow control members disclosed herein is that they may be configured to permit viscous materials to flow in one direction allowing the carrier tube to be detached after the viscous material has been delivered to the envelope. Thus permitting shorter surgery times and anaesthesia for the patient, resulting in a faster recovery and less chance of complications.

The second assembly may comprise a filler tube received through the first assembly to communicate with the interior of the envelope and a filler material dispenser mountable to a proximal end of the filler tube. The dispenser assembly may feed into a static mixer, a distal end of the static mixer carrying the attachment device, the arrangement being such that, when the second assembly is fast with the first assembly and the withdrawing device is attached to the first assembly, a second closed system is created which enables fluid to be withdrawn from the interior of the envelope by the withdrawing device to create a low pressure region in the envelope. A “low” pressure may be defined as a pressure below ambient pressure.

Whether the filler material is a single part, two part, etc., it can be premixed and delivered through the filler tube rather than having to go through a static mixer. Alternatively, the mixing can be through a dynamic mixer. Also, the in situ curing filler material usually relies on a catalyst and or cross-linker. That molecule required to initiate the chemical reaction can be added into the mixture by having it coated on the surfaces the filler material is in contact with. This includes but is not limited to, the static mixer, inner lining or filler tube, inner lining of envelope etc.

The dispenser may contain filler material, the filler material preferably being of the same class or type of material as the material of the envelope so that, when the envelope has been charged with the filler material and the filler material has been allowed to set, a tissue prosthesis is formed which is elastically deformable. The envelope is filled with the filler material initially up until the envelope reaches its relaxed configuration (i.e., its premolded form). Then, when the filling continues, it undergoes elastic deformation for up to 10 times its relaxed volume, or for up to 3, 4, 5, 6, 7, 8, or 9 times its relaxed volume or until it fills to conform substantially to the cavity of the nucleus where the substantiality of the fill is not limited by the limitations of the apparatus.

In certain embodiments, the envelope may be resilient and elastically deformable. The in situ curing material may also be resilient and elastically deformable. When the systems combine, they form a resilient and elastically deformable implant. When the envelope and in situ material combine, they take on the properties substantially similar to that of the envelope, or to that of the in situ curing material, or the combined system may take on completely different mechanical properties (possibly due to the fact that when they combine, they undergo a chemical reaction which changed the properties altogether). By “elastically deformable” it is meant that the prosthesis can be deformed by the application of a force and, upon removal of the force, the tissue prosthesis substantially returns to its undeformed state. In certain embodiments, the filler material may be of a different class or type than the material of the envelope. For example, but not limited to, a polyurethane envelope filled with a silicone filler material, a silicone envelope with a polyurethane filler material, a polyester envelope filled with a silicone filler, polyester envelope filled with polyurethane, or other combinations of acceptable filler material and acceptable envelope material. Further, the envelope may be a polyethylene envelope filled with either a polyurethane or a silicone filler. Combinations of the materials also apply. For example, the filler may be a combination of silicone and polyurethane.

The system may include an obturating device receivable in one of the tubes of the first assembly for tamping a part of the tissue prosthesis into position after formation of the tissue prosthesis. The obturating device may carry a locking member at its proximal end for locking to a working cannula of the system so that, after tamping of the part of the tissue prosthesis, the working cannula and the obturator can be removed simultaneously.

In certain embodiments, there may be provided a tissue prosthesis insertion system which includes an assembly comprising a plurality of nested tubes, one of which is a carrier tube for carrying a component of a tissue prosthesis at its distal end and another of which is a filler tube received with clearance in the carrier tube to define a passage between the filler tube and the carrier tube, the proximal end of the filler tube and the proximal end of the carrier tube being in sealing engagement; and a withdrawing device attachable to the assembly so that, when the withdrawing device is attached and the component of the tissue prosthesis is mounted on the distal end of the carrier tube, a closed system is formed which allows the withdrawing device to be used to increase the volume of the closed system to form a low pressure region at least in the component.

The assembly may comprise a stiffening member received in the carrier tube, a proximal end of the stiffening member and a proximal end of the assembly carrying complementary engaging formations for enabling the stiffening member to engage sealingly with at least one of the plurality of nested tubes to create an initial closed system, operation of the withdrawing device forming a low pressure region in the interior of the component, in use, to cause the component to collapse around the stiffening member. The system may include a filler tube insertable into the carrier tube after removal of the stiffening member to contribute to the formation of a further closed system which is then acted on by the withdrawing device to increase the volume of the closed system to reduce the pressure in the interior of the component.

The withdrawing device may be operable to test the integrity of the system to ensure that there are no leaks in the system.

In certain embodiments, there may be provided a tissue prosthesis insertion system which includes a working cannula for accessing a site in a patient's body percutaneously and/or minimally invasive manner for carrying out a tissue prosthesis insertion procedure at the site; and an obturating device receivable in the cannula for tamping a part of a tissue prosthesis into position after formation of the tissue prosthesis.

In certain embodiments, there may be provided a tissue prosthesis component which includes an envelope of an elastically deformable material, the envelope defining an access opening; and a flow control member arranged in the access opening, the flow control member being configured to permit withdrawal of fluid from an interior of the envelope prior to filling the envelope with a filler material.

The flow control member may be a flow control valve which, in a rest condition, defines a withdrawal opening to allow the passage of certain fluids in both directions. The envelope may have a neck portion, the neck portion defining the access opening and the flow control member being arranged within the neck portion.

In certain embodiments, there may be provided methods of preparing a first assembly of a tissue prosthesis system for insertion into a patient's body, the methods comprising providing the first assembly which comprises a plurality of nested tubes, one of the tubes being a carrier tube; mounting a component of the prosthesis on a distal end of the carrier tube, the component being of an elastically deformable material; inserting a stiffening member into the first assembly so that the stiffening member extends into an interior of the component and causing a proximal end of the stiffening member to sealingly engage a proximal end of the first assembly; attaching a withdrawing device to the first assembly so that the withdrawing device is in fluid communication with the interior of the component; and operating the withdrawing device to reduce the pressure in the interior of the component to cause the component to collapse about the stiffening member.

The methods may include attaching the withdrawing device to a fluid port of the first assembly in a sealing manner. The withdrawing device may be a syringe which is attached by a Luer lock mechanism to the fluid port of the first assembly.

After the component has been collapsed about the stiffening member, the methods may include placing a protective sheath about the component. More particularly, the methods may include placing the protective sheath about the component by sliding the protective sheath over the component, the protective sheath constituting one of the tubes of the nested tubes of the first assembly. Further, the methods may include treating one of the protective sheath and the component with a lubricating medium to facilitate relative displacement between the protective sheath and the component.

The methods may include using the withdrawing device to test the integrity of the combination of the first assembly and the component and the stiffening member attached to the first assembly.

In certain embodiments, there may be provided methods of forming a tissue prosthesis at a site in a patient's body, the methods including providing a first assembly comprising a plurality of nested tubes, one of the tubes being a carrier tube with a component of the prosthesis carried at a distal end of the carrier tube; inserting the first assembly into a cannula placed in the patient's body; magnetically attaching a second assembly to a proximal end of the first assembly; and charging a filler material from the second assembly into the component and allowing the filler material to set.

The methods may include, initially, preparing the first assembly as described above.

The methods may include, once the distal end of the first assembly is at the desired location at the site in the patient's body, withdrawing the protective sheath to expose the component, the component being an envelope of an elastically deformable material. Further, the methods may include using the withdrawing device to test the integrity of the first assembly either after or before withdrawing the protective sheath.

The methods may include removing the stiffening rod prior to magnetically attaching the second assembly to the first assembly. Further, the methods may include causing the second assembly to engage sealingly with the first assembly so that, together with the component and the withdrawing device, a closed system is formed.

After the second assembly has been attached to the first assembly, the methods may include operating the withdrawing device to create a low pressure in the component. Further, the methods may include using the withdrawing device to test the integrity of the system comprising the two assemblies and the component attached to the first assembly.

The methods may include dispensing the filler material from a dispenser of the second, assembly. Preferably, the methods include purging filler material from the dispenser prior to attaching the dispenser to a static mixer constituting a part of the second assembly.

The methods may include, during filling of the component via a filler tube extending from the static mixer, operating the withdrawing device at least to maintain, or increase, the volume of the closed system.

The methods may include, after filling the component, detaching the carrier tube from the tissue prosthesis formed by the combination of the component and the filler material contained in the component. The carrier tube may be detached prior to the filler material having cured or set or after the filler material has at least partially set. The methods may include detaching the carrier tube from the tissue prosthesis when the required pressure has been reached in the component. In the case of intervertebral disc nucleus prosthesis, the required pressure may be that which inhibits distraction of the disc.

In certain embodiments, the methods may include detaching the tissue prosthesis by relative axial motion between the carrier tube and a displacement device of the first assembly. The displacement device may be a further tube arranged about the carrier tube and the relative axial motion may be effected and affected by withdrawing the carrier tube relative to the displacement device. In other embodiments, the methods may include detaching the tissue prosthesis by filling the component with filler material to the extent that the component is released from the carrier tube. In further embodiments, the methods may include detaching the tissue prosthesis by manipulating the carrier tube relative to the component to cause separation of a part of the component attached to the carrier tube from a remainder of the component, the separation occurring ng at a zone of weakness in the component. The manipulation may involve rotating the carrier tube with respect to the component.

The methods may include, after formation of the tissue prosthesis, tamping a part of the tissue prosthesis into position. If necessary or desirable, the methods may include, before placing the component in position at the site, preparing the site. The methods may include preparing the site by removing degenerative tissue from the site prior to placing the component at the site.

In certain embodiments, there may be provided equipment for forming a tissue prosthesis in situ at a site in a patient's body, the equipment comprising a delivery device displaceably receivable in a lumen of an introducer, the delivery device defining a passageway; an envelope carried at a distal end of the delivery device, the envelope being of a biologically inert, elastically deformable material capable of being expanded to conform to an interior surface of a cavity formed at the site: and a supply of a filler material chargeable in a fluent state into the envelope through the passageway of the delivery device, the filler material being of the same class of material as the envelope to form, when cured, together with the envelope, a unified prosthesis.

The equipment may include an aperture forming element to form an aperture into the site, the aperture forming element being receivable through the introducer for delivery to the site. The aperture forming element may, for example, be a trocar.

Further, the equipment may include a tissue removal mechanism insertable through the aperture for removing tissue, if required, to form the cavity. The tissue removal mechanism may comprise mechanical, ultrasonic, laser, Argon gas or radio frequency ablation mechanisms, or the like in combination with suction and irrigation. For example, the tissue removal mechanism may be a reaming-type tool.

The equipment may include a dispenser containing the supply of filler material. Further, the equipment may include a sensing arrangement configured to sense a parameter of the filler material charged into the envelope. The sensing arrangement may comprise a pressure sensor for sensing the pressure of filler material charged into the envelope, a temperature sensor for sensing the temperature of the filler material charged into the envelope, be configured to sense the quantity of filler material charged into the envelope and/or comprise a flow rate sensor for sensing the rate of flow of the filler material into the envelope. Further, the sensing arrangement may be configured to sense the presence of air bubbles in the filler material charged into the envelope.

In certain embodiments, there may be provided equipment for forming a tissue prosthesis in situ at a site in a patient's body, the equipment comprising a tubular delivery device, the delivery device defining a passageway, an envelope of the prosthesis being mountable to a distal end of the delivery device to be received in a cavity at the site; a filler member receivable in the passageway of the delivery device, the filler member being receivable with clearance in the passageway to define a gap to enable fluid to be manipulated or evacuated at least from the envelope, at least prior to the filler material being charged into the envelope; and a removal mechanism carried by the delivery device for enabling the envelope to be removed from the delivery device after the envelope has been charged with filler material via the filler member.

The equipment may include a tubular introducer and an aperture forming element, such as a trocar, to form an aperture at the site, the aperture forming element being receivable through the introducer for delivery to the site.

Further, the equipment may include a tissue removal mechanism insertable through the aperture for removing tissue, if required, to form the cavity.

The introducer and the delivery device may include a retaining arrangement for retaining the delivery device with respect to the introducer.

In addition the equipment may include a supply of filler material attachable to a proximal end of the filler member. The filler material may be a mixture of a plurality of parts and the supply of filler material may comprise a dispenser defining a plurality of chambers in each of which one part of the filler material is received prior to use. The dispenser may further comprise a mixer arranged intermediate an outlet of the dispenser and the proximal end of the filler member for mixing the filler material prior to charging it into the envelope.

A proximal end of the delivery device may carry a connector for connection to an evacuating mechanism such as an evacuation pump.

The equipment may include the envelope, the envelope being of an elastomeric material capable of expanding to up to about 3, 4, 5, 10, 40, 50, 100, or 150 times its relaxed state. Preferably, the envelope is expanded to be stretched and retained under tension after being charged with the filler material. The envelope may include a neck portion, the neck portion defining a zone of weakness for facilitating separation of the envelope from the delivery device.

FIGS. 25-28, illustrate an exemplary assembly of a tissue prosthesis insertion system designated generally by thereference numeral10. Theassembly10 comprises a plurality of nestedtubes12. As shown inFIG. 28, the set of nestedtubes12 comprises an inner,carrier tube14 on which a component, in the form of an envelope,16 of a tissue prosthesis is mounted, thecomponent16 being mounted on a distal end of thecarrier tube14. Thecarrier tube14 is received within a push-offtube18 which is used for removing theenvelope16, after filling, from thecarrier tube14 as will be described in greater detail below.

The nestedtubes12 further include aprotective sheath20, arranged about the push-offtube18. As illustrated inFIGS. 26 and 28, theprotective sheath20 is of a length to cover theenvelope16, thesheath20 projecting beyond a distal end of theenvelope16 when in its operative, protective position. It is to be noted that the nestedtubes12 are shown, in use, mounted in a workingcannula22 used for inserting thefirst assembly10 percutaneously to deliver theenvelope16 into a site at a patient's body in which the prosthesis is to be formed. The nestedtubes12 are all of a metal material such as a steel material which is bio-compatible.

Thefirst assembly10 further includes a stiffening member in the form of a stiffeningrod24. The stiffeningrod24 is of a length to project from a proximal end of thefirst assembly10 through a lumen26 (FIG. 28) of thecarrier tube14 to be received in an interior28 of theenvelope16.

Acollar assembly30 is arranged at a proximal end of the nestedtubes12. Thecollar assembly30 comprises afirst collar32 secured to a proximal end of thecannula22. Thecannula22 has a pair of diametrically opposed, longitudinally extending slits, one of which is shown at34 inFIG. 25 of the drawings, arranged distally of thecollar32. Theprotective sheath20 is slidably arranged relative to thecannula22 and has a pair of opposed, radially outwardly extendingtabs38 arranged at its proximal end. Thetabs38 project through theslits34 in thecannula22 to enable a clinician to manipulate theprotective sheath20.

The push-offtube18 has acollar36 arranged at its proximal end, thecollar36 being connected to thecollar32 of thecannula22 via a bayonet fitting. Thecarrier tube14 carries a Y-connector42 at its proximal end, the Y-connector42 extending from acollar40. Thecollar40 attaches to thecollar36 of the push-offtube18. The Y-connector42 carriers amagnetic mount44 at its proximal end. Themagnetic mount44 carries a plurality ofannular magnets46. Thesemagnets46 are rare earth magnets and are covered by acover member48.

The Y-connector42 further includes abranch limb50 defining aconnection port52 for a withdrawing device. Theconnection port52 is in communication with a passage (not shown) defined between thecarrier tube14 and, initially, the stiffeningrod24. The stiffeningrod24 carries a securing formation in the form of amount54 at its proximal end. Adistal part56 of themount54 is tapered and engages a taperedsocket58 defined by themagnetic mount44 in a sealing or closing manner so that, once a withdrawing device has been attached to theport52, a closed system is formed.

More particularly, once theenvelope16 has been attached to the distal end of thecarrier tube14, the stiffeningrod24 is inserted through thelumen26 of thecarrier tube14 to be received in theinterior28 of theenvelope16. When the distal end of the stiffeningrod24 is received in theenvelope16, thedistal part56 of themount54 of the stiffeningrod24 sealingly engages with thesocket58 in themagnetic mount44 of the Y-connector42 to form a substantial seal, or a hermetic seal.

A withdrawing device in the form of a syringe62 (FIG. 30) is connected via a Luer fitting64 to theport52 of the Y-connector42 to form a closed system. Aplunger66 of thesyringe62 is drawn in the direction ofarrow68. This increases the volume of the closed system, reducing the pressure in theinterior28 of theenvelope16 and causing theenvelope16 to collapse about the distal end of the stiffeningrod24.

Thetabs38 of theprotective sheath20 are gripped by an operator assembling thefirst assembly10 and are urged in the direction of arrow70 (FIG. 26) to cause theprotective sheath20 to slide over and protect theenvelope16. To facilitate sliding movement between theprotective sheath20 and theenvelope16, a distal end of thefirst assembly10 can be immersed in a suitable lubricating medium such as, for example, water. In this regard it should be noted that theenvelope16 is made of silicone material rendering it hydrophobic. Thus, the water acts as a lubricant and enables theprotective sheath20 to be slid over theenvelope16. Instead of immersing the distal end of thefirst assembly10 in the lubricating medium, an internal surface of theprotective sheath20 could, optionally, be coated with a lubricating medium of a hygroscopic or hydrophilic material such as a hydrogel. Alternatively, rather than treating the inner surface of the protective sheath, the protective sheath itself may be made from lubricious materials which include, but not limited to, polytetrafluoroethylene (Teflon), acetal, polypropylene, polyethylene. All of the above mentioned materials may also be a treatment option for the inner lining of the protective sheath. Further, should the protective sheath be made from the described polymers, they may also be treated to improve the lubricity.

After retracting thesheath20 in the direction opposite to that ofarrow70, the integrity of thefirst assembly10 is tested for leaks by further withdrawing theplunger66 of thesyringe62 in the direction ofarrow68. If theplunger66 does not return to its previous position, this is an indication that there is a leak in thefirst assembly10 and remedial action can be taken to locate the leak. Conversely, should theplunger66 return to its previous position, this is an indication that the integrity of thefirst assembly10 is intact and the procedure can proceed.

Instead of pulling on theplunger66 of thesyringe62, testing of the integrity of thefirst assembly10 could involve pushing on theplunger66 of thesyringe62 and then releasing theplunger66. If theplunger66 does not return to its original position that is an indication that there is a leak in the system such as may occur if theenvelope16 is torn.

FIGS. 29-32, show a tissue prosthesis insertion system which is designated generally by thereference numeral80. Thesystem80 includes thefirst assembly10 and asecond assembly82. Thesecond assembly82 comprises afiller tube84 including astatic mixer86 at a proximal end of thefiller tube84. Thestatic mixer86 is secured to a distal end of afiller material dispenser88. Thefiller material dispenser88 has a screw-threadedattachment89 for engaging a screw-threadedboss90 at a proximal end of thestatic mixer86. A distal end of thestatic mixer86 carries an attachment device in the form of a secondmagnetic mount92. As illustrated inFIG. 31, themagnetic mount92 comprises a pair of annular rare earth magnets94 closed off by acover96. Themount92 also includes atapered fitting98. Thetapered fitting98 of themount92 and the taperedsocket58 of themount44 define complementary engaging formations. Thus, thetapered fitting98 is received within thesocket58 of themagnetic mount44 of the Y-connector42 in a hermetically sealing manner, the fitting98 and thesocket58 constituting a Luer slip fitting. Thus, once again, once thesyringe62 has been attached to theport52 of the Y-connector42, a closed system is formed.

The benefit of magnetically attaching thesecond assembly82 to thefirst assembly10 is that the requirement for relative rotation between the two

assemblies

10 and82 for attachment to each other is obviated. This also enables thecannula22 of thefirst assembly10 more accurately to be retained in position, in use. It also maintains the engagement of the two

assemblies

10 and82 during filling of theenvelope16. The filler material used for forming the tissue prosthesis is a silicone rubber material. To inhibit curing of the filler material prior to its being charged into theenvelope16, the filler material is retained in two, separate parts. For this purpose, thedispenser88 includes twoseparate reservoirs100, in each of which one part of the filler material is initially received. Eachreservoir100 has a plunger (not shown) associated with it for dispensing the parts of the filler material simultaneously from thereservoirs100 into thestatic mixer86 where the parts are mixed prior to being charged into thefiller tube84 to be injected into the interior28 of theenvelope16. The plungers are displaceable together with each other via a suitable displacing device (also not shown), for example, a pneumatic gun.

After removal of the stiffeningrod24, thesecond assembly82 is attached to thefirst assembly10 via the

magnetic mounts

44 and92. More particularly, the part of thesecond assembly82 comprising thestatic mixer86 with thefiller tube84 projecting from thestatic mixer86 is magnetically attached to thefirst assembly10 via the

magnetic mounts

44 and92 with the fitting98 sealingly engaging in thesocket58. Prior to attaching thedispenser88 to thestatic mixer86, filler material is purged from thereservoirs100 by urging the plungers towards the threadedend89 of thedispenser88 to expel a portion of filler material from thereservoirs100 to ensure that the correct ratio of the two parts of the filler material is dispensed. Thedispenser88 is then attached to thestatic mixer86.

The pressure in theinterior28 of theenvelope16 is again lowered by withdrawing theplunger66 of thesyringe62 in the direction ofarrows68. This serves to collapse theenvelope16 prior to the filler material being charged via thefiller tube84 into the interior28 of theenvelope16. To enable the pressure in theinterior28 of theenvelope16 to be lowered, thefiller tube84 is a loose fit within thecarrier tube14 to create an annular passage102 (FIG. 32) via which air, gas or certain other fluids can be withdrawn from theinterior28 of theenvelope16 by thesyringe62.

After lowering the pressure in the interior of theenvelope16, the integrity of thesystem80 is again checked by further attempting to withdraw theplunger66 from thesyringe62 in the direction of thearrows68. Should theplunger66 remain in its withdrawn position, this is an indication that there is a leak in the system and remedial action can be taken to locate the leak. Conversely, should theplunger66 return to its previous position, this is an indication that the integrity of thesystem80 is intact and the clinician can proceed. Once again, instead of pulling theplunger66, testing could involve pushing theplunger66 and determining whether or not it returns to its original position. If not, that is an indication that there is a leak in thesystem80 and remedial action can be taken to locate the leak.

Referring generally toFIGS. 33-37, to insert the nucleus prosthesis into the disc, an incision in made in the patient's skin and an annulotomy is performed on theannulus126 of thedisc124 in a minimally invasive manner to form anopening132. This enables access to be gained to the interior of thedisc124. To perform the annulotomy, thecannula22 is inserted through the incision until a distal ends abuts theannulus126. An annulotomy performing tool, such as a trocar or a guide wire plus dilator (not shown), is inserted through thecannula22 and pierces theannulus126 to enable access to be gained to the nuclear material of thedisc124. If necessary, a nucleotomy is performed to remove the nuclear material. However, in certain circumstances, the degenerative process may have dehydrated, extruded or shrunken the nuclear material so that a cavity has already been formed and the necessity to perform the nucleotomy is obviated.

Whether or not a nucleotomy is performed, once the cavity in thedisc124 is present, thefirst assembly10 is inserted into thecannula22. As indicated above, thefirst assembly10 comprises thecarrier tube14 with theenvelope16 mounted on a distal end of thecarrier tube14, the push-offtube18 and theprotective sheath20, with theprotective sheath20 extending over theenvelope16.

Once theenvelope16 is in position within thedisc124, theprotective sheath20 is withdrawn by urging thetabs38 of theprotective sheath20 in the direction opposite to that of thearrow70, thetabs38 being received withinrecesses104 of thecollar32 of thecannula22.

Theassembly10 is locked in position relative to the workingcannula22 by the bayonet fitting of thecollar36 of the push-offtube18 engaging thecollar32 of thecannula22.

The stiffeningrod24 is removed and thesecond assembly82 is attached to thefirst assembly10, as previously described. Some filler material is purged from thereservoirs100 of thedispenser88 and thedispenser88 is then attached to the proximal end of thestatic mixer86. This re-forms the closed system enabling air to be removed from theenvelope16 by operating thesyringe62 and pulling itsplunger66 in the direction ofarrows68.

The plungers of thedispenser88 are then urged towards the distal end of thedispenser88 to discharge material from thereservoirs100. The parts of the filler material discharged from thereservoir100 are mixed together in thestatic mixer86 before being fed into thefiller tube84. Theplunger66 of thesyringe62 is continued to be withdrawn in the direction ofarrow68 during passage of the filler material along thefiller tube84 at least to maintain or to increase the volume of the closed system to remove air from theenvelope16 as the filler material is charged into theenvelope16. Thefiller material84 is conveyed through thefiller tube84 into the interior28 of theenvelope16 through a tissue prosthesis component in the form of afiller valve106. Thefiller valve106 will be described in greater detail below.

As the filler material enters the interior28 of theenvelope16, it causes theenvelope16 to expand to conform to the shape of the cavity within the intervertebral disc. It will be appreciated that, due to the resilient flexibility of theenvelope16, theenvelope16 will readily conform to the shape of the cavity and theenvelope16 need not be of any particular pre-configured dimensions.

FIGS. 33-35, illustrate the tissue prosthesis component in the form of thefiller valve106 of theenvelope16 is described in greater detail. It is to be noted that theenvelope16 has a bulbous body portion108 (FIG. 32) integrally formed with aneck portion110. Theenvelope16 is attached to the distal end of thecarrier tube14 via theneck portion110. Thevalve106 is received within theneck portion110 of theenvelope16. Thevalve106 is a duck bill valve having a pair of opposed operating members or operating flaps112. The operating flaps112, when in their rest condition, as shown inFIGS. 33-35 or the drawings, do not close fully and aslit114 is defined between the operatingflaps112 of thevalve106. This is desirable so that, prior to filler material being charged into the interior28 of theenvelope16, air can be withdrawn from theinterior28 of theenvelope16 via theslit114 using thesyringe62.

Once the filler material has filled the interior28 of theenvelope16, it occludes theslit114 or, instead, presses down on the operating flaps112 to cause them to deform to close theslit114. Also, the filler material could have sufficient viscosity to inhibit extrusion of the filler material outwardly through theslit114. It will be appreciated that, once the filler material has set, it no longer matters whether or not theslit114 is fully closed.

To inhibit overfilling of theenvelope16, the envelope is mounted on thecarrier tube14 such that as theenvelope16 fills with tiller material, any excess filler material will “extrude” between theneck portion110 of theenvelope16 and thecarrier tube14 causing theenvelope16 to be released from thecarrier tube14.

After the desired quantity of filler material has been charged into theenvelope16, thesecond assembly82 is detached from thefirst assembly10 by breaking the magnetic bond between the

magnetic mounts

44 and92. Thefiller tube84 is withdrawn from the interior of thecarrier tube14.

Theenvelope16 is detached from thecarrier tube14 by relative displacement between thecarrier tube14 and the push-offtube18. More particularly, thecarrier tube14 is withdrawn from the push-offtube18 by detaching thecollar40 of the Y-connector42 from thecollar36 of the push-offtube18 and withdrawing thecarrier tube14. This causes the proximal end of theneck portion110 of theenvelope16 to come into abutment with the distal end of the push-offtube18 causing detachment of theenvelope16 from thecarrier tube14. The push-offtube18 is then removed. The tissue prosthesis134 (FIGS. 36 and 37), comprising theenvelope16 filled with the filler material, is retained in position within theintervertebral disc124 of the patient. Additional methods for removing the envelope may include, for example, an external or internal cutting mechanism on the tubes which can sever the implant from the delivery apparatus, means of twisting and crimping the neck of the implant (in certain embodiments, this may both seal and detach the implant, and if the means in which the envelope is held onto the carrier tube is purely an interference fit or just tight fit, then pulling on the carrier tube can result in detachment of the envelope (the tube can also be rotated to detach).

As shown inFIGS. 36 and 37, after removal of thecarrier tube14, at least a part of theneck portion110 of theenvelope16 may protrude through theannulus126 of theintervertebral disc124. In addition a residue of filler material may be present in the distal end of the workingcannula22. Therefore, prior to removal of the workingcannula22, anobturator136 is inserted into alumen138 of thecannula22. Theobturator136 comprises a blunt-endedrod140 which is a tight fit within thelumen138 of thecannula22.

Theobturator136 is used to urge any residue of filler material into the disc cavity and to tamp the part of theneck portion110 of theenvelope16 into the disc cavity, as shown inFIG. 37. Theprosthesis134 is thus entirely contained within thedisc cavity134 with minimal, if any, protrusion into theannulus126 of thedisc124.

Theobturator136 can, if desired, be locked to the workingcannula22 by anattachment collar142 carried at a proximal end of theobturator136 locking to thecollar32 of the workingcannula22 in a bayonet fitting manner. This allows theobturator136 to be retained in position during setting of the filler material and inhibits extrusion of filler material from theenvelope16 and/ or from the disc cavity. After completion of the tamping and setting process, the workingcannula22 and theobturator136 are removed.

Tamping theneck portion110 of theenvelope16 into thedisc cavity122 inhibits prosthesis expulsion and excessive loading on theaperture132 in theannulus126 of thedisc124. In addition, the fact that there is no remnant of theenvelope16 in theannulus124 enhances closure of theaperture132 in theannulus124.

It is an advantage of this (and other embodiments) that a tissue prosthesis insertion system is provided which is simple to operate by a clinician. The assemblies are easily connected together using the magnetic connection which improves the stability of the device and obviates the need for relative rotation of the assemblies relative to one another to connect them together. In addition, the use of the protective sheath protects the envelope against damage while it is being inserted into and positioned in the patient's body. The sheath is relatively simple to operate by the clinician thereby improving the performance of the system as a whole. Further, the use of the syringe as a low pressure generating device simplifies the system and precludes the need for complicated pumps, etc. Also, due to the fact that the syringe provides a closed system, it is not necessary to continuously withdraw gas out of the envelope while it is being charged with filler material. This further simplifies operation of the system.

Referring toFIGS. 38 and 39,reference numeral10 generally designates another exemplary embodiment of a prosthesis delivery system. Theprosthesis delivery system10 includes a plurality of nestedtubes12 shown inFIG. 39. In some embodiments, the nested tube will be 3, 4, 5, or 6. Anoutermost tube14 of the nestedtubes12 functions as a cannula in which the remaining tubes are received. The remaining tubes form part of aprosthesis delivery apparatus16. The tubes of the nestedtubes12 have a flaredwall portion18. The flaredwall portion18 of the nested tubes mates12 with atapered end20 of astatic mixer22 of a dispensingarrangement24 of theapparatus16 of thesystem10.

Thecannula14 further includes a manipulatingarrangement26, arranged at a proximal end of thecannula14, for connecting and effecting manipulation of the nestedtubes12.

Afirst tube14 of the nested tubes is the cannula which is used for insertion of theprosthesis delivery apparatus16 percutaneously to a site in which a prosthesis is to be inserted.

Thesystem10 is intended for use in the insertion of an intervertebral disc nucleus prosthesis in position in a disc after performance of a nucleotomy, if necessary, on a disc to remove the natural nucleus of the disc. The nucleus may have herniated through an annulus of the disc due to degeneration of the disc. In such circumstance, it may not be necessary to perform a nucleotomy on the disc.

The prosthesis includes anenvelope28. Theenvelope28 is carried on the end of acarrier tube30. Theenvelope28 is an expansible envelope of an elastically deformable material which is charged with a filler material to fill a cavity of the disc left by removal of the natural nucleus. Typically, the envelope is of a silicone material which is capable of expanding up to 1000% its relaxed state without plastically deforming. The filler material used with theenvelope28 is also of a silicone material and is dispensed from adispenser32 of the dispensingarrangement24. The filler material is charged into theenvelope28, in use through afiller tube34. Thefiller tube34 is nested within thecarrier tube30.

Afurther tube36 is arranged outwardly of thecarrier tube30 and is used to push off theenvelope28 from thecarrier tube30 after being filled with the filler material and the filler material has at least partially set or cured.

It will be noted that, in this embodiment, each of the

tubes

14,30,34 and36 has the flaredportion18 so that all the tubes mate with thetapered end20 of thestatic mixer22 of the dispensingarrangement24. Further, a proximal portion of the nestedtubes12 projects proximally of thetapered end20 of thestatic mixer22 to surround thestatic mixer22 as shown in.FIG. 38. The

tubes

14,30,34 and36 are locked together once nested. Further, the

tubes

30 and34 may seal hermetically once nested and locked together.

The manipulatingarrangement26 of thecannula14 includes a rupturing mechanism for rupturing the cannula after placement of a distal end of theprosthesis delivery apparatus16. The rupturing arrangement comprises at least a pair of opposed longitudinally extending lines of weakness, one of which is shown at38 inFIG. 39. The other line of weakness is diametrically opposed to the shown line ofweakness38. The lines ofweakness38 divide the cannula into two

shells

40 and42. The manipulatingarrangement26 comprises a pair ofopposed tabs44. Eachtab44 is integrally formed with one of the

shells

40,42 of thecannula14. Thetabs44 are used for connecting the nestedtubes12 to thecannula14. Also, by pulling radially on thetabs44, thecannula14 ruptures along the lines ofweakness38 facilitating withdrawal of thecannula14 from theprosthesis delivery apparatus16.

A gap46 (FIG. 39) is defined between thecarrier tube30 and thefiller tube34. Thegap46 communicates with a port48 (FIG. 38) and with the interior of theenvelope28. Theport48, in use, forms part of aboss50 and an evacuation apparatus (not shown) is connected to theport48 to enable the interior of theenvelope28 to be evacuated either prior to or as the filler material is charged into theenvelope28.

The silicone used for expanding theenvelope28 is of the type which, prior to use, is maintained in two separate parts. Thus, thedispenser32 has at least twocompartments52, in each of which one part of the silicone material is stored, prior to being fed through thestatic mixer22, where mixing of the parts takes place, and being charged into theenvelope28.

In use, an incision is formed in the skin of the patient. Thecannula14, with a trocar (not shown) contained in a lumen of thecannula14, is inserted through the incision to the disc on which the operation is to be performed. The trocar is used to perform an annulotomy on an annulus of the disc. Once that operation has been completed, the trocar is withdrawn. A device (not shown) is inserted through thecannula14 to perform the nucleotomy, if necessary. The device could, for example, be a mechanical device such as a reamer to ream the degenerative nuclear material from the intervertebral disc.

After completion of the nucleotomy, the device is withdrawn. Theprosthesis delivery apparatus16 is then inserted into the lumen of thecannula14 and theenvelope28 is inserted through the annulotomy aperture into the cavity of the disc formed as a result of the nucleotomy. The filler material is dispensed from thedispenser32, through thestatic mixer22 and thefiller tube34 into the interior of theenvelope28 while, simultaneously, a suction is maintained on theport48 and thegap46.

In an embodiment, thecannula14 is then removed by rupturing it along the lines ofweakness38 by pulling radially outwardly on thetabs44.

Once this has occurred, the push offtube36 is free to be manipulated relative to thecarrier tube30 by being urged in a direction of arrow54 (FIG. 39) by means of a manipulatingring56 carried at a proximal end of the push offtube36. Pushing off theenvelope28 from thecarrier tube30 allows theprosthesis delivery apparatus16 to be withdrawn from the patient's body.

In another embodiment, thecannula14 remains in place. Theenvelope28 is pushed off from thecarrier tube30 by withdrawing thecarrier tube30 relative to the push offtube36 in a direction opposite to thearrow54. Thecannula14 is the final item to be removed with the remaining nestedtubes12 still contained in and attached to thecannula14.

FIGS. 40-42, illustrates certain embodiments of aprosthesis delivery system10, in this embodiment, thesystem10 includes a further component in the form of a cover tube60 (FIG. 40). Thecover tube60 constitutes a sheath and, at least initially, protects theenvelope28 of the prosthesis when it is inserted into thecannula14.

For this purpose, a distal end of thecover tube60 is slotted, as shown byslots62. In these embodiments, twoslots62 are provided to define a pair of opposed resiliently flexible leaves64. The leaves64 are able to be displaced outwardly in the direction ofarrows66. Thus, in use, thecover tube60, which has substantially the same length as thecannula14, is placed over theprosthesis delivery apparatus16 so that theenvelope28 is received between theleaves66 at the distal end of thecover tube60. The entireprosthesis delivery apparatus16, including thecover tube60, is then inserted into thecannula14 and the distal end of thecover tube60 protects theenvelope28.

Thecover tube60 is arranged between thecannula14 and the push-offtube36. It will, however, be appreciated that, if thecover tube60 is appropriately dimensioned, it can, itself, act as the push-off tube, the push-offtube36 then being omitted.

A proximal end of thecover tube60 carriesconnectors68. Theseconnectors68 engage with thetabs44 of thecannula14 so that thecover tube60 engages with and connects to thecannula14 to enable the remaining tubes of the nestedtubes12 to move towards a distal end of thetubes12 so that theenvelope28 can protrude beyond the end of thecover tube60 and the distal end of thecannula14 as shown inFIG. 38 of the drawings. Thetabs44, in turn, engage with the manipulatingring56 to retain thecannula14 in position relative to theprosthesis delivery apparatus16.

In the embodiment shown inFIG. 41, thecover tube60 has a flaredportion18 to nest with the remainingtubes12 of theprosthesis delivery system10.

InFIG. 42 of the drawings, a set of nestedtubes12 is provided which does not have the flaredportion18 and is mountable to a distal end of thestatic mixer22.

It is an advantage of these embodiments that thecover tube60 obviates the need for lubricants to enable theenvelope28 to be inserted into a lumen of thecannula14. Thecover tube60 serves to protect theenvelope28 as theprosthesis delivery apparatus16 is inserted into thecannula14.

It will be appreciated that this embodiment, in use, the incision is of such a size that at least part of thestatic mixer22 can be inserted through the incision. Due to the flaredportion18 of the nestedtubes12, the overall length of theprosthesis delivery apparatus16 and thesystem10, itself is significantly shorter than would otherwise be the case. Because of this, theentire system10 has improved stability and balance. The stability and balance improves because the lever arm of the system (with the pivot point of the system being at the docking point at the annulus) has now decreased. Since the length of the system has shortened, the length which the material must travel to the envelope decreases, therefore the pressure required to deliver the material also decreases. Due to the decreased delivery pressure, the surgeon requires less work (effort) to deliver the material. Less effort means that the surgeon's movements are more stable and less jerky. This stability allows the clinician a higher degree of control in maneuvering thesystem10 both to the site at which the prosthesis is to be delivered as well as while forming the prosthesis at the site. This is enhanced due to the fact that the nesting of thetubes12 about thestatic mixer22 also improves the rigidity of theentire system10 resulting in less free movement of a distal end of theprosthesis delivery apparatus16 of thesystem10. This further enhances the clinician's control over thesystem10. Since the working cannula is fixed and docked relative to the patient, and all the other nested tubes lock to the working cannula, the positioning and deployment of the envelope within the disc space is consistent and repeatable. Also, since all the tubes are fixed relative to each other, during any process of the implant procedure, the risk of damage to the envelope is minimised because movement (laterally and or axially) of the envelope is minimised. Excessive movement of the envelope during any part of the implant procedure increases its chances of being damaged by either the surrounding tissue or other tubes (in particular the working cannula).

In certain embodiments, there is provided an intervertebral disc implant which includes an envelope constructed of at least one stretchable and/or elastically deformable elastomeric material, the envelope including an attaching formation for attachment to an introducer to enable the envelope, in a collapsed state, to be introduced into a volume of an intervertebral disc that has undergone a nucleotomy; and a filler material receivable in the envelope via the introducer to cause the envelope to expand elastically to conform substantially to the volume in which the envelope is received, in use.

In certain embodiments, there is provided an intervertebral disc implant which includes a first object constructed of at least one stretchable and/or elastically deformable elastomeric material, the first object being in communication with second object for attachment to a third object to enable the first object, in a first state, to be introduced into a volume of an intervertebral disc that has undergone a nucleotomy; and a material receivable in the first object via the second object which results in expansion, or partial expansion of the first object such that the first object substantially conforms to the volume in which the first object is received, in use.

In certain embodiments, there is provided an intervertebral disc implant which includes an envelope constructed of at least one stretchable and/or elastically deformable elastomeric material, the envelope including means for attaching an introducer to enable the envelope, in a collapsed state, to be introduced into a volume of an intervertebral disc that has undergone a nucleotomy; and means for introducing a filler material into the envelope via the introducer to cause the envelope to expand elastically to conform substantially to the volume in which the envelope is received, in use.

In some embodiments, the envelope is of a silicone material. In some aspects, the envelope is constructed with at least one silicone material.

In some embodiments, the attaching formation may comprise a filler tube mountable to the introducer, the attaching formation may include a closure device to inhibit back flow of filler material. In some embodiments, the attaching formation may comprise a filler tube in communication with the introducer, the attaching formation may include a closure device to inhibit back flow of filler material. In some aspects, the attaching formation may comprise a filler tube in communication with the introducer, the attaching formation may comprise a closure means for inhibiting back flow of filler material. Any suitable closure device may be employed such as, for example, but not limited to, a one-way, or non-return, valve, a filler tube extending outwardly from the remainder of the envelope to be closed off in a suitable manner or a filler tube extending into the interior of the envelope and which is crimped closed by the surrounding filler material upon withdrawal of the introducer.

In certain embodiments, the filler material may comprise a plurality of discrete, biocompatible, or substantially biocompatible elements. The elements may include, singly or in combination, beads, pellets, elongate elements, irregular shaped elements, collapsible elements, expansible elements, preformed elements, shape memory elements, partially cured elements, uncured elements, cured elements. The elements may be biocompatible plastics, biocompatible metals, biocompatible ceramics, organic or biological elements, or a combination of the foregoing. Further, the elements may be provided in a mixture of sizes.

The elongate elements may be selected from the group consisting of fibres, lengths of filamentary elements such as lengths of string, bristle carrying elements such as bottle brush-like elements, and helical elements such as lengths of coiled wires, or combinations thereof.

The discrete elements may be arranged in suspension in a filler within the volume. In certain aspects, the filler is an elastomeric, curable filler.

In certain aspects, each expansible element may be configured to change from a first configuration for insertion into the envelope to a second configuration which causes the envelope to conform substantially to the volume. In certain aspects, the at least one expansible element may be configured to change from a first configuration for insertion into the envelope to a second configuration. In certain aspects, at least one expansible element may be configured to change from a first configuration into a second configuration wherein the second configuration causes the envelope to partial conform to the volume. Further, each expansible element may be configured to be received, in its first configuration, in the introducer for introduction into the envelope.

In certain embodiments, each expansible element may, in its rest condition, adopt its second configuration. Further, each expansible element may include a biocompatible, shape memory alloy, such as, but not limited to nitinol, which causes the element to adopt its second configuration in the envelope after ejection from the introducer.

In certain embodiments, the filler material may be a foamed material which is introduced in a compressed state via the introducer into the interior of the envelope where it expands to its relaxed state to cause the envelope to conform to the volume. In certain embodiments, the filler material may be contain at least one foamed material which is introduced in a first state via the introducer into the interior of the envelope where it expands to a second state to cause the envelope to conform, or substantially conform, to the volume. The foamed material may be a polymeric material such as a polyethylene.

In certain embodiments, the filler material may comprise a plurality of discrete bands of a resiliently flexible material. In certain embodiments, the filler material may comprise at least in part a plurality of discrete bands of a resiliently flexible material. The bands may be configured to be arranged concentrically within the envelope. The bands may have a height approximating that of the volume.

In certain embodiments, the envelope may carry at least one layer of a tissue ingrowth material. In certain embodiments, the envelope may also including, tissue ingrowth materials. In some aspects, where a layer is used, the layer may be a polyester material such as Dacron®.

In certain embodiments, there is provided an intervertebral disc implant which includes an envelope, the envelope including an attaching formation for attachment to an introducer to enable the envelope, in a collapsed state, to be introduced into a volume of an intervertebral disc that has undergone a nucleotomy; and a filler material receivable in the envelope after placement of the envelope in the volume of the disc, in use, to cause expansion of the envelope to conform to the volume, the filler material comprising a plurality of discrete, elongate elements introducible, via the introducer, into an interior of the envelope.

The envelope may be of an expansible material such as an elastomeric material having an elongation of at least 100% and, in some aspects, up to about 1000%, for example, silicone. Elastomeric materials such as silicone can have an elongation up to 250%, 500%, 750%.

In certain embodiments, there is provided an intervertebral disc implant which includes an envelope, the envelope including means for attachment to an introducer to enable the envelope, in a collapsed state, to be introduced into a volume of an intervertebral disc that has undergone a nucleotomy; and a filler material receivable in the envelope and means for placement of the envelope in the volume of the disc, in use, to cause expansion of the envelope to conform to the volume, the filler material comprising a plurality of discrete, elongate elements introducible, the introducer means, into an interior of the envelope.

The envelope may carry at least one layer of a tissue ingrowth material. Further, the envelope, in certain embodiments, may define a filler opening and may include a closure element for closing the opening after introduction of the filler material. In certain aspects the envelope may have a filler opening means and may include a closure means for closing the opening after introduction of the filler material.

In certain embodiments the elongate element may be selected from the group consisting of fibres, lengths of filamentary elements, bristle carrying elements and helical elements, or combinations thereof.

The elongate elements may be arranged in suspension in the filler within the volume. In some embodiments, the filler may be an elastomeric, curable filler.

In certain embodiments, the elongate elements may comprise a plurality of discrete bands of a resiliently flexible material. The bands may be configured to be arranged concentrically within the envelope.

In certain embodiments, the elongate elements may be expansible elements. Each expansible element may be configured to change from a first configuration for insertion into the envelope to a second configuration which causes the envelope to conform substantially to the volume. Each expansible element may be configured to be received, in its first configuration, in the introducer for introduction into the envelope. Further, each expansible element may, in its rest condition, adopt its second configuration.

In certain embodiments, there is provided an intervertebral disc implant which includes an envelope of a stretchable and elastically deformable elastomeric material, the envelope including an attaching formation for attachment to an introducer to enable the envelope, in a collapsed state, to be introduced into a volume of an intervertebral disc that has undergone a nucleotomy; and a filler material receivable in the envelope via the introducer to cause the envelope to expand elastically to conform substantially to the volume in which the envelope is received, in use, the filler material being a foamed material which is introduced in a compressed state via the introducer into the interior of the envelope where it expands to its relaxed state to cause the envelope to conform to the volume.

The foamed material may be a polymeric material. The envelope may carry at least one layer of a tissue ingrowth material. The envelope may define a filler opening and may include a closure element for closing the opening after introduction of the packing material.

In certain embodiments, there is provided an intervertebral disc implant which includes an envelope, the envelope including an attaching formation for attachment to an introducer to enable the envelope, in a collapsed state, to be introduced, in a minimally invasive manner, into a volume of an intervertebral disc that has undergone a nucleotomy; and a filler material receivable in the envelope after placement of the envelope in the volume of the disc, in use, to cause expansion of the envelope to conform to the volume, the filler material comprising, in combination, a curable filler material and a plurality of discrete, biocompatible elements contained, in use, in the filler material within the envelope.

The elements may include, singly or in combination, beads, elongate elements and expansible elements. The elongate elements may be selected from the group consisting of fibres, lengths of filamentary elements, bristle carrying elements and helical elements.

Each expansible element may be configured to change from a first configuration for insertion into the envelope to a second configuration which causes the envelope to conform substantially to the volume. Further, each expansible element may be configured to be received, in its first configuration, in the introducer for introduction into the envelope. Each expansible element may, in its rest condition, adopt its second configuration.

The filler may be an elastomeric, curable filler.

In certain embodiments, there is provided an intervertebral disc implant which includes an envelope of a stretchable and elastically deformable elastomeric material, the envelope including an attaching formation for attachment to an introducer to enable the envelope, in a collapsed state, to be introduced into a volume of an intervertebral disc that has undergone a nucleotomy; and a filler material receivable in the envelope via the introducer to cause the envelope to expand elastically to conform substantially to the volume in which the envelope is received, in use, the filler material being an elastomeric material having a viscosity of at least 500 cP. In certain aspects, the filler material may have a viscosity of at least 1000 cP, of at least 5000 cP, of at least 10000 cP, of at least 50000 cP, of at least 100000 cP, of at least 500000 cP.

In certain embodiments, there is provided an intervertebral disc implant which includes an envelope receivable in a volume of an intervertebral disc that has undergone a nucleotomy, the envelope defining a plurality of chambers, the chambers being configured so that, when at least certain of the chambers contain a filler material, the envelope conforms substantially to the volume of the disc; a filler material receivable in the at least certain of the chambers; and at least one of the chambers having a filler mechanism associated with it.

The chambers may be defined by wall portions of the envelope, wall portions of some of the chambers being of a different wall thickness than wall portions of other chambers. In addition, wall portions of some of the chambers may be of a different material than wall portions of other chambers. Still further, the filler material receivable in at least one of the chambers may differ from the filler material that is receivable in at least one other of the chambers.

The envelope may include an attaching formation for attachment to a tubular introducer to enable the envelope, in a collapsed state, to be introduced, in a minimally invasive manner, into the volume of the disc.

Each chamber in which filler material is receivable may have a filler mechanism associated with it. The filler mechanism may be a one-way device that, upon closure, inhibits back flow of filler material. Preferably, the filler mechanism of an outer chamber of the envelope may be implemented as the attaching formation.

In certain embodiments, the system for implanting an intervertebral disc implant, comprises:

an implant as disclosed herein; and an introducer, the introducer comprising a plurality of filler tubes, each tube communication independently of any other tube with its associated chamber of the envelope for charging filler material into the associated chamber.

In certain embodiments, there is provided an intervertebral disc implant which includes at least one element which changes from a first configuration for insertion into a volume of an intervertebral disc that has undergone a nucleotomy to a second configuration in which the at least one element conforms substantially to the volume, the at least one element being configured to be received, in its first configuration, in an introducer to be inserted into the volume of the disc.

The at least one element, in its first configuration, may be elongate and, in its second configuration, may adopt a shape conforming substantially to the volume. The at least one element may include a biocompatible, shape memory alloy which causes the element to adopt its second configuration in the volume after ejection from the introducer.

Further, in certain embodiments, the at least one element, in its relaxed state, may be in the first configuration, the at least one element including a retention device for retaining the at least one element in the second configuration after ejection from the introducer.

In certain embodiments, the implant may include an envelope receivable in a collapsed state in the volume; and a plurality of the elements receivable in the envelope, the plurality of elements causing the envelope to expand substantially to conform to the volume.

In certain embodiments, there is provided a system for implanting an intervertebral disc implant as disclosed herein the systems including an introducer having a proximal and a distal end, a mount for the envelope of the implant being arranged at or adjacent the distal end of the introducer; a source of filler material connectable to the proximal end of the introducer; and a displacement mechanism for displacing the filler material along the introducer to be ejected from the introducer into the envelope, in use.

The introducer may comprise at least one tubular member. Instead, the introducer may comprise at least two tubular members arranged in a telescopic fashion, the tubular members being reciprocally displaceable relative to one another.

An innermost one of the tubular members may carry the displacement mechanism. The displacement mechanism may comprise a ratchet arrangement for urging the filler material along the introducer into the envelope.

Further, the envelope may include a flow control device arranged at an inlet opening to the envelope for inhibiting back flow of the filler material from the envelope. The equipment may include a flow control defining member, the flow control defining member being separate from the envelope and being arranged at the inlet opening to the envelope.

A distal end of the filler member may carry an engaging member which engages the flow control device to at least partially open the flow control device and to allow the interior of the envelope to be evacuated prior to being charged with the filler material. The envelope may carry a marker arrangement on an exterior surface for enabling the envelope to be used to assess dimensions and a shape of the cavity and positioning of the envelope in the cavity.

The filler material may be of an elastomeric material capable of absorbing shock and withstanding compressive, tensile, bending and torsional forces. The envelope and the filler material may be of an elastomeric material having a Shore Hardness in the range of about 5 to 90 A. The shore hardness may be between 5 and 15 A, 15 and 25 A, 25 and 35 A, 35 and 45 A, 45 and 55 A, 55 and 65 A, 65 and 90 A. Preferably, the envelope and the filler material are of a silicone rubber material.

The envelope may be of an elastomeric material capable of expanding to up to 3, 4, 5, 10, 25, 50, 75 or 100 times its relaxed state. The envelope is preferably expanded to be stretched and retained under tension after being charged with the filler material.

The envelope may include a neck portion, the neck portion defining a zone of weakness for facilitating separation of the envelope from the delivery device. Further, the envelope may include a flow control device arranged at an inlet opening to the envelope for inhibiting back flow of the filler material from the envelope. The equipment may include a flow control defining member, the flow control defining member being separate from the envelope and being arranged at the inlet opening to the envelope.

The envelope may carry a marker arrangement on an exterior surface for enabling the envelope to be used to assess dimensions and a shape of the cavity and positioning of the envelope in the cavity.

The filler material may be of an elastomeric material capable of absorbing shock and withstanding compressive, tensile, bending and torsional forces. More particularly, the envelope and the filler material may be of an elastomeric material having a Shore Hardness in the range of about 5 to 90 A. The shore hardness may be between 5 and 15 A, 15 and 25 A, 25 and 35 A, 35 and 45 A, 45 and 55 A, 55 and 65 A, 65 and 90 A. The envelope and the filler material may be of a silicone rubber material.

In certain embodiments, there is provided a tissue prosthesis which comprises an envelope of a biologically inert, elastically deformable material capable of being expanded to conform to an interior surface of a cavity formed at a site in a patient's body; and a filler material received in a fluent state in the envelope, the filler material being of the same class of material as the envelope to form, when cured, together with the envelope, a unified structure.

The envelope may be of an elastomeric material capable of expanding to up to 3, 4, 5, 10, 25, 50, 75 or 100 times its relaxed state. Further, the filler material may be of an elastomeric material capable of absorbing shock and withstanding compressive, tensile, bending and torsional forces. The envelope may be expanded to be stretched and retained under tension after being charged with the filler material.

Both the envelope and the filler material may be of an elastomeric material having a Shore Hardness in the range of between about 5 to 90 A. The shore hardness may be between 5 and 15 A, 15 and 25 A, 25 and 35 A, 35 and 45 A, 45 and 55 A, 55 and 65 A, 65 and 90 A The envelope and the filler material may be of a silicone rubber material. Preferably, the envelope and the filler material are of a silicone rubber material. However, to promote bonding between the envelope and the filler material, the envelope and the filler material may be of different grades of silicone rubber material and may be pre-treated in different ways prior to use.

The envelope may include a neck portion, the neck portion defining a zone of weakness for facilitating separation of the envelope from a delivery device. Further, the envelope may include a flow control device arranged at an inlet opening to the envelope for inhibiting back flow of the filler material from the envelope. In an embodiment, the prosthesis may include a flow control defining member, the flow control defining member being separate from the envelope and being arranged at the inlet opening to the envelope.

In certain embodiments, there may be provided a tissue prosthesis which comprises an envelope of a foraminous, chemically inert material shaped to conform, or substantially conform, to an interior surface of a cavity formed at a site in a patient's body in which the envelope is to be placed; and a filler material received in a fluent state in the envelope, the filler material being of an elastomeric material which, prior to being cured, is urged into foramens of the envelope to form an integrated structure which inhibits relative movement between the envelope and the filler material, in use, and once the filler material has cured.

The envelope may be of a knitted biological or synthetic polymeric material. More particularly, the envelope may be of a knitted polyester material, such as polyethylene terephthalate (PET). Further, the envelope may be coated with a material of the same class as the filler material.

The filler material60 (see, e.g.,FIG. 7) may also be constructed of a silicone rubber material which is able to absorb shocks and withstand compressive, tensile, bending and torsional forces imparted to it by movement of the

vertebrae

12 and14. In addition, due to the fact that thefiller material60 is the same class or type as the material of theenvelope38, once the filler material has cured in theenvelope38, a unified or single, integrated structure is formed which is resistant to delamination and relative movement between theenvelope38 and thefiller material60.

One component of certain embodiments is the use of at least one envelope to confine the filler material. Depending on the particular embodiment, the envelope may function to partially contain, substantially contain, or contain the at least one tiller material. The function of the envelope to contain the filler material may vary from fully containing the filler material to something less than fully containing the filler material. In certain embodiments, the envelope may be a balloon type structure, mesh-like structure, a band-like structure, may be comprised of a multi cavity like structure, may be a foldable structure and/or a foldable structure that has a shape memory or combinations thereof. In some aspects, the envelope may be expandable and/or stretchable up to 50%, 100%, 200%, 300%, 400%, 500%, 600%, 700% or up to 1000%, or greater than 1000% of its relaxed volume. in other embodiments, the envelope may be inelastic, or substantially inelastic. In some aspects of the disclosed embodiments, means for confining the filler material are provided. For example, but not limited to, the structures disclosed in this application. In some embodiments, the envelope may be configured to sufficiently contain the filler material at the desired location before the implant, during the method of implant and/or after the implant.

In certain embodiments, the biomaterial may be in the form of a biocompatible or substantially biocompatible polymer composition comprising a plurality of parts capable of being aseptically processed or sterilized, stably stored, and mixed at the time of use in order to provide a flowable composition. In some embodiments, the polymer composition may contain optionally, other ingredients such as antioxidants, and dyes. In some aspects, upon mixing, the composition is sufficiently flowable to permit it to be delivered to the desired site and there fully cured under physiologically conditions. In some aspects, the component parts are themselves flowable, or can be rendered sufficiently flowable, in order to facilitate their mixing and use.

Additionally, the devices disclosed herein are considered novel in their own right, and can be used with any suitable biomaterial. In certain embodiments, the devices may be used in combination with a curable silicone based polymer composition comprising a plurality of parts capable of being aseptically processed or sterilized, stably stored, and mixed at the time of use in order to provide a flowable composition and initiate cure. Those skilled in the art will, in turn, appreciate the manner in which such polymer compositions can be manipulated to produce cured and curing polymers with desired combination of properties within the scope of certain embodiments. The silicone can be chemically crosslinked, e.g., by the addition of multifunctional or branched OH-terminated crosslinking agents or chain extenders. The optimal level of chemical cross-linking improves the compression set of the material, reduces the amount of the extractable components, and improves the biodurability of the silicone polymer. This can be particularly useful in relatively soft silicone polymers, such as those suitable for the repair of damaged cartilage. Additional tillers may be added to the polymer composition such as silica, to alter the hardness, compression set, tensile strength, tear strength, viscosity, other physical or chemical properties, or combinations thereof. In this manner a balancing of the physical and/ or chemical properties with respect to the overall characteristics of the polymer, can be achieved.

Additionally, certain polymer systems may contain at least one or more, biocompatible or non biocompatible catalysts that can assist in controlling the curing process, including the following periods: (1) the scorch time (2) the setting period, and finally, (3) the final cure of the biomaterial. Together these three periods, including their absolute and relative lengths, and the rate of acceleration or cure within each period, determines the cure kinetics or profile for the composition. Suitable examples of the catalyst for the formed polymer will depend upon the polymer material selected. In certain aspects where the polymer is a silicone based polymer the catalyst may be selected from, but not limited to the following: tin, platinum, peroxide.

As applied to intervertebral disc repair, the inclusion of an “additive” in the prepolymer, previously described and presently preferred by applicants in formulations for joints other than the disc, is not presently preferred (though remains optional) for use in the disc. When present, such an additive can provide several desirable features, both in the formulation and use of the prepolymer itself, as well as in the mixed composition. These features include an improved combination of such properties as moisture cure characteristics, cross-linking, viscosity, compression fatigue, and stability.

Certain preferred compositions provide certain desirable properties, including, but not limited to, hardness, strength, cure characteristics and combinations thereof.

When cured, suitable materials can be homogeneous, providing the same physico-chemical properties throughout, or they can be heterogeneous and exhibit varying features or properties. An example of a heterogeneous composition, e.g., for use as an intervertebral disc replacement, is a composition that mimics the natural disc by providing a more rigid outer envelope (akin to the annulus) and a more liquid interior core (akin to the nucleus). Such heterogeneous compositions can be prepared by the use of a single composition, e.g., by employing varying states of cure and/or by the use of a plurality of compositions, including varying compositions and/or ratios of the same ingredients used to form the composition.

Suitable compositions for use certain embodiments are those polymeric materials that provide an optimal combination of properties relating to their manufacture, application, and in situ use. In the uncured state, such properties include component miscibility or compatibility, process ability, and the ability to be adequately sterilized or aseptically processed and stored. In the course of applying such compositions, suitable materials exhibit an optimal combination of such properties as flow ability, mold ability, and in situ curability. In the cured state, suitable compositions exhibit a desired combination of such properties as strength (e.g., tensile and compressive), modulus, biocompatibility and biostability.

When cured, certain of the disclosed compositions demonstrate a desirable combination of properties, in terms of their conformational stability and retention of physical shape, resilience during load and unload conditions in situ, dissolution stability, biocompatibility, and physical performance, as well as physical properties such as density and surface roughness, and mechanical properties such as load-bearing strength, tensile strength, shear strength, shear fatigue resistance, impact absorption, wear resistance, and surface abrasion resistance. Such performance can be evaluated using procedures commonly accepted for the evaluation of natural tissue and joints, as well as the evaluation of materials and polymers in general. In particular, a preferred composition, in its cured form, exhibits mechanical properties that approximate or exceed those of the natural tissue it is intended to provide or replace. In some aspects, certain compositions may be capable of deforming and recovering resiliently in situ without plastic deformation, or substantial plastic deformation. In some aspects, certain compositions may be capable of deforming and recovering resiliently in situ with an acceptable level of plastic deformation. In some aspects, certain compositions may be capable of deforming and recovering resiliently in situ without compression set, or substantial compression set.

It should be appreciated that certain compositions may be produced that have a desired combination of the physical and chemical properties discussed in this application.

With respect to those polymer compositions that are uncured, components of such compositions, and the compositions themselves, should be miscible, compatible and stable under conditions used for sterilization and during storage and in the course of delivery. They are also capable of flowing to an in situ location, and being cured in situ, using a suitable catalyst, thereafter the cured composition is suitably amenable to conforming, shaping and/or contouring, by the use of the device embodiments disclosed herein. Over the course of its use in the body the cured, contoured composition exhibits physiological, physical-chemical and mechanical properties suitable for use in extended in situ applications.

To achieve these desirable uncured and delivery properties, a “polymer system”, as used herein refers to the component or components used to prepare a polymeric composition. In an embodiment, a polymer system comprises the components necessary to form two parts (as discussed elsewhere herein, together with other ingredients (e.g., catalysts, stabilizers, plasticizers, antioxidants, dyes and the like). Such adjuvants or ingredients can be added to or combined with any other component thereof either prior to or at the time of or after mixing, delivery, and/or curing.

In choosing an optimal volume ratio for a given formulation, the following may be taken into consideration. The viscosity of the reactive parts in this temperature range of less than about 10° C., less than about 20° C., less than about 30° C., less than about 40° C., less than about 50° C., less than about 70° C., must be such to provide an acceptable degree of mixing and injection flow rate without mechanical failure of any component of the delivery system including cartridge, static mixer, gun and other components. Preferably, the biomaterial is sufficiently flowable to permit it to be delivered (e.g., injected) into the balloon). While such a material can be as thick as the bone cement paste, the preferred viscosity is less than 1000Pa·s, 100 Pa·s, 80 Pa·s, 60 Pa·s, 40 Pa·s, 20 Pa·s, 15 Pa·s, 10 Pa·s, 8 Pa·s, or 6 Pa·s. In some aspects, one preferred viscosity is less than 100 Pa·s. The composition of both reactive parts must be such that these parts are homogeneous and phase stable in the temperature range of the application. The max temperature of the reaction exotherm is proportional to the concentration of the reactive groups in the mixed polymer. A high concentration of the reactive groups might evolve too high reaction exothermal energy and therefore may cause thermal damage to the surrounding tissues. The preferable implant-tissue interface temperature is below 70° C., 50° C., or more preferable below 40° C. It is desirable in some embodiments that, the reactive parts stay liquid, or substantially liquid, during mixing. The complete or partial solidification of the reactive part when it comes into contact with another reactive part or any component of the delivery system or during mixing may be unacceptable. The certain volume ratio of the components can be achieved by different ways such as use of the dual-compartment cartridges with constant volume ratio or by using the injectors with delivery rates independently variable for each component.

Many mixing devices and methods have been used for multiple part biomaterials, such as bone cement and tissue sealant, used in operating rooms. Static mixers and manual dispenser guns are commonly used for tissue sealant and other multi-component biomaterial mixing and delivery.

It is important that the two parts of polyurethane pre-polymer are mixed quickly and completely in the operating room in a sterile fashion. The number of mixing elements may vary and depends on the composition of the selected polymer. For example, with certain silicone based polymers, it is possible to use between 6 and 20 mixing elements, between 8 and 15 mixing elements, or between 10 and 12 mixing elements.

In certain embodiments, in situ curability May be dependent on the reaction rate, which can be measured by induction time and cure time. In general, fast cure (short induction time) will improve in situ curability and result in less leachable components. However, induction time should also be balanced with adequate working time needed for polymer injection.

A cured biomaterial of that may be used with certain embodiments preferably exhibits a compression modulus of between about 0.1 MPa and about 50 MPa, and more preferably between about 1 MPa and about 25 MPa, when measured using ASTM method D575A at a physiological strain range between 3 and 20%. In certain embodiments, compositions having a compression modulus considerably below these levels will tend to either bulge or extrude from annular defects that may exist or appear, while those having a modulus considerably above these levels will tend to be too hard and cause stress shielding and abnormal high contact stress on the endplate.

In certain embodiments, theenvelope38 is made from a silicone rubber material having the following characteristics:

a Shore hardness (A scale) in the range from about 20-50;

a tensile strength in the range from about 2700 kPa to 11000 kPa;

an elongation of between about 400% and 800%; and

a tear strength of between about 1700 kg/m and 4500 kg/m.

Thefiller material60 is also of a silicone rubber material which, prior to use, is stored in two separate parts. Thefiller material60, comprising the combined parts, when mixed in a ratio of 1:1 and cured, has the following characteristics:

a Shore hardness (A scale) in the range from about 20 to 40, more particularly, about 25 to 30 and, optimally, about 28;

a tensile strength in the range form about 7000 kPa to about 9500 kPa, more particularly, about 8000 kPa to about 9000 kPa and, optimally, about 8500 kPa;

an elongation in the range from about 550% to 700%, more particularly, about 600% to 650% and optimally, about 640%; and

a tear strength in the range from about 1000 to 2000 kg/m, more particularly, about 1250 kg/m to 1750 kg/m and, optimally, about 1500 kg/m.

One example of a suitable material for the filler material has the following characteristics after mixing the parts in a 1:1 ratio and after curing:

a Shore hardness (A scale) of 28;

a tensile strength of 8439 kPa;

an elongation of 639%; and

a tear strength of 1500 kg/m.

Thefiller material60 may be treated to contain 5%, by volume, barium sulphate to appear radio-opaque under X-ray, CT, fluoroscopy and MRI. In addition, thefiller material60 contains a catalyst and has a scorch time of between about 1.5 to 2.5 minutes with a curing time of about 5 minutes. When thefiller material60 is charged into theenvelope38 it causes inflation or expansion of theenvelope38 in an elastically deformable manner. Expansion of theenvelope38 can occur to such an extent that, where necessary, the expandedenvelope38 distracts the

vertebrae

12 and14 to restore the original spacing between the

vertebrae

12 and14. By using radio-opacity in thefiller material60, distraction of the

vertebrae

12 and14 can be monitored in real time using a fluoroscope or the similar equipment.

Further, theenvelope38 conforms to the shape of thecavity36. Because theenvelope38 expands within thecavity36 and conforms closely to the shape of thecavity36, theenvelope38 self anchors within thecavity36 and “extrusion” of aunified prosthesis100, comprising theenvelope38 and thefiller material60, formed through theaperture30 previously formed in theannulus16 of the disc is inhibited.

The material for the envelope may, depending on the grade or class of material used, be post cured for a period of time. This is affected by placing the mouldedenvelope38 into an oven, for example, for a period of about 1 to 4 hours at a temperature of about 150° C. to 180° C.

By having the material of theenvelope38 and thefiller material60 of the same type, but different grades or classes, chemical bonding between the materials is enhanced which encourages the formation of theprosthesis100.

An embodiment of the biomaterial was studied to characterize the mechanical and wear behavior of the implant.

Fatigue testing was performed to evaluate the mechanical and wear performance of the implant over its intended life. Fatigue testing in compression, flexion/extension, lateral bending and axial rotation were conducted to mimic in vivo physiological ranges. Specimens were loaded to 10 million cycles in compression as suggested by ASTM 2346-05 and 5 million cycles in flexion/extension, lateral bending and axial rotation.

The test implant was an annulus model (Silicone Shore Hardness 60 A) with a complete implant (filler material—CSM-2186-14 (Nusil Technologies) and jacket material—MED-4830 (Nusil Technologies) and Calf Serum 30 g/L solution (as per ISO/DIS 18192-1)) injected according to expected surgical procedure. Six implants were created.

The annulus model was placed between two Perspex constraining plates which prevent the model from bulging superiorly and inferiorly. Through the annulotomy, the implant was delivered using the equipment described herein until the implant had completely filled the cavity of the annulus model. The annulus model and the implant was placed inside a water bath set to 37° C. and let to cure for at least 1 hour.

6 specimens were glued to the test platens and left to dry for 24 hours. The specimens and test platens were then connected to the spine simulator. The test stain was filled with calf serum and maintained at 37±3° C.

The test execution was as follows:

- 1) A compression load of 100N and 600N was applied and the heights of the specimens at these loads were measured. This height was taken as the reference heights
- 2) Specimens were cyclically loaded under the following conditions:
  - Compression
    - Load range:
      - 100N to 2000N for 10 000 cycles
      - 600N to 1500N for 990 000 cycles
    - Load frequency: 2 Hz
  - Flexion/Extension
    - Bending range: +6/−3°
    - Range frequency: 1 Hz
    - Lateral Bending
      - Bending Range: ±2°
      - Range frequency: 1 Hz
    - Axial Rotation
      - Bending Range: ±2°
      - Range frequency: 1 Hz
- 3) After the completion of the 1 million compression cycles a 100N and 600N load was reapplied to measure the height change.
- 4) This process was repeated another 9 times such that the specimens underwent 10 million compression cycles.
- 5) At the completion of the cycling loading the specimens were left to recover for 24 hours a then 100N and 600N load was reapplied to measure the height change.

After each million compression cycles the calf serum test medium was collected and analyzed

Since literature publications have suggested the standing load results in approximately 0.5 MPa of pressure in the lumbar discs while disc pressures whilst lifting is suggested to be between 1.0 to 2.3 MPa, it was believed that choosing a loading regime between 600N to 1500N and 600N to 2000N would represent a worse case scenario. The flexion/extension, lateral bending and axial rotations ranges are comparable to human in vivo conditions as suggested ISO/DIS18192-1. The frequency of 2 Hz was chosen so as to not overheat the samples.

In the fatigue test, one of the six specimens was destroyed due to it slipping from the stainless steel platen at about the 5.8 million cycle mark. Tears in the annulus were noticed in all test stations at the 3 million cycle mark.

Observations of the CDD graded to the scale below.

Grade 1=Jacket peeling observed

Grade 2=Minor cracks observed

Grade 3=Progression of minor cracks observed

Grade 4=Major crack

Wear particles collected in the test medium were subjected to SEM (Scanning Electron Microscope). The results characterized the size with respect to shape factor, roundness and equivalent circle diameter. The test medium was collected every million cycles and wear particles extracted. The number of particles found per million cycles was collated. The number of particles found per sample per million cycles ranged from 137 to 797 particles. The average number of particles per million cycles was approximately 500 particles. Most particles had a shape factor of between 0.9 and 1 indicating that most of the particles collated were round. The equivalent circle diameter for most particles was between 0.1 and 0.3 μm.

EDX (Energy dispersive X-ray spectroscopy) analysis of the wear particles showed no trace of barium, while silicon, gold and palladium were detected. The detection of gold and palladium was due to contamination via the SEM analysis. A sample of an untested nucleus specimen was also analyzed under EDX to determine the detectability of barium. The analysis showed barium was detected but the wear particles collected from the fatigue testing did not show any signs of barium. According to supplier of the composition, the barium sulfate particles contained within the filler material is approximately 1 μm. Hence the EDX analysis is sensitive enough to detect the presence of barium sulfate particles, but the lack of traces detected by the EDX for the implant indicated that the implant had not worn, or the wear had not been significant enough.

All 5 specimens passed the acceptance criteria which required the specimens to not split up into more than 3 distinct pieces which are smaller than the size of the annulotomy. This criterion was chosen as the mechanical function of the CDD will remain even if it has broken up so long as the CDD is adequately constrained within the annulus. So long as the implant is able to maintain its total volume it will still function as required. The 5 specimens all remained intact in one piece when the annulus remains essentially intact. In the

tests involving Specimens

2 and 4, it was noted that the simulated annulus failed leading to a grading of higher than 1 for these tests at some point beyond 5 million cycles. It is noted that a protocol involving the replacement of the annulus after a set number of cycles, e.g., 2 million, may more closely represent the natural regeneration of the annulus that occurs in the body and provide a better measure of the performance of the CDD. In spite of these shortcomings in the simulated annulus, the structural integrity of the 5 specimens remained intact after the fatigue testing and hence the acceptance criteria were met. The EDX analysis on the wear particles generated from the testing procedure showed no signs of barium or platinum and hence not from the nucleus filler material. The acceptance criteria also required no more than 10% of the volume lost. From visual observation of the 5 specimens, there were no sites where significant parts of the implants were worn away. Specimens tested where the annulus model did not fail remained fully intact with no cracks. The remaining two specimens where the annulus failed had cracks present in them but nonetheless remained intact as one functional body. Accordingly, the implant is capable of withstanding in vivo conditions for 10 years equivalent with supra-physiological loading.

Supra physiological loads in the lumbar spine may be encountered during accidents, thus evaluation of the impact performance of the implant is required.

The test set up for shock testing was as follows:

1) Specimens were loaded in compression to 100N to measure the reference height.

2) A shock load of 3000N at a rate of 200 kN/min was then applied.

3) Specimens were then unloaded to 100N at a rate of 200 kN/min and hold for 20 seconds to measure the reference height.

This particular test was performed because a shock load rate of 250 mm/min or greater has been suggested by ASTM draft standard WK4863.


	Specimen	Permanent deformation (mm)

	2.1	0.5
	2.2	0.5
	2.3	0.4
	2.4	0.3
	2.5	0.3
	2.6	0.4
	Mean	0.45
	Std. dev.	0.09

The mean permanent height loss for the specimens was 0.45 mm or 3.2%. The permanent deformation of the implant constrained within an annulus model is less than 4%.

In vivo, the lumbar discs encounter both static and dynamic loading. Conducting static testing is essential in understanding the creep and recovery behavior of the implant under a constant load.

1) Specimens were loaded compression to 100N to measure the reference height and then unload.

2) Specimens were loaded in compression to 600N and held continuously for 16 hours.

3) A load of 100N was applied to measure the height following static creep

4) Specimen was unloaded for 8 hours for recovery.

5) 100N load was reapplied to measure the recovery and permanent deformation from that measured instep 1.

6) Steps 1 to 5 was repeated.

This test was performed because a 600N load over 16 hours is approximately equivalent to a person standing continuously for 16 hours.

The loading regime of the specimens aimed to simulate a person standing continuously for two 16 hour periods followed by 8 hours of rest over 48 hour period. At the first 600N compression load all specimens crept less than 0.2 mm over the 16 hour period which is equivalent to less than 1.5% height loss. At the second 600N load all test specimens crept less that 0.2 mm, again equivalent to less than 1.5% height loss.

The specimens were also subjected to a 100N reference height before the commencement of testing. The 100N load was also applied before and after the 8 hour no load (rest periods). In average height loss at 100N load at the end of testing was 0.2 mm when compared to the reference height. The maximum height loss at 100N load occurred after the second 600N loading period and it showed the height loss at this load was approximately 0.3 mm when comparing to the reference height.

This indicates the implant looses minimal height after constant static loading. The static creep of the implant constrained within an artificial annulus model creeps less than 2% over a 16 hour period.

Other nucleus replacement prostheses, mainly hydrogels require fluid absorption to form the required dimensional characteristics and thus swelling tests are essential in the mechanical characterization process. The implant is not made from a hydro-expanding material. It allows water molecules to pass through, therefore this test was not considered necessary. It was included in this protocol for completeness and to verify the above claim.

Specimens were dried in an oven at temperatures above 100 degrees for a minimum of 4 hours.

1) Specimens were placed within a swell test jig with a plastic plate placed on top.

2) The jig was then filled with Ringer's solution.

3) A LVDT transducer was used to measure the height change over a 48 hour period.


	Max. sensor	Min. sensor	Fluctuation	Height Change
	deflection	deflection	Range	after 48 hours
Specimen	(mm)	(mm)	(mm)	(mm)

1	0.02	−0.02	0.04	−0.01
2	0.01	−0.01	0.02	0.01
3	0.01	0.00	0.01	0.01
4	0.00	−0.02	0.02	−0.01
5	0.00	−0.03	0.03	−0.02
6	0.00	−0.02	0.02	−0.01
Mean	0.01	−0.02	0.02	−0.01
Std. dev.	0.01	0.01	0.01	0.01

The results the mean height change after 48 hours soaking in Ringer's Solution was 0 mm. The maximum change in height occurred onspecimen 5 with a 0.03 mm. The results indicate that the CDD is not affected by swelling through fluid absorption as opposed to hydrogels.

Previous clinical studies of other prostheses have raised concern with extrusion of the device. Therefore, it is important to evaluate the risk of extrusion with the CDD. The proposed surgical procedure used to implant the CDD is through the creation of an annulotomy. Therefore this extrusion test will be done on a similar sized annulotomy in an artificial annulus model (this being the worst case opening in the annulus). Because of the characteristics of the implant, it is doesn't really lend itself to extrusion. This test was performed for completeness and no extrusion of any kind or severity was expected.

The implant was partially filled to a volume between 1.5 to 2 ml inside the annulus cavity to represent a worse case scenario since it was believed that partially filled CDD specimens have a greater chance of extrusion due to their relative size to the annulotomy opening.

- 1) Specimens were fatigue loaded for 200,000 compression cycles under the following conditions:
  - Compression
    - Load range: 600N to 2000N
    - Frequency: 2 Hz
  - Flexion/Extension
    - +6/−3° Frequency: 1 Hz
    - Frequency: 1 Hz

Partially filled implants (30 to 50% fill) were subjected to fatigue testing in compression and flexion/extension. The position of the annulotomy was positioned such that the annulotomy underwent tension during the flexion cycle. During this cycle the implant and the encompassing annulus model are flexed to 6 degrees. This accompanied with the compression cycles subjected the implant to conditions that would induce expulsion. After 200,000 cycles no expulsions or protrusions were observed in any of the test specimens. Detachment between the superior section of the annulus and the stainless steel test platen occurred in

specimens

3 and 4 after the 200,000 cycles.

A partially filled implant (30 to 50% fill) was chosen as a smaller sample would more likely extrude than a fully filled CDD as the size of the annulotomy remained the same. Also the implant was inflated through the annulotomy and hence the proximal end of the implant sits at the inner edge of the annulotomy. In addition to this test, no expulsions were observed during the fatigue test in which the implant was subjected to multi directional testing to 10 years equivalent with an annulotomy present. From the literature expulsion studies have been conducted using cadaveric models. This test was performed in an artificial annulus model as it would allow testing to be conducted to 200,000 cycles which would otherwise not be possible in a cadaveric test model due to tissue degeneration.

No expulsions or protrusions were observed for all 6 test articles after 200,000 cycles hence the acceptance criteria were met. In addition no expulsions were observed during any point of the fatigue test.

Due to the viscoelastic nature of the implant, it is expected to creep under an applied load. This test aims to evaluate this. An implant specimen was filled into a 25.4 mm diameter cylindrical mould to approximately 10.5 mm in height.

1) The specimen was placed between delrin platens

2) The specimen was then subjected to a 253N (0.5 MPa) compression load for 16 hours.

3) Specimen was then unloaded (no load applied) for 8 hours to recovery.

4) Steps 2 and 3 were repeated a further three times such that the specimen was subjected to four 16 hour loading regimes over a four day per period.


	Time Point	Height Loss (%)

	End of first session	−3.47
	Start of 2^ndsession	−0.71
	End of 2^ndsession	−4.18
	Start of 3^rdsession	−1.10
	End of 3^rdsession	−4.44
	Start of 4^thsession	−1.69
	End of 4^thsession	−4.53

The results show a gradual decrease in height during the loading periods (approximately 3.5% per 16 hour period). During the 8 hour rest periods the specimen recovered approximately 80% of the height loss. During loading on the fourth day aspects of recovery was observed. The implant showed signs of permanent deformation and recovery after loading due to its viscoelastic properties.

Conducting mechanical tests on aged samples is critical in ensuring the mechanical performance of the implant is not compromised over time. Samples were aged using heat as proposed by the literature. The implants were aged using a 10 degree temperature acceleration method suggested by the literature. All specimens were subjected to 11 hours in a dry oven at 177° C. and then placed in a saline water bath for 46 days at 87° C. This subjected the specimens to 24 years equivalent worth of aging. It has been suggested that an increase of 10 degrees C. doubles the aging process. Therefore placing the samples to the above heating conditions will be equivalent to at least 24 years worth of aging.

Specimens were glued to the test platens and left to dry for 24 hours. The specimens and test platens were then connected to the spine simulator. The test stain was filled with calf serum and maintained at 37±3° C.

The test execution was as follows:

- 1) A compression load of 100N and 600N was applied and the heights or the specimens at these loads were measured. This height was taken as the reference heights
- 2) Specimens were cyclically loaded under the following conditions:
  - Compression
    - Load range:
      - 600N to 2000N for 10 000 cycles
      - 600N to 1500N for 990 000 cycles
    - Load frequency: 2 Hz
  - Flexion/Extension
    - Bending range: +6/−3°
    - Range frequency: 1 Hz
  - Lateral Bending
    - Bending Range: ±2°
    - Range frequency: 1 Hz
  - Axial Rotation
    - Bending Range: ±2°
    - Range frequency: 1 Hz
- 3) After the completion of the 1 million compression cycles a 100N and 600N load was reapplied to measure the height change.

All specimens were loaded to 100N and 600N and the heights measured at this load. After the specimens were subjected to cyclic load the 100N and 600N load was reapplied to measure the heights. These values were compared to the reference heights.


	Height loss at 100N	Height loss at 600N
Specimen	reference load	reference load

3.1	0.53	1.4
3.2	0.49	1.3
3.3	0.44	1.3
3.4	0.45	1.1
3.5	0.55	1.3
3.6	0.46	1.2
Mean	0.49	1.3
Std. dev.	0.1	0.1

The average height loss at the 100N and 600N reference loads was 0.49 mm and 1.3 mm, respectively. The height measurements after 1 million cycles showed the aged specimens performed better than the fatigue specimens in terms of height loss.

No cracks were observed on any of the specimens and aging does not have any serious adverse mechanical effects on the CDD.

Height maintenance is an important mechanical function in a nucleus replacement device. This test aims to evaluate the dynamic fatigue properties of the CDD constrained within an artificial annulus model.

The filler material (CSM-2186-14) was injected into the annulus cavity via a 4 mm annulotomy and left to cure for 24 hours.

1) Specimen was placed between the two delrin platens (seeFIG. 10.1)

2) Specimens were subjected to a 509N compressive load to reduce the creep affects.

3) The specimen was then subjected to a cyclic compression loading between 509N and 1730N at 2 Hz for 100,000 cycles.

The change in peak height during the cyclic loading and the change in height during the cyclic loading was measured.

The maximum and minimum height (at 509N and 1730N load respectively) of the samples was recorded for the predetermined cycles. A reduction in height during the 1 million cycles (dynamic creep) was evident in both samples where the greatest observable difference was recorded betweencycles 1 and 5,000. The rate of height loss (dynamic creep) plateaus out between cycles 5,000 to 100,000.

Cycling the specimens between 509N (0.5 MPa) and 1730N (1.7 MPa) is approximately equivalent to a person standing in a relaxed position to and lifting a 20 kg. Cycling the implant in this fashion is thus a gross over-exaggeration of what a person would encounter in everyday life however the aim was to test the lifecycle of the device in a worst case scenario at accelerated loading conditions and thus justified.

The dynamic creep of the CDD constrained within an annulus model over 100,000 cycles was less than 5%.

A finite element analysis of the implant was also performed, and the following items were observed from the model.

The implant is believed to restore the nucleotomy model to near-physiological axial displacement when the implant completely fills the nucleotomy volume. Data indicates that the implant axial displacement approaches the result provided by the intact model. In contrast to this, the untreated nucleotomy results in an abnormally low axial stiffness.

The extent of the nucleotomy relative to the nucleus volume does not have as pronounced effect on the axial stiffness when compared to the extent the implant fills the nucleotomy. This is apparent when the implant model (based on a finite element analysis) (100% filling of nucleotomy) is compared with the partial implant (see,FIG. 86). The partial implants and new inflation models (30%, 70%) do not show significant difference between each other. This phenomenon relies on the assumption that a void remains between the implant and the nucleotomy in the partial-fill implant.

In reference toFIGS. 3-7, when thenucleus pulposus18 has been removed, aresidue64 remains about the inner surface of the annulus fibrosis and on theend plates20 of the

vertebrae

12 and14. Thisresidue64 is of an irregular shape. Therefore, in charging theenvelope38 with thefiller material60, it is necessary to monitor the charging of thefiller material60 into theenvelope38. This is done by a sensing arrangement. In one embodiment, the sensing arrangement comprises apressure sensor66 at an inlet to theenvelope38. In another embodiment, the sensing arrangement comprises avolume sensor68 arranged at an outlet of thedispenser62 for monitoring the volume offiller material60 dispensed. The sensing arrangement:could, in addition or instead, be a flow rate sensor which monitors the rate of flow of thefiller material60.

Yet a further method of monitoring filling of theenvelope38 is monitoring back flow offiller material60 from between theenvelope38 and the distal end of thedelivery device40. As thefiller material60 oozes out it may loosen theenvelope38 allowing thedelivery device40 to be removed.

InFIGS. 43-76,reference numeral10 generally designates an intervertebral disc implant in accordance with various embodiments. Theimplant10 comprises anenvelope12 in which afiller material14 is received. Theimplant10 is intended for use in replacing a nucleus pulposus of anintervertebral disc16 arranged between

adjacent vertebrae

18,20. Generally, the procedure is formed in a minimally invasive manner as will be described in greater detail below. It will also be appreciated that the procedure may be conducted in a percutaneous manner as described herein and in greater detail below.

It will be appreciated that thedisc16 comprises anannulus22 circumscribing a nucleus pulposus. Theintervertebral disc implant10 is intended to replace a degenerate nucleus pulposus of thedisc16. Thus, theimplant10 is implanted after thedisc16 has undergone a nucleotomy to remove the nucleus pulposus.

In the embodiments illustrated inFIGS. 43 to 53, theenvelope12 of theimplant10 is of a stretchable and elastically deformable elastomeric material such as a silicone material.Various filler materials16 can be used with theenvelope12 in order to mimic as closely as possible the biomechanical actions of a natural, healthy nucleus pulposus.

In the embodiment shown inFIGS. 43a,43band43c, thefiller material14 comprisesbeads24 held in suspension in a curableelastomeric material26. Theelastomeric material26 is, once again, preferably a silicone material.

Thebeads24 are of a biocompatible material. Thus, for example, thebeads24 could be of a suitable biocompatible plastics material, a biocompatible metal material, a biocompatible ceramic material or suitable biological material such as proteoglycans. Thebeads24 may be homogenous in the sense that all the beads are of the same size and same material. Instead, thebeads24 may be of different sizes and different materials in order to obtain particular biomechanical characteristics for theimplant10.

In certain embodiments, the beads need not be spherical in shape. They could, instead, be any one of bullet shaped, polygonal, triangular, heart shaped, kidney shaped, ovoid, oblong, crescent shaped, cubic, elongated, conical, trapezoidal, prismatic irregular, or combinations thereof. In some aspects, a preferred shape is one which allows for convenient and unobstructed insertion. Thus, preferably, thebeads24 have radiussed corners and/or edges to minimise the risk of damaging theenvelope12.

The beads may range in size from 0.01 mm to 5 mm and, optimally, any size in order that thebeads24 can be introduced into the interior of theenvelope12 by an introducer.

In the embodiment shown inFIGS. 44a,44band44c, thefiller material14 comprises elongate, filamentary elements carried in suspension in thesilicone26. The filamentary elements are “string-like” elements which are, once again, of suitable biocompatible materials. The elements typically have lengths not exceeding 1 cm. Once again, the lengths of thefilamentary elements26 may all be the same or they may differ to obtain the desired biomechanical characteristics for theimplant10.

InFIGS. 45a,45band45c, thefiller material14 comprisesfibres30 in suspension in thesilicone26. Thefibres30 are, typically, of lengths less than 3 mm. As in the case of other disclosed embodiments, the fibres are made up of suitable biocompatible materials. Thefibres30 are selected either to all be of substantially the same material and lengths or they may be of different materials and of different lengths to obtain the desired biomechanical characteristics for theimplant10.

FIGS. 46a,46band46cillustrate certain embodiments in which thefiller material16 comprises spherical elements contained in theenvelope12. Thespherical elements32 are of suitable biocompatible materials such as biocompatible plastics, biocompatible metals, biocompatible ceramics or biological material. The spherical objects may be in a range of sizes not exceeding 3 mm to 4.5 mm (e.g., not exceeding 3, 3.25, 3.5, 3.75, 4, 4.25, 4.5, etc.) in order to be able to be introduced into the interior of theenvelope12 via an introducer as will be described in greater detail below.

Thespherical elements32 are typically provided in a range of sizes to provide compacted packing of thefiller material14 within the interior of theenvelope12 but still allowing compressive stresses on thedisc16 to be transmitted to theannulus22 of the disc.

InFIGS. 47a,47band47c, thefiller material14 comprises one or more lengths of string-like elements34. Eachelement34 may typically have a length less than 10 cm and a diameter less than 3.5 mm to 4 mm. Sufficient lengths ofelements34 are provided to pack the interior of theenvelope12 to provide the necessary weight bearing functions of theimplant10. Theseelements34 are, once again, of biocompatible material.

Referring now toFIGS. 48a,48band48c, thefiller material14 comprises a plurality of short lengths offibre36. Thefibres36 are, typically, about 2 to 3 mm long and are of biocompatible materials. Thefibres36 are packed into the interior of the envelope in a compacted state in order to impart the required biomechanical characteristics to theimplant10. Once again, thefibres36 may be of different materials and different lengths.

InFIGS. 49a,49band49c, thefiller material14 comprises a plurality of bottlebrush-like elements38. Thebottlebrush elements38 are of the form having a central spine with bristles projecting radially outwardly from the spine. The bristles are folded on to the spine for introduction into theenvelope12 via an introducer.

Once again, thebottlebrush elements38 are packed, in a compacted state, within an interior of theenvelope12 to impart the necessary biomechanical characteristics to theimplant10. Thebottlebrush elements38 may be of biocompatible plastics materials. In addition, the bottlebrush elements may be in the form of biocompatible metals/biocompatible plastics combinations. An example of this would be abottlebrush element38 having a metal spine with plastics bristles. Still further, thebottlebrush elements38 could be of all metal construction. Theelements38 typically have a length of less than about 1 cm, preferably about 5 mm. When the bristles are folded on to the spine for insertion into the introducer, theelement38 may have a diameter not greater than about 3.5 mm to 4 mm.

Once again, if desired, bottlebrush elements of mixed sizes and materials may be used together to impart the desired biomechanical characteristics to theimplant10.

Referring now toFIGS. 50a,50band50c, thefiller material14 comprises lengths of helical or coiledwires40. Thecoiled wires40 are packed, to be in a compacted state, in the interior of theenvelope12 in order to provide the necessary biomechanical characteristics. The coiled wires, in their relaxed state, may typically be less than about 1 cm in length, preferably, about 5 mm in length. Thewires40 may be of biocompatible plastics or biocompatible metals. As in the previous embodiments,wires40 of different lengths and different materials may be used together, if desired, in theimplant10.

In the embodiment shown inFIGS. 51a,51band51c, thefiller material14 comprises a plurality ofdiscrete bands42 of a resiliently flexible, biocompatible material arranged concentrically within theenvelope12 to form theimplant10. Thebands42 have a thickness not exceeding about 1 mm and a height not exceeding of about 9 mm.

Thefiller material14 in the embodiments illustrated inFIGS. 52a,52band52care made from a foamedmaterial44. The foamedmaterial44 is introduced, in a compressed state, via the introducer into the interior of theenvelope12. Once the introducer is withdrawn, the foamedmaterial44 expands to a relaxed state to cause theenvelope12 to conform to the volume in which it is placed. Typically, the foamedmaterial44 is a polymeric material such as a polyethylene.

InFIGS. 53a,53band53c, thefiller material14 is silicone oil having a viscosity of at least 500 cPs. This material exhibits surprisingly good biomechanical characteristics and mimics closely a natural, healthy nucleus pulposus of an intervertebral disc.

In the embodiments described above, as previously described, theenvelope12 is generally of a silicone material which has an elongation of up to 1000%. where it can expand elastically without plastically deforming. In certain circumstances, it may not be necessary to have the envelope have such extensive elongation and, if desired, the envelope could be made of other materials in appropriate circumstances, such as, for example, woven metal fibres such as stainless steel, nitinol, chrome cobalt, titanium, or the like, or combinations thereof. Instead, the envelope may be of a plastics material such as a polymeric material like polytetrafluoroethylene.

Further, in the embodiments described above, theimplant10 makes use of an envelope. In certain circumstances, theimplant10 may not require anenvelope12. In the embodiments illustrated inFIGS. 54 and 55, theinsert10 comprises anelongate element48 of a suitable resiliently flexible material, such as a silicone material. In this embodiment, theelement48 is inserted into the volume resulting after the nucleotomy has been performed on thedisc16 in an elongated state as shown inFIG. 54 of the drawings. Use of astylet50 maintains the elongate element in its extended state. When theelongate element48 is inserted into the volume, thestylet50 is withdrawn causing theelongate element48 to adopt the configuration shown inFIG. 55 in which theelement48 substantially fills the volume. In a similar embodiment to this, a plurality ofsuch elements48 are used, either side by side or one on top of the other in layers, to conform to the volume. In the latter case, theelements48 may, if desired, be inserted into an envelope (not shown).

FIGS. 56 and 57 show a similar embodiment ofimplant10 in which theimplant10 comprises a plurality of doughnut-like members52 interconnected serially to form animplantable element54. Once again, theimplantable element54 has astylet56 associated with it to aid implantation.

In a relaxed state, theimplantable element54 adopts the configuration shown inFIG. 57. Theimplantable element54 is implanted, in its first configuration, as shown inFIG. 56, into the volume of thedisc16. Withdrawal of thestylet56 causes theimplantable element54 to be compressed, as shown inFIG. 57, into a second configuration in which it conforms substantially to the volume of thedisc16.

Once again, in a similar manner to the embodiment described above with reference toFIGS. 54 and 55, a plurality of theimplantable elements54 may be used, either side by side or in layers to conform to the volume of thedisc16. In this case, theimplantable elements54 may be received in an envelope (not shown).

Referring now toFIGS. 58 and 59, yet a further embodiment of animplant10 is illustrated.

In this embodiment, theimplant10 comprises an elongateimplantable element58 which, optionally, has a stiffeningspine60. Theimplantable element58 is, typically, an elastomeric material such as, for example, silicone. Thespine60 is of a shape forming material or shape memory alloy such as nitinol.

Theimplantable element58 is inserted via an introducer into the volume of thedisc16. One or more lengths of theimplantable elements58 may be used to cause theimplantable elements58 to conform to the shape of the volume in order to function as a replacement nucleus pulposus of thedisc16.

InFIG. 60, an embodiment similar to that described above with reference toFIGS. 58 and 59 is illustrated. In this embodiment, theimplant10 comprises two, coiled implantable elements. Eachimplantable element62 has a coiled shaped in its relaxed state. This coiled shape may be imparted by a stiffening spine of shape forming alloy such as nitinol (not shown). Instead, theimplantable elements62 may be formed in such a manner that, in their relaxed state, they adopt a coiled configuration.

In this embodiment, theimplantable elements62 are straightened for introduction into the volume of thedisc16. Once in the volume, theimplantable elements62 coil in oppositely directed orientations substantially to fill the volume resulting from removal of the original nucleus pulposus of thedisc16.

InFIGS. 61 and 62, theimplant10 comprises a single,implantable element64. Theimplantable element64 is of an elastomeric material, such as silicone, and, in its relaxed states, is in a shape which will substantially conform to the volume of the disc into which theelement64 is to be imparted.

To aid in implantation of theelement64, a plurality ofcuts66 are made in the element. Thesecuts66 cause “hinges”68 to be formed about which the parts of the element on either side of thecut66 can hinge to straighten theelement64 to be implanted via an introducer into the vacated volume of thedisc16.

The embodiments of the implants shown inFIGS. 63 and 64 are similar to those shown inFIGS. 61 and 62. In the embodiment shown inFIG. 63 of the drawings, theimplant10 comprises a singleimplantable element70 formed into a snake-like configuration, in its relaxed state. Theimplantable element70 has a convex profile. The embodiment shown inFIG. 64 of the drawings is of a similar form with the distinction that animplantable element72 of theimplant10 of the embodiment shown inFIG. 64 has a concave profile. Once again, in both embodiments, the

implantable element

70,72 is extended into a straight configuration for implantation via an introducer. Once in the volume of thedisc16, the

implantable element

70,72 adopts its relaxed, illustrated configuration substantially to conform to the volume of thedisc16.

Yet a further embodiment of animplant10 is shown inFIGS. 65-67. Once again, with reference to the previous embodiments, like reference numerals refer to like parts, unless otherwise specified.

In this embodiment, an attachingformation74 of theenvelope12 is shown. It is to be understood that theenvelope12 of each of the embodiments described above also includes such an attaching formation. The attachingformation74 is used for attaching the envelope to an introducer76 (FIG. 74). The attachingformation74 is in the form of a filler tube. Thefiller tube74, in this embodiment, extends radially outwardly from the body of theenvelope12. A closure device in the form of a duck-billedvalve78 is arranged at a distal end of thefiller tube74. When theintroducer76 is inserted into thefiller tube74, it causes thevalve78 to open. Withdrawal of theintroducer76 from thefiller tube74 causes thevalve78 to close.

In this embodiment, theenvelope12 has anannular region80 of a reasonably rigid material. The material of theannular region80 is more rigid than material forming upper andlower members82 of a central part of theenvelope12. Theannular region80 of theenvelope12 bears against theannulus22 of thedisc16, in use. When thefiller material14 is charged into the interior of theenvelope12, themembers82 expand outwardly as shown by theupper member82 inFIG. 66 of the drawings to bear against the

vertebrae

18,20 and so cause theenvelope12 to conform substantially to the volume of thedisc16.

It is to be noted that bothmembers82 carry, on their outer surfaces, a layer oftissue ingrowth material84. Thematerial84 is, typically, a polyester material such as that sold under the registered trade mark Dacron.

Theannular region80 is of a substantially non-stretchable material while themembers82 are made to stretch and expand in volume. The material of theannular region80 is still sufficiently flexible to enable theenvelope12 to be collapsed to be inserted via an introducer into the vacated volume of thedisc16.

FIGS. 68-73 show various embodiments of amulti-chambered envelope12. As shown inFIG. 69, theenvelope12 has a plurality ofchambers86, each of which is fed by acollapsible delivery tube88. Eachdelivery tube88 has a valve (not shown) at its distal end. Filler material is introduced into each of thechambers86 of theenvelope12 via the associateddelivery tube88. Thus, filling of each of thechambers86 can occur independently. In addition, the filler material received in eachchamber86 may differ from the filler material received in anyother chamber86. Still further, certain of thechambers86 may, in certain circumstances, not have any filler material at all.

A sample of the construction of theenvelope12 is shown inFIGS. 71-73. Theenvelope12 has anupper member90 and alower member92 interconnected by a sidewall94. A plurality ofpartitions96 extend in the interior of theenvelope12 between theupper member90 and thelower member92. Thepartitions96 are configured to have strong compressive load bearing capabilities but to collapse in shear as shown inFIG. 73 of the drawings. Thus, for introduction of the envelope into the vacated volume of thedisc16, thepartitions96 are collapsed, as shown inFIG. 73 by moving the

members

90 and92 laterally relative to each other.

It will be appreciated that various other configurations ofmulti-chambered envelopes12 can be formed by using different materials for different chambers of the envelope and/or filling the various chambers withdifferent filler materials14, as described above.

InFIGS. 74 and 75, a system, in accordance with another embodiment, for implanting an intervertebral disc implant is shown and is illustrated generally by thereference numeral100. Thesystem10 comprises theimplant10 and anintroducer76. Theintroducer76 has an elongate tubular element102 on a distal end of which is received the attachingformation74 of theenvelope12. Anon-return valve78 is arranged at a distal end of the attachingformation74. In the embodiment illustrated inFIGS. 74 and 75, the filler material comprises theballs32 of the embodiment described above with reference toFIGS. 46a,46band46c.

Theannulus22 of thedisc16 is accessed percutaneously in a patient and an opening is made through theannulus22. The degenerate nucleus pulposus is removed using ablation, lasers or mechanical means to create a vacated volume. Theintroducer76 with theenvelope12 in a collapsed configuration on the distal end of the tubular member102 is inserted through the incision so that theenvelope12 is within the volume of thedisc16.

Filler material

14 is fed through the tubular member102 of theintroducer76 into the interior of theenvelope12 to cause theenvelope12 to expand to conform to the volume of thedisc16. In the embodiment shown inFIGS. 74 and 75, the filler material is fed through the introducer via an appropriate displacement mechanism, such as a pump (not shown). Once theenvelope12 has expanded to conform to the volume, charging offiller material14 into the interior of theenvelope12 ceases. The tubular member102 of theintroducer76 is withdrawn from the attachingformation74 of theenvelope12. Withdrawal of the tubular member102 causes thevalue78 to close inhibiting leakage of thefiller material14 from within theenvelope12.

It will be appreciated that theballs32 have been shown merely as one example of the type offiller material14 used with theintroducer76.Other filler materials14 having discrete elements are also able to be injected into theenvelope12 of theimplant10 using theintroducer76.

InFIG. 76, part of another embodiment of an introducer is illustrated. In this embodiment, the displacement mechanism for chargingfiller material14 into the interior of theenvelope12 comprises adisplaceable element104. Thedisplaceable element104 is a sleeve received within the tubular member102 of theintroducer76 and which is able to reciprocate relative to the tubular member102. An inner surface of thesleeve104 carries aratchet arrangement106. By reciprocating thesleeve104 relative to the tubular member102

filler material

14 can be fed along theintroducer76 into the interior of theenvelope12 by means of the ratchet arrangement. Theintroducer76 of the embodiment shown inFIG. 76 of the drawings is useful for introducing elongate elements into the interior of the envelope or, in certain circumstances, such as the embodiments shown inFIGS. 54-64 directly into the volume where no envelope is used. An example of animplant10 which would use theintroducer76 of the embodiment ofFIG. 76 is that shown inFIGS. 47a,47band47cas well as the embodiment shown inFIGS. 51a,51band51c.

It is to be noted that theimplant10 may be used to deliver bioactive substances to theannulus22 of theintervertebral disc16. The bioactive substances may be substances which induce cell growth and/or cell reproduction. Further, theimplant10 may be used as a drug delivery means for active and/or prophylactic treatment at the site of implantation. Substances to be delivered may include may include gene telomerase, proteins, cells, autologous chondrocytes and autologous bone marrow derived mesenchymal stem cells.

Hence, it is an advantage of certain embodiments, that an intervertebral disc implant is provided which can mimic the biomechanical characteristics of a natural, healthy nucleus fibrosis of an intervertebral disc. It is a particular advantage of certain embodiments that an implant and system are provided which enables the implant to be inserted in a minimally invasive manner thereby obviating the need for drastic surgery. By use of discrete elements for thefiller material14, the biomechanical properties of theimplant10 can be tailored to particular requirements as desired by a clinician.

The disc is a highly viscoelastic structure and this makes it a very efficient and effective shock absorbing unit. In a healthy disc, the NP is well hydrated with a very gel like consistency and under the various modes of loading, the NP is pressurised and deformed, directing the incident load radially onto the AF and end plates. This creates an intradiscal pressure and load transfer between adjacent vertebrae is facilitated as the AF fibers are maintained in tension from the hoop stresses which result from the intradiscal pressure. This cooperative mechanism between the NP and AF provides the disc with the ability to sustain compressive loads retain the separation required between the adjacent vertebrae and provides controlled movement. With the onset of disc degeneration, brought upon by age or injury, there is a disruption in the balance between the NP and AF resulting in a destabilization of the motion segment. Common parameters which are used to evaluate the mobility and stability of the motion segment are neutral zone (NZ) and range of motion (ROM). In disc degeneration, the NZ (or joint laxity) increases along with its ROM. As the disc degenerates and becomes dehydrated, the NP shrinks and the ability to act as a shock absorbing, energy dissipating mechanism is compromised. A shrinkage in the NP results in a loss in the intradiscal pressure which then alters the stress distribution through the disc and since the intradiscal pressure is lost, the hoop stresses are lost also. Without the hoop stresses, the annulus is not able to be maintained in a taught orientation, eventually leading to delamination and shearing of the annular layers. The loss in intradiscal pressure also creates an increased laxity in the joint and an increase in the joint laxity means that there is a greater range of motion from the neutral position that is unsupported and unresisted, indicating an increased level of instability in the segment, adding more stress on the posterior articulating elements and adjacent segments to sustain the loads.

As it can be shown in the kangaroo motion segment study, by implanting a nucleus prosthesis, more specifically, one of the prostheses disclosed herein into a degenerate disc or at least a nucleotomised disc, the NZ and ROM of the motion segment is capable of being restored to that of an intact disc.

Specifically, the objectives of this study were to evaluate the biomechanical properties of the device using a cadaveric kangaroo lumbar spine model. The specific research question was whether kinematic variables differ when treating a motion segment with nucleotomy or nucleotomy then implantation with the exemplary device?

Ten kangaroo spine lumbar motion segments (L3/L4 and L5/L6) with all musculature, ligamentous tissue and posterior elements removed were separated into two equal groups. All specimens were tested in an intact state (pretreatment) prior to undergoing either a nucleotomy (nucleotomy) or undergoing a nucleotomy with implantation of a conformable elastomeric NR device (such as the devices disclosed herein) and then retested. All samples where tested in lateral bending and flexion-extension on a custom built jig attached and tested at 3.4 deg/sec with loads of −1.4 Nm to 1.4 Nm. Kinematic data were collated from the load displacement curve included; Neutral Zone (NZ), Range of motion (ROM), and Hysteresis. NZ is defined as the range which the specimen displaces with zero loads; ROM is defined as range from the start position to the point of maximal displacement in a given direction; and Hysteresis is defined as the energy difference between loading and unloading cycles on a stress-strain curve.

Before and after treatment analysis was performed using the Student Paired t-test with alpha set at 0.05. Results were presented as median percentage change compared with control with 95% confidence intervals for difference of means.

In flexion-extension the ROM of the nucleotomy and implant group increased by 24% (CI 5% to 65%) and 12% (CI −6% to 30%) respectively when compared to pretreatment. The NZ in the nucleotomy and implant group increased by 124% (CI 20% to 202%) and 0.5% (CI 7% to 31%) respectively when compared to pretreatment. In lateral bending, the ROM of the nucleotomy and implant group increased by 35% (Cl 6% to 72%) and 5% (CI −22% to 42%) respectively when compared to pretreatment. The NZ in the nucleotomy and implant group increased by 69.8% (25% to 256%) and 0.5% (CI −28% to 33%) respectively when compared to pretreatment.

Accordingly, in this study, there was an increase in motion segment laxity after nucleotomy during sagital and coronal movements of flexion-extension and lateral bending, which is reversed with implantation of the exemplary device. The data suggests that the exemplary device can restore the biomechanical changes in a de-nucleated motion segment.

Additionally, an embodiment of the implant disclosed herein was implanted into a 41 year old male who presented with lower back pain for 4½ years following a work related injury in 2003. He subsequently underwent a posterior decompression surgery in 2005 which resulted in relief of pain for a brief time but then continued to complain of back pain which he rates at 9 out of 10 and bilateral leg pain. He had significant restriction of all activities of daily living and was taking high doses of narcotic analgesics to control his pain. He has no other medical co-morbidities nor does he have any ongoing legal issues related to his work injury. A physical examination revealed a cooperative, pleasant gentleman who overall has good balance and station. The movements of the thoracolumbar spine were painful and grossly restricted in the sagittal plane. Lower limb neurology was nearly normal. The straight leg raising test was positive on the right side.

An MRI scan of the LS spine showed degeneration of the L4-L5 disc. The adjacent discs appeared to be well hydrated. Radiographs of the lumbo-sacral spine showed normal alignment. The patient had no relief of symptoms following a whole range of non-operative treatment modalities, including physiotherapy and spinal injections. He was eventually considered for the procedure disclosed herein.

He underwent a partial nucleus replacement procedure on 27 Dec. 2007 and the immediate post-operative period was uneventful. At the six week mark after surgery, the patient had about an 80% reduction in his back pain and about a 90% reduction in his leg pain. He is presently undergoing physiotherapy to increase his activity levels and the narcotic analgesics are being tapered. The short term results have been very encouraging.

In one of the embodiments, a polymeric material, more specifically an elastomer, and preferably a silicone, of a particular hardness is used for a nucleus prosthesis. The hardness of the material may be in the range of 1-20 A or 21-40 A or 41-60 A or 61-80 A or greater than 81 A Shore Hardness, but preferably 25 A. Materials like silicones are well suited for a nucleus prosthesis application because it is a viscoelastic material which means it is capable of providing the shock absorbing requirements of the motion segment. Under a given load, the prosthesis deforms and is capable of distributing the applied load radially to evenly distribute the load across the endplate and to the annulus. This reduces the risk of the implant subsiding into the endplates and restores the intradiscal pressure which restores the hoop stresses to the annulus. More importantly, the nucleus prosthesis is elastically deformable. Thus, the application of force will cause the nucleus prosthesis to deform elastically so that, once the force has been removed, the prosthesis will return to its relaxed, undeformed state.

Therefore, some beneficial characteristics of the implant disclosed herein may include, for example, shock absorption, restore hoop stresses, provide required range of motion, restore biomechanics, within the required range of hardness (shore hardness) (less chance of implant subsidence), using same class of materials results in homogeneity, fast curing, substantially biocompatible, in mild to moderate disc degeneration the implant is not only load distributing but also load bearing, substantially silicone, silicone composites, polyurethane, cellulose, collagen based, elastin based.

It will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made to the inventions as shown in the embodiments without departing from the spirit or scope of the inventions as broadly described. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive.