US20050154462A1 - Laterally insertable artificial vertebral disk replacement implant with translating pivot point - Google Patents

Abstract

An implant that can be placed between two vertebrae using a lateral insertion method is described. The implant is characterized by having a first end plate and a second end plate with a hemi-cylindrical spacer extending from the second end plate. The hemi-cylindrical spacer fits within a socket on the first end plate and allows for pivotal or rotational motion and also for twisting motion.

Description

CLAIM OF PRIORITY
• This application claims priority under 35 USC 119 to U.S. Patent Application No. 60/526,724, filed on Dec. 2, 2003 and entitled “ARTIFICIAL VERTEBRAL DISK REPLACEMENT IMPLANT WITH TRANSLATING PIVOT POINT AND LATERAL IMPLANT METHOD,” which is hereby incorporated by reference.
CROSS-REFERENCE TO RELATED APPLICATIONS
• This application is related to U.S. Provisional Application No. 60/422,039, filed Oct. 29, 2002, entitled “ARTIFICIAL VERTEBRAL DISK REPLACEMENT IMPLANT WITH TRANSLATING PIVOT POINT AND METHOD,” U.S. patent application Ser. No. 10/684,668, filed Oct. 14, 2003, entitled “ARTIFICIAL VERTEBRAL DISK REPLACEMENT IMPLANT WITH CROSSBAR SPACER AND METHOD,” U.S. patent application Ser. No. 10/684,669, filed Oct. 14, 2003, entitled “ARTIFICIAL VERTEBRAL DISK REPLACEMENT IMPLANT WITH TRANSLATING PIVOT POINT AND METHOD,” U.S. Provisional Application No. 60/422,011, filed Oct. 29, 2002, entitled “TOOLS FOR IMPLANTING AN ARTIFICIAL VERTEBRAL DISK AND METHOD,” U.S. patent application Ser. No. 10/685,134, filed Oct. 14, 2003, entitled “TOOLS FOR IMPLANTING AN ARTIFICIAL VERTEBRAL DISK AND METHOD,” U.S. Provisional Application No. 60/422,022, filed Oct. 29, 2002, entitled “ARTIFICIAL VERTEBRAL DISK REPLACEMENT IMPLANT WITH A SPACER AND METHOD,” U.S. Provisional Application No. 60/422,021, filed Oct. 29, 2002, entitled “ARTIFICIAL VERTEBRAL DISK REPLACEMENT IMPLANT WITH CROSSBAR SPACER AND METHOD,” U.S. patent application Ser. No. 10/685,011, filed Oct. 14, 2003, entitled “ARTIFICIAL VERTEBRAL DISK REPLACEMENT IMPLANT WITH SPACER AND METHOD,” U.S. patent application Ser. No. ______, filed ______, entitled “METHOD OF LATERALLY INSERTING AN ARTIFICIAL VERTEBRAL DISK REPLACEMENT IMPLANT WITH TRANSLATING PIVOT POINT,” (KLYCD-05007US6), U.S. patent application Ser. No. ______, filed ______, entitled “LATERALLY INSERTABLE ARTIFICIAL VERTEBRAL DISK REPLACEMENT IMPLANT WITH A CROSSBAR SPACER,” (KLYCD-05008US6), U.S. patent application Ser. No. ______, filed ______, entitled “METHOD OF LATERALLY INSERTING AN ARTIFICIAL VERTEBRAL DISK REPLACEMENT IMPLANT WITH A CROSSBAR SPACER,” (KLYCD-05008US7), U.S. patent application Ser. No. ______, filed ______, entitled “LATERALLY INSERTABLE ARTIFICIAL VERTEBRAL DISK REPLACEMENT IMPLANT WITH A SPACER,” (KLYCD-05010US4), U.S. patent application Ser. No. ______, filed ______, entitled “METHOD OF LATERALLY INSERTING AN ARTIFICIAL VERTEBRAL DISK REPLACEMENT IMPLANT WITH A SPACER,” (KLYCD-05010US5), all of which are incorporated herein by reference.
FIELD OF ART
• This field of art of this disclosure is directed to an artificial vertebral disk replacement and method.
BACKGROUND
• The spinal column is a biomechanical structure composed primarily of ligaments, muscles, vertebrae and intervertebral disks. The biomechanical functions of the spine include: (1) support of the body, which involves the transfer of the weight and the bending movements of the head, trunk and arms to the pelvis and legs, (2) complex physiological motion between these parts, and (3) protection of the spinal cord and nerve roots.
• As the present society ages, it is anticipated that there will be an increase in adverse spinal conditions which are characteristic of aging. For example, with aging comes an increase in spinal stenosis (including, but not limited to, central canal and lateral stenosis), and facet joint degeneration. Spinal stenosis typically results from the thickening of the bones that make up the spinal column and is characterized by a reduction in the available space for the passage of blood vessels and nerves. Facet joint degeneration results from the constant load borne by the facet joints, and the eventual wear that results. Pain associated with both conditions can be relieved by medication and/or surgery.
• In addition, to spinal stenosis, and facet joint degeneration, the incidence of damage to the intervertebral disks is also common. The primary purpose of the intervertebral disk is to act as a shock absorber. The disk is constructed of an inner gel-like structure, the nucleus pulposus (the nucleus), and an outer rigid structure comprised of collagen fibers, the annulus fibrosus (the annulus). At birth, the disk is 80% water, and then gradually diminishes with time, becoming stiff. With age, disks may degenerate, and bulge, thin, herniate, or ossify. Additionally, damage to disks may occur as a result disease, trauma or injury to the spine.
• The damage to disks may call for a range of restorative procedures. If the damage is not extensive, repair may be indicated, while extensive damage may indicate full replacement. Regarding the evolution of restoration of damage to intervertebral disks, rigid fixation procedures resulting in fusion are still the most commonly performed surgical intervention. However, trends suggest a move away from such procedures. Currently, areas evolving to address the shortcomings of fusion for remediation of disk damage include technologies and procedures that preserve or repair the annulus, that replace or repair the nucleus, and that advance implants for total disk replacement. The trend away from fusion is driven both by issues concerning the quality of life for those suffering from damaged intervertebral disks, as well as responsible health care management. These issues drive the desire for procedures that are minimally invasive, can be tolerated by patients of all ages, especially seniors, and can be performed preferably on an out patient basis.
• Most recently, there has been an increased interest in total disk replacement technology. A number of artificial disks are beginning to appear in the medical device marketplace. These artificial disks vary greatly in shape, design and functionality. With these devices go tools and methods for insertion between vertebrae thereof.
• Accordingly, there is a need in the art for innovation in technologies and methods that advance the art in the area of minimally invasive intervertebral disk replacement. This not only enhances the quality of life for those suffering from the condition, but is responsive to the current needs of health care management.
BRIEF DESCRIPTION OF THE DRAWINGS
• FIG. 1A is a posterior view of an embodiment of the assembled implant of the invention.FIG. 1B is a cross-section of the device shown inFIG. 1A.FIG. 1C is a posterior view of two bottom plates of the implant of the embodiment of the invention.FIGS. 1D and 1E are posterior views of the embodiment of the implant of the invention shown inFIG. 1A illustrating the operation of the device in bending to the left and bending to the right, respectively.
• FIG. 2A is a side view of the implant ofFIG. 1A showing the implant in flexion.FIG. 2B is a side view of the implant showing the implant in extension.FIG. 2C is a partial cross-sectional view of a side view of the implant of an embodiment of the invention.FIG. 2D is a partial cross-sectional view of an alternative embodiment of the implant of the invention having a protuberance adjacent the socket.
• FIG. 3A is a top view of a portion of an embodiment of the assembled implant of the invention.FIG. 3B is a top view of an embodiment of the implant of the invention showing a rotation to the right.FIG. 3C is a top view of an embodiment of the implant of the invention showing a rotation to the left.
• FIG. 4A andFIG. 4B show perspective views of the first and second inner surfaces of the first end plate and the second end plate of an embodiment ofimplant100.
• FIG. 5A is a posterior view of the embodiment of the implant of the invention after being implanted between two vertebral bodies.FIG. 5B is a side view of the embodiment of the implant of the invention after being implanted between two vertebral bodies.
• FIG. 6A is a rear view of an alternate embodiment of the invention having two plates.FIG. 6B andFIG. 6C show perspective views of the first and second inner surfaces of the first end plate and the second end plate of an alternative embodiment ofimplant600.FIG. 6D is a cross sectional view of the embodiment shown inFIG. 6A.
• FIG. 7A is a top view of an embodiment of a cutting tool of the invention used to prepare the vertebral bodies for the implant.FIG. 7B is a side view of the embodiment of the cutting tool of the invention from the distal end.FIG. 7C is a distal end view of an embodiment of the cutting tool of the invention.
• FIG. 8A is a side view of an embodiment of the implant lateral insertion tool of the invention.FIG. 8B is a top view of the embodiment of the implant lateral insertion tool of the invention.FIG. 8C is a distal end view of the embodiment of the implant lateral insertion tool of the invention.FIG. 8D is a top view of an embodiment of the implant lateral insertion tool holding an embodiment of the implant.
• FIG. 9 is a block diagram illustrating the steps of a method for inserting the implant between vertebral bodies.
DETAILED DESCRIPTION
• The following description is presented to enable any person skilled in the art to make and use what is disclosed. Various modifications to the embodiments described will be readily apparent to those skilled in the art, and the principles defined herein can be applied to other embodiments and applications without departing from the spirit and scope of what is disclosed and defined by the appended claims. Thus, what is disclosed is not intended to be limited to the embodiments shown, but is to be accorded the widest scope consistent with the principles and features disclosed herein. To the extent necessary to achieve a complete understanding of what is disclosed herein, the specification and drawings of all patents and patent applications cited in this application are incorporated herein by reference.
• FIG. 1A shows an embodiment of theimplant100 having a four-piece configuration. The designations, “A” for anterior, “P” for posterior, “RL” for right lateral, and “LL” for left lateral are given in the drawings for spatial orientation. These designations give the relationship of all faces of embodiments of the disclosed intervertebral implant from the superior perspective; i.e. looking down the axis of the spine. Theimplant100 has apair131 of first end plates, orupper end plates110 that are configured to mate with a first vertebra. Theupper end plate110 ofimplant100 has a firstouter surface112 from which afirst keel114 extends with a first set ofteeth115. Additionally, theimplant100 has apair133 of second end plates, orlower end plates120 that are configured to mate with a second vertebra. Thelower end plate120 has a secondouter surface122 from which akeel124 extends with a second set ofteeth125. A pair of pivoting or articulating elements orspacers130 that are part of thepair133 oflower end plates120 acts as an articulating element, or spacer between thefirst end plate110 and thesecond end plate120 and facilitates pivotal or rotational and also twisting movement of thefirst end plate110 and thesecond end plate120, relative to each other. In the embodiments described, the pair of articulating elements, orspacers130 is curved or convex, as will be discussed in more detail below.
• Several configurations ofimplant100 are contemplated. For instance,FIG. 6A illustrates a posterior view of an alternate embodiment of the implant shown inFIG. 1A. Theimplant600 ofFIG. 6A is in the form of a two-piece implant600 having afirst end plate610 and asecond end plate620. The first end plate, orupper end plate610 is configured to mate with a first vertebra, and a second end plate, orlower end plate620 is configured to mate with a second vertebra. The firstinner surface616 of theupper end plate610 has a socket orfirst cavity636 formed therein. A pivoting or articulation element, orspacer630 is formed onsecond end plate620. Thespacer630 at least partially engages thefirst socket636, and facilitates pivotal or rotational and also twisting movement of thefirst end plate610 and thesecond end plate620, relative to each other. Thespacer630 andcorresponding socket636 are dimensioned so that they are hemi-cylindrical (FIG. 6D), while in another embodiment shown inFIG. 6B andFIG. 6C, the articulating element, orspacer630 andcorresponding socket636 are hemispherical.
• Theupper end plate610 ofimplant600 has a firstouter surface612 from which afirst keel614 extends with a first set ofteeth615. In one embodiment, whenimplant600 is inserted between vertebrae, thefirst keel614 extends longitudinally across the firstouter surface612, about perpendicular to the sagittal plane of the spine. In another embodiment, thefirst keel614 extends longitudinally only partially across the firstouter surface612, about perpendicular to the sagittal plane of the spine. Theteeth615 in the two embodiments with complete or partial extension of thekeel614 across the firstouter surface612 of theupper end plate610 point towards the left lateral face ofimplant600 when the embodiment is meant to be put into a slot in a vertebral body from the left lateral approach to the spine. This orientation is shown in the figures, and is particularly evident where thekeel614 is fully displayed, as inFIG. 1A andFIG. 6A, for example. Alternatively, theteeth615 point towards the right lateral face ofimplant600 when the embodiments are meant to be put into a slot in a vertebral body from the right lateral approach to the spine.
• The firstouter surface612 abuts the vertebral body when theimplant600 is implanted. Thefirst keel614 extends into the vertebral body to anchorimplant600 into position, and is perpendicular to the median sagittal plane of the spine, in which extension and flexion occur. Thefirst keel614 in this orientation offers substantial stability during extension and flexion for theimplant600 inserted between the vertebrae of a patient. Additionally, thefirst keel614 in this embodiment is preferably aligned with and supports the articulation ofimplant600. The firstinner surface616 withsocket636 at least partially engages thespacer630 of the implant and opposes thesecond end plate620. The firstinner surface616 can form a planar surface that is parallel to the firstouter surface612, or can form a planar surface that is not parallel to the firstouter surface612.
• Thelower end plate620 has a secondouter surface622 from which akeel624 extends with a second set ofteeth625. In one embodiment, whenimplant600 is inserted between vertebrae, thesecond keel624 is about perpendicular to the sagittal plane of the spine. As described above for the firstupper end plate610, in one embodiment, thesecond keel624 extends longitudinally across the secondouter surface622, while in another embodiment, thesecond keel624 extends longitudinally partially across the secondouter surface622. Theteeth625 in the two embodiments with complete or partial extension of thesecond keel624 across the secondouter surface622 of thelower end plate620 point towards the left lateral face ofimplant600 when the embodiment is meant to be put into a slot in a vertebral body from the left lateral approach to the spine. This orientation is shown in the figures, and is particularly evident where thesecond keel624 is fully displayed, as inFIG. 1A andFIG. 6A, for example. Alternatively, theteeth625 point towards the right lateral face ofimplant600 when the embodiments are meant to be put into a slot in a vertebral body from the right lateral approach to the spine.
• The secondouter surface622 abuts the vertebral body when theimplant600 is implanted. Thesecond keel624 extends into the vertebral body to anchorimplant600 into position, and is perpendicular to the median sagittal plane of the spine, in which extension and flexion occur. Thesecond keel624 in this orientation offers substantial stability during extension and flexion for theimplant600 inserted between the vertebrae of a patient. Additionally, thesecond keel624 in this embodiment is aligned with and supports the articulation ofimplant600. Thesecond end plate620 with secondinner surface626 having thespacer630 opposes thefirst end plate610 with firstinner surface616 havingsocket636. Thespacer630 of secondinner surface626 at least partially engagessocket636 of first upper surface. The secondinner surface626 can form a planar surface that is parallel to the secondouter surface622, or can form a planar surface that is not parallel to the secondouter surface622.
• The firstinner surface616 of thefirst end plate610 can be parallel to the secondinner surface626 of thesecond end plate620 when theimplant600 is assembled and is in a neutral position (i.e., the position where thefirst end plate610 has not rotated relative to the second end plate620). Alternatively, the firstinner surface616 of thefirst end plate610 can be non-parallel to the planar surface of the secondinner surface626 of thesecond end plate620 when theimplant600 is assembled and in a neutral position. This non-parallel orientation of thefirst end plate610 and thesecond end plate620 allows the plates to pivot to a greater degree with respect to each other. Additionally, factors such as the height and position of thespacer630, and the, can also be adjusted in order to increase the degree that thefirst end plate610 and thesecond end plate620 can pivot relative to each other. Other factors that effect the degree of movement of thefirst end plates110 or610 relative to thesecond end plates120 or620 forimplant100 orimplant600 will discussed below.
• Whenimplant600 is inserted between vertebrae the planar surfaces corresponding to the first and secondouter surfaces612,622 and the first and secondinner surfaces616,626 of the first andsecond end plates610,620 lie within, or substantially within, the axial plane of the body. Similarly, the first andsecond keels614,624 are aligned in the axial plane, or perpendicular to the sagittal plane of the vertebrae. The first andsecond keels614,624 extend into the vertebral bodies to anchorimplant600 into position, and are perpendicular to the median sagittal plane of the spine, in which extension and flexion occur. The first andsecond keels614,624 in this orientation offer substantial stability during extension and flexion forimplant600 inserted between the vertebrae of a patient. Additionally, the first andsecond keels614,624 in this embodiment are aligned with and support the axis of articulation ofimplant600 defined by an RL to LL orientation.
• The lateral orientation of the keels allow the implants to be inserted into the spine using a lateral approach as opposed to an anterior or posterior approach. The lateral approach is advantageous, because the spinal nerves in the spinal cavity are minimally undisturbed when the implants are inserted laterally into the spine. In comparison to a posterior insertion approach in which the spinal nerves can be substantially disturbed, the spinal nerves are bypassed and relatively undisturbed when the implant is inserted laterally between the vertebral bodies from the side of the spine. Although an anterior insertion approach has its benefits, the lateral insertion approach can allow the present implant and associated implantation tools, to be inserted into the spine with less disturbance of the patient's internal organs. This can translate into less time and risk associated with preparing the spine for insertion as well as inserting the implant itself into the spine. Further, the laterally oriented keels offer substantial stability to the vertebral bodies during extension, flexion and lateral bending of the spine.
• In the embodiment shown inFIG. 1A andFIG. 6A, the first andsecond keels114,124 and614,624 includeports148,152 and648,652, respectively, that facilitate bone ingrowth. For example, bone from the vertebral bodies can grow thorough theports148,152 and648,652, and aid in securing the first andsecond keels114,124 and614,624, and thereby for securingimplants100 and600 once inserted between vertebral bodies. In addition, surfaces defined by the first andsecond keels114,124 and614,624 and the first and secondouter surfaces112,122 and612,622 ofimplants100 and600 can be roughened in order to promote bone ingrowth into these defined surfaces ofimplants100 and600. In other embodiments theports148,152 and648,652, the first andsecond keels114,124 and614,624, and the first and secondouter surfaces112,122 and612,622 ofimplant600 can be coated with materials that promote bone growth such as for example bone morphogenic protein, BMP, or structural materials such as hyaluronic acid, HA, or other substance which promotes growth of bone relative to and into thekeels614,624,keel ports648,652, and other external surfaces of theimplant600.
• Further, a combination of the two embodiments shown inFIG. 1A andFIG. 6A can be used to create a three-piece implant as will also be appreciated by those of ordinary skill in the art. For example, thefirst end plate610 ofFIG. 6A with itssocket636 from a two-piece embodiment can be combined with twosecond end plates120 ofFIG. 1A from a four-piece embodiment to form an implant. Similarly, thesecond end plate620 withspacer630 of a two piece embodiment, such asFIG. 6A, can be combined with twofirst end plates110 from a four-piece design, such asFIG. 1A, to achieve an implant. The features described herein for an interspinous implant for lateral insertion between adjacent vertebrae are applicable to two-, three-, or four-piece embodiments. None of these configurations depart from the scope of the invention.
• FIG. 1B depicts thepair131 of first orupper end plates110 and thepair133 of second orlower end plates120 in cross-section. Each upper andlower end plate110,120 has akeel114,124 with a set ofteeth115,125. As forimplant600, different embodiments ofimplant100 may have complete or partial extension of the first andsecond keels114,124 across the first and secondouter surfaces112,122 of the upper andlower end plates110,120. Theteeth115,125 point towards the left lateral face ofimplant100 when the embodiment is meant to be put into a slot in a vertebral body from the left lateral approach to the spine, and alternatively, theteeth115,125 point towards the right lateral face ofimplant100 when the embodiments are meant to be put into a slot in a vertebral body from the right lateral approach to the spine.
• InFIG. 1B, thesocket136 formed in the firstinner surface116 offirst end plate110 has a firstelongated sidewall150, a corresponding second elongated sidewall152 (shown inFIG. 3B), anend wall154, and anopen end156. The open ends156 of each of thefirst end plates110 are oriented so that the open ends156 face each other. Each of the first andsecond end plates110,120 has afirst end138,141 and asecond end139,143. The ends139 of thefirst end plate110 face each other, as do theends143 of thesecond end plate120. Thelower plates120 each have an articulating element, orspacer130, which is convex and hemi-cylindrical, that engage thesocket136. The concave hemi-cylindricalinner surface135 of thesocket136 is sloped to allow thepair131 of first orupper end plates110 to easily slide, or rock, side-to-side on the articulating element, orspacer130 and slide, or ride, forward and backward with enough looseness of fit to allow for some twisting in order to emulate the motion of the vertebral bone and intervertebral disk tissue. This arrangement, thus, has a sliding or translating pivot point. It is evident fromFIG. 1B that the first andsecond keels114,124 are aligned with and support the axis of articulation of theupper end plate110 about thespacer130 for this embodiment. This axis of articulation is longitudinally oriented with respect to the vertebrae, or about perpendicular to the sagittal plane of the spine. The alignment of the first andsecond keels114,124 with the axis of articulation offers substantial stability during flexion and extension whenimplant100 is inserted between the vertebrae of a patient.
• As shown inFIG. 1C, the articulating element, orspacer130 has four sides: a firstelongated sidewall140, a secondelongated sidewall142, athird end wall143, and afourth end wall146. Thethird end wall144 is flush with theend143 of thelower end plate120 of the implant. Thethird end wall144 has aprofile height160 and thefourth end wall146 has aprofile height162. Comparing theprofile heights160,162 to each other at the same point on the secondinner surface126 of thesecond end plate120, the overall profile height of thethird end wall144 is greater than the fourth end wall146 (i.e.,160>162). Thus, it is evident that theupper surface135 ofsocket136 slopes downwardly from theend wall144 to theend wall146. Together spacers130 comprise an articulating element that has a high surface where thethird end walls144 abut each other and slope to a lower surface adjacent tofourth end walls146.
• InFIG. 1C, the edges of the articulating element orspacer130 are eased or rounded to allow for further range of motion of thepair131 ofupper end plates110 relative to thepair133 oflower end plates120. As will be appreciated by those of skill in the art, the overall height of thethird end wall144 and thefourth end wall146 can be equivalent while still having an effective thirdend wall height160 that is greater than the effective fourthend wall height162 due to the overall slope of the secondinner surface126. Alternatively, the overall height of thethird end wall144 and thefourth end wall146, can be different with thethird end wall144 having a height greater than thefourth end wall146, thus eliminating the need for the secondinner surface126 to have a slope or further increasing the net difference between the height of the third end wall and the forth end wall. Further, although thespacer130 is depicted such that thethird end wall144 is flush with thesecond end143, those of skill in the art will appreciate that thespacer130 could also be configured such that thethird end wall144 is recessed relative to theend143 of the second end plate. In such a configuration, thethird end wall144 and theend143 would not be flush.
• FIGS. 1D and 1E illustrate posterior views of theimplant100 showing the clearance for left and right lateral bending. Typically, left and right lateral bending ranges from 3-5°. As evident from these figures, the length of thespacer130 can be less than the length of thesocket136. As shown, the open ends156 of the sockets facilitate movement of the articulating elements, orspacers130 within thesocket136 to accommodate side-bending movement.
• FIG. 2A andFIG. 2B are views of theintervertebral implant100, which depict the motion of thefirst end plate110 relative to thesecond end plate120. InFIG. 2A andFIG. 2B, a side view ofimplant100 is depicted, showingfirst end plate110 withsocket136 and thesecond end plate120 with the articulating element orspacer130. As is apparent from the figures, the sloping of the firstinner surface116 of thefirst end plate110 facilitates rotation of the spacer and socket in an anterior A direction and a posterior P direction. As depicted, the firstinner surface116 slopes from a high point at about where the socket is located to low points at theends111 and113 of theupper end plate110. As shown inFIG. 2A, theimplant100 is positioned to achieve flexion (i.e., forward bending) in a range up to about 15°, but more preferably 10°, while inFIG. 2B, theimplant100 is positioned to achieve extension (i.e., backward bending) in a preferable range of up to about 5°.
• FIG. 2C andFIG. 2D show cross sections ofimplant100 through the sagittal plane of the vertebrae.FIG. 2C is a cross-section of the side view of theintervertebral implant100 showing the mating of thespacer130 to thesocket136.FIG. 2D illustrates an alternate embodiment of thefirst end plate110 wherein thesocket136 hasridges268,269 forming a protuberance that extends into thechannel264,265 respectively on thesecond end plate120. As will be appreciated by those of skill in the art, theprotuberances268,269 can extend partially into the channel, such as the configuration shown, or can have a channel conforming shape such that when the spacer and socket are moved to achieveflexion272 or extension274 the protuberance orridge268,269 extends into thechannels264,265. This embodiment allows the firstinner surface116 and secondinner surface126 of thefirst end plate110 and thesecond end plate120 to be flat and non-sloping as shown while still allowing for the implant to emulate forward and backward bending and allow for the blocking of the motion of the socket relative to the spacer. In this embodiment, it is noted that the first andsecond keels114,124 are aligned with and support the articulation offirst end plate110 about thespacer130 for this embodiment, and where the articulation is about perpendicular to the sagittal plane of the spine.
• Turning now toFIG. 3A, a top view of one-half of theintervertebral implant100 is shown. Each of the topfirst end plate110 and the bottomsecond end plate120 have abores376 for receiving pins of an implant tool. Thefirst keel114 on thefirst end plate110 is positioned so that it is aligned in the same plane with thesecond keel124 on thesecond end plate120. Additionally, the length ofspacer130 from thethird end wall144 to thefourth end wall146 is shorter than the length of thesocket136 from theend wall154 to theopen end156, so that the fit of the spacer with the socket is somewhat loose. The loose fit of thespacer130 in thesocket136 allows thefirst end plate110 to be able to twist somewhat relative to thesecond plate120. This twisting action would generally be about an axis that is perpendicular to the first and secondinner surfaces116,126 of the first andsecond end plates110,120, respectively. Thus,implant100 of this embodiment allows the spine to have movement in three orthogonal degrees of freedom, namely (1) forward and backward bending movement, (2) lateral side-to-side bending, and (3) twisting movement.FIGS. 3B and 3C show the relative rotation of the first orupper end plate110 to the second orlower end plate120 to achieve rotation about acentral axis378. This rotation results in about a 3°-6° rotation about the axis (i.e., 3° of torso twisting in each direction).
• FIG. 4A andFIG. 4B show views of the first and second end plates,110,120.FIG. 4A shows a perspective view of asecond end plate120 of theintervertebral implant100. The secondinner surface126 of thesecond end plate120 is shown with a hemi-cylindrical spacer130 formed therefrom, and channels orgrooves264,265 extending about thespacer130. As illustrated inFIG. 4A, thechannels264,265 are formed on two sides of thespacer130. However, as will be appreciated by those of skill in the art, thechannels264,265 can alternatively surround thespacer130. The channels allow the sides of thespacer130 to be made more perpendicular so as to create a greater blocking wall thus preventing the socket of theupper plate100 from moving too much anteriorly or posteriorly relative to thelower plate120.FIG. 4B shows a perspective view of thefirst end plate110, with a firstinner surface116 that opposes the secondinner surface126. The firstinner surface116 has a hemi-cylindrical socket136 formed therein. Thesocket136 ofFIG. 4B is configured to mate with thespacer130 ofFIG. 4A.
• FIG. 4candFIG. 4dshow views of the first and second end plates,110,120 for an alternative embodiment ofimplant100.FIG. 4cshows a perspective view of an embodiment of the secondinner surface126 of the second orlower end plate120 ofimplant100. The secondinner surface126 of thelower end plate120 has ahemispherical spacer130 formed therefrom.FIG. 4dshows a perspective view of an embodiment of the firstinner surface116 of the first orupper end plate110 ofimplant100, which opposes the secondinner surface126. The firstinner surface116 of theupper end plate110 has a socket orcavity136 formed therein. In the embodiment ofFIG. 4d, thesocket136 has a concave hemispherical surface. Thesocket136 allows thefirst end plate110 to pivot or rotate onspacer130.
• In the embodiments shown inFIG. 4A andFIG. 4B, it is noted that the first andsecond keels114,124 are aligned with and support the articulation of thefirst end plate110 about thespacer130, relative to thesecond end plate120. The first andsecond keels114,124 in this orientation offer substantial stability during extension and flexion forimplant100 inserted between the vertebrae of a patient. Additionally, the first andsecond keels114,124 in these embodiments are aligned with and support the lateral axis of articulation ofimplant100, which is perpendicular to the sagittal plane of the spine. Additionally, as evidenced from the perspective views ofFIG. 4A andFIG. 4B, the perimeter shape of the upper andlower end plates110,120 can be configured to correspond to the perimeter shape of a vertebral disk. As will be appreciated by those of ordinary skill in the art, the perimeter shape of theupper end plate110 and thelower end plate120 can be the same.
• FIG. 5A andFIG. 5B show the implant after insertion between the vertebrae of a patient.FIG. 5A illustrates a posterior view of the implant shown inFIG. 1A implanted between vertebral bodies in a spine.FIG. 5A illustrates thespinal column500 and the cauda equina504 (a collection of lumbar and sacral nerve roots that fill the caudal end of the spinal cord) withindividual nerves506 exiting the cord between lumbar vertebrae. Theimplant100 is positioned between twovertebral bodies520,521 such that the first andsecond keels114,124 lie in a plane parallel to coronal or frontal plane of the body, or perpendicular to the sagittal plane of the vertebrae.FIG. 5B illustrates a side view of the implant inserted betweenvertebral bodies520,521, for embodiments of the implant as that shown inFIG. 1A, orFIG. 6A. The gap between thefirst end plate110 and thesecond end plate120 at the anterior “A” face ofimplants100,600 is greater than at the posterior “P” face ofimplants100,600. The greater gap at the anterior face vs. the posterior face ofimplants100,600 results in the flexion (forward bending) movement being facilitated to a greater degree than extension (backward bending) movement. Thus, for these embodiments, an example of a forward bending movement of up to 10° can be achieved while a backward bending movement of 5° will be achieved. These embodiments showimplants100,600 inserted between two vertebrae with twofirst keels114 extending from thefirst end plate110, and twosecond keels124 extending from thesecond end plate120. The first andsecond keels114,124 are about perpendicular to the sagittal plane of the spine, and support the articulation of thefirst end plate110 relative to thesecond end plate120, about thespacer130.
• The embodiments ofimplants100,600 can be made of medical grade titanium, stainless steel or cobalt chrome. Other materials that have appropriate structural strength and that are suitable for implantation into a patient can also be used.
• One class of materials contemplated for use inimplant100 is the class of biocompatible polymers. Copolymers, blends and composites of polymers are also contemplated for fabrication of parts of the disclosed device. A copolymer is a polymer derived from more than one species of monomer. A polymer composite is a heterogeneous combination of two or more materials, wherein the constituents are not miscible, and therefore exhibit an interface between one another. A polymer blend is a macroscopically homogeneous mixture of two or more different species of polymer.
• One group of biocompatible polymers are the polyaryl ester ketones which has several members, which include polyetheretherketone (PEEK), and polyetherketoneketone (PEKK). PEEK has proven as a durable material for implants, as well as meeting criteria of biocompatibility. Medical grade PEEK is available from Victrex Corporation under the product name PEEK-OPTIMA. Medical grade PEKK is available from Oxford Performance Materials under the name OXPEKK, and also from CoorsTek under the name BioPEKK. Still another interesting group of biocompatible polymers are polyalkyl biocompatible polymers, such as polyethylenes, polypropylenes, and the like.
• These medical grade biocompatible polymers are also available as reinforced polymer materials. To reinforce a polymeric material, fillers, are added to a polymer, copolymer, polymer blend, or polymer composite. Fillers are added to modify properties, such as mechanical, optical, and thermal properties. In this case, fillers, such as carbon fibers, are added to reinforce the polymers mechanically to enhance strength for certain uses, such as load bearing devices.
• In addition to disclosure of embodiments of an intervertebral implant, tools for preparing and inserting an intervertebral implant are also disclosed.FIG. 7A through 7D show an embodiment of a tool for preparing vertebral bodies to receiveimplants100,600, whileFIG. 8A throughFIG. 8D show an embodiment of a tool for inserting embodiments of the disclosedintervertebral implants100,600.
• FIG. 7A throughFIG. 7C are the top view, the side view, and an end view of thecutting tool700. Thecutting tool700 has ahandle710 at its proximal end for controlling the tool during operation. As will be appreciated by those of skill in the art, thehandle710 can be removable or affixed to the cutting end. Thedistal end702 of thetool700 is solid head has anupper surface705, and alower surface706. Theupper surface705 has afirst blade712 mounted thereon, and thelower surface706 has asecond blade714 mounted thereon. Preferably thefirst blade712 is about centered with theupper surface705, and thesecond blade714 is about centered with thelower surface706. The first andsecond blades712,714 are oriented to cut a space in a first and second intervertebral body for the first andsecond keels114,124 ofimplants100,600. The space is perpendicular to the sagittal plane of the vertebrae, and allows for the lateral insertion of theimplants100,600.FIG. 7C is a view of the distal end of thecutting tool700 showing thebeveled end716 and the first andsecond blades712,714. The height h of thehead702 of thecutting tool700 approximates the distance between two vertebral bodies or the height of the disk space. In this embodiment of cuttingtool700, theblades712,714 extend above and below thehead702.
• As will be appreciated by those of skill in the art, the tool shown inFIG. 7A can be modified such that instead of cutting keel-receiving channels in the upper and lower vertebral bodies at the same time, two tools are provided so that only one vertebral body is cut for keel-receiving channels at a time. For example, an alternative embodiment of cuttingtool700 has a first tool with a single blade mounted on thehead702. A second tool could be provided having a single blade mounted on thehead702, and additionally on the opposing surface, a guide. The guide on the surface opposite the surface with the blade is designed to engage with the first keel receiving channel cut the first vertebrae with the first tool to ensure that the second cut is optimally aligned with the first cut.
• FIG. 8A throughFIG. 8D depict an embodiment of the implanting tool used to insert theimplant600 ofFIG. 6A between vertebral bodies.FIG. 8A is a side view of theimplantation tool800 that has ahandle810 and animplant holder820. Theimplant holder820 has animplant conforming surface824 and fourpins822 for holding thefirst end plate610 and thesecond end plate620implant600. The conformingsurface824 is curved to follow the convex outer LL edges of the first andsecond end plates610,620, respectively, for an implant inserted from the left lateral side of a patient. Theimplant600 nests within a conformingsurface824 and is held bypins822.FIG. 8C shows the distal view of the end of the tool with fourpins822 for securing the first and second end plate of the implant.
• A variety of kits can be assembled that include an implant100 (or600) sized for a particular patient. The kit could also includeseveral cutting tools700 and several implantingtools800 or a single handle that cooperates with cutting ends702 and implantation ends820.
• FIG. 9 is a block diagram showing the basic steps of the method for laterally inserting the embodiments ofimplants100,600. First the spine is exposed through alateral access910, then the intervertebral disk is removed laterally920, if necessary. A tool, such as the one depicted inFIG. 7A is inserted laterally between the vertebral bodies to create channels in the bodies to receive the keels of the implant. The implant is then inserted laterally930 between two vertebrae and the wound is closed940. This procedure can be followed for either a left lateral approach or right lateral approach. For a left lateral approach, theteeth115,125 of upper andlower keels114,124 would be pointed towards the left lateral face of the device in order to aid in retaining embodiments ofimplants100,600 in place. For a right lateral approach, the teeth would point towards the right lateral face of the device.
• What has been disclosed herein has been provided for the purposes of illustration and description. It is not intended to be exhaustive or to limit what is disclosed to the precise forms described. Many modifications and variations will be apparent to the practitioner skilled in the art. What is disclosed was chosen and described in order to best explain the principles and practical application of the embodiments described herein, thereby enabling others skilled in the art to understand the various embodiments and various modifications that are suited to the particular use contemplated. It is intended that the scope of what is disclosed be defined by the following claims and their equivalence.

Claims (27)

1. An intervertebral implant comprising:

a first end plate with a first inner surface;

a second end plate with a second inner surface opposing the first inner surface, where the second inner surface has an articulating element formed thereon; and

an attachment mechanism adapted to engage a vertebral body, wherein the attachment mechanism is adapted to extend, when implanted, along a lateral direction with respect to the vertebral body.

2. The implant ofclaim 1 wherein the articulating element allows movement of the vertebral body in between flexion to extension directions.

3. The implant ofclaim 1 wherein the attachment mechanism is aligned with and supports the articulating element.

4. The implant ofclaim 1 wherein the articulating element further comprises an elongated hemi-cylindrical structure protruding from the second inner surface and an elongated cavity in the first inner surface adapted to receive the hemi-cylindrical structure.

5. The implant ofclaim 1 wherein the attachment mechanism is a keel upstanding from at least one of the first end plate and the second end plate.

6. An intervertebral implant comprising:

a first end plate adapted to mate with a first vertebral body further comprising:

a first inner surface;

a first outer surface; and

at least one keel on the first outer surface, wherein the keel is adapted to be perpendicular to a sagittal plane of the first vertebral body when implanted thereto;

a second end plate adapted to mate with a second vertebral body further comprising;

a second inner surface opposing the first inner surface, wherein the second inner surface has a spacer coupled thereto; and

a second outer surface.

7. The implant ofclaim 6 wherein the spacer allows bending from flexion to extension.

8. The implant ofclaim 6, where the keel is aligned with and supports the spacer.

9. The implant ofclaim 6, further comprising at least one keel on the second outer surface, wherein the keel is oriented perpendicular to the sagittal plane when implanted to a second vertebral body.

10. The implant ofclaim 9 wherein the keel is supports the spacer.

11. An intervertebral implant comprising:

a first end plate adapted to mate with a first vertebral body further comprising:

a first inner surface;

a first outer surface; and

at least one keel on the first outer surface, where the keel is adapted to be perpendicular to the sagittal plane of the vertebrae when implanted thereto;

a second end plate adapted to mate a second vertebrae, comprising:

a second inner surface opposing the first inner surface, where the second inner surface has extending spacer therefrom;

a second outer surface; and

at least one keel on the second outer surface, where the keel is adapted to be perpendicular to the sagittal plane of the vertebral body when implanted thereto.

12. The intervertebral implant ofclaim 11 wherein the spacer allows bending from flexion to extension.

13. The intervertebral implant ofclaim 11 wherein the keels on the first outer surface and the second outer surface support the spacer.

14. The intervertebral implant ofclaim 11 wherein the first end plate and second end plate have a lateral dimension longer than an anterior-posterior dimension.

15. An interspinous disk replacement implant adatped to be inserted between adjacent vertebral bodies, the implant having a first end plate, a second end plate, and an articulating element formed on the second end plate, the improvement comprising the implant having at least one keel that is about perpendicular to the sagittal plane of a vertebral body.

16. The implant ofclaim 15 wherein the articulating element is hemi-cylindrical.

17. An interspinous disk replacement implant adapted to be inserted between adjacent vertebral bodies, the implant having an articulating unit with a first end plate having a first inner surface with a first socket therein, a second end plate having a second inner surface opposing the first inner surface, the second inner surface with an articulating element formed thereon, where the articulating element is at least partially received in the first socket, the improvement of the implant comprising the implant having at least one keel extending from the articulating unit that is about perpendicular to the sagittal plane of a vertebral body.

18. The implant ofclaim 17 wherein the articulating element is hemi-cylindrical.

19. An interspinous disk replacement implant having a first end plate, a second end plate, and an articulating element between formed on the second end plate, the improvement comprising the implant having an attachment mechanism that supports the articulating element, the attachment mechanism adapted to laterally engage an adjacent vertebrae.

20. The implant ofclaim 19 wherein the attachment mechanism is at least one keel.

21. The implant ofclaim 19 wherein the articulating element is hemi-cylindrical.

22. An interspinous disk replacement implant having an articulating unit with a first end plate having a first inner surface with a first socket therein, a second end plate having a second inner surface opposing the first inner surface, the second inner surface with an articulating element formed thereon, where the articulating element is at least partially received in the first socket, the improvement of the implant comprising the implant having an attachment mechanism is aligned with and supports the articulating element, the attachment mechanism adapted to laterally engage an adjacent vertebrae.

23. The implant ofclaim 22 wherein the attachment mechanism is at least one keel.

24. The implant ofclaim 22 wherein the articulating element is hemi-cylindrical.

25. A kit to insert an interspinous disk replacement implant in a spine, the kit comprising:

an interspinous disk replacement implant adapted for lateral insertion into the spine; and

at least one tool for preparing the spine to receive the implant.

26. An interspinious implant comprising:

a first end plate having a first anterior end, a first posterior end and two first lateral ends extending between the first anterior and posterior ends;

a second end plate having a second anterior end, a second posterior end and two second lateral ends extending between the second anterior and posterior ends;

a spacer extending from the second end plate, the spacer having an elongated hemi-cylindrical configuration;

a first keel protruding from a first outer surface of the first end plate, wherein the first keel is oriented lengthwise between the two first lateral ends; and

a second keel protruding from a second outer surface of the second end plate, wherein the second keel is oriented lengthweise between the two second lateral ends.

27. An interspinous implant adapted to be inserted between adjacent vertebral bodies comprising:

an implant body having a first outer surface adapted to mate with a first vertebral body and a second outer surface adapted to mate with a second vertebral body;

an articulating element within the implant body, the articulating element having an elongated spacer and corresponding elongated socket;

a first keel protruding from the first outer surface and oriented generally parallel to the articulating element.

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