US20080228192A1 - Cannula - Google Patents

Abstract

A bone cement cannula, the cannula comprising: a tube including a section adapted for plastic deformation; and a lumen in the tube capable of resisting forces of a viscous material propelled therethough at a pressure of at least 100 atmospheres.

Description

RELATED APPLICATIONS
• This application claims the benefit under 119(e) of a US provisional application titled “Cannula”, filed on Jan. 26, 2006, and having Ser. No. 60/763,003, the disclosure of which is incorporated herein by reference.
• This application also claims the benefit under 119(e) of a US provisional application titled “Tools and methods for treating bones”, filed on Sep. 28, 2005, and having Ser. No. 60/721,094, the disclosure of which is incorporated herein by reference.
• This application also claims the benefit under 119(e) to U.S. application 60/762,789 entitled “Methods, Materials and Apparatus for Treating Bone and other Tissue” filed Jan. 26, 2006, with the same inventors as this application, the disclosure of which is incorporated herein by reference.
• This application also claims priority from U.S. application Ser. No. 11/360,251 entitled “Methods, materials, and apparatus for treating bone and other tissue filed on Feb. 22, 2006 the disclosure of which is incorporated herein by reference.
• This application is related to PCT Applications Nos. PCT/IL00/00056, filed Jan. 27, 2000, published as WO 00/44321; PCT/IL00/00058, filed Jan. 27, 2000, published as WO 00/44319; PCT/IL2004/000527, filed Jun. 17, 2004, published as WO 04110300; PCT/IL2005/000812, filed Jul. 31, 2005; the disclosures of all of which are incorporated herein by reference.
FIELD OF INVENTION
• The present invention relates to devices and methods for delivery of material into an organ, for example cannulae for delivery of bone cement during an orthopedic procedure.
BACKGROUND OF THE INVENTION
• Surgical and/or interventional treatment of fractured bones, osteoporotic bones, deformed bones and the like occasionally includes the use of various types of bone fillers, in order to reinforce and stabilize the bone, restore its original configuration and alleviate pain.
• Vertebral fractures, for example, may be treated using the vertebroplasty technique, during which bone cement (e.g. PMMA) is injected into the vertebral body through a cannula with a diameter of approximately 1 to 4 mm. Current vertebroplasty procedures typically rely upon a needle and stylet assembly, such as a Jamshidi needle.
• The currently available needle and stylet are typically made of a rigid inflexible material, e.g., metal. A typical procedure includes approaching the bone, under fluoroscopy, with a needle and cannula assembly, followed by removal of the stylet. The remaining cannula serves as a channel through which the bone cement is delivered into the bone from a reservoir connected to the cannula. Most commonly employed bone cements are not X-ray transparent.
• US patent application 2004/0054377 by Foster teaches a flexible cannula made from a single continuous piece of tubing. The proximal end of the cannula is made flexible by removing material from the wall of the cannula, preferably in a spiral pattern. The disclosure of this application is fully incorporated herein by reference. Foster's cannula has a grasping device at the distal end and is designed and constructed for removal of objects from soft tissue. Foster contemplates neither delivery of cement via the cannula nor use of the cannula in orthopedic procedures.
• U.S. Pat. No. 6,719,761 to Reiley teaches use of steering wires to deflect (curve) a distal end of a cannula for injecting bone cement, apparently low viscosity cement is used. The disclosure of this patent is fully incorporated herein by reference.
• U.S. Pat. No. 6,875,219 to Arramon teaches a cannula with a deformable distal tip. Deformation is achieved by inserting the cannula over a curved guide. The disclosure of this patent is fully incorporated herein by reference.
• US patent application publication number 2004/0260303 to Carrison, the disclosure of which is incorporated herein by reference, describes a pivoting cannula attachment to a reservoir, with the pivot adjacent a connector to the reservoir.
SUMMARY OF THE INVENTION
• An aspect of some embodiments of the invention relates to a plastically deformable bone cement cannula. Optionally, plastic deformation of the cannula by hand permits a desired positioning of a cement reservoir attached thereto, relative to the cannula, imaging equipment and/or the patient. Optionally, a rigid stylet prevents plastic deformation of the cannula during insertion. Such stylet is optionally provided as a straight stylet or as a curved stylet. In an exemplary embodiment of the invention, the deformation uses less than 2 Kg force. Optionally, the deformation does not damage tissues inside the body as the cannula is deformed.
• In an exemplary embodiment of the invention, insertion in a straight line is provided by the cannula in an un-deformed configuration, which may be easier, and then the cannula is distorted to a form suitable for another use, for example, during injection and/or imaging.
• In an exemplary embodiment of the invention, the cannula is stiff enough so that it maintains its deformation during injection of material therethrough. Optionally, the injected material is viscous, for example, viscous bone cement, injected at a high pressure, for example, at least 50 Atmospheres, at least 100 Atmospheres, at least 150 Atmospheres, at least 200 Atmospheres and/or intermediate or smaller numbers. In an exemplary embodiment of the invention, the viscosities used are between 100 and 3000 Pascal-second, for example 300-2000, for example, between 500 and 1000. Intermediate values may be used as well. In an exemplary embodiment of the invention, the cannula includes a series of joints which facilitate plastic deformation in a desired manner. In an exemplary embodiment of the invention, the joints are provided as joint areas including patterns of cuts and/or other weakening in the cannula body material. Optionally, the cuts are discrete. Optionally, the cuts are through cuts. Alternatively, at least some of the cuts are notches or other thinning of the cannula material. Optionally, another weakening type is provided, for example, by chemical treatment and/or mechanical and/or heat treatment.
• In an exemplary embodiment of the invention, the cuts and/or weakening are designed to designate particular parts of the cannula to act as plastically deformed segments, at which a significant portion of the overall deformation is provided.
• In an exemplary embodiment of the invention, the cuts and/or weakening are designed to facilitate a particular direction and/or degree of deformation or range of degrees. Optionally, the cuts are designed to reduce spacings in the cannula body, for example, spacings between lips of cuts.
• Optionally such design includes one or more of cut shape, cut size, number of cuts, depth, radial profile, number of groups of cuts, relative size of cuts in different groups and/or relative position of cuts in different groups.
• In an exemplary embodiment of the invention, cut/weakening design and/or distribution takes into account expected applied forces.
• In an exemplary embodiment of the invention, at least some of the cuts tend to at least partially close during deformation. Optionally, the tendency to partially close is related to a degree of bending the cut is subjected to. Optionally, partial closing reduces leaking of a material injected through the cannula. Optionally, the cuts are covered to reduce leaking of a material injected through the cannula. In an exemplary embodiment of the invention, a covering which substantially reduces leaking through the slits at a pressure of 100 to 200 or 300 atmospheres is provided. The covering may be, for example, internal or external, for example, of Teflon. Optionally, a more viscous cement is used with the cannula, to reduce leakage. In an exemplary embodiment of the invention, a cement is selected which reduces leakage in other means, for example, the cement may include a liquid phase and a solid phase, with the solid particles being of the order of the narrow dimensions of the slits or larger. Optionally, leakages is reduced once the solid particles are at least 10%, at least 35%, at least 60%, at least 80% or larger of such narrow dimensions, for example, being at least 0.01 mm, 0.05 mm, 0.1 mm, 0.3 mm, or intermediate or greater in size.
• In an exemplary embodiment of the invention, the joints each comprises an asymmetric cut design, in which a greater spacing between lips is provided on one side of the cut, so that bending in the direction of that side, tends to reduce the spacing.
• In an exemplary embodiment of the invention, the joints are arranged in a line parallel to the cannula axis.
• In an exemplary embodiment of the invention, a manufacturing process imparts flexibility to a workpiece by incising a series of cuts therein. Optionally, the process is carried out by an automated machine including control circuitry. Incision of cuts may be, for example, by one or more of lasers, chemical etching, water jets and rotating abrasive discs.
• In an exemplary embodiment of the invention, the joints (e.g., cuts and/or weakening) are designed to support deformation outside a body or adjacent to a point of entry of the cannula into the body (e.g., at a proximal end thereof).
• In an exemplary embodiment of the invention, each joint permits a deformation of 5, optionally 10, optionally 15 degrees or lesser or greater or intermediate values. Optionally, a total deformation of 45, optionally 90, optionally 135, optionally 180 degrees or smaller, intermediate values or greater is achieved and/or is designated as a design set point where there is minimal leakage. The length of cannula subject to deformation may vary with the total deformation implemented and/or the number of slits employed, for example, being 20 mm, 30 mm, 40 mm, or greater, smaller or intermediate in size. In an exemplary embodiment of the invention, 13 cuts provide a total deformation of 130 degrees. Greater or smaller numbers of cuts/deformation regions may be provided, for example, 7, 10, 15 or smaller, intermediate or greater numbers.
• Optionally, the degree of supported deformation of a deforming segment is selected to reduce leakage and/or straightening behavior. Optionally, leakage is reduced by increasing the number of joints to the point where the product of the joint by the leakage through the joint is minimized. In general, for a desired bending angle, as the number of joints increases, the leakage is typically reduced.
• In an exemplary embodiment of the invention, the cannula includes a plastically deformable tube. Optionally, the tube is a flexible tube which contains internal and/or external supports to counteract change after deformation. Optionally, the supports are designed for a particular degree and/or direction of plastic deformation.
• An aspect of some embodiments of the invention relates to a bone cement cannula with at least two fill ports. Optionally, the fill ports are deployed at different angles with respect to the main cannula axis. In an exemplary embodiment of the invention, a single port is used for injection of cement. Optionally, the other port is used for guiding of a stylet or other guide tool through the cannula.
• In an exemplary embodiment of the invention, unused ports are covered, plugged and/or removed from a cement flow path by a stopcock.
• An aspect of some embodiments of the invention relates to a stylet, at least part of the stylet being flexible, so that angled insertion of the stylet into the patient's body is facilitated. In an exemplary embodiment of the invention, the stylet and/or a cannula is introduced into a bone, for example a vertebra. In yet another exemplary embodiment of the invention, the device is introduced into the body during laparoscopic surgery. Optionally, the stylet and/or cannula comprise a handle at their proximal end. Optionally, said handles are made of a polymer. Optionally, said handles interlock with each other. In an exemplary embodiment of the invention, the interlocking arranges the parts in a correct orientation. Optionally, the interlocking prevents inadvertent rotation or axial motion of one part relative to the other.
• An aspect of some embodiments of the invention relates to a device, intended to serve as a channel for the delivery of material and/or devices/instruments into the body. In an exemplary embodiment of the invention, bone void filler, such as PMMA, is delivered via the device into a bone, for example a vertebral body. In one embodiment of the invention, the device comprises at least a cannula. Optionally, the device comprises a cannula and stylet, and may be used for accessing the target organ as well. In an exemplary embodiment of the invention, the cannula and stylet are assembled and interlocked. Optionally, cannula and stylet are interlocked at proximal handles thereof.
• In an exemplary embodiment of the invention, the device is constructed from biocompatible materials. Optionally, the device is constructed from metal, such as stainless steel or a nickel-titanium alloy such as NiTinol. Optionally, at least a portion of device is formed form a polymer.
• In an exemplary embodiment of the invention, the deformable cannula is designed to withstand the loads acting on it during usage, for example torque during insertion into a bone and/or removal therefrom.
• Optionally, a proximal end of the cannula includes a connection means for attaching to a delivery device, for example a Luer-lock type connector.
• Optionally, the cannula comprises at least one marker, for instance to indicate insertion depth and/or facilitated cannula bending direction. Such marking may be, for example, visible to human eye and/or under imaging, such as x-ray imaging.
• In an exemplary embodiment of the invention, the cannula tapers at its distal end and/or is otherwise shaped, for example, to serve as a trocar.
• An aspect of some embodiments of the invention relates to a cement provision cannula with an axial hole suitable for a stylet and through which cement leakage is reduced or absent. Optionally, the size of the hole reduces leakage. Alternatively or additionally, the properties of the cement used reduce leakage, for example, viscosity and/or grain size. Alternatively or additionally, the cannula and/or delivery system include a plug which selectively closes the axial hole once the stylet is removed.
• There is also provided in accordance with an exemplary embodiment of the invention, a bone cement cannula, the cannula comprising:
• (a) a tube including a section adapted for plastic deformation;
  (b) a lumen in the tube capable of resisting forces of a viscous material propelled therethough at a pressure of at least 100 atmospheres.
• Optionally, said section adapted for plastic deformation comprises a series of separate joints formed in an outer wall of the cannula. Optionally, at least one of said joints is formed by at least one cut. Optionally, at least one of said cuts is configured to close as the cannula deforms.
• In an exemplary embodiment of the invention, at least one of said joints is formed by non-penetrating weakening of the cannula wall.
• In an exemplary embodiment of the invention, said joints facilitate a desired deformation configuration of the cannula.
• In an exemplary embodiment of the invention, said joints are sealed.
• In an exemplary embodiment of the invention, the cannula comprises an outer sealing layer.
• In an exemplary embodiment of the invention, the cannula comprises an inner sealing layer.
• In an exemplary embodiment of the invention, said section is adapted to remain outside of a body.
• There is also provided in accordance with an exemplary embodiment of the invention, a cannula, comprising:
• (a) a tube including a section adapted for plastic deformation;
  (b) a lumen in the tube, said lumen at least partially filled with a bone filling material.
• In an exemplary embodiment of the invention, said section adapted for plastic deformation comprises a deformable sleeve.
• In an exemplary embodiment of the invention, said section adapted for plastic deformation comprises a flexible tube and a configuration support for said tube.
• There is also provided in accordance with an exemplary embodiment of the invention, a bone cement cannula, the cannula comprising:
• (a) a tube including a tube lumen providing a channel of fluid communication between at least one injection aperture and a connector body; and
  (b) at least two inlet ports defined in said tube.
• Optionally, one of said ports is axially oriented.
• Optionally, at least one of said ports is trans-axially oriented.
• In an exemplary embodiment of the invention, the cannula comprises a port path selector adapted to selectively allow flow from one of said ports.
• In an exemplary embodiment of the invention, the cannula comprises a port path blocker adapted to selectively allow block back-flow out of one of said ports.
• There is also provided in accordance with an exemplary embodiment of the invention, a manufacturing process for a surgical tool, the method comprising:
• (a) determining a pattern of cuts which will impart a desired deformability to a work piece;
  (b) imparting the desired plastic deformability to the work piece by incising the pattern of cuts therein to produce a surgical tool; and
  (c) forming said work piece into a cannula suitable for bone cement injection.
• There is also provided in accordance with an exemplary embodiment of the invention, a method of delivering cement, comprising:
• (a) providing a cannula with an axial guide-wire exiting through an axial hole thereof and said cannula including a side exit port;
  (b) inserting said cannula into a bone;
  (c) removing said stylet; and
  (d) injecting cement through said cannula such that less than 20% of the cement exits through the axial hole.
• There is also provided in accordance with an exemplary embodiment of the invention, a method of injecting a viscous material into a patient, comprising:
• (a) inserting a cannula into a patient;
  (b) bending said cannula over a length of at least 20 mm; and
  (c) injecting a viscous material through said cannula.
BRIEF DESCRIPTION OF DRAWINGS
• In the Figures, identical structures, elements or parts that appear in more than one Figure are generally labeled with the same numeral in all the Figures in which they appear. Dimensions of components and features shown in the Figures are chosen for convenience and clarity of presentation and are not necessarily shown to scale. The Figures are listed below.
• FIG. 1 is a flow diagram illustrating a cement provision method, in accordance with an exemplary embodiment of the invention;
• FIG. 2 is a front view of a deformable cement cannula with stylet inserted, in accordance with some exemplary embodiments of the present invention;
• FIG. 3A is a perspective view of a deformable cement cannula prior to deformation in accordance with some exemplary embodiments of the present invention;
• FIG. 3B (inset) is magnification of a portion of the exemplary cannula showing slits according to the embodiment illustrated inFIG. 3A;
• FIGS. 4A and 4B illustrate the cannula depicted inFIGS. 3A and 3B after deformation, in accordance with an exemplary embodiment of the invention;
• FIG. 4C is a diagrammatic representation of slits according toFIGS. 3B and 4B illustrating exemplary geometric considerations;
• FIG. 5 is a plan view of the cannula ofFIG. 3A;
• FIG. 6 illustrates a deformed cannula including a sleeve according to an exemplary embodiment of the invention;
• FIG. 7 is a perspective view of a deformable cement cannula prior to deformation in accordance with some exemplary embodiments of the present invention illustrating a lateral ejection port and a penetrating distal tip;
• FIG. 8A is a perspective view of a deformable cement cannula including external support prior to deformation in accordance with an exemplary embodiment of the invention;
• FIG. 8B is a perspective view of the cannula ofFIG. 8A, after deformation in accordance with an exemplary embodiment of the invention;
• FIGS. 9A and 9B are side cross-sectional views of a plastically deformable cannula according to exemplary embodiments of the invention before and after plastic deformation respectively;
• FIGS. 10A and 10B are side cross-sectional views of a cannula with multiple fill ports according to exemplary embodiments of the invention without and with a port cover respectively;
• FIGS. 10C and 10D are side cross-sectional views of a cannula with multiple fill ports according to exemplary embodiments of the invention with a port closure valve open and closed respectively;
• FIGS. 10E and 10F are side cross-sectional views of a cannula with multiple fill ports according to exemplary embodiments of the invention with a stopcock directed towards an axial and a radial port respectively;
• FIG. 11 is a flow diagram illustrating a method of manufacture according to exemplary embodiments of the invention; and
• FIG. 12 is a schematic side cross-sectional view of a sealed-tip cannula, with an axial aperture for a stylet, in accordance with an exemplary embodiment of the invention.
DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTSOverview of Method
• FIG. 1 is a flow diagram illustrating amethod100 of cement provision, in accordance with an exemplary embodiment of the invention. At102, a cannula is inserted, optionally with or without the aid of a stylet. Such stylet may be, for example, rigid or flexible, straight or bent. Optionally,insertion102 is monitored104 via a medical imaging apparatus such as, for example, a fluoroscope or conventional X-ray camera. If the optional stylet has been employed, it may be removed106 at this stage.
• At108, plastic deformation of the cannula is performed (it is noted that the cannula can be deformed before insertion), for example to be curved. At110 a bone cement reservoir and/or delivery system are attached to a proximal end of the cannula. The order in which108 and110 are performed is optionally reversed. In some cases, the reservoir is integral with the cannula.
• Aninjection112 of cement or other viscous material is then performed.
• Plastic deformation108 andattachment110 are optionally performed in consideration of subsequent injection monitoring114. Because the bone cement and/or injection reservoir may not be X-ray transparent,deformation108 is performed so that an attached cement reservoir will be outside of a relevant portion of a field of view of an X-ray image taken duringinjection112. X-rays are often obtained from a directional perpendicular to the body, e.g., along the axis of the unbent cannula, but this is not always the case and the cannula deformation may be changed.
• Injection112 may be undertaken using a suitable injection device connected to the cement reservoir. In an exemplary embodiment of the invention, a high viscosity bone cement is employed and a high pressure injection device is employed, for example as described in U.S. application Ser. No. 11/360,251, the disclosure of which is incorporated herein by reference. Alternatively, a syringe or other delivery system is used. The delivered material may be, for example, PMMA or calcium-based material (such as calcium phosphate or calcium sulfate).
• Optionally, a vibrator is attached to the cannula, for example, at a connector of the reservoir thereto, to facilitate flow of cement therethrough.
• Optional injection112 is monitored via a medical imaging apparatus such as, for example, a fluoroscope or conventional X-ray camera. Such monitoring may be, for example, periodically or throughout theinjection114.
• Wheninjection112 is complete as indicated by monitoring114, the cement reservoir is disconnected116 and the cannula is removed118. The order in which116 and118 are performed is optionally reversed.
Plastic Deformation
• A cannula according to exemplary embodiments of the invention is plastically deformable, as opposed to flexible. “Plastic deformation” as used herein refers to a change in shape which requires an input energy to implement, and another energy input, for example, of similar order, to reverse. In an exemplary embodiment of the invention, the input energy required for plastic deformation is sufficiently small that it can be applied manually, optionally with one hand. Optionally, once deformed, the cannula will not un-deform under forces applied to it by injecting cement therethrough and/or without external forces.
• In an exemplary embodiment of the invention, the deformation is facilitated to be in a certain direction and/or one plane. Optionally, once the cannula is deformed, a weight of a cement reservoir attached thereto will tend to preserve the deformation and/or assist in resisting forces applied by injection of cement therethrough.
• In an exemplary embodiment of the invention, the deformation is limited in extent and/or degree. Optionally, a desired maximum angle of deformation is facilitated by the construction and/or design of the cannula. While application of excessive force may cause additional bending beyond this maximum angle, such additional bending would be beyond the scope of designed deformation. Such additional bending may cause kinking of the cannula and/or leakage therefrom. In an exemplary embodiment of the invention, a weight of a cement reservoir attached to the cannula does not provide excessive force sufficient to deform and/or over-deform the cannula. Optionally, the reservoir provides sufficient force to deform the cannula until the reservoir rests against the patient and/or other support.
• The degree of plastic deformability may be governed to some extent by materials employed in construction of the cannula. Some materials have a higher degree of plasticity than others. Some materials have an elastic memory which causes them to tend to return to their original shape when a deforming force is removed. In exemplary embodiments of the invention, such as described below, deformation is facilitated by the geometry/structure of the cannula and/or supports provided thereto.
Slit Cannula
• FIG. 2 is a front view of an assembled Cannula/stylet apparatus200 according to an exemplary embodiment of the invention, showing a partial cross-section view of handles thereof. In an exemplary embodiment of the invention, the handle orientation is matched to the slit orientation (described below), so that in typical use, the forces applied by a doctor to insert the cannula will not be in the same direction as forces that are used to bend the cannula. Optionally, the handle direction is used to indicate the desired deformation direction.
• Cannula212 includes a series ofslits224 designed to impart a desired plastic deformation capability to a specific portion of the cannula.Cannula212 optionally includes ahandle222 at its proximal end.
• Stylet214 is inserted throughcannula212 via an inner lumen of the cannula. A cuttingtip218 ofstylet214 optionally protrudes from a distal end ofcannula212.Distal tip218 is optionally adapted to puncture and penetrate the skin, soft tissue and/or cortical bone.Tip218 may be, for example, of diamond type, drill type, bevel type or J-type, or of other tip types known in the art.
• Optionally, a distal tip of the cannula is formed of a radio opaque material of different opacity and/or there is a step in diameter between the cannula and the stylet, so that transition is clearer on an x-ray image.
• Optionally,stylet214 is equipped with aproximal handle220. In an exemplary embodiment of the invention, handles222 and220 engage one another via anengagement mechanism216, for example a threaded connection. Optionally, a spring is provided to elastically couple the components. Analternative locking mechanism217 is shown as well, in which a tongue on one handle snap-locks to a groove on the other handle. Such snap-locking may be, for example, by rotation or by axial motion.
• In an exemplary embodiment of the invention,stylet214 is rigid. Optionally, a rigid stylet supportscannula212 during insertion and prevents deformation ofcannula212 until such deformation is desired. In an exemplary embodiment of the invention, the stylet is removed before deformation is undertaken. Optionally, a lumen ofcannula212 is adapted to comply with a diameter ofstylet214. For example, an inner cannula lumen of 2.7 mm may be provided with a stylet of 2.6 mm.
• In an alternative embodiment,stylet214 is curved. Alternatively or additionally,stylet214 is flexible, for example, at a portion corresponding toslit series224.
• In an exemplary embodiment of the invention,stylet214 has a preferred orientation (e.g., is beveled) which optionally matches an angled/beveled tip of the cannula.
• In an exemplary embodiment of the invention designed for use in a fractured vertebral body,stylet214 has a diameter of about 1.4-2.6 mm. It is noted that viscous material may be provided to other bone sand/or other parts of the body using the apparatus and methods described herein. The cannula optionally has an inner diameter of about 2.7 mm and an outer diameter of about 3 mm. When employed in a vertebroplasty procedure, the assembledcannula stylet200 is introduced into the body, sodistal tip218 penetrates skin, soft tissue and vertebra.Stylet214 is then disconnected fromcannula212 which remains in situ as described with regard to method100 (FIG. 1).
• FIG. 3A illustrates anexemplary cannula212 withstylet214 removed. The straight configuration ofcannula212 is optionally used for device introduction.Cannula212 comprises a series ofslits224, which facilitate plastic deformation.FIG. 3B (inset) is an enlargement of part of series ofslits224 showing the slits in greater detail.
• The pattern of the slits enlarged inFIG. 3B includes two rows ofslits226,228 and230,232. The rows are displaced 180 degrees relative to each other with respect to the circumference ofcannula212. In the depicted exemplary embodiment, each row includes 12 slits, but other numbers may be provided. The slits may penetrate the cannula wall completely, or they may be perforations or grooves etched in the cannula wall.
• FIGS. 4A and 4B (inset) illustrate plastic deformation ofcannula212 ofFIGS. 3A and 3B. As seen most clearly in inset4B, slits230 and232 on the inner side of the bend caused by the deformation tend to close as a result of the deformation.Slits226 and228 on the outer side of the bend caused by the deformation tend to remain the same size or open slightly as a result of the deformation. The closing is explained in greater detail with regards toFIGS. 4C and 5.
• In an exemplary embodiment of the invention, slits226 and228 are characterized by a width of, for example, 0.03 mm. Cannula thickness can be, for example, 0.03 mm. During plastic deformation, this width increases, for example to about 0.3 mm, for some of the slits or sections thereof (e.g., the outer slits). In the exemplary embodiment of the invention depicted inFIGS. 3A;3B;4A and4B, the initial width of slits in the row along the inside of the curve produced by plastic deformation (230,232) is larger than the initial width of the slits in the row along the outside of the curve produced by plastic deformation (226,228).
• In an exemplary embodiment of the invention,cannula212 is constructed so that thelarger slits230,232 on the inside of the curve resulting from plastic deformation tend to close during deformation whilesmaller slits226,228 on the inside of the curve resulting from plastic deformation tend to open or stay a same width during deformation. This is described in greater detail inFIG. 4C, below.
• In an exemplary embodiment of the invention, total cement leakage (or risk thereof) through the slits is less whencannula212 is plastically deformed to a certain degree than when the cannula is straight.
Optional Sleeve
• FIG. 6 is a perspective view of acannula212 fitted with asleeve238 to prevent leakage of cement injected through the cannula.Sleeve238 is deployed to cover the slits. While the sleeve is depicted on the outside of the cannula, it may optionally be provided as an inner coating. Alternatively or additionally, an external coating may be applied tocannula212 to reduce leakage. In an exemplary embodiment of the invention,sleeve238 adheres to cannula212 with sufficient force to prevent or reduce leakage of bone cement being injected at pressures in the range of 100 to 300 (or 50 to 200) atmospheres. Optionally,sleeve238 extends beyond the portion of the cannula which is slit. In an exemplary embodiment of the invention,sleeve238 is non-compliant so that during cement injection at high pressure, the sleeve diameter remains the same. Optionally,sleeve238 is made of a polymer with sufficient wall thickness for stability under the relevant injection pressure. Optionally,sleeve238 is placed overcannula212 during use (e.g., after insertion of the cannula, or prior thereto). Optionally,cannula212 is provided withsleeve238 in place.
• In an exemplary embodiment of the invention, the slit cannula provides mechanical support for the sleeve, which may be, for example, coated on or adhered to the cannula.
• In some cases, additional strengthening may be desired, for example, by providing an additional sleeve over the sleeve, or by providing compression rings which prevent flow out between the sleeve and the cannula body, at the sleeve edge. Optionally, a compression ring is provided for each set of or for more than one set of slits.
• In an exemplary embodiment of the invention, an inner coating is provided to reduce friction between the cement and the cannula. Alternatively or additionally, an outer coating is provided to prevent adhesion of the cannula to hardening cement. Such coatings may also serve to reduce leakage. An exemplary thickness is 0.1 mm.
• Optionally, one or more of chemical resistance (to cement), friction reduction and/or sticking prevention are provided by a cover. Exemplary cover materials include PTFE, ETFE, PFA, or FEP—Teflon® or other materials with suitable properties. Optionally, a heat-shrinking sleeve is used, which may be heat shrunk while manufacturing or after bending (e.g., with a heat gun).
Bending Location
• In an exemplary embodiment of the invention, series ofslits224 deployed oncannula212 designed so that they are located substantially or wholly outside a patient body during use, for example, at least 60%, at least 75% or more of the deformable area is outside the patient. Optionally, plastic deformation ofcannula212 bends the cannula towards the surgeon so that attachment of a cement reservoir is convenient. In an exemplary embodiment of the invention, a marking (not shown in the Figure) oncannula212 indicates preferred deformation orientation (e.g., towardlarger cuts230,232).
• In an exemplary embodiment of the invention, the deforming area is selected to reduce kinking of the cannula and/or reduce the amount of bending at each point and thus the local straightening force applied when injecting cement.
• In an exemplary embodiment of the invention, the length of the cannula between the deforming area and the distal tip is between 100 mm and 150 mm. Optionally, 100 mm is used for the upper spine and 150 for the lower back.
• In an exemplary embodiment of the invention, the use of a bending cannula allows the cement reservoir to be closer to the bone. Reduction in distance may be useful, for example, for one or more of reducing resistance to flow, reducing dead volume of cement and/or for reducing temperature changes of the cement as it flows. Optionally, the use of a bending cannula obviates the need for a separate short flexible tube and its associated connectors and possible need for manual manipulation. In an exemplary embodiment of the invention, the total length of the cannula including the bending region is for example, 150 mm, for example, 100 mm straight and 50 mm bending. A longer straight and/or bending area may be provided, for example, to give a cannula length of 200 mm.
Self-Penetrating Cannula
• FIG. 7 illustrates an exemplary embodiment of acannula712 with aradial injection aperture710 and apenetration tip720.Penetration tip720 optionally serves in place ofstylet tip218 as described above. A separate stylet may be provided for ensuring thatcannula712 does not bend during insertion. In some embodiments, no stylet is used.
• Optionally, multiple fill ports are provided, for example as described below.
• Multiple ports and/or a penetrating tip are optionally provided with any of the cannula designs described herein.
Detailed Exemplary Slit Design
• FIG. 4C shows a detail of an exemplary slit design, in accordance with an exemplary embodiment of the invention. In the detail shown, there are two slits,228 (from the outer bend) and232 (from the inner bend).Slit228 includes abase cut246 and abeam cut248. As shown inFIG. 5, a second base cut may be provided on the other side of the cannula.Slit232 includes abase cut236 and abeam cut244.
• In an exemplary embodiment of the invention, the various slits define aportion240 in the general shape of a rectangle that is defined by the base cuts (and the lines connecting them) which is plastically deformed when the cannula is deformed. In some cases, the deformation extends a short distance away from the cuts/rectangular area, for example, from the base cuts. In an exemplary embodiment of the invention,portion240, even if deformed is robust enough to maintain the deformed configuration of the cannula. In an exemplary embodiment of the invention,portion240 acts as a bending bar.
• In an exemplary embodiment of the invention, base cut246 serves to limit the deformation toportion240 and/or guide the deformation region. Optionally, the edges of base cut246 and/or base cut236 are rounded to prevent tearing and/or reduce stress concentrations.
• In an exemplary embodiment of the invention, when bent towardsslit232, beam cut244 tends to close. Optionally, beam cut244 is pre-formed to be open, so that it can close lip to lip.
• In an exemplary embodiment of the invention, base cut236 tends to close when the cannula is bent and includes a cut-out so as to facilitate lip to lip matching. Optionally, the cuts are not straight lines, but curved in anticipation of lip-to-lip meeting in a deformed configuration.
• In an exemplary embodiment of the invention, the bending of the cannula envelope is at beam cut248, so that there is less strain in the cannula.
• In an exemplary embodiment of the invention, at least some of the cuts may be replaced by other weakening methods, for example, etching, chemical treatment, thinning and/or heat treatment. Alternatively or additionally, elongation properties of plastically deforming areas may be enhanced to reduce and/or prevent tearing.
• In an exemplary embodiment of the invention, beam cut248 is provided as a weakened area. Optionally, some ofportion240 is weakened. Optionally, the weakened area is selected so that crumpling and possible kinking of the cannula lumen are avoided.
• While the figure shows a symmetric design with opening at one side and closing at the other, this is not essential. For example, the amount of resistance to bending at either side need not be equal. In one example, slit228 does not exist and part ofportion240 is weakened to facilitate deformation thereof when slit232 is closed by the deformation of the cannula. Optionally, one or more wedge sections are removed fromportion240, instead of weakenings, extending from base cut236 towards base cut246 (which need not exist in this embodiment).
• In another example, the slit design comprises only a wedge shaped slit generally aligned withbeam cut244 and narrowing in the direction of the outside of the bend. At the tip of the slit, a strain relief cut-out is optionally provided. Optionally, a plain slit on the outside bending side of the cannula is provided.
• In an exemplary embodiment of the invention, the exact shapes, dimensions and/or mechanical properties of the cuts and nearby regions are determined using finite element software. For example, by setting the thickness of the cannula and searching for values for the dimensions ofportion240 and/or selecting amount various shapes and/or other parameters until a best solution is found. Optionally, a best solution is one with minimal working, minimal chance of tearing, minimal leakage potential and/or minimal narrowing of the lumen by buckling.
• In an exemplary embodiment of the invention, the cannula is made of metal (e.g., stainless steel 304 or 316), as this typically allows a bigger inner diameter for a same outer diameter.
• FIG. 5 is a plan view of a bendable cannula. As can be appreciated, the final geometry of the cannula typically depends not on a single slit area as shown inFIG. 4C, but on a plurality of such slit areas. In an exemplary embodiment of the invention, the series of slits is selected to achieve a desired final geometry. It is noted that the deformation need not match this geometry, for example, by providing more or less deformation. However, in an exemplary embodiment of the invention, the design is optimized for one or more deformation configurations.
• In an exemplary embodiment of the invention, the deformation is that of a simple bending. Such deformation is optionally facilitated by providing multiple slit sections to act as joints (bending areas). These sections are optionally provided as equal-design joints, each of which bends about a same amount, for example 10 degrees, in the same direction (e.g., same bending direction. The distance between the joints can be used to set the bending radius. For example, a length of deformable area of 30 mm can provide a 19 mm bending radius for a 90 degree bend. In an exemplary embodiment of the invention, the cannula is designed for a 130 degree bend, which will allow resting of the cement reservoir on the patient's back. Optionally, a bend of about 90 degrees is provided, for example, to move the cement reservoir out of a line of sight of an x-ray imager. Optionally, the degree of bending varies among the joints, for example, increased bending per joint being provided at one or the other end of the deformable area and/or at a center thereof.
• In an exemplary embodiment of the invention, the deformation is not a plain curve. For example, an S-shaped curve can be provided if a first series of joints face one way and a second series of joints face another way. A non-planar (3D) deformation can be facilitated if the base cuts do not all lie on a line parallel to the cannula axis, for example lying on a spiral or lying on two or more such parallel or non-parallel lines.
• Optionally, the cannula is pre-bent and then cut, so the joints define a deformation on a curved element, rather than on a straight element. Optionally, such joints define a straightened (or straighter) configuration of the cannula.
• FIG. 5 also illustrates that each slit (e.g.232) comprises abeam cut244 and two base cuts,234 and236. Optionally, these base slits improve stress distribution along the length ofcannula212. Optionally, greater stress distribution reduces unwanted crimping of walls of the cannula.
• While specific numbers, shapes and distributions/arrangements of slits are depicted in the figures and text, it is stressed that the scope of the invention any number and/or arrangement and/or shape and/or dimensions and/or spacing of slits employed to facilitate plastic deformation of a bone cement cannula. In an exemplary embodiment of the invention, the slits are distributed along the entire length ofcannula212, rather than the proximal part only. Optionally, an offset of at least 5 mm, at least 10 mm or more is provided between the last joint and the connector. Optionally, this area is used to anchor the above described optional flexible sleeve.
• In an exemplary embodiment of the invention, the configuration ofcannula212 after bending is such that the cement (or other viscous material) flows in a non-straight path (e.g., curved path or piecewise linear) for a substantial distance. A potential advantage over a pivoting design, where a single joint provides a large angular change between parts of the cannula is that at each point in the non-straight path, the straightening forces may be small. Alternatively or additionally, flow of non-fluids may be facilitated by gradual direction changes. Alternatively or additionally, the mechanism for pivoting (e.g., with an alignment of the flow path with the pivot center) may be complicated. Alternatively or additionally, leakage at integral metal joints with small angles may be relatively small (and in some cases ignored). Alternatively or additionally, deformation of metal at small angles is possible, potentially allowing complicated (to make) joints to be dispensed with and formed directed out of the cannula body.
Supported Deformation
• Cannula212 is an example of a cannula where the cannula body itself provides support for the deformed configuration of the cannula. In alternative embodiments, this is not the case.
• FIGS. 8A and 8B show acannula812 including adeformable section820, arigid section826 ending at atip710, and aconnector828, for providing cement into the cannula.FIG. 8A showscannula812 in a straight configuration andFIG. 8B showscannula812 in a bent configuration.
• In an exemplary embodiment of the invention,deformable section820 comprises aflexible tube824 and a construct which sets a bending state of the tube.
• In an exemplary embodiment of the invention, as pictured, this construct comprises one ormore bars870 and880, coupled to either side oftube824. In the example shown afirst block860 is provided at one side of the tube and is pivotally attached tobars870,880, for example, using one or more pins822. Asecond block850 is provided at a second end of the tube and is attached tobars870,880, using a sliding attachment, for example, with one or more slidingpins830. Optionally, each side of the tube has one sliding and one pivoting pin. In an exemplary embodiment of the invention, the friction of the sliding connection and/or the pivoting connection are set to resist straightening forces, while allowing manual deformation.
• In an exemplary embodiment of the invention, bars870 and880 serve to resist twisting forces associated with inserting and/or removing the cannula from the body.
• An alternative construct is that of a goose-neck covering for tube824 (goose-neck not shown). Another alternative construct is a tube of plastically deformable material. Another alternative construct is a providing one or more metal wires which are malleable. Such wires may be provided, for example, outside oftube824 or embedded therein.
Flexible Connector
• FIG. 9A is a cross-sectional side view of acannula912 including aflexible section900. Optionally, the flexible section is thicker than the rest of the cannula, but being outside the body, this may be acceptable. Optionally, atissue stop902 is provided, for example, as a rigid ring or as a movable ring, which prevents penetration ofsection900 into the body.Section900 can be, for example, a deformable section as described above.
• FIG. 9B showscannula912 in a bent configuration, withoutoptional tissue stop902.
Method of Manufacture
• FIG. 11 is a flowchart of anexemplary method1100 of manufacture of a deformable cannula in accordance with exemplary embodiments of the invention.
• At1110, a work piece is provided, for example, a flat metal sheet, a metal tube, a tube with an end formed thereon and/or a tube with a handle fitted thereon. Optionally, a long tube suitable for multiple cannulae is provided. In some embodiments, the cannula is formed of a polymer, rather than a metal tube.
• At1120, the work piece is engaged by a cutting device including control circuitry, for example, a computer.
• At1130, the cutting device is programmed for cutting a desired pattern, for example, by etching, laser cutting, water cutting, e-beam cutting, machining, abrasion and/or other metal working methods known in the art. Optionally, the device is preprogrammed.
• At1140 the program is executed to form the slits and/or other weakenings. Optionally, the program also forms cement inlet and/or outlets.
• Optionally, laser heating and/or electron-beam heating are used to annealportions240, and thereby improve their ductability. This may be done on a same device or on a different device.
• At1150, the deformable cannula is removed from the cutting device. Optionally, a handle is attached. Optionally, if the work piece was provided as a sheet, it is now welded or otherwise formed into a tube.
Distal Aperture
• FIG. 12 is a schematic side cross-sectional view of a sealed-tip cannula1200, with anaxial aperture1202 for astylet1204, in accordance with an exemplary embodiment of the invention. A second,side exit port1206, is shown for exit of cement.
• In an exemplary embodiment of the invention,aperture1202 is smaller than a grain size of the cement used and/or is small relative to a viscosity of the cement used, so there is little leakage there through oncestylet1204 is removed. In an exemplary embodiment of the invention, the ratio of cement flow through the axial aperture and the side port(s) is better than 3:1, better than 4:1, better than 6:1, better than 10:1 or intermediate values.
• In an exemplary embodiment of the invention, the area ratio between the aperture and the port is at least 1:5, 1:8, 1:10, 1:15, 1:20 or intermediate or greater values. Such ratios may reduce the leakage.
• Alternatively or additionally, a closing mechanism is provided. In one example, a plug (not shown) is pushed along the stylet and plugsaperture1202. Optionally, the plug is provided as a forward part of the cement delivery system. Optionally, such a plug travels along a bent cannula and is too wide to exit throughside exit port1206.
• In another example, a trap-door mechanism1208 is provided which closes, either on its own or due to cement pressure, oncestylet1204 is removed.
• In another example, aplug1210, for example, a ball, is attached to the inside of the cannula and plugsaperture1202 when cement flows thereto.
Multiple Loading Ports
• In an exemplary embodiment of the invention, a cannula is provided with multiple loading ports. This may be useful for a non-deforming cannula, where an axial loading port is used for entry of a stylet and a side loading port is provided for injecting cement without a cement delivery system blocking a line of sight of a doctor and/or imaging system and/or without applying torque to the patient. Typically, cement is injected after the stylet removed.
• An alternative reason for providing multiple ports is that it may be desirable to provide a plurality of materials into the patient (e.g., bone cements of varying viscosities), without detaching a high-pressure (or other) delivery system. An alternative reason for providing multiple ports is for pressure relief at the cannula.
• FIG. 10A shows acannula1002 including anaxial port740 and aside port730.FIG. 10B shows that after use of the axial port, it may be closed using acap1010, for example, a threaded cap. A similar cap may be used forside port730.
• FIG. 10C (axial open) andFIG. 10B (axial closed), show a trap-door valve1020 which selectively closes anaxial port740 of acannula1004. A potential advantage of a trap-door valve is that backpressure closes it and/or may assist in sealing it. Thus, for example, entry of cement throughport730 will tend to closedoor1020 and thus sealport740. Application of a greater pressure atport740, will reopen the port.
• In an exemplary embodiment of the invention, the trap-door does not lie flush with the cannula inner surface. Rather a space (not shown) is provided between the door and the surface, for example, a wedge shape space, to ensure that flow of cement fromport730 will close the door, rather than force it to remain open. Alternatively or additionally, an elastic closing hinge is used.
• FIG. 10E (axially open) andFIG. 10F (axially closed) show acannula1006, in which a rotating valve, such as a stopcock valve, selectively makes one of the ports patent.
Other Tissue and General Comments
• While the above application has focused on the spine, other tissue can be treated as well, for example, compacted tibia plate and other bones with compression fractures and for tightening implants, for example, hip implants or other bone implants that loosened, or during implantation. Optionally, for tightening an existing implant, a small hole is drilled to a location where there is a void in the bone and material is extruded into the void.
• It should be noted that while the use in bones of the above methods and devices provide particular advantages for bone and vertebras in particular, optionally, non-bone tissue is treated, for example, cartilage or soft tissue in need of treatment. Optionally, the delivered material includes an encapsulated pharmaceutical and is used as a matrix to slowly release the pharmaceutical over time. Optionally, this is used as a means to provide anti-arthritis drugs to a joint, but forming a void and implanting an eluting material near the joint. In an exemplary embodiment of the invention, the eluting material is of a high viscosity and or is a soft non-flowing material.
• In another embodiment, the injected material is a nucleus for a disc.
• It will be appreciated that the above described apparatus and methods of implanting and treating may be varied in many ways, including, changing the order of steps, which steps are performed more often and which less often, the arrangement of elements, the type and magnitude of forces applied and/or the particular shapes used. In particular, various tradeoffs may be desirable, for example, between applied forces, degree of resistance and forces that can be withstood. Further, the location of various elements may be switched, without exceeding the spirit of the disclosure, for example, the location of the cement outlet. In addition, a multiplicity of various features, both of method and of devices have been described. It should be appreciated that different features may be combined in different ways. In particular, not all the features shown above in a particular embodiment are necessary in every similar exemplary embodiment of the invention. Further, combinations of the above features are also considered to be within the scope of some exemplary embodiments of the invention. In addition, some of the features of the invention described herein may be adapted for use with prior art devices, in accordance with other exemplary embodiments of the invention. The particular geometric forms used to illustrate the invention should not be considered limiting the invention in its broadest aspect to only those forms, for example, where a cylindrical tube is shown, in other embodiments a rectangular tube may be used. Although some limitations are described only as method or apparatus limitations, the scope of the invention also includes apparatus programmed and/or designed to carry out the methods.
• Also within the scope of the invention are surgical kits which include sets of medical devices suitable for delivering cement or other viscous materials and suitable material. Section headers are provided only to assist in navigating the application and should not be construed as necessarily limiting the contents described in a certain section, to that section. Measurements are provided to serve only as exemplary measurements for particular cases, the exact measurements applied will vary depending on the application. When used in the following claims, the terms “comprises”, “comprising”, “includes”, “including” or the like means “including but not limited to”.
• It will be appreciated by a person skilled in the art that the present invention is not limited by what has thus far been described. Rather, the scope of the present invention is limited only by the following claims.

Claims (21)

1. A bone cement cannula, the cannula comprising:

(a) a tube including a section adapted for plastic deformation; and

(b) a lumen in the tube capable of resisting forces of a viscous material propelled therethough at a pressure of at least 100 atmospheres.

2. A cannula according toclaim 1, wherein said section adapted for plastic deformation comprises a series of separate joints formed in an outer wall of the cannula.

3. A cannula according toclaim 2, wherein at least one of said joints is formed by at least one cut.

4. A cannula according toclaim 3, wherein at least one of said cuts is configured to close as the cannula deforms.

5. A cannula according toclaim 2, wherein at least one of said joints is formed by non-penetrating weakening of the cannula wall.

6. A cannula according toclaim 2, wherein said joints facilitate a desired deformation configuration of the cannula.

7. A cannula according toclaim 2, wherein said joints are sealed.

8. A cannula according toclaim 1, comprising an outer sealing layer.

9. A cannula according toclaim 1, comprising an inner sealing layer.

10. A cannula according toclaim 1, wherein said section is adapted to remain outside of a body.

11. A cannula according toclaim 1, wherein said section adapted for plastic deformation comprises a deformable sleeve.

12. A cannula according toclaim 1, wherein said section adapted for plastic deformation comprises a flexible tube and a configuration support for said tube.

13. A cannula, comprising:

(a) a tube including a section adapted for plastic deformation; and

(b) a lumen in the tube, said lumen at least partially filled with a bone filling material.

14. A bone cement cannula, the cannula comprising:

(a) a tube including a tube lumen providing a channel of fluid communication between at least one injection aperture and a connector body; and

(b) at least two inlet ports defined in said tube.

15. A cannula according toclaim 14, wherein one of said ports is axially oriented.

16. A cannula according toclaim 14, wherein at least one of said ports is trans-axially oriented.

17. A cannula according toclaim 14, including a port path selector adapted to selectively allow flow from one of said ports.

18. A cannula according toclaim 14, including a port path blocker adapted to selectively allow block back-flow out of one of said ports.

19. A manufacturing process for a surgical tool, the method comprising:

(a) determining a pattern of cuts which will impart a desired deformability to a work piece;

(b) imparting the desired plastic deformability to the work piece by incising the pattern of cuts therein to produce a surgical tool; and

(c) forming said work piece into a cannula suitable for bone cement injection.

20. A method of delivering cement, comprising:

(a) providing a cannula with an axial guide-wire exiting through an axial hole thereof and said cannula including a side exit port;

(b) inserting said cannula into a bone;

(c) removing said guide-wire; and

(d) injecting cement through said cannula such that less than 20% of the cement exits through the axial hole.

21. A method of injecting a viscous material into a patient, comprising:

(a) inserting a cannula into a patient;

(b) bending said cannula over a length of at least 20 mm; and

(c) injecting a viscous material through said cannula.

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