US20100185204A1 - Apparatus and method for performing spinal surgery - Google Patents

Abstract

A cutting guide for use in spinal surgery includes a body member with a first surface and an opposite, second surface. The cutting guide includes slots and corner holes to guide surgical instruments therethrough. The cutting guide can also include at least one fixation tab with a hole for receiving a fixation device therethrough. A scaffold device includes a sidewall defining an internal cavity. The scaffold device also includes at least one fixation tab with a hole for receiving a fixation device therethrough.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS
• This application is a continuation-in-part of U.S. patent application Ser. No. 11/925,569 filed Oct. 26, 2007; which is a divisional of U.S. patent application Ser. No. 10/701,599 filed Nov. 6, 2003 (now U.S. Pat. No. 7,303,565 and issued Dec. 4, 2007); which is a divisional of U.S. patent application Ser. No. 10/043,266 filed Jan. 14, 2002 (now U.S. Pat. No. 6,761,723 and issued Jul. 13, 2004), the disclosures of which are hereby incorporated herein by reference in their entireties.
BACKGROUND OF THE INVENTION
• This invention relates to the field of spinal surgery. More specifically, this invention relates to apparatuses for creating cavities in vertebral bodies and in intervertebral discs located between the vertebral bodies. This invention also relates to methods for creating such cavities. Once the cavities are created with the apparatuses and according to the methods of the present invention, an intervertebral prosthetic device, designed to replace a damaged intervertebral disc, can be implanted in the cavities. Moreover, the implanted device may be used in vertebral body fusion or in reconstruction of mobile discs through spinal arthroplasty (i.e., disc replacement).
• The human spine is a flexible structure comprised of twenty-five vertebrae. Intervertebral discs separate and cushion adjacent vertebrae. The intervertebral discs act as shock absorbers and allow bending between the vertebrae.
• An intervertebral disc comprises two major components: the nucleus pulposus and the annulus fibrosis. The nucleus pulposus is centrally located in the disc and occupies 25-40% of the disc's total cross-sectional area. The nucleus pulposus usually contains 70-90% water by weight and mechanically may function like an incompressible hydrostatic material. The annulus fibrosis surrounds the nucleus pulposus and resists torsional and bending forces applied to the disc. Thus, the annulus fibrosis serves as the disc's main stabilizing structure. A healthy disc relies on the unique relationship of the nucleus and annulus to one another. The top and bottom surfaces of intervertebral discs abut vertebral body endplates.
• Individuals with damaged or degenerated discs often experience significant pain. The pain results, in part, from instability in the intervertebral joint due to a loss of hydrostatic pressure in the nucleus pulposus, which leads to a loss of disc height and altered loading of the annulus fibrosis.
• A conventional treatment for degenerative disc disease is spinal fusion. In one such surgical procedure, a surgeon removes the damaged natural disc and then fuses the two adjacent vertebral bodies into one piece. The surgeon fuses the vertebral bodies by grafting bone between the adjacent vertebrae and sometimes uses metal rods, cages, or screws to hold the graft in place until the graft heals. Other fusion procedures do not require surgical removal of the disc.
• Although spinal fusion may alleviate pain associated with degenerative disk disease, it also results in loss of motion at the fused vertebral joint. Lack of motion at the fused site puts abnormal loads on the adjacent discs above and below the fusion. This additional pressure may cause the adjacent discs to degenerate and produce pain, thereby recreating the problem which originally existed. To remedy the problems associated with spinal fusion, various prosthetic devices were developed to replace the damaged disc with a suitable biomechanical equivalent.
• Existing prosthetic devices have met with limited success in reproducing the biomechanics of a natural disc. For example, U.S. Pat. No. 4,759,769 to Hedman et al. discloses a synthetic disc having upper and lower plates hinged together. Although the hinged disc allows forward bending between adjacent vertebrae, the hinged disc does not allow axial compression or lateral flexion. Nor does it allow axial rotation of the vertebral column at the site of the implant. Therefore, the Hedman et al. device lacks many of the biomechanics of a natural disc.
• Likewise, the prosthetic disc device disclosed in U.S. Pat. No. 4,309,777 to Patil does not replicate natural motion between adjacent discs. The Patil device includes two cups, one overlapping the other and spaced from the other by springs. The cups move only in a single axial dimension. Thus, the Patil device does not enable natural flexion of the spine in any direction. In addition, the highly constrained motion of the Patil device can lead to high device/tissue interface stresses and implant loosening.
• Many synthetic devices connect to the vertebral bodies by conventional mechanical attachments, such as pegs or screws, which are known to loosen under cyclic loading conditions. Other synthetic devices use plastic or elastomeric components which, over a lifetime, produce debris from wear and possible unknown side effects.
• In response to these and other known problems associated with synthetic prosthetic disc devices, U.S. Pat. No. 5,827,328 to Buttermann, which is incorporated herein by reference in its entirety, discloses an intervertebral synthetic prosthetic device designed to replace the biomechanical functionality of a failing intervertebral disc. One embodiment of the Buttermann device includes a first fixation member for implantation in a first vertebral body, a second fixation member for implantation in a second vertebral body adjacent the first vertebral body, and a compressible member that is positioned between the first and second fixation members. The Buttermann device overcomes the aforementioned problems with synthetic devices.
SUMMARY OF THE INVENTION
• There is a need for improved apparatuses and methods by which cavities can be created in vertebral bodies and in an intervertebral disc. Once the cavities are created, an intervertebral prosthetic device designed to replace a damaged intervertebral disc, such as the one described in U.S. Pat. No. 5,827,328, can be implanted in the cavities.
• According to one embodiment of the invention, a cutting guide for use in removing bone from a vertebral body is provided. The cutting guide comprises a cutting guide body including a first surface with a first edge to face toward and to contact the vertebral body and a second, opposite surface to face away from the vertebral body. The first edge includes at least two concave portions. The cutting guide further comprises first and second slots for guiding a cutting tool to cut into the vertebral body along a length of the first and second slots. The slots extend from the first surface to the second surface. The first and second slots are positioned to intersect each other. The cutting guide further comprises an additional slot extending from the first surface to the second surface. The additional slot is configured to slide over a positioning pin inserted into the vertebral body or intervertebral disc to temporarily position the cutting guide on the vertebral body.
• In yet another embodiment of the present invention, a scaffold device for use in removing bone from a vertebral body is provided. The scaffold device comprises a sidewall defining an internal cavity. The sidewall includes a first edge to face toward and to contact the vertebral body, and a second, opposite edge to face away from the vertebral body. The scaffold device further comprises a first fixation tab protruding from the sidewall. The fixation tab includes a through-hole to receive a fixing device therethrough to fix the scaffold device to a vertebral body.
• In one aspect of the present invention, a cutting guide is provided for use in removing bone from a vertebral body. The cutting guide includes a sidewall that defines an internal cavity. In addition, the sidewall has (i) a first edge to face toward and to contact a vertebral body in at least three points and (ii) a second, opposite edge to face away from the vertebral body. The first edge includes at least two concave portions and at least one convex portion oriented generally perpendicular to the at least two concave portions.
• The sidewall of the cutting guide may be comprised of four walls arranged to form a rectangular cross-section. At least one of the four walls may include a hole extending from the first edge to the second edge to receive a fastener therethrough. Further, the first edge of the sidewall may be concave along a first of the four walls and along an opposite second of the four walls, and it may be convex along a third of the four walls and along an opposite fourth of the four walls. The concave first edge along the first wall may be a mirror image of the concave first edge along the second wall. Similarly, the convex first edge along the third wall may be a mirror image of the convex first edge along the fourth wall. Moreover, although the concave and convex edges may each comprise one smooth surface, they also may be formed by a plurality of adjacent surfaces.
• In another aspect of the invention, a chisel guide is provided for use in cutting bone of a vertebral body. The chisel guide includes a first block member to be positioned adjacent the vertebral body and a second block member connected to the first block member. The second block member has a channel, formed on one side thereof, which terminates at the first block member.
• In one embodiment of the chisel guide, the first block member and the second block member may be formed as one integral piece. Further, the second block member may extend beyond the perimeter of the first block member in at least one dimension to form a shoulder with the first block member. For example, the second block member may have a width greater than the width of the first block member such that the second block member forms a pair of opposed shoulders with respect to the first member.
• Another aspect of the invention relates to a cutting guide and chisel guide combination for use in removing bone from a vertebral body. The combination includes a cutting guide having a sidewall defining an internal cavity. The sidewall, in turn, has a first edge to face toward and to contact a vertebral body in at least three points and a second, opposite edge to face away from the vertebral body. The combination also includes a chisel guide. The chisel guide has a first block member and a second block member connected to the first block member. The first block member is adapted to be inserted into the internal cavity of the cutting guide to position the first block member adjacent the vertebral body such that a passage remains between a first side of the first block member and an inner surface of the sidewall of the cutting guide.
• In the aforementioned cutting guide and chisel guide combination, the first and second block members may be formed as an integral piece. Moreover, the second block member may be solid. In addition, the second block member may extend beyond the perimeter of the first block member, in at least one dimension, to form a shoulder with the first block member. For example, the second block member may have a width which is greater than the width of the first block member so that the second block member forms a pair of opposed shoulders with respect to the first block member. Finally, the second block member may include a channel which is formed on one side thereof and which terminates at the first block member.
• In yet another aspect of the invention, an apparatus for use in removing bone from a vertebral body is provided. This apparatus includes a shaft and a reamer. The shaft has a first end and a second end, and the second end of the shaft is connectable to a power source. The reamer is connected to the first end of the shaft. The reamer includes at least one cutting member and a collection space to collect bone fragments cut by the cutting member. A slot, through which the bone fragments pass into the collection space, is adjacent the at least one cutting member.
• The reamer may be detachably connected to the first end of the shaft. In addition, the reamer may have a circular cross-section. Various power sources, such as a drill, may be used to rotate the second end of the shaft. In one embodiment, the cutting member is positioned on a bone engaging surface of the reamer. The bone engaging surface of the reamer may be flat, except for the cutting implement and slots associated therewith.
• In still a further aspect of the invention, an apparatus for creating a cavity in a vertebral body endplate and in an intervertebral disc is provided. The apparatus includes a handle, a first arm, and a second arm movable toward the first arm upon actuation of the handle. The apparatus also includes a first cutting implement that is mounted to the first arm and that has a generally circular sidewall that terminates in a first cutting edge. The first cutting edge faces away from the first arm. In one embodiment of the cavity creating apparatus, the first cutting edge also may face away from the second arm. In another embodiment, the first cutting edge may face toward the second arm.
• In addition, the apparatus may also include a second cutting implement mounted to the second arm and having a generally circular sidewall that terminates in a second cutting edge, the second cutting edge facing away from the second arm and facing toward the first cutting edge so that, upon actuation of the handle, the first and second cutting edges move toward each other. The cutting edges of the cutting implements may be serrated. The cutting implements also may be rotatably mounted to their respective arms. Moreover, in an embodiment having two cutting implements, the cutting implements may be mounted to rotate about the same axis of rotation.
• In yet a further aspect of the invention, a tensioner apparatus for use in determining a proper elongation distance in a prosthesis implanted in a vertebral body is provided. The tensioner apparatus includes a first arm and a second arm, each having a handle portion and a separator portion. A pivot joins the first arm to the second arm and separates the separator portions from the handle portions. In addition, at least one tension measuring element is positioned on the first arm; the tension measuring element may be a strain gage.
• The tensioner apparatus also may include at least one strain gage positioned on the second arm. Moreover, the strain gages positioned on the first and second arms may be part of a Wheatstone bridge and may be positioned on the separator portions of the first and second arms, respectively.
• The invention also contemplates a method of creating a cavity in a vertebral body. The cavity creating method includes removably attaching a cutting guide to an outer surface of a vertebral body. The cutting guide has a cavity therein. The method also includes puncturing through the outer surface and cortical bone of the vertebral body along a perimeter of the cavity in the cutting guide, removing the punctured cortical bone of the vertebral body to expose bone in the interior of the vertebral body, and removing the bone in the interior of the vertebral body.
• The method of creating a cavity in a vertebral body may also include inserting a chisel guide in the cavity in the cutting guide. In this method, the puncturing step may include using the chisel guide to guide a chisel, having a chisel blade, along a perimeter of the cavity in the cutting guide. Alternatively, the puncturing step may be accomplished by using a motorized sagittal saw. Regardless of whether a chisel and chisel guide or a sagittal saw is used to puncture through the outer surface and cortical bone, the step of removing the bone in the interior of the vertebral body may be accomplished using a reamer.
• The invention further contemplates a method of creating an intervertebral disc cavity. The method includes providing an apparatus including a first arm having a first cutting implement attached thereto, a second arm, and a handle. The method also includes positioning the first arm in a cavity in a first vertebral body, compressing the handle of compressor so that the first and second arms move in a direction towards each other, cutting through the nucleus pulposus of the intervertebral disc with the first cutting implement, and removing the nucleus pulposus of the intervertebral disc to create the intervertebral disk cavity. This method also may include positioning the second arm of the compressor in a cavity in a second vertebral body, wherein the second arm has a second cutting implement thereon; and cutting through the nucleus pulposus of the intervertebral disc with the second cutting implement.
• The method for creating an intervertebral disc cavity may also include, prior to the step of positioning a first arm of a compressor in a cavity in a first vertebral body, attaching a cutting guide to a surface of the first vertebral body, the cutting guide defining a cavity; cutting through the surface and cortical bone of the first vertebral body along an inside perimeter of the cavity in the cutting guide; removing the cut cortical bone of the first vertebral body to expose bone in an interior of the first vertebral body; removing the bone in the interior of the first vertebral body to create the first vertebral body cavity; and removing the cutting guide from the first vertebral body. Further, the method also may include attaching the cutting guide to a surface of the second vertebral body; cutting through the surface and cortical bone of the second vertebral body along the inside perimeter of the cavity in the cutting guide; removing the cut cortical bone of the second vertebral body to expose the bone in the interior of the second vertebral body; and removing the bone in the interior of the second vertebral body to create the second vertebral body cavity.
• In addition, the invention contemplates a method of applying a predetermined load to an implanted device. The implanted device has a fixation member implanted within a vertebral body and a compressible member implanted within an intervertebral disc. The method includes providing a tensioner including a first arm and a second arm each having a handle portion and a separator portion. A pivot pin joins the first arm to the second arm and separates the separator portions from the handle portions. At least one strain gage is positioned on the first arm. The method also includes inserting the first and the second arms into the fixation member, and moving the handle portions toward each other to thereby move the separator portions away from each other until one of the separator portions contacts an upper member of the fixation member and the other of the separator portions contacts a lower member of the fixation member. The method further includes elongating the fixation member with the tensioner, and monitoring a voltage measured by the at least one strain gage, the voltage being representative of the load applied by the tensioner and thus the reactive load experienced by the compressible member of the implanted device.
BRIEF DESCRIPTION OF THE DRAWINGS
• These and other features, aspects, and advantages of the present invention will become more apparent from the following description, appended claims, and accompanying exemplary embodiments shown in the drawings, which are briefly described below.
• FIG. 1A is a top perspective view of a cutting guide;
• FIG. 1B is a top view of the cutting guide ofFIG. 1A;
• FIG. 1C is a side elevation view of the cutting guide ofFIG. 1A;
• FIG. 1D is a side elevation view of a cutting guide having an alternative shape;
• FIG. 2A is a top perspective view of a chisel guide;
• FIG. 2B is a top view of the chisel guide ofFIG. 2A;
• FIG. 2C is a side elevation view of the chisel guide ofFIG. 2A;
• FIG. 2D is a front elevation view of the chisel guide ofFIG. 2A;
• FIG. 3A is a top perspective view of the chisel guide inserted into the cutting guide;
• FIG. 3B is a top perspective view of a chisel for use with the cutting guide and chisel guide ofFIG. 3A;
• FIG. 3C is a perspective view of the chisel ofFIG. 3B inserted into the cutting guide and chisel guide combination ofFIG. 3A;
• FIG. 4A is an exploded side view, in cross section, of a rotatable shaft and reamer;
• FIG. 4B is an exploded perspective view of the rotatable shaft and reamer ofFIG. 4A;
• FIG. 4C is a perspective view of the rotatable shaft and reamer ofFIGS. 4A and 4B;
• FIG. 5A is a perspective view of an endplate and nucleus cutter;
• FIG. 5B is a side elevation sectional view, in cross section, of the endplate and nucleus cutter ofFIG. 5A;
• FIG. 5C is a side elevation section view, in cross section, of an alternative embodiment of the endplate and nucleus cutter;
• FIG. 6A is a side elevation view of a compressor having a pair of endplate and nucleus cutters mounted thereto;
• FIG. 6B is a side elevation view of a distractor having one endplate and nucleus cutter mounted thereto;
• FIG. 6C is an enlarged side elevation view, in cross section, of encircled area6C-6C inFIG. 6A with the screw removed;
• FIG. 7 is a side elevation view of a tensioner apparatus;
• FIG. 8 is a schematic view of a cutting guide affixed to a curved surface of a vertebral body;
• FIG. 9A is a schematic view of a cutting guide and chisel guide combination and a chisel engaged in the cutting guide and chisel combination to cut through the bone of the vertebral body;
• FIG. 9B is a schematic view of a cutting guide affixed to a vertebral body and a sagittal saw positioned in the cutting guide to cut through the bone of the vertebral body;
• FIG. 10 is a schematic view of a vertebral body with a section of the cortical bone removed from the vertebral body;
• FIG. 11 is a schematic view of a reamer, positioned in the cutting guide, for drilling into the vertebral bone of the vertebral body to create a cavity;
• FIG. 12A is a schematic view of two adjacent vertebral bodies having cavities therein and a compressor having two endplate and nucleus cutters thereon;
• FIG. 12B is a schematic view of the compressor shown in AG.12A with the endplate and nucleus cutters inserted into the cavities of the adjacent vertebral bodies;
• FIG. 13 is a schematic, cut-away left side view of an intervertebral prosthetic device implanted in adjacent vertebral bodies and in an intervertebral disc;
• FIG. 14 is a schematic, cut-away left side view of a cavity in a vertebral body, showing the tensioner positioned therein;
• FIG. 15 is a schematic, cut-away left side view of the adjacent vertebral bodies having an intervertebral prosthetic device implanted therein, wherein the vertebral bodies are provided with bone shavings to induce bone grafting;
• FIG. 16 is a schematic left side view of the adjacent vertebral bodies with the cortical bone repositioned to cover the cavities in the vertebral bodies;
• FIG. 17A is a schematic view of a vertebral body having a cavity therein and an alternative embodiment of the distractor having one endplate and nucleus cutter thereon;
• FIG. 17B is a schematic view of the distractor shown inFIG. 17A with the endplate and nucleus cutter inserted into the cavity of the vertebral body and forced downward into the nucleus pulposus of the intervertebral disc;
• FIG. 18 is a schematic, cut-away left side view of the vertebral body and intervertebral disc ofFIG. 17B having a prosthetic device positioned therein;
• FIG. 19A is a schematic view of a rotatable dome-shaped cutter;
• FIG. 19B is a schematic, cut-away left side view of a vertebral body having a cavity formed therein by the rotatable dome-shaped cutter ofFIG. 19A;
• FIG. 20 is a top perspective view of a cutting guide according to another embodiment;
• FIG. 21 is a top perspective view of a cutting guide according to yet another embodiment;
• FIG. 22 is a top perspective view of a scaffold according to an embodiment; and
• FIG. 23 is a top perspective view of a scaffold according to another embodiment.
• FIG. 24 is a top perspective view of a cutting guide with a protruding spike according to yet another embodiment.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
• Referring now to the drawings, wherein like numerals indicate like parts, and initially toFIGS. 1A-1C and8, there will be seen a cuttingguide20 for use in removingbone22 from avertebral body24. The cutting guide is designed to be placed into contact with the outer surface of thevertebral body24 to “guide” a surgical instrument as it cuts through the cortical bone of the vertebral body, as shown in FIGS.8 and9A-9B and as later described in more detail. In this regard, the cuttingguide20 has a sidewall that defines aninternal cavity34 extending through the cuttingguide20. The sidewall generally has fourwalls26,28,30,32 arranged to form a rectangular cross-section. Although thecavity34 is preferably rectangular in cross section, thewalls26,28,30,32 can be configured to define a cavity that is square in cross-section or any other suitable geometric shape.
• The cuttingguide20 has afirst edge38 to face toward and to contact thevertebral body24. The cutting guide also has a second, oppositeedge36 to face away from thevertebral body24. Thefirst edge38 of the cutting guide is contoured to contact the vertebral body in at least three points, although it will be understood that thefirst edge38 can have four or more points of contact with a vertebral body. Thefirst edge38 includes bothconcave portions40 andconvex portions42 configured to fit against the curved, outer surface of thevertebral body24. Thesecond edge36 of the cuttingguide20 is substantially planar.
• Theconcave portions40 of thefirst edge38 are oriented generally perpendicular to theconvex portions42. In particular, theconcave portions40 are formed along thefirst edge38 ofopposite walls26,30, and theconvex portions42 are formed along thefirst edge38 ofopposite walls28,32. The concave first edge along thewall26 preferably is a mirror image of the concave first edge along thewall30. Similarly, the convex first edge alongwall28 preferably is a mirror image of the convex first edge alongwall32. In addition, as can be seen best inFIG. 1B, theconcave portion40 of thefirst edge38 ofwall26 preferably terminates before it reaches either end of thewall26 to create flattenedportions41; the same is true of the concave portion ofwall30. These flattenedportions41 add stability to the cuttingguide20 when it is positioned against the vertebral body, as later described. Further, although theconcave portions40 andconvex portions42 may be smooth surfaces, they also may be formed by a plurality of adjacent straight surfaces. For example, as can be seen inFIG. 1C, theconvex portion42 preferably is a smooth, curved surface; however, it will be understood that the convex portion can be formed by a plurality ofstraight segments41′, as shown, for example, inFIG. 1D.
• A plurality ofholes44 pass through the cuttingguide20 fromedge36 to edge38. Theseholes44 are adapted to receivefasteners48, as shown inFIG. 8, to secure the cuttingguide20 to thevertebral body24. Although theholes44 can be positioned anywhere alongedges36,38, it is preferable that they be positioned to extend throughwalls28,32 havingconvex portions42. In addition, althoughFIGS. 1A-1C show sixholes44, one of ordinary skill in the art will understand that fewer or more holes can be employed in the cuttingguide20 without departing from the broadest scope of the invention. Moreover, in a cutting guide having more than fourholes44, a surgeon need not position fasteners in all holes, but, in fact, may only need fasteners in twoholes44 to secure the cuttingguide20 to the vertebral body, depending on the surface contour of the vertebral body. In one preferred embodiment, three or fourholes44 would receive afastener48.
• Turning toFIGS. 2A-2D, there is shown achisel guide50 for use in cutting bone of avertebral body24. The chisel guide50 can be used in combination with the cuttingguide20 to guide achisel62, or osteotome, as seen inFIG. 3B, toward thecortical bone22 of thevertebral body24. Thechisel62 then can cut through thebone22 to expose the inside of thevertebral body24, as will be later described in more detail. Thechisel guide50 includes afirst block member54 to be positioned towards thevertebral body24 and asecond block member52 connected to thefirst block member54. Although theblocks52,54 may be separate pieces joined together to form thechisel guide50, they preferably are solid and integrally molded or machined as one piece. Thesecond block52 preferably extends beyond the perimeter of thefirst block54 in at least one dimension to form ashoulder56 with respect to thefirst block54. For example, thefirst block54 has a first width W1, and thesecond block52 has a second width W2 greater than the first width W1, thereby formingopposed shoulders56 with respect to thefirst block54. In addition, thesecond block52 can have achannel58 formed in atop side60 thereof. Thechannel58 terminates at thefirst block54. Thechannel58 may receive aprojection59 on achisel62, as shown inFIG. 3B, when thechisel guide50 is positioned in the cuttingguide20.
• Although theblocks52,54 can have approximately the same height, they are vertically offset from each other, thereby creating tworidges76,78. As later described in detail, thefirst ridge76, formed by part of thesecond block52, is designed to engage theflat edge36 of the cuttingguide20. Similarly, thesecond ridge78, formed by part of thefirst block54, serves as a chisel guiding edge by abutting asurface63 on thechisel62 to prevent thechisel62 from penetrating too deep into thevertebral body24. In this way, thesurface63 can act as a safety stop.
• Thesecond block52 of thechisel guide50 has twoside surfaces68,70, abottom surface72, and two connectingsurfaces64,66 extending between eachside surface68,70 and thebottom surface72, as shown most clearly inFIGS. 2C and 2D. The connecting surfaces64,66 not only make it easier to position thechisel guide50 in the cuttingguide20, they also provide the surgeon with access to at least onehole44 formed inedge36 so thatfasteners48 can be driven through theholes44 in theedge36 while thechisel guide50 is positioned in the cuttingguide cavity34, as shown inFIG. 3A. Accordingly, although the connectingsurfaces64,66 are shown as being slanted, they could be any shape which provides sufficient access toholes44 inedge36; for example, thesurfaces64,66 could be curved.
• FIGS. 3A-3C show a combination of the cuttingguide20 and thechisel guide50, how they engage each other, and how thechisel62 can be inserted and guided into the cuttingguide20 by thechisel guide50. Thefirst block54 of thechisel guide50 is designed to fit in thecavity34 of the cuttingguide20 so that theshoulders56 and theridge76 of thesecond block52 abut theflat edge36 of the cuttingguide20. Theshoulders56 are designed to abut two opposite walls of the cuttingguide20 whenever thechisel guide50 is inserted in the cuttingguide20. When so positioned, the cuttingguide20 and thechisel guide50 create a restrictedpassage80 for insertion of thechisel62; thepassage80 is between a first side of thefirst block54 and an inner surface of the sidewall of the cuttingguide20.
• Thepassage80 is sized so that ablade82 of thechisel62 can pass therethrough in a controlled direction, as shown inFIG. 3C. Thechisel62 can have aprojection59 on oneside61 thereof which slidably engages thechannel58 in thetop side60 of thesecond block52. When the cuttingguide20 is affixed to avertebral body24, and thechisel guide50 is positioned in thecavity34 of the cuttingguide20 to create thepassage80, a surgeon can insertchisel blade82 into thepassage80 to make a straight cut into thebone22 of thevertebral body24. The chisel can be inserted into the restrictedpassage80 until thesurface63 on thechisel62 abuts thesecond ridge78 on thefirst block54. In this position, a first cut can be made into thevertebral body24 along afirst wall26 of the cuttingguide20.
• After the first cut is made, thechisel guide50 can be rotated 180 degrees from the orientation shown inFIG. 3A to create a passage for thechisel blade82 adjacent anopposite wall30 of the cuttingguide20, at which a second cut can be made into thevertebral body24. The second cut is substantially parallel to the first cut. In this regard, the first width W1 of thefirst block54 preferably is less than or equal to the inner distance between thewalls28,32.
• As mentioned above, the cuttingguide20 can be rectangular or square. If the cuttingguide20 has a rectangular shape, as shown inFIG. 1A, then the surgeon can use a second chisel guide to make cuts alongwalls28,32. The first block member of this second chisel guide has a width less than or equal to the inner distance between thewalls26,30. Using this second chisel guide, the surgeon can make third and fourth cuts substantially perpendicular to the first and second cuts along the inner edges ofwalls28,32. As a result, a substantiallyrectangular cut202 can be made in a controlled manner into thevertebral body24. This surgical technique will be described in more detail in connection withFIGS. 9A and 10.
• If the cutting guide is square in shape, after the first and second cuts the surgeon can rotate asingle chisel guide 90 degrees clockwise from the orientation ofFIG. 3A, to make a third cut into the vertebral body alongwall28. Further, after the third cut, the surgeon can rotate the chisel guide 180 degrees, to make a fourth cut into the vertebral body alongwall32.
• FIGS. 4A-4C show areamer90 and arotatable shaft92 for removing or coring bone out of the vertebral body. Afirst end96 of theshaft92 has aplate98 affixed thereto. On theplate98, there are a plurality ofpins100 and preferably aboss102 that face away from asecond end94 of theshaft92. Theboss102, which is preferably cylindrical, can matingly engage acorresponding bore110 in thereamer90, as later described. Thesecond end94 of theshaft92 is adapted to engage a power source, such as a hand or power drill, which is adapted to rotate theshaft92.
• Referring toFIGS. 4B and 4C, thereamer90, which is preferably circular in cross section, includes aplate104 at afirst end106. Theplate104 is adapted to engage theplate98 on theshaft92. Specifically, theplate104 has afront surface105 with a plurality ofchannels108 and abore110 therethrough. Thebore110 passes through a central portion of theplate104. Thechannels108 are adapted to receive thepins100 ofplate98, and thebore110 is adapted to fit over theboss102, to mount thereamer90 to theshaft92. Thepins100 are tight-fit into thechannels108 so that when theshaft92 is rotated, for example, by a drill, thereamer90 is rotated in unison with theshaft92. In addition, thereamer90 has acollection space112 for capturingbone shavings118 as the reamer rotates and removes bone from thevertebral body24.
• To remove bone from thevertebral body24, thereamer90 includes at least one cuttingmember114 positioned at a second,bone engaging end116 of thereamer90. The cuttingmember114 preferably comprises a plurality of blades. Theblades114 extend angularly from thebone engaging end116 of thereamer90, as seen inFIG. 4A. Aslot120, which preferably is rectangular, is positioned adjacent eachblade114. When asurface117 of thebone engaging end116 of thereamer90 is positioned adjacent cancellous bone and rotated, theblades114 shave through the bone and the interior of avertebral body24. Thebone shavings118 pass through theslots120 and into thecollection space112. Theshavings118 can be collected and stored in thecollection space112 for later use as needed. Thesurface117 of thebone engaging end116 is flat except forblades114 andslots120.
• As shown inFIGS. 4A-4C, thereamer90 has acylindrical portion109 which is adapted to be journalled into thecavity34 of the cuttingguide20, as shown inFIG. 11. Thecylindrical portion109 includes acontact surface107 on theplate104. Thecontact surface107 is on the side opposite thesurface105 that abuts theplate98 at thefirst end96 of theshaft92. When thecylindrical portion109 is inserted to the maximum depth to which the surgeon should bore into avertebral body24, thecontact surface107 abuts thesecond edge36 of the cuttingguide20. The contact between theplate104 and thesecond edge36 of the cuttingguide20 prevents the surgeon from inadvertently reaming too far into thevertebral body24.
• Referring now toFIGS. 5A-5C and6A-6C, a cutting implement that can be mounted to acompressor160 or adistractor500 in accordance with the invention will now be described. The cutting implement can be made to cut through an endplate (208 inFIG. 13) of avertebral body24 and the nucleus pulposus of theintervertebral disc200 adjacent thevertebral body24. Turning first toFIGS. 5A-5B, there is shown an example of a cutting implement which may be used in conjunction with thecompressor160 ordistractor500. Specifically, the exemplary cutting implement is in the form of an endplate andnucleus cutter130 having a substantiallycircular sidewall132 that terminates in acutting edge134. The diameter of the substantially circular sidewall will depend on the size of the nucleus pulposus to be removed. The maximum diameter of the sidewall should be greater than the minimum diameter of the nucleus pulposus and/or the diameter of theprosthesis220,230 to be implanted. In addition, thecutting edge134 can be smooth or, alternatively, serrated. Thecutting edge134 may be thinner than thesidewall132 and may be tapered to asharp end137. In addition, the endplate andnucleus cutter130 has a base136 to which thesidewall132 is attached. Thebase136 and thesidewall132 define an essentially hollowcylindrical cavity138. Extending from the base136 in thecavity138 is aprojection140 that contains ascrew hole188 adapted to receive ascrew142. Although theprojection140 may extend only part way into thecavity138, it can extend beyond thesharp edge137, as shown inFIG. 5B. In the embodiment ofFIG. 5B, the tip ofprojection140 can be used to create a notch in an endplate, thereby bracing the endplate andnucleus cutter130 relative to the endplate. Theprojection140 then can serve as an axis of rotation. This bracing effect enables a surgeon to cut through the endplate with thesharp end137 of the endplate andnucleus cutter130 without risk that the endplate andnucleus cutter130 will inadvertently slide from its proper position relative to the endplate surface.
• An alternative embodiment of the endplate andnucleus cutter130 is shown inFIG. 5C. The only difference between this embodiment and the one shown inFIG. 5B is that theprojection140′ is cylindrical in shape and has a concave end. An advantage of employing the embodiment ofFIG. 5C with the embodiment ofFIG. 5B on asingle compressor160 is that when thesharp edges137 of the two endplate andnucleus cutters130 approach each other, the tip of theprojection140 will be partially journalled into the concave end portion of theprojection140′.
• With respect toFIG. 6A, thecompressor160 includes ahandle162, which has two scissor-like members164,166 pivotally joined at apivot167, such as a pin. Thefirst member164 is joined at apin168 to afirst arm170. Achannel172 is located in thefirst arm170, and aprojection pin174 extending from thesecond member166 can slide in thechannel172. Similarly, thesecond member166 is joined at apin176 to asecond arm178. Thesecond arm178 is substantially parallel to thefirst arm170. In addition, like thefirst arm170, thesecond arm178 has achannel180 in which aprojection pin182 extending from thefirst member164 can slide.
• In the preferred embodiment shown inFIG. 6A, an endplate andnucleus cutter130 is attached to anend portion186 of thefirst arm170 and faces toward thesecond arm178. Similarly, an endplate andnucleus cutter130 is attached to anend portion186 of thesecond arm178 and faces toward the first arm170 (i.e., toward the other endplate and nucleus cutter130).
• When thehandle162 is compressed by pressingmembers164,166 toward each other, the projection pins174,182 slide in theirrespective channels172,180, and the first andsecond arms170,178 move toward each other in parallel. In addition, as the first andsecond arms170,178 move toward each other, thearms170,178 maintain their approximately parallel orientation. Moreover, as the first andsecond arms170,178 approach each other in parallel, the endplate andnucleus cutters130 also approach each other. Preferably, the endplate andnucleus cutters130 on the first andsecond arms170,178 share a common central axis so that, when thehandle162 is fully compressed, the cuttingedges134 of the endplate andnucleus cutters130 on the first andsecond arms170,178 contact each other.
• The endplate andnucleus cutters130 can be either fixedly mounted or rotatably mounted to thearms170,178 of thecompressor150. When the endplate andnucleus cutters130 are fixedly mounted, the surgeon can manually rotate thecutters130 by swinging thehandle162 of thecompressor150 side-to-side. This side-to-side motion, combined with compression of thehandle162, enables the cuttingedges134 to cut through the endplate and nucleus pulposus of the damaged disc. Alternatively, the endplate andnucleus cutters130 may be rotatably mounted to the compressor. A motor or other drive source can be connected to thecutters130 to rotate them relative to thearms170,178 of thecompressor150.
• Thecompressor160 is shown having two endplate andnucleus cutters130 thereon which face inward and toward each other. Thecompressor160 is used, as later explained in detail, when a surgeon wants to implant aprosthetic device220 having twofixation members222, one of which is to go into avertebral body24 above aproblematic disc200 and the other of which is to go into thevertebral body24 below the problematic disc.
• In some situations, however, the surgeon needs to implant only onefixation member222, for example, as shown inFIG. 19B, and as will be described below. In such situations, adistractor500, which has one outwardly facing endplate andnucleus cutter130 is preferred.FIG. 6B shows adistractor500 having one endplate andnucleus cutter130 on afirst arm514 which faces outward and away from asecond arm510. Similarly, an outwardly facingplate540 is rotatably attached to thesecond arm510 by means of an axle542. Theplate540 is designed to be placed against an endplate in a vertebral body and to remain immobile relative thereto. As the endplate andnucleus cutter130 of thedistractor500 is either manually rotated by the surgeon (in an embodiment where the endplate andnucleus cutter130 is fixedly mounted to the distractor500) or rotates as a result of a motor applied thereto (in an embodiment where the endplate andnucleus cutter130 is rotatably mounted to the distractor500), the endplate andnucleus cutter130 will cut through one endplate in avertebral body24, while theplate540 remains pressed against the other endplate in thevertebral body24. Theplate540 does not abrade the vertebral body against which it is placed because it does not rotate with respect to that endplate.
• Thedistractor500 has two scissor-like members502,504 which together form ahandle506. The scissor-like members502,504 are rotatably attached to one another by apin518. In addition, the first scissor-like member504 is rotatably connected to thefirst arm514 by means of apin522. Aprojection pin526 extending from the first scissor-like member504 is adapted to slide in aslot508 in thesecond arm510. Similarly, the second scissor-like member502 is rotatably connected to thesecond arm510 by means of apin520. Further, aprojection pin524 extending from the second scissor-like member502 is adapted to slide in aslot512 in thefirst arm514.
• When thehandle506 of thedistractor500 is compressed, thehandle members502,504 pivot with respect to each other atpin518, thereby correspondingly increasing the distance between the projection pins524,526. As the distance between the projection pins524,526 increases, the pins slide forward in theirrespective slots512,508. Simultaneously, the distance between therotating pins522,520 and hence the distance between the first andsecond arms514,510 increases. In this manner, by compressing thehandle506, a surgeon can produce parallel distraction of thearms510,514 to increase the distance between the endplate andnucleus cutter130 and theplate540.
• When thearms514,510 of thedistractor500 are inserted into acavity206 in avertebral body24 and the handle is subsequently compressed, theplate540 will move in one direction to contact theendplate208 of thevertebral body24, whereas the endplate andnucleus cutter130 will move in an opposite direction to contact theother endplate208 of thevertebral body24. Continued compression of thedistractor500 and rotation of the endplate andnucleus cutter130 will force thecutter130 through theendplate208 and nucleus pulposus of theintervertebral disc200 adjacent thereto.
• Various methods exist by which an endplate and nucleus cutter can be connected to anarm170,510 of acompressor160 ordistractor500, respectively. For example, as shown inFIGS. 5B and 6C, thehead148 of thescrew142 is contained within aconnective plate146, which forms part of anarm170,178 of thecompressor160 or anarm510,514 of thedistractor500. The threadedportion150 of thescrew142 passes through aspacer144 and thebase136 and terminates in theprojection140. Theconnective plate146 has ahole184 through which the threadedportion150 of thescrew142 passes; the diameter of thehole184 in theconnective plate146 is smaller than the diameter of thehead portion148 of the screw. The height of thehead portion148 is approximately the same as that of arecess158 inplate146, thereby allowing thehead portion148 to sink into theconnective plate146, as shown inFIG. 5B.
• The preceding discussion provides one way in which the endplate andnucleus cutter130 can be fixedly mounted to theend portion186 of the arm of acompressor160 or adistractor500. However, those of ordinary skill in the art will understand that the endplate andnucleus cutter130 can be mounted to theend portion186 in other ways. For example, in one preferred method, which is more permanent and integral in nature, the endplate and nucleus cutter is attached to theend portion186 by riveting or otherwise suitably fastening the base136 directly to theend portion186, without use of aconnective plate146 or aspacer144.
• Moreover, thescrew142 could be adapted to be connected to (or be part of) a rotatable shaft which, in turn, is connected to a motor, such as a drill, to provide automatic rotation of the endplate andnucleus cutter130. In this manner, the endplate andnucleus cutter130 can be mounted so that theconnective plate146 can rotate independently of thecompressor160 or distractor500 (if driven, for example, by a motor, not shown). Rotation of theconnective plate146 will cause a corresponding rotation of the endplate andnucleus cutter130 attached thereto. Rotational friction can be avoided due to agap152 between theplate146 and the base136 generated by thespacer144. Moreover, if the two endplate andnucleus cutters130 ofFIG. 6A are mounted to rotate, they can share generally the same axis of rotation.
• Finally, it should also be readily apparent to one of ordinary skill in the art that the endplate andnucleus cutter130 could have a cutting surface similar to thesurface117 of thebone engaging end116 of thereamer90 shown inFIGS. 4A-4C.
• The preceding discussion, provided a general description of how the endplate andnucleus cutter130 can be attached to thecompressor160 anddistractor500. A detailed description follows. To attach the endplate andnucleus cutter130 to thecompressor160, thespacer144 is positioned on the side of thearm170,178 from which the endplate andnucleus cutter130 is to project. Thespacer hole154 is aligned with thehole184 through theconnective plate146. The endplate andnucleus cutter130 is then centrally positioned on top of thespacer144 so thathole188 in theprojection140 is aligned with both thehole154 in thespacer144 and thehole184 in theconnective plate146. The threadedportion150 ofscrew142 is then inserted through thehole184 in theconnective plate146 and thehole154 in thespacer144 until the threadedportion150 engages a mutually engaging threaded portion156 of thehole188. By turning thescrew142, the threadedportion150 of thescrew142 engages the threaded portion156 of thehole188, thereby holding the endplate andnucleus cutter130 onto thearm170. In addition, thehead portion148 of thescrew142 is received by therecess158 in theconnective plate146, thereby minimizing height H. Various alternative methods may be used to attach the endplate andnucleus cutter130 to thearms170,178 of acompressor160; however, the height H (as shown inFIG. 6C) should be less than the height of thecavity206 formed invertebral body24, as later described.
• Connecting the endplate andnucleus cutter130 to thedistractor500, as shown inFIG. 6B, is readily achieved by inverting the orientation of the endplate and nucleus cutter ofFIG. 6A. If this orientation is chosen, a recess, similar to therecess158 formed on the side of thearm170 shown inFIG. 6C (i.e., adapted to receive thehead portion148 of the screw142) should be formed on the other side of thearm170. However, as both the first andsecond arms514,510 of the distractor will be inserted into thesame cavity206, the height (H) of the first arm514 (with the endplate andnucleus cutter130 attached thereto) plus the height (X) of the second arm510 (with theplate540 attached thereto) must be less than the height of thecavity206 in thevertebral body24.
• In mounting the endplate andnucleus cutter130 to create the embodiment shown inFIG. 6B, the surgeon must place thespacer144 on the opposite side of thearm170 as that shown inFIG. 6C. When this is completed, thescrew142 can be journalled through ahole184 in thearm514 and through thehole154 in thespacer144, in a manner similar to that of the embodiment shown inFIG. 6C. The threadedportion150 of thescrew142 may then engage the correspondingly threaded portion156 in theprojection140, thereby holding the endplate andnucleus cutter130 against thearm514.
• It will be understood that an endplate andnucleus cutter130 can be mounted to devices having a configuration different than thecompressor160 anddistractor500. For example, an endplate andnucleus cutter130 can be attached to an end of a single arm, and a surgeon can grip the opposite end of the single arm to position the endplate andnucleus cutter130 appropriately to cut through the endplate and the nucleus pulposus of a damaged disc. The single arm can be bent to provide additional leverage.
• After a cavity is formed in theintervertebral disc200 by either thecompressor160 or thedistractor500, an appropriate prosthetic device is implanted in the cavity. The implanted device can include twofixation members222 and acompressible member224, as shown inFIG. 13, or, in an alternative embodiment, the implanteddevice230 can include asingle fixation member222 and a compressible member, as shown inFIG. 18. Once the implanted device is in place, the surgeon must restore the intervertebral distance, i.e., the distance between two adjacent vertebrae; this is achieved by tensioning the implanted device. That is, the load applied by the implanted device between the vertebrae on opposite sides of the excised, damaged intervertebral disc should be sufficient to recreate the approximate disc height of a healthy intervertebral disc. To do so, the surgeon can use atensioner300, as shown inFIG. 7. Thetensioner300 can be used to measure the tension or load applied to thecompressible member224 by the fixation member(s)222. That is, thetensioner300 can be used to determine when thefixation member222 has been elongated sufficiently to apply the proper force (or load) on thecompressible member224, as will be more fully described in connection withFIG. 14.
• Thetensioner300 shown inFIG. 7 includes first andsecond arms302,304, each of which has ahandle portion306,308 and aseparator portion310,312. Thearms302,304 are connected by a pivot pin316, which separates theseparator portions310,312 from thehandle portions306,308. Positioned on at least one (and preferably both) of theseparator portions310,312 is at least one tension measuring element. The tension measuring element preferably is astrain gage314 comprised of resistors or other suitable load cell devices. It should be understood, however, that the tension measuring element may be a torque needle, a spring, a transducer other than a strain gage, or other suitable device for measuring tension. The strain gages314 can be cemented, glued, or otherwise fastened on theseparator portions310,312. In a preferred embodiment, thestrain gages314 are part of Wheatstone bridge circuits. Leads from thestrain gages314 are connected bywires318 to acircuit monitoring device320 which can measure the resistance and voltage across thegages314.
• When thehandle portions306,308 of thetensioner300 are compressed, i.e., moved toward each other, theseparator portions310,312, by means of the pivot pin316, move away from each other. If theseparator portions310,312, when moved away each other, contact a generally immobile surface, continual compression of thehandle portions306,308 will cause theseparator portions310,312 to bend slightly in the vicinity of the strain gages314. As theseparator portions310,312 bend, thestrain gages314 are stretched or compressed, as appropriate, thereby changing the resistance of the resistors. As the resistance changes, the voltage across thestrain gages314 correspondingly changes, where the current in the circuit is constant. By monitoring the voltage, a surgeon can determine when a predetermined load has been reached, the voltage being representative of the predetermined load.
• A method of creating a cavity in a vertebral body will now be described with respect toFIGS. 8-16.FIG. 8 shows the anterior aspects of twovertebral bodies24 separated by anintervertebral disc200. A cuttingguide20 is positioned on a side surface of the uppervertebral body24 such that thewalls26,30 having the concave edges are substantially parallel to the vertebral body endplates208. The concave andconvex portions40,42 of the cuttingguide20 are shaped so as to fit against the curved surface of thevertebral body24. As the surface geometry of vertebral bodies varies somewhat between patients, typically either a three-point or four-point contact is achieved between the cuttingguide20 and thevertebral body24.
• As the cuttingguide20 is held against thevertebral body24, a drill bit is journalled through one of theholes44 in the cuttingguide20, and a hole is drilled into thevertebral body24. A fastener48 (e.g., drill bit, screw, nail, or pin) is then journalled through thehole44 in the cutting guide and is received by the hole drilled into thevertebral body24. If thefastener48 is, for example, a screw, the screw would be turned into the hole in thevertebral body24 by conventional means, thereby securing the cuttingguide20 to thevertebral body24. If thefastener48 is a pin or a nail, it can be driven into thevertebral body24 by tapping with a hammer or similar device. This process is then repeated forother holes44 in the cuttingguide20 until the cutting guide is secured to thevertebral body24. As a result, a plurality offasteners48 hold the cuttingguide20 onto thevertebral body24. Although the figures disclose the use of fourfasteners48, any suitable number of fasteners can be used.
• By journalling thefasteners48 through theholes44, the cuttingguide20 can slide off thefasteners48 while the fasteners remain secured to thecortical bone22, provided no part of thefasteners48 has a diameter larger than the diameter of theholes44. This ability to slide the cuttingguide20 facilitates removal of the cutting guide20 (for purposes of removing arectangular section204 ofcortical bone22, as later described), while preserving the ability to reposition quickly the cuttingguide20 on the vertebral body24 (for purposes of reaming thevertebral body24, as later described). In addition, to avoid sliding the cuttingguide20 completely off of thefasteners48, it is possible to usefasteners48 having a length much greater than the cumulative depth of the cuttingguide20 and the holes drilled into the cortical bone. Usingfasteners48 of this nature will allow the surgeon to slide the cuttingguide20 away from thevertebral body24 to a sufficient distance at which thecortical bone22 of thevertebral body24 can be accessed. In this regard, the surgeon can remove a generallyrectangular section204 ofcortical bone22 and then quickly and easily reposition the cuttingguide20 on thevertebral body24, as is necessary before the vertebral body's24 interior cancellous bone may be removed byreamer90, as later described.
• Turning now toFIG. 9A, there is shown avertebral body24 having a cuttingguide20 affixed thereto. Positioned in the cuttingguide20 is achisel guide50 and ablade82 of achisel62. The width W1 of thefirst block member54 is less than or equal to the inner distance between twosidewalls28,30 of the cuttingguide20. Theshoulders56 and theridge76 on thesecond block52 of thechisel guide50 rest against theflat edge36 of the cuttingguide20. In addition, theblade82 of achisel62 is channeled through thepassage80 created between the cuttingguide20 and thechisel guide50.
• Once theblade82 is positioned against thecortical bone22 of thevertebral body24, the free end of thechisel60 can be tapped to drive theblade82 into thecortical bone22. In this manner, thechisel blade82 punctures through thecortical bone22 and cuts into the cancellous bone in the interior of thevertebral body24, thereby forming a first cut. In a preferred embodiment, when theblade82 of thechisel62 is driven into thevertebral body24 to a maximum allowable depth, thesurface63 on thechisel62 abuts thesecond ridge78 on thefirst block54, thereby preventing theblade82 from being driven further into thevertebral body24. In this fashion, thesurface63 can act as a safety stop.
• Due to the controlled manner of supporting the chisel62 (i.e., by using the chisel guide50), the surgeon can ensure a nearly straight cut through thebone22 of thevertebral body24. The nearly straight cut occurs along one side of an inside perimeter of thecavity34 of the cuttingguide20. In addition, preferably fluoroscopy or radiographs are used to ensure that the transverse cuts made into and through the bone (to the depth limited by thesurface63 on thechisel62 abutting thesecond ridge78 on the first block54) are generally parallel to theendplates208 of thevertebral body24.
• Once the first transverse cut is made, the surgeon removes the chisel guide50 from the cuttingguide20, rotates it 180 degrees toward anopposite wall30, slides it back into the cuttingguide20, and creates a second cut into thecortical bone22 of thevertebral body24. This rotation will allow the surgeon to ensure that the cut made by theblade82 of thechisel62 is approximately parallel to the first cut.
• After the first and second cuts are complete, the surgeon removes thechisel guide50 and, if the cuttingguide20 is rectangular, inserts a second chisel guide. The width of the first block member of this second chisel guide is less than or equal to the inner distance between the upper andlower walls26,30 of the cuttingguide20. The second chisel guide is inserted into the cuttingguide20 at anorientation 90 degrees from the chisel-guide orientation shown inFIG. 3A, to create a passage for the chisel blade that is substantially perpendicular to the first and second cuts. In this position, a third cut can be made alongwall28. Next, the second chisel guide is rotated 180 degrees, in order that a fourth cut can be made alongwall32. The four completed cuts form a substantiallyrectangular cut202 into thecortical bone22 along an inner perimeter of the cuttingguide20.
• Alternatively, the surgeon can chisel along the inner perimeter of the cuttingguide20 without using achisel guide50. Moreover, if a square cutting guide is employed, then only a single chisel guide would be necessary; after a first cut is made, that is, the chisel guide could be rotated 90, 180, and 270 degrees from its first orientation in the square cutting guide to make second, third, and fourth cuts, respectively, into thevertebral body24.
• FIG. 9B shows an alternative manner by which cuts can be made in thecortical bone22 of thevertebral body24. Rather than using a chisel62 (with or without a chisel guide50), the surgeon can use asagittal saw46 to make the cut into thecortical bone22. The surgeon can also use the sagittal saw46 to make preliminary shallow cuts in thecortical bone22 and, afterward, use thechisel guide50 and/or chisel62 to make final cuts.
• As shown inFIG. 10, aftercut202 is made in thecortical bone22, the cuttingguide20 is either removed or withdrawn along thefasteners48 to a distance sufficient to allow access to thecortical bone22 and therectangular cut202. In either case, some or all of thefasteners48 can remain in thecortical bone22 of the vertebral body. Once the cuttingguide20 is removed or withdrawn,section204 of cortical bone22 (defined by cut202) is removed using an osteotome, thereby exposing the cancellous bone in the interior of thevertebral body24. After thesection204 is removed, the cuttingguide20 is re-affixed to thevertebral body24 by journalling thefasteners48 projecting from thevertebral body24 through theholes44 in the cuttingguide20, as shown inFIG. 11.
• Once the cuttingguide20 is re-affixed to thevertebral body24, the surgeon can use areamer90 to drill acavity206 in thevertebral body24 as shown inFIG. 11. The bone which is removed to form thecavity206 is cut intobone shavings118 by cutting implement114 on thesecond end116 of thereamer90. Theshavings118 pass through theslots120 in theend116 of thereamer90 and into thecavity112 in thereamer90. When thevertebral body cavity206 is both wide enough and deep enough to accept afirst fixation member222 of aprosthetic device220 which will rest in acavity206 ofFIG. 12A, such as shown inFIG. 13, the surgeon stops reaming and removes theshavings118 from thecavity112 in thereamer90. Theshavings118 can be used after implantation of aprosthetic device220 to promote bone ingrowth into theprosthetic device220, as later described. Thefirst fixation member222 then can be temporarily placed in the cavity and centered using fluoroscopy. If thefirst fixation member222 cannot be properly centered (i.e., if thecavity206 is slightly too mall), the surgeon can use a mechanical burr or curette to remove sufficient bone to allow thefirst fixation member222 to fit within thecavity206. Thefixation member222 then is removed from thecavity206.
• After thecavity206 is formed in the uppervertebral body24, the surgeon goes through the same process with respect to the lowervertebral body24 to form acavity206 therein, as shown inFIG. 12A. Once the twocavities206 are created, thefasteners48 can be removed from thecortical bone22 of thevertebral bodies24.
• After thefasteners48 are removed, acompressor160, having cutting implements on each of its first andsecond arms170,178, is adjusted so that the cutting implements can simultaneously pass into thecavities206 in thevertebral bodies24. The cutting implements preferably are endplate andnucleus cutters130. Prior to compression of thecompressor160, fluoroscopy can be used to ensure that the cutting implements are centered in thecavities206 in thevertebral bodies24.
• Where endplate andnucleus cutters130 are used as the cutting implements, upon compression of thehandle162, as shown inFIG. 12B, the twoarms170,178 and the endplate andnucleus cutters130 are brought towards each other. By compressing thehandle162, the generallycircular cutting edges134 of the endplate andnucleus cutters130 move in an axial direction and cut through the endplates208 (shown cut-through inFIG. 13) of the respectivevertebral bodies24 and then through the nucleus pulposus of theintervertebral disc200 separating thevertebral bodies24; the annulus fibrosis of thedisc200 remains intact. When the endplate andnucleus cutters130 contact each other in a central portion of thedisc200, compression is stopped.
• To facilitate cutting, the endplate andnucleus cutters130 can be manually rotated during compression; that is, thecompressor160 can be twisted side-to-side during compression. Or, if the endplate andnucleus cutters130 are mounted for mechanical rotation to thecompressor arms170,178, thecutters130 can be mechanically rotated during compression to facilitate cutting.
• After thecompressor160, and its dual endplate andnucleus cutters130, are removed from thevertebral bodies24, the portions of theendplates208 and theintervertebral disc200, through which the generallycircular cutting edges134 of the endplate andnucleus cutters130 were forced, are removed, thereby creating a generallycylindrical channel212 from the lowervertebral body24 through theintervertebral disc200 and to the uppervertebral body24. Thechannel212, which is formed, in part, by thecavities206 in thevertebral bodies24, will hold the entireprosthetic device220 as shown inFIG. 13.
• A suitable prosthetic device for implantation inchannel212 is described in U.S. Pat. No. 5,827,328, incorporated herein by reference in its entirety. It is preferable that all parts of theprosthetic device220,230 be formed or machined from a biocompatible material, such as cobalt-chrome alloy. Initially, acompressible member224 of an appropriate size and with appropriate angulation is selected based on the size and location of thedisc200 to be replaced and on the size of the patient. More specifically, choosing the propercompressible member224 will depend both on the size of the annulus fibrosis in the particular disc200 (which had its nucleus pulposus removed) and on the approximate lordosis of the motion segment level of thedisc200 that is being replaced. Once thecompressible member224, which may include a series of springs, is selected, it is inserted into thecavity206 in one of thevertebral bodies24. Thecompressible member224 then is pushed into the hole in theintervertebral disc200 that originally contained the nucleus pulposus. Thecompressible member224 then is oriented so as to maintain lordosis (i.e., the thicker portions of thecomponent224 are placed anteriorly, as shown inFIG. 13).
• After thecompressible member224 is in place, afirst fixation member222 is positioned in one of thecavities206 in thevertebral bodies24. Thefixation member222 is then connected to thecompressible member224, and the lordotic alignment is rechecked. Next, asecond fixation member222 is positioned in thecavity206 in the othervertebral body24 and is connected to the other side of thecompressible member224, thereby completing implantation of theprosthetic device220.
• Each of thefixation members222 has anupper plate260 and alower plate262. A plurality of verticallyadjustable struts264 are positioned between the upper andlower plates260,262. When thestruts264 are unlocked, their height can be easily changed. When thestruts264 are locked, their height remains constant.
• Once thefixation members222 are properly positioned in thevertebral bodies24, the tension or load experienced by thecompressible member224 of theprosthetic device220 needs to be adjusted to optimize the normal loading and compression (i.e., the functionality) of theparticular disc200 being replaced. To do so, the surgeon inserts theseparator portions310,312 of atensioner300 into the upper one of thefixation members222. Upon compression of the tensioner'shandle portions306,308, theseparator portions310,312 move away from each other into contact with the upper andlower plates260,262, respectively, forcing theplates260,262 toward theendplates208 of thevertebral body24. In this manner, thetensioner300 elongates thefixation member222 until a proper elongation distance between theplates260,262 is achieved. Theseparator portions310,312 preferably are positioned so that their tips contact the center of theplates260,262. As theplates260,262 move away from each other, theunlocked struts264 will increase in length. When theupper plate260 contacts theupper endplate208 of the upper vertebral body, and thelower plate262 contacts and encounters resistance from thecompressible member224, continual compression of thehandle portions306,308 will cause a slight bending in the tensioner'sseparator portions310,312.
• As previously described, the slight bending of theseparator portions310,312 will deform thestrain gages314, thereby changing their resistance which, in turn, changes the voltage potential across thegages314. By monitoring the change in voltage caused when theseparator portions310,312 are opened (closed), and by amplifying and calibrating the voltage to known loads, a surgeon can determine whether thefixation member222 has been suitably lengthened to properly tension, i.e., properly load, thecompressible member224. More specifically, the surgeon can calculate what load should be applied to afixation member222 to cause a desired corresponding reactive force or load from thecompressible member224; the more the surgeon expands thefixation member222, the greater the reactive force from thecompressible member224. The voltage measured by thetensioner300 is representative of the load applied to thefixation member222. Thus, the surgeon uses thetensioner300 to monitor the load applied to thefixation member222. When the applied load equals a predetermined desired load, the surgeon knows that thefixation member222 has been lengthened or elongated the appropriate amount to place thecompressible member224 under the proper degree of tension.
• When thefixation member222 reaches the proper length, the verticallyadjustable struts264 are locked, thereby maintaining proper tension or load in thecompressible member224. After thefirst fixation member222 is properly lengthened, the same procedure may be used to properly lengthen theother fixation member222 in the othervertebral body24.
• Thestruts264 can be locked to maintain the proper length of thefixation member222, i.e., the proper elongation distance between the upper andlower plates260,262, in a variety of ways. For example, the struts can be configured for adjustment like a crutch, that is, by having a hole through an outer casing and a plurality of holes through an adjustable inner member. When the inner member is adjusted to the proper height, a fastener can be inserted through the hole in one side of the casing, through the corresponding hole in the inner member, and then through the hole in the other side of the casing. The fastener immobilizes the inner member with respect to the casing and maintains the proper elongation distance between the upper andlower plates260,262.
• Clamps also can be used to maintain the proper elongation distance between theplates260,262. The clamps are C-shaped in cross section and have a length equal to the elongation distance. The C-shaped cross section of the clamps leaves a slit or opening along their length. The clamps also are resiliently flexible. When the slit of a clamp is pressed against a strut, the slit widens so that the clamp can be slid around the strut. Once around the strut, the clamp returns to its initial shape. The clamps thus can be positioned on thestruts264 to substantially surround thestruts264 and maintain the proper elongation distance between theplates260,262.
• A tripod also can be used to maintain the proper distance between theplates260,262. In this preferred method, the surgeon selects a tripod of an appropriate height, that is, of a height equal to the desired elongation distance, and slides it into thefixation member222. The surgeon then positions the legs of the tripod on thelower plate262, preferably against threestruts264, and positions the top of the tripod against theupper plate260.
• After the length of thefixation members222 is fixed (i.e. by locking thestruts264 in each of thefixation members222 when the proper amount of tension is experienced by the compressible member224), the surgeon can use radiographs or fluoroscopy to confirm that theprosthetic device220 is properly positioned and aligned. Once confirmed, the bone shavings118 (bone graft) stored in thecavity112 of thereamer90 are placed into thecavities206 in thevertebral bodies24, as shown inFIG. 15. In time, thebone shavings118 will induce new bone to grow in thevertebral bodies24 during the healing process. It is also possible to place bone cement, bone substitute, or bone morphogenic protein, rather thanbone shavings118, into thecavities206. In addition, it is possible to use both bone cement combined withbone shavings118.
• As shown inFIG. 16, after thebone shavings118 and/or the bone cement are placed into thecavities206 in thevertebral bodies24, thepieces204 ofcortical bone22 are replaced in thecuts202 in thevertebral bodies24 from which they came. Thepieces204 can be fixed to thevertebral bodies24 using traditional methods, such as by a bone screw, plate, or bone cement, thereby enclosing thecavities206 containing thebone shavings118 and theprosthetic device220.
• The aforementioned describes one method by which to create a cavity in an intervertebral disc. It is also possible, as shown inFIGS. 17A and 17B, to use adistractor500 of the type shown inFIG. 6B to surgically implant aprosthetic device230 through only onevertebral body24. Specifically, after acavity206 is created in an upper (or lower)vertebral body24 by areamer90 in the manner previously discussed, the scissor-like members502,504 of adistractor500 are separated, thereby bringing thearms510,514 together. Thearms510,514, having one outward facing cutting implement thereon, preferably an endplate andnucleus cutter130, can then be inserted into thecavity206.
• When scissor-like members502,504 are compressed, thearms514,510 are separated, and thearm514 having the endplate andnucleus cutter130 thereon is pushed against theendplate208 that is to be partially removed (to thereby provide access to thedisc200 below or above). As thehandle506 is compressed and, if necessary, twisted, the endplate andnucleus cutter130 can be pushed downward (or upward) to cut through theendplate208 of thevertebral body24 and into the nucleus pulposus of theintervertebral disk200 below (or above) thevertebral body24. During this cutting process, theplate540 on theopposite arm510 acts as a brace by pushing against theendplate208 above (or below) theendplate208 through which the endplate andnucleus cutter130 is forced. When thedistractor500 is twisted side to side, theplate540 will remain fixed with respect to theendplate208 against which it is positioned; this will prevent any inadvertent shaving of bone from theendplate208 against which theplate540 is positioned. In this manner, the endplate andnucleus cutter130 makes a generally circular cut through theendplate208 and into theintervertebral disc200 below (or above) theendplate208.
• Once the cut has been made, thedistractor500 and endplate andnucleus cutter130 attached thereto is removed from thecavity206. The portion of theendplate208 located within the generally circular cut may then be removed. In addition, the nucleus pulposus of thedisk200 can be removed using a commercially available soft tissue ablator, thereby forming a well232, the location of which is shown inFIG. 18. The sides of the well232 are formed by the remaining disk annulus, and the bottom of the well232 is formed bynon-removed disc200 or by theendplate208 of thevertebral body24 below (or above) theintervertebral disc200.
• With respect toFIGS. 19A and 19B, after the well232 is formed, theendplate208 below (or above) theintervertebral disc200 may then be prepared to accept an alternative discprosthetic device230. In this fashion, a rotating dome-shapedendplate reamer400 can be used to abrade theendplate208 on the side of theintervertebral disc200 opposite thevertebral body24 which accepted thedistractor500. Theendplate reamer400 creates a dome-shapedindentation402 in theendplate208 which corresponds to the shape of the side of the alternative discprosthetic device230 which will be positioned against it. In this manner, theendplate208 is shaped to be congruent with theprosthetic device230. In addition, thereamer400 can be used to roughen the bone surface ofendplate208, which encourages bone ingrowth into theprosthetic device230.
• Upon removal of the nucleus pulposus of thedisk200, aprosthetic device230 of the type shown inFIG. 18, i.e., a device having acompressible member224 and oneexpandable fixation member222, can be inserted into the well232 and thecavity206 in thevertebral body24. Fluoroscopy is used to ensure that thedevice230 is properly positioned, and atensioner300 is used, in the manner previously described, to determine whether the device is subject to the proper amount of loading. When the proper amount of loading is applied, thestruts264 in the device will be locked, in the manner previously described, to maintain the load. After theprosthetic device230 is properly inserted and subject to the proper load,bone shavings118 and/or bone cement can be poured into thecavity206 in thevertebral body24, as previously described. Finally, and similarly to the aforementioned manner of closing acavity206 in avertebral body24, the previously removedpiece204 ofcortical bone22 is repositioned and fused to thevertebral body24.
• For both of the previously described methods in which the nucleus pulposus of anintervertebral disk200 is removed, it should be readily apparent to one of ordinary skill in the art these methods would be enhanced by acompressor160 having or working in conjunction with motors to cause the endplate and nucleus cutters to rotate. Such rotation would make it easier for thecutting edge134 of an endplate andnucleus cutter130 to cut through both theendplate208 of avertebral body24 and the nucleus pulposus of anintervertebral disc200.
• FIGS. 20 and 21 illustrate alternative variations of the cutting guide. InFIG. 20, the cuttingguide400, like cuttingguide20, is designed to be placed into contact with the outer surface of thevertebral body24 to guide a surgical instrument as it cuts through the cortical bone of thevertebral body24. The cuttingguide400 includes a generally rectangular-shaped body with fourwalls426,428,430,432. The cuttingguide400 also includes a first surface (not shown) with afirst edge438 andsecond surface430 with asecond edge436. The first edge438 (and first surface) is contoured to contact thevertebral body24 and includesconcave portions440 on either side of aflat portion441. Thesecond surface430 of the cuttingguide400 is generally planar. Thesecond surface430 of thecutting edge400 faces away from the vertical body at thesecond edge436.
• The cutting guide includes a plurality ofholes444 that pass through the cuttingguide400 from the first surface to the opposite,second surface430. Theholes444 are adapted to each receive afastener48 to secure the cuttingguide400 to thevertebral body24. Thefasteners48 may be needles, pins, wires, or any other suitable fastening device, and are similar to the fasteners described with reference toFIG. 8. Although sixholes444 are shown, not allholes444 must be used while securing the cutting guide to thevertebral body24, and/or fewer ormore holes444 may be used.
• Thesecond surface430 of the cuttingguide400 includesslots450 for an oscillating saw (not shown). InFIG. 20, fourslots450 are shown. However, any other suitable number ofslots450 may be used. Theslots450 pass through the cuttingguide400 from the first surface to the oppositesecond surface430. Theslots450 guide the positioning of a saw as it cuts into the cortical bone of thevertebral body24 in order to cut a window (opening) into thevertebral body24.
• The cuttingguide400 includes corner holes452 positioned at the end of theslots450. The corner holes452 are provided such that when the window is cut into thevertebral body24, a rounded corner is formed in the window. The rounded corner minimizes any stress-risers in the cortical bone to avoid cracks at the corners of the window. A drill is guided by the corner holes452 to cut and create the rounded corner.
• In the embodiment shown inFIG. 20, the cuttingguide400 includestabs460 or ears. Afirst tab460 protrudes out fromwall428, while a second andopposite tab460 protrudes out fromwall432. Eachtab460 includes anopening462. Thetabs460 are designed to allow a surgeon to incorporate additional fixation devices as desired. A screw, such as a bone screw, can be inserted into each of theopenings462 and inserted into adjacent vertebral bodies. Twotabs460 are shown, but fewer ormore tabs460 may be used.
• The cuttingguide400 also includes acentral hole458 positioned in the center of theslots450. Thecentral hole458 is provided to receive afastener48 to affix the cuttingguide400 to the vertebral body. Alternatively, thecentral hole458 is a guide for a drill, reamer, cutting guide holder (sometimes referred to as a joystick), or other surgical device.
• The cuttingguide400 further includes aslot451 andadditional opening442. Theslot451 andopening442 are provided to receive a pin (not shown) to assist in positioning the cuttingguide400 on a vertebral body. A pin can be inserted through theslot451 and into the vertebral body or disc. The cuttingguide400 is slidable along theslot451 around the pin to adjust the position of the cuttingguide400 and to temporarily position the cuttingguide400 on the vertebral body. A pin can also be inserted into theopening442 and into the vertebral body to position the cuttingguide400 on the vertebral body.
• Turning toFIG. 21, another embodiment of a cuttingguide500 is shown. The cuttingguide500 is similar to cuttingguide400, except that cuttingguide500 does not include thetabs460 and includesadditional holes521a,512b,512c.
• A plurality of small holes are provided on the cuttingguide500 adjacent to thecorner hole452. The small holes are provided to permit fixation pins (not shown) to be inserted to align the cuttingguide500 on thevertebral body24. A set of threeholes512a,512b,512care positioned adjacent each of the corner holes452. Fixation pins, such as needles, wires, etc., are driven into thevertebral body24 to fix the cuttingguide500 to thevertebral body24. If the surgeon determines that the cuttingguide500 is not properly located on thevertebral body24, then the surgeon may translate the cuttingguide500 in the proximal-distal or anterior-posterior directions by 1 to 2 mm. For example, threeholes512a,512b,512care shown with a distance d of approximately 1 to 2 mm between each of theholes512a,512b,512c. The surgeon can merely pick up the cuttingguide500 and slide theguide500 off of the fixation pins and reset the cuttingguide500 on the fixation pins in a different one of theholes512a,512b,512c.
• According to an embodiment, the cuttingguide400,500 is designed to act as a platform for attachment of additional surgical instruments. For example, a drill, endplate cutter, guide for the implant, tube holder, stop for a reamer, or other instrument, may be attached to the cuttingguide400,500. Thecentral opening458 can be a guide for a surgical instrument.
• Turning toFIG. 22, there is shown ascaffold device600 for providing a platform for use with additional surgical instruments. Thescaffold device600 is designed to be placed into contact with the outer surface of thevertebral body24 to guide or provide a platform for additional surgical instruments, such as a drill, chisel guide and chisel, endplate cutter, implant guide, tube holder, stop for the reamer, etc. Thescaffold600 includes a sidewall that defines acavity634 extending through thescaffold600. The sidewall generally has fourwalls612,614,616,618 arranged to form a rectangular cross-section. Thewalls612,614,616,618 can be arranged to form any other suitable shape. Thescaffold600 includes afirst edge636 and a second, oppositeedge638. Thefirst edge636 faces toward and contacts thevertebral body24 and is contoured to fit thevertebral body24. Thefirst edge636 is shown to include a series of flattenedportions637a,637b,637cto fit against thevertebral body24. Thefirst edge636 can include any other suitable configuration, such as convex or concave portions, to fit thevertebral body24. Thesecond edge638 is substantially planar.
• Thescaffold600 includes a plurality ofholes644, which are similar toholes444. Theholes644 extend through thescaffold600 from thesecond edge638 to thefirst edge636. Theholes644 are designed to receivefasteners48, such as shown inFIG. 8. Theholes644 can be positioned anywhere alongedges636,638. Furthermore, fewer ormore holes644 can be used to fix thescaffold600 to thevertebral body24.
• In the embodiment shown inFIG. 22, thescaffold600 includestabs660 or ears. Afirst tab660 protrudes out fromwall618, while a second andopposite tab660 protrudes out fromwall614. Eachtab660 includes anopening662. Thetabs660 are designed to allow a surgeon to incorporate additional fixation devices as desired. A screw, such as a bone screw, can be inserted into each of theopenings662 and inserted into adjacent vertebral bodies. Twotabs660 are shown, but fewer ormore tabs660 may be used.
• Thescaffold600 also includesslot651 andadditional hole642. Theslot651 andhole642 are similar to slot451 andopening442 inFIG. 20. Theslot651 andhole642 are provided such that a pin can be inserted through theslot651 orhole642 and into the vertebral body to temporarily position thescaffold600 on the vertebral body.
• Thescaffold600 may be used affixed to avertebral body24 after the cuttingguide400,500 has been used to create a window into the cortical bone of thevertebral body24. After removal of the cuttingguide400,500 from thefasteners48, thescaffold600 may be attached to thevertebral body24 via positioning of thefasteners48 intoholes644. Thescaffold600 can then serve as a cutting guide or platform in use with other surgical instruments, such as a chisel guide and chisel, reamer, etc.
• FIG. 23 illustrates another embodiment of ascaffold device700. Thescaffold700 includes a sidewall withwalls712,714,716,718 and acavity734. Thescaffold700 also includes afirst edge736 and an oppositesecond edge738. Thescaffold700 is similar toscaffold600, except thatscaffold700 does not include tabs or ears.
• FIG. 24 illustrates another embodiment of ascaffold device800. Thescaffold device800 is similar toscaffold700 inFIG. 23. However, thescaffold800 includes a protruding stud or spike810 to fix thescaffold800 to a vertebral body or disc. The protrudingspike810 is configured to be inserted into and attached to a vertebral body or disc. Thespike810 includes a pointed orsharp end812 that allows thespike810 to be pushed into and attached to the vertebral body.
• It will be understood that the cuttingguide400,500, orscaffold600,700,800 may be used in place of or in conjunction with cuttingguide20, thechisel guide50, thereamer90, thecompressor160, and thedistractor500.
• It also will be understood that the cuttingguide20, thechisel guide50, thereamer90, thecompressor160 and thedistractor500 and their associated endplate andnucleus cutters130, the facingplate540 of thedistractor500, thetensioner300, theendplate reamer400, and the chisel can be made of stainless steel or other suitable material.
• Apparatuses and methods for performing spinal surgery have been described according to the present invention. Many modifications and variations may be made to the apparatuses and methods described and illustrated herein without departing from the spirit and scope of the invention. Accordingly, it should be understood that the apparatuses and methods described herein are illustrative only and are not limiting upon the scope of the invention.

Claims (17)

1. A cutting guide for use in removing bone from a vertebral body, comprising:

a cutting guide body including (i) a first surface with a first edge to face toward and to contact the vertebral body and (ii) a second, opposite surface to face away from the vertebral body, the first edge including at least two concave portions;

first and second slots for guiding a cutting tool to cut into the vertebral body along a length of the first and second slots, the slots extend from the first surface to the second surface, the first and second slots positioned to intersect each other; and

an additional slot extending from the first surface to the second surface and configured to slide over a positioning pin inserted into the vertebral body to temporarily position the cutting guide on the vertebral body.

2. The cutting guide according toclaim 1, wherein the cutting guide body comprises four side walls extending between the first surface and second surface.

3. The cutting guide according toclaim 1, further comprising a corner hole positioned at an intersection between the first and second slots, the corner hole extending from the first surface to the second surface to guide a cutting tool, the corner hole configured to receive a drill to cut a rounded corner between the first and second slots.

4. The cutting guide according toclaim 3, further comprising third and fourth slots, the third slot intersecting with the first slot and the fourth slot, the fourth slot configured to intersect with the second slot and third slot.

5. The cutting guide according toclaim 4, further comprising a corner hole positioned at each intersection of the slots.

6. The cutting guide according toclaim 1, further comprising a hole extending from the first surface to the second surface to receive a fastener therethrough.

7. The cutting guide according toclaim 2, further comprising a first fixation tab protruding from one of the four side walls, the fixation tab including a hole to receive a fixation device therethrough to releasably fix the cutting guide to a vertebral body.

8. The cutting guide according toclaim 6, further comprising a second fixation tab protruding from a side wall opposite to the one of the four side walls with the first fixation tab, the second fixation tab including a hole to receive a fixation device therethrough to releasably fix the cutting guide to a vertebral body.

9. The cutting guide according toclaim 1, wherein the cutting guide provides a platform for attachment of a surgical instrument.

10. The cutting guide according toclaim 1, further comprising a protruding spike to fix the cutting guide to a vertebral body.

11. The cutting guide according toclaim 3, further comprising a plurality of fixing holes extending from the first surface to the second surface to receive a fastener therethrough to releasably fix the cutting guide to a vertebral body, the plurality of fixing holes are positioned adjacent the corner hole.

12. The cutting guide according toclaim 5, further comprising a plurality of fixing holes extending from the first surface to the second surface to receive a fastener therethrough to releasably fix the cutting guide to a vertebral body, a set of the plurality of fixing holes are positioned adjacent each of the corner holes.

13. A scaffold device for use in removing bone from a vertebral body, comprising:

a sidewall defining an internal cavity, the sidewall including (i) a first edge to face toward and to contact the vertebral body and (ii) a second, opposite edge to face away from the vertebral body;

a first fixation tab protruding from the sidewall, the fixation tab including a through-hole to receive a fixing device therethrough to fix the scaffold device to a vertebral body.

14. The scaffold device according toclaim 13, wherein the sidewall comprises four walls arranged to form a rectangular cross-section.

15. The scaffold device according toclaim 13, wherein the sidewall comprises four walls, and wherein the scaffold device further comprises a second fixation tab protruding from one of the four walls opposite the first fixation tab, the second fixation tab including a through-hole to receive a fixing device therethrough to fix the scaffold device to a vertebral body.

16. The scaffold device according toclaim 14, wherein at least one of the four walls includes a hole extending from the first edge to the second edge to receive a fastener therethrough.

17. The scaffold device according toclaim 13, wherein the sidewall includes a slot extending from the first edge to the second edge, and configured to slide over a positioning pin inserted into the vertebral body or intervertebral disc to temporarily position the scaffold on the vertebral body.

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