Abstract:
Instruments and methods for distracting an intervertebral space and inserting and impacting artificial intervertebral discs. A parallel distractor comprising a plying device with attached opposing forks operable to distract an intervertebral space. A method of distracting an intervertebral space comprising the steps of inserting a distractor having opposing forks into an intervertebral space and inserting an inserter/impactor between the opposing ramped surfaces of the distractor to insert/impact an artificial implant in the intervertebral space. A system for distracting an intervertebral space employing a parallel distractor, inserter/impactor and artificial intervertebral implant.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     The present application is a continuation of United States patent application Ser. No. ______(to be assigned)______, filed Feb. 20, 2004 contemporaneously herewith, entitled “Wedge Ramp Distractor and Related Methods for Use in Implanting Artificial Intervertebral Discs”, which is a continuation-in-part application of U.S. patent application Ser. No. 10/425,267 (filed Apr. 29, 2003) entitled “Wedge Plate Inserter/Impactor and Related Methods for Use in Implanting an Artificial Intervertebral Disc”, which is a continuing application of U.S. patent application Ser. No. 10/282,356 (filed Oct. 29, 2002) entitled “Instrumentation and Methods For Use In Implanting an Artificial Intervertebral Disc”, which is a continuing application of U.S. patent application Ser. No. 10/256,160 (filed Sep. 26, 2002) entitled “Artificial Intervertebral Disc Having Limited Rotation Using a Captured Ball and Socket Joint With a Solid Ball and Compression Locking Post”, which is a continuing application of U.S. patent application Ser. No. 10/175,417 (filed Jun. 19, 2002) entitled “Artificial Intervertebral Disc Utilizing a Ball Joint Coupling”, which is a continuing application of U.S. patent application Ser. No. 10/151,280 (filed May 20, 2002) entitled “Tension Bearing Artificial Disc Providing a Centroid of Motion Centrally Located Within an Intervertebral Space”, which is a continuing application of both U.S. patent application Ser. No. 09/970,479 (filed Oct. 4, 2001) entitled “Intervertebral Spacer Device Utilizing a Spirally Slotted Belleville Washer Having Radially Extending Grooves” as well as U.S. patent application Ser. No. 10/140,153 (filed May 7, 2002) entitled “Artificial Intervertebral Disc Having a Flexible Wire Mesh Vertebral Body Contact Element”, the former being a continuing application of U.S. patent application Ser. No. 09/968,046 (filed Oct. 1, 2001) entitled “Intervertebral Spacer Device Utilizing a Belleville Washer Having Radially Extending Grooves” and the latter being a continuing application of both U.S. patent application Ser. No. 09/970,479 (detailed above) as well as U.S. patent application Ser. No. 10/128,619 (filed Apr. 23, 2002) entitled “Intervertebral Spacer Having a Flexible Wire Mesh Vertebral Body Contact Element”, which is a continuing application of both U.S. patent application Ser. No. 09/906,119 (filed Jul. 16, 2001) and entitled “Trial Intervertebral Distraction Spacers” as well as U.S. patent application Ser. No. 09/982,148 (filed Oct. 18, 2001) and entitled “Intervertebral Spacer Device Having Arch Shaped Spring Elements”. All of the above mentioned applications are hereby incorporated by reference herein in their respective entireties. 
     
    
     FIELD OF THE INVENTION  
       [0002]     This invention relates generally to systems and methods for use in spine arthroplasty, and more specifically to instruments for distracting an intervertebral space and inserting and impacting artificial intervertebral discs, and methods of use thereof.  
       BACKGROUND OF THE INVENTION  
       [0003]     The bones and connective tissue of an adult human spinal column consists of more than twenty discrete bones coupled sequentially to one another by a tri-joint complex that consists of an anterior disc and the two posterior facet joints, the anterior discs of adjacent bones being cushioned by cartilage spacers referred to as intervertebral discs. These more than twenty bones are anatomically categorized as being members of one of four classifications: cervical, thoracic, lumbar, or sacral. The cervical portion of the spine, which comprises the top of the spine, up to the base of the skull, includes the first seven vertebrae. The intermediate twelve bones are the thoracic vertebrae, and connect to the lower spine comprising the five lumbar vertebrae. The base of the spine is the sacral bones (including the coccyx). The component bones of the cervical spine are generally smaller than those of the thoracic spine, which are in turn smaller than those of the lumbar region. The sacral region connects laterally to the pelvis. While the sacral region is an integral part of the spine, for the purposes of fusion surgeries and for this disclosure, the word spine shall refer only to the cervical, thoracic, and lumbar regions.  
         [0004]     The spinal column is highly complex in that it includes these more than twenty bones coupled to one another, housing and protecting critical elements of the nervous system having innumerable peripheral nerves and circulatory bodies in close proximity. In spite of these complications, the spine is a highly flexible structure, capable of a high degree of curvature and twist in nearly every direction.  
         [0005]     Genetic or developmental irregularities, trauma, chronic stress, tumors, and degenerative wear are a few of the causes that can result in spinal pathologies for which surgical intervention may be necessary. With respect to the failure of the intervertebral disc, and the insertion of implants and/or height restorative devices, several methods and devices have been disclosed in the prior art that achieve immobilization and/or fusion of adjacent bones by implanting artificial assemblies in or on the spinal column. More recently, the development of non-fusion implant devices, which purport to permit continued natural movement in the tri-joint complex, have provided great promise as a preferably alternative to fusion devices. The region of the back that needs to be corrected, as well as the individual variations in anatomy, determine the appropriate surgical protocol and implantation assembly. Generally, the preparation of the intervertebral space for the receipt of fusion or non-fusion devices involves removing the damaged disc material and thereafter distracting the adjacent vertebral bones to their appropriate distance apart. Once the proper height of the intervertebral space is restored, the fusion or non-fusion device can be implanted.  
         [0006]     It is an object of the invention to provide instrumentation and methods that enable surgeons to more accurately, easily, and efficiently implant fusion or non-fusion devices. Other objects of the invention not explicitly stated will be set forth and will be more clearly understood in conjunction with the descriptions of the preferred embodiments disclosed hereafter.  
       SUMMARY OF THE INVENTION  
       [0007]     The preceding objects are achieved by the invention, which includes, among other aspects, an inserter/impactor (sometimes referred to herein as an “inserter/impactor”) useful for holding and manipulating artificial intervertebral discs, a wedge-ramp distractor, and a parallel insertion distractor, the latter two items being useful for distracting an intervertebral space and inserting an artificial intervertebral disc therein.  
         [0008]     More particularly, the systems and methods disclosed herein are intended for use in spine arthroplasty procedures, and specifically for use with the systems and methods described herein in conjunction with the systems and methods in conjunction with the systems and methods described in U.S. patent application Ser. No. 10/282,356 (filed Oct. 29, 2002) entitled “Instrumentation and Methods For Use In Implanting an Artificial Intervertebral Disc” (hereinafter referred to as “the &#39;356 application”) as well as U.S. patent application Ser. No. 10/256,160 (filed Sep. 26, 2002) entitled “Artificial Intervertebral Disc Having Limited Rotation Using a Captured Ball and Socket Joint With a Solid Ball and Compression Locking Post” (hereinafter referred to as “the &#39;160 application”) as well as U.S. patent application Ser. No. 09/906,127 (filed Jul. 16, 2001) entitled “Insertion Tool For Use With Intervertebral Spacers”, the entirety of which is incorporated by reference herein (hereinafter referred to as “the &#39;127 application”). However, it should be understood that the systems and methods described herein are also suitable for use with other systems and methods without departing from the scope of the invention.  
         [0009]     While the instrumentation described herein (e.g., the inserter/impactors and distractors) will be discussed for use with the artificial intervertebral disc of  FIGS. 1   g - n  of the &#39;356 application (hereinafter, such figures will merely be referred to as “ FIGS. 1   g - n ”), such discussions are merely by way of example and not intended to be limiting of their uses. Thus, it should be understood that the instrumentation and methods can be used with any of the artificial intervertebral discs disclosed in the &#39;356 or &#39;160 applications, or any other artificial intervertebral disc having (or being modifiable or modified to have) suitable features therefor. Moreover, it is anticipated that the features of the artificial intervertebral discs (e.g., plate surfaces, engagement holes, and baseplate teeth) that are used by the inserter/impactors and distractors discussed herein to hold and/or manipulate the artificial intervertebral disc can be applied, individually, or collectively or in various combinations, to other trials, spacers, artificial intervertebral discs, or other orthopedic devices as stand-alone innovative features for enabling such trials, spacers, artificial intervertebral discs, or other orthopedic devices to be more efficiently and more effectively held and/or manipulated by the inserter/impactors and/or distractors described herein or by tools having suitable features. In addition, it should be understood that the invention encompasses instrumentation and methods for implanting artificial intervertebral discs, spacers, trials (static or dynamic), and/or other orthopedic devices, that have one or more of the features disclosed herein, in any combination, and that the invention is therefore not limited to artificial intervertebral discs, spacers, trials, and/or other orthopedic devices having all of the features simultaneously.  
         [0010]     Preferably, with regards to each artificial intervertebral disc to be implanted, a plurality of sizes of the artificial intervertebral disc would be available (e.g., the artificial intervertebral disc  160  of  FIGS. 1   g - n ). That is, preferably, a plurality of the same type of artificial intervertebral disc would be available, each of the plurality having a respective width and depth dimension combination that allows it to fit within a correspondingly dimensioned intervertebral space. For example, the plurality of artificial intervertebral discs could include artificial intervertebral discs having widths being either 35 mm or 40 mm, and depths ranging from 14 mm to 18 mm in 1 mm increments, for a total of 10 discs. It should be understood that the artificial intervertebral discs can be offered in a variety of dimensions without departing from the scope of the invention, and that the dimensions specifically identified and quantified herein are merely exemplary. Each of the plurality of artificial intevertebral discs preferably further includes features that can be used by the inserter/impactors (described below) and/or the wedge-ramp and parallel insertion distractors (described below) and/or the inserter/impactor or other instruments described in the &#39;356 application.  
         [0011]     With regard to features that can be used by the inserter/impactors described here and in the &#39;356 application, each artificial intervertebral disc includes an anteriorly facing flat surface, flanked by two anteriolaterally facing flat surfaces (one on each side of the anteriorly facing flat surface), and, to provide for holding of the disc for an anterior insertion approach, a hole spaced from the anteriorly facing flat surface, the hole having a longitudinal axis parallel to the anteriorly facing flat surface. The holding pin of the inserter/impactor fits within the hole, and the angled flat surfaces of the disc fit against the correspondingly angled flat surfaces of the inserter/impactor, and operation of the inserter/impactor pulls the holding pin toward the flat surface of the inserter/impactor opposite the pin, to rigidly hold the disc by the lower baseplate. The holding pin protrudes from the wedge-shaped extended surface of the distal end of the inserter/impactor and is restricted from upward movement with respect to the distal head by the presence of the wedge-shaped extended surface of the distal end of the inserter/impactor. More particularly, with any attempted upward movement of the holding pin, the pin encounters the upper surface of the channel in which the pin travels, preventing any such upward movement. When the intervertebral disc is held in this manner, rotation of the disc about a longitudinal axis relative to the inserter/impactor is prevented by interference of the corners of the disc&#39;s flat surfaces and the corners of the inserter/impactor&#39;s flat surfaces, similar to the manner in which a wrench holding a nut prevents rotation of the nut relative to the wrench. Further, when the disc is held in this manner, rotation of the disc about a lateral axis of the disc relative to the inserter/impactor is prevented by interference of the inwardly facing surface of the first baseplate (e.g., upper baseplate) of the disc and the corresponding surface (e.g., upper surface) of the wedge on the distal end, and by interference of the inwardly facing surface of the second baseplate (e.g., lower baseplate) of the disc and the correspoding surface (e.g., lower surface) of the wedge on the distal end. It is preferable that the wedge on the inserter/impactor will interfere between the first and second baseplates (e.g., upper and lower) so that the surfaces of the first and second baseplates align at a preferred 15 degrees angle of lordosis when the disc is held by the inserter/impactor.  
         [0012]     Preferably, in order to provide for a holding of the disc for two additional (here, anteriolateral) insertion approaches, each disc also include two additional holes, one spaced apart from one of the anteriolaterally facing flat surfaces, and the other spaced apart from the other of the anteriolaterally facing flat surfaces. Accordingly, operation of the inserter/impactor can fit the holding pin into either of these two additional holes, and hold the anteriolaterally facing flat surface (the one associated with the hole into which the pin is fit) of the disc against the flat surface of the inserter/impactor opposite the pin. It should be understood that preferably, in order to facilitate these two additional approaches, the angle separating the anteriorly facing flat surface of the disc and one of the anteriolaterally facing flat surfaces of the disc is equal to the angle separating the anteriorly facing flat surface and the other of the anteriolaterally facing flat surfaces.  
         [0013]     With regard to features that can be used by the wedge-ramp distractor and the parallel insertion distractor of the present invention, each artificial intervertebral disc includes fixation teeth on the outwardly facing surface of the baseplate. Preferably, to permit them to ride in the grooves of the wedge-ramp distractor, two sets of teeth straddle the convex dome on the outwardly facing surface of each baseplate, and the teeth in each set are in straight rows. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]      FIGS. 1   g - n  of the &#39;356 application show front ( FIG. 1   g ), side cutaway ( FIG. 1   h ), top ( FIG. 1   i ), perspective cutaway ( FIG. 1   j ), bottom cutaway ( FIG. 1   k ), top cutaway ( FIG. 11 ), bottom perspective ( FIG. 1   m ), and top perspective ( FIG. 1   n ) views of an exemplary artificial intervertebral disc for use with the present invention.  
         [0015]      FIGS. 2   a - c  show side ( FIG. 2   a ), perspective ( FIG. 2   b ), and close-up perspective ( FIG. 2   c ) views of a wedge plate inserter/impactor of the present invention.  
         [0016]      FIGS. 3   a - d  show bottom ( FIG. 3   a ), side ( FIG. 3   b ), top ( FIG. 3   c ), and side cutaway ( FIG. 3   d ) views of a distal end of a wedge plate inserter/impactor of the present invention.  
         [0017]      FIGS. 4   a - b  show top ( FIG. 4   a ) and side ( FIG. 4   b ) views of a wedge plate inserter/impactor of the present invention holding an exemplary artificial intervertebral disc.  
         [0018]      FIGS. 4   c - e  show top ( FIG. 4   c ), side ( FIG. 4   d ), and side cutaway ( FIG. 4   e ) views of a distal end of a wedge plate inserter/impactor of the present invention holding an exemplary artificial intervertebral disc.  
         [0019]      FIG. 5  shows a close-up perspective view of a preferred embodiment of the distal end of a wedge plate inserter/impactor of the present invention.  
         [0020]      FIG. 6  shows a close-up perspective view of the distal end of a wedge plate inserter/impactor of the present invention according to  FIG. 5  holding an exemplary artificial intervertebral disc.  
         [0021]      FIG. 7  shows a perspective view of a wedge ramp distractor of the present invention.  
         [0022]      FIG. 8  shows a perspective view of the wedge ramp distractor of the present invention according to  FIG. 7  in disassembled form.  
         [0023]      FIG. 9  shows a perspective view of the wedge ramp distractor of the present invention according to  FIG. 7  having inserted therein the wedge plate inserter/impactor of the present invention according to  FIG. 5  holding an exemplary artificial intervertebral disc.  
         [0024]      FIG. 10  shows a perspective view of a parallel insertion distractor of the present invention in disassembled form.  
         [0025]      FIG. 11  shows a perspective view of a parallel insertion distractor of the present invention holding an exemplary artificial intervertebral disc. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0026]     While the invention will be described more fully hereinafter with reference to the accompanying drawings, it is to be understood at the outset that persons skilled in the art may modify the invention herein described while achieving the functions and results of the invention. Accordingly, the descriptions that follow are to be understood as illustrative and exemplary of specific structures, aspects and features within the broad scope of the invention and not as limiting of such broad scope. Like numbers refer to similar features of like elements throughout.  
         [0027]     A preferred embodiment of an artificial intervertebral disc (e.g., artificial intervertebral disc  160 ) for use with the instrumentation of the present invention is referenced and described in the &#39;356 application, and the same description is hereby incorporated by reference herein. The artificial intervertebral disc illustrated in  FIGS. 1   g - n  of the &#39;356 application is discussed herein with reference to such figures, as an example of an artificial intervertebral disc suitable for use with the present invention.  
         [0028]     A preferred embodiment of a wedge plate inserter/impactor of the present invention will now be described.  
         [0029]     Referring now to  FIGS. 2   a - 4   e ,  FIGS. 2   a - c  side ( FIG. 2   a ), perspective ( FIG. 2   b ), and close-up perspective ( FIG. 2   c ), and perspective ( FIG. 4   d ) views of a wedge plate inserter/impactor of the present invention.  FIGS. 3   a - d  show bottom ( FIG. 3   a ), side ( FIG. 3   b ), top ( FIG. 3   c ), and side cutaway ( FIG. 3   d ) views of a distal end of a wedge plate inserter/impactor of the present invention.  FIGS. 4   a - b  show top ( FIG. 4   a ) and side ( FIG. 4   b ) views of a wedge plate inserter/impactor of the present invention holding an exemplary artificial intervertebral disc.  FIGS. 4   c - e  show top ( FIG. 4   c ), side ( FIG. 4   d ), and side cutaway ( FIG. 4   e ) views of a distal end of a wedge plate inserter/impactor of the present invention holding an exemplary artificial intervertebral disc.  
         [0030]     It should be understood that the illustration and reference herein to the artificial intervertebral disc shown in  FIGS. 1   g - n  of the &#39;356 application is merely to show an example of one type of artificial intervertebral disc that is contemplated by, encompassed by, and suitable for use with, the present invention, and that such illustration and reference herein is not meant to limit the scope of the present invention or limit the uses of the present invention. Rather, any other artificial intervertebral disc (or any other orthopedic device) having suitable features for being used with the instrumentation and methods described herein are contemplated by the present invention. Indeed, the features suitable for manipulation (e.g., angled flat surfaces with adjacent holes and/or opposing notches, and/or inwardly facing baseplate surfaces) are encompassed by the present invention, regardless of to what orthopedic device they may be applied. Other exemplary suitable artificial intervertebral discs include, but are not limited to, the artificial intervertebral discs described in the &#39;160 application with regard to  FIGS. 8   a - y ,  9   a - t ,  10   a - t ,  11   a - j , and  12   a - o  thereof and by the accompanying descriptions therefor (e.g., embodiments identified as the first, second, third, fourth, and fifth preferred embodiments of the fourth embodiment family, etc.). It should be noted that, as can be seen from  FIGS. 1   g - n  of the &#39;356 application, that the artificial intervertebral disc shown in  FIGS. 1   g - n  of the &#39;356 application has features similar to those of these other suitable artificial intervertebral discs of the &#39;160 application, and it should be understood that such similar features are structurally and functionally as described in the &#39;160 application. Such similar features include an inwardly facing surface of the upper baseplate, and a convex structure on the lower baseplate, the convex structure having an inwardly facing surface.  
         [0031]     And, while the instrumentation described herein (e.g., the inserter/impactor) as well as the instrumentation described in the &#39;356 application (e.g., the inserter/impactor described therein) will be discussed for use with the artificial intervertebral disc of  FIGS. 1   g - n  of the &#39;356 application, such discussions are merely by way of example and not intended to be limiting of their uses. Thus, it should be understood that the tools can be used with any of the artificial intervertebral discs disclosed in the &#39;356 application or the &#39;160 application, or any other artificial intervertebral disc having (or being modifiable or modified to have) suitable features therefor. Moreover, it is anticipated that the features of the artificial intervertebral disc (e.g., the angled flat surfaces and the inwardly facing baseplate surfaces, and accompanying holes) that are used by the tool discussed herein (or in the &#39;356 application) to hold and/or manipulate these devices (certain features, it should be noted, were first shown and disclosed in the &#39;160 application, the &#39;127 application, and/or the &#39;356 application) can be applied, individually or collectively or in various combinations, to other trials, spacers, artificial intervertebral discs or other orthopedic devices as stand-alone innovative features for enabling such trials, spacers, artificial intervertebral discs, or other orthopedic devices to be more efficiently and more effectively held and/or manipulated by the tools described herein (or in the &#39;356 application) or by other tools having suitable features. In addition, it should be understood that the invention encompasses artificial intervertebral discs, spacers, trials (static or dynamic), and/or other orthopedic devices, that have one or more of the features disclosed herein (or in the &#39;356 application), in any combination, and that the invention is therefore not limited to artificial intervertebral discs, spacers, trials, and/or other orthopedic devices having all of the features simultaneously.  
         [0032]     Preferably, for each artificial intervertebral disc to be implanted, a plurality of sizes of the artificial intervertebral disc would be available. That is, preferably, a plurality of the same type of artificial intervertebral disc would be available, each of the plurality having a respective width and depth dimension combination that allows it to fit within a correspondingly dimensioned intervertebral space. For example, the plurality of artificial intervertebral discs could include artificial intervertebral discs having widths being either 35 mm or 40 mm, and depths ranging from 14 mm to 18 mm in 1 mm increments, for a total of 10 discs.  
         [0033]     The inserter/impactor  4000  is provided primarily for holding, inserting, repositioning, removing, impacting, extracting, and otherwise manipulating an artificial intervertebral disc having features suitable for being manipulated by the inserter/impactor. (However, it can also be used to hold, insert, reposition, remove, impact, extract, and otherwise manipulate any other orthopedic device having suitable features therefor. For example, it should be understood that distraction of an intervertebral space can be accomplished in conjunction with a cooperating tool or spacer that can be gripped by the inserter/impactor.) Exemplary suitable artificial intervertebral discs include, but are not limited to, the artificial intervertebral disc  160  described herein and the artificial intervertebral discs described in the &#39;160 application with regard to  FIGS. 8   a - y ,  9   a - t ,  10   a - t ,  11   a - j , and  12   a - o  thereof and by the accompanying descriptions therefor (e.g., embodiments identified as the first, second, third, fourth, and fifth preferred embodiments of the fourth embodiment family, etc.). Regarding the features suitable for being manipulated by the inserter/impactor  4000 , such features include those discussed above as being suitable features on the disc  160 , namely, an anteriorly facing flat surface on the second (e.g., lower) baseplate of the trial or disc, flanked by two anteriolaterally facing flat surfaces (one on each side of the anteriorly facing flat surface), and, to provide for holding of the trial or disc for an anterior insertion approach, a hole spaced from the anteriorly facing flat surface, the hole having a longitudinal axis parallel to the anteriorly facing flat surface. Further regarding the features suitable for being manipulated by the inserter/impactor, such features further include the inwardly facing surfaces of the baseplates of the disc.  
         [0034]     More particularly, the inserter/impactor  4000  includes a shaft  4020  having a distal end  4040  that has angled flat surfaces  4200   a - c  corresponding to and fittable against angled flat surfaces of the artificial intervertebral disc (e.g., the surfaces  180   a - c  of the artificial intervertebral disc  160 ) to be implanted. The distal end  4040  has angled flat surfaces  4200   d - f  corresponding to and fittable against angled flat surfaces of the artificial intervertebral disc (e.g., the surfaces  180   d - f  of the artificial intervertebral disc  160 ) to be implanted. The distal end  4040  has a wedge-shaped extension  4042  including upper  4200   g  and lower  4200   h  wedge surfaces corresponding to and fittable against the inwardly facing surfaces of the artificial intervertebral disc (e.g., the lower surface  164   a  of the upper baseplate  168   a  of the disc  160 , and the upper surface  164   b  of the lower baseplate  168   b  of the disc  160 , respectively) to be implanted. For example, in an anterior approach for the disc  160  (as shown in  FIGS. 4   a - e ),  180   a  and  180   d  facing  4200   a  and  4200   d ,  180   b  and  180   e  facing  4200   b  and  4200   e ,  180   c  and  180   f  facing  4200   c  and  4200   f , and  164   a  facing  4200   g  and  164   b  facing  4200   h.    
         [0035]     The inserter/impactor  4000  holds the disc  160  in a preferred position with respect to the inserter/impactor  4000 . (It should be understood that the surfaces of the wedge-shaped extension  4042  can be modified within the scope of the present invention to hold the disc  160  (or another orthopedic device) at positions other than those illustrated herein.) In the illustrated embodiment of the inserter/impactor  4000  in use with the disc  160 , the preferred position is with the baseplates  168   a,b  of the disc  160  angled at 15 degrees of lordosis with respect to one another. More particularly, preferably, the upper and lower surfaces (e.g.,  4200   g  and  4200   h ) of the wedge-shaped extension  4042  protrude from the distal end  4040  and are formed to hold the baseplates  168   a,b  such that they are angled at 15 degrees of lordosis with respect to one another. A surface (e.g., lower surface  4200   h ) of the wedge-shape extension  4042  that mates with an inwardly facing surface of a baseplate (e.g., the lower baseplate  168   b ) of a disc (e.g.,  160 ) may be correspondingly shaped (e.g., curved or flat) for interaction or mating with the disc baseplate (e.g., the lower surface  4200   h  of the wedge-shaped extension as illustrated is curved to accommodate the surface of the shield of the disc). Preferably, the forward surface  4200   i  of the wedge-shaped extension  4042  has a concave curvature towards the shaft  4020  of the inserter/impactor  4000 , also for accommodating the curvature of the surface of the shield of the disc.  
         [0036]     Also preferably with regard to the preferred positioning, the wedge surfaces of the distal end  4040  protrude from a distance midway with respect to the top and bottom of the distal end  4040  and span (e.g., right to left or vice-versa) the entire distal face of the distal end  4040 , and the surfaces  4200   d - f  above the wedge on the distal end  4040  are respectively perpendicular to the wedge&#39;s upper surface  4200   g  such that each is disposed in parallel with its respective corresponding surface of the disc  160  when the disc  160  is held by the inserter/impactor  4000  at the appropriate lordosis angle. (And, accordingly, are angled approximately 15 degrees with respect to the surfaces below the wedge  4200   a - c .) Preferably, for an anterior approach, the wedge-shaped extension  4042  is designed and shaped to fit with its antero-lateral confronting surfaces ( 4200   d,f  and  4200   a,c ) tightly against the correspondingly antero-laterally facing surfaces ( 180   d,f  and  180   a,c ) of the disc  160 , but such that its anterior confronting surfaces ( 4200   e  and  4200   b ) are slightly spaced from the anteriorly facing surfaces ( 180   d  and  180   b ) of the disc  160 , when the disc is held by the inserter/impactor  4000 . This is primarily to address manufacturing issues (in some cases, tolerances may not be adequately defined to ensure that all of those surfaces fit tightly against their corresponding surfaces), so that if there are manufacturing anomalies, any slight tolerance differences that may exist are nevertheless still adequate to ensure at least the tight fitting of the antero-lateral confronting surfaces, so that manipulation of the disc  160  is possible (e.g., in the manner of a wrench against an angled nut). This can be achieved, e.g., by designing the anterior confronting surfaces ( 4200   e  and  4200   b ) to each be slightly greater in length than the corresponding anteriorly facing surfaces ( 180   e  and  180   b ) of the disc baseplates, while still being angled with respect to the antero-lateral confronting surfaces ( 4200   d,f  and  4200   a,c ) at the same angle the antero-laterally facing surfaces ( 180   d,f  and  180   a,c ) of the disc baseplates are angled with respect to the anteriorly facing surfaces ( 180   e  and  180   b ) of the disc. The increased length of the anterior confronting surfaces on the wedge extension results in the slight clearance between the anteriorly facing surfaces ( 180   e  and  180   b ) of the disc and the corresponding anterior confronting surface ( 4200   e  and  4200   b ) of the wedged distal end, thereby ensuring that the disc will be fully seated against the antero-lateral confronting surfaces of the distal end despite possible manufacturing, material or other inevitable variations in tolerances of the artificial intervertebral disc or the inserter/impactor. As noted above, similar in this regard to the manner in which a wrench engages a nut, this fitting increases the mechanical advantage toward repositioning the disc in the intervertebral space. It should be noted, inasmuch as the inserter/impactor  4000  described herein can engage the disc from the antero-lateral angles as well, the anterior confronting surfaces ( 4200   e  and  4200   b ) should also be longer than the antero-laterally facing surfaces ( 180   d,f  and  180   a,c ) of the disc, so that a similar fitting occurs when the disc is held from the antero-lateral angles. Stated broadly, the primary confronting surfaces (e.g., the anterior confronting surfaces) of the inserter/impactor are preferably slightly longer than the primary confronted surfaces (e.g., anteriorly facing surfaces) of the disc for any given holding orientation.  
         [0037]     Further, the inserter/impactor  4000  includes a holding pin  4080  that extends from the wedge  4042  along a longitudinal axis of the shaft  4020 , the pin  4080  having a distal end  4100  that is bent downwardly. The holding pin  4080  is spring loaded (e.g., by a spring  4090 ) in a central channel of the shaft  4020 , so that it is biased toward the shaft  4020  (preferably, the bent end  4100  of the pin  4080  prevents it from entering the central channel). The holding pin  4080  is restricted from upwardly lateral movement with respect to the distal end of the inserter/impactor by the presence of the wedge-shaped extension  4042  of the distal end  4040  of the inserter/impactor  4000 . More particularly, with any attempted upward movement of the holding pin  4080 , the pin encounters the upper surface of the channel in which the pin  4080  travels, preventing any such upward movement. The holding pin  4080  is preferably heat treated (e.g., cold formed) to increase material quality (e.g., strength).  
         [0038]     A flange  4110 , mechanically connected to the pin  4080  and translating adjacent the shaft  4020 , can be pushed distally to overcome the bias of the spring  4090  to space the pin  4080  away from the wedge  4042 . (An alternative configuration is one in which the flange  4110  and the pin  4080  are formed from a single piece, rather than being mechanically connected.) In this extended position, the pin  4080  can be inserted in a hole (e.g.,  182   b ) in the baseplate (e.g.,  168   b ) of the artificial intervertebral disc (e.g.,  160 ). Releasing the flange  4110  allows the spring  4090  to pull the pin  4080  back, causing the anteriorly facing surface  180   b  of the baseplate  168   b  to be held against the lower central flat surface  4200   b  of the inserter/impactor  4000  and the anterioloaterally facing flat surfaces  180   a,c  of the artificial intervertebral disc  160  to be held against the other corresponding flat surfaces  4200   a,c  of the inserter/impactor  4000 . This can be further understood in light of the description of the manner in which the inserter/impactor of the &#39;160 application functions to grip an orthopedic device, which is included in the &#39;160 application and incorporated by reference herein. Simultaneously, the anteriorly facing surface  180   e  of the baseplate  168   a  is pulled against the upper central flat surface  4200   e  of the inserter/impactor  4000  and the anterioloaterally facing flat surfaces  180   d,f  of the artificial intervertebral disc  160  is pulled against the other corresponding flat surfaces  4200   d,f  of the inserter/impactor  4000 . Additionally, the upper and lower wedge surfaces ( 4200   g,h ) interfere between the inwardly facing surfaces  164   a,b  of the disc baseplates, causing the baseplate to be angled at a 15 degree lordosis angle, with the lower surface  164   a  of the upper baseplate  168   a  held against the upper surface  4200   g , and the upper surface of the shield being held against the lower surface  4200   h , as best shown in  FIGS. 4   a - e.    
         [0039]     A knob  4120 , threaded on the shaft  4020 , can be rotated about the longitudinal axis of the shaft  4020  to push the flange  4110  farther proximally, to pull the pin  4090  tighter and therefore lock its position (the interference of the threads of the knob-shaft interface prevents the knob  4120  from moving distally unless the knob  4120  is reverse rotated to effect that result) to more securely hold the baseplate  168   b , and reverse rotated to unlock and loosen the pin  4080 .  
         [0040]     When the disc  160  is held in this manner, rotation of the disc  160  about a longitudinal axis (of the disc  160 ) relative to the inserter/impactor  4000  is prevented by interference of the corners of the disc&#39;s  160  flat surfaces ( 180   a - c  and  180   d - f ) and the corners of the inserter/impactor&#39;s  4000  flat surfaces ( 4200   a - c  and  4200   d - f ), similar to the manner in which a wrench holding a nut prevents rotation of the nut relative to the wrench. Further, the holding of the disc  160  in this manner allows for some repositioning of the disc  160  in the intervertebral space via rotation of the disc  160  in either direction about the longitudinal axis of the intervertebral space. Further when the disc is held in this manner, rotation of the disc about a lateral axis (of the disc  160 ) relative to the inserter/impactor  4000  is prevented by interference of the inwardly facing surface  164   a  of the first baseplate (e.g., upper baseplate) of the disc and the upper surface  4200   g  of the wedge on the distal end  4040 , and by interference of the inwardly facing surface  164   b  of the second baseplate (e.g., lower baseplate) of the disc and the lower surface  4200   h  of the wedge on the distal end  4040 . Accordingly, the holding of the disc in this manner allows for some repositioning of the disc in the intervertebral space via rotation of the disc in either direction about the longitudinal or latitudinal axis of the intervertebral space  
         [0041]     In some embodiments, when the artificial intervertebral disc  160  is held by the inserter/impactor  4000 , the flat surfaces  180   a - c  are more closely confronted by the angled flat surfaces  4200   a - c  of the inserter/impactor  4000 , compared with the flat surfaces  180   d - f  being less closely confronted by the angled flat surfaces  4200   d - f  of the inserter/impactor  4000 . As such, the structure of the artificial intervertebral disc  160  having the flat surfaces  180   d - f  (e.g., the upper baseplate  168   a ) has slightly more rotation and angulation freedom relative to the inserter/impactor  4000  when being held, compared to the structure of the artificial intervertebral disc  160  having the flat surfaces  180   a - c  (e.g., the lower baseplate  168   b ). This permits the artificial intervertebral disc  160  to adjust to the intervertebral space (e.g., to the angulation of the adjacent vertebral endplates, defining the intervertebral space, relative to one another) as it is being inserted thereinto. That is, typically, the adjacent vertebral endplates will be lordotically angled with respect to one another as a result of the intervertebral space being prepared and distracted.  
         [0042]     Preferably, in order to provide for a holding of the disc  160  for two additional (here, anteriolateral) insertion approaches, each disc  160  also includes two additional holes  182   a  and  182   c , one (e.g.,  182   a ) spaced apart from one of the anteriolaterally facing flat surfaces (e.g.  180   a ), and the other (e.g.  182   c ) spaced apart from the other of the anteriolaterally facing flat surfaces (e.g.  180   c ). Accordingly, operation of the inserter/impactor  4000  can fit the holding pin  4080  into either of these two additional holes  182   a  or  182   c , and hold the associated anteriolaterally facing flat surface (the one associated with the hole into which the pin  4080  is fit) of the disc  160  against the flat surface of the inserter/impactor  4000  opposite the pin  4080 . For example, in a first anteriolateral approach for the disc  160 ,  180   a  and  180   d  facing  4200   b  and  4200   e ,  180   c  and  180   f  not confronted, and  180   b  and  180   e  facing  4200   c  and  4200   f , and in a second anteriolateral approach for the disc  160 ,  180   b  and  180   e  facing  4200   a  and  4200   d ,  180   a  and  180   d  not confronted, and  180   c  and  180   f  facing  4200   b  and  4200   e . It should be understood that preferably, in order to facilitate these additional approaches, the angle separating the anteriorly facing flat surface of the disc  160  and one of the anteriolaterally facing flat surfaces of the disc  160  is equal to the angle separating the anteriorly facing flat surface and the other of the anteriolaterally facing flat surfaces. Preferably, the surfaces are angled with respect to one another at an angle of 33.4 degrees.  
         [0043]     It should also be understood that the inclusion of additional adjacent angulated surfaces (or placing the angulated surfaces in other locations on the disc or other orthopedic device), and/or including corresponding holes adjacent to such surfaces, can provide the surgeon with additional approaches, e.g., other anteriolateral approaches, directly lateral approaches, posteriolateral approaches, and/or directly posterior approaches. For example, a trial or disc can have angled surfaces (and corresponding holes) along the entire perimeter of one or both of the baseplates, and thus enable the surgeon to engage the trial or disc from a number of angles, including anterior, posterior, lateral, anteriolateral, and posteriolateral angles.  
         [0044]     The inserter/impactor  4000  further includes at a proximal end a cap  4140  for use as an impact surface if the disc  160  must be impacted further into the intervertebral space after insertion, or forcibly extracted from the intervertebral space. A mallet can be used to strike the cap  4140  (in a distal direction for impaction, or in a proximal direction (using the flange of the cap  4140 ) for extraction). It should be noted a striking of the cap  4140  will translate the striking force to the baseplates through the shaft  4020  and the flat surfaces, but will not damage the holding pin  4080  because the holding pin  4080  is spring loaded in the central channel and thus buffered from the striking force thereby. The distal end  4040  of the inserter/impactor  4000  further preferably includes at least one vertebral body stop  4202  that protrudes longitudinally with respect to the shaft  4020 , from the surfaces of the distal end. The stops help prevent the inserter/impactor from being used to insert the disc (or other orthopedic device) too far into the intervertebral space.  
         [0045]     Accordingly, the inserter/impactor  4000  can be used to grip the artificial intervertebral disc to be implanted, and hold the same during insertion and/or removal of the same, and is useful for a variety of surgical approach angles.  
         [0046]     Now referring to  FIGS. 5 and 6 , a preferred embodiment of inserter/impactor  4000  is described. In this embodiment at least one vertebral body stop  4202  has a ramped configuration, the ramp tapering from its peak adjacent the distal face of distal end  4040  toward the proximal end of inserter/impactor  4000 . This configuration of the stop  4202  assists in preventing the inserter/impactor  4000  from overinserting the disc (or other orthopedic device) into the intervertebral space and also permits the inserter/impactor to  4000  to be employed in conjunction with the distractor shown in  FIGS. 7-9 , as described below.  
         [0047]     As best seen in  FIG. 6 , in a preferred embodiment inserter/impactor  4000  is sized such that its thickness, excluding stop(s)  4202 , is less than that of disc  160  so that the disk  160  has the largest profile of any part introduced in the intervertebral space. Diminishing the profile of the inserter/impactor  4000  has the benefit of minimizing the possibility of unintentional injury to the intervertebral space, as well as permitting the inserter/impactor  4000  to be inserted between the wedge-ramps (described below) while holding the disc  160 .  
         [0048]     Now referring to  FIGS. 7-9  a preferred embodiment of a distractor is disclosed. A distractor  5000  comprises essentially a pair of identical ramps  5100  facing one another and converging toward one another, and a connecting member (e.g., c-clip)  5200  having extensions (e.g., legs)  5210  for operably connecting ramps  5100  to each other. The use of multiple pieces eases cleaning of the distractor  5000  in an autoclave, and the use of the c-clip  5200  allows the ramps  5100  to be doubly-hinged to one another for ease of extraction of the ramps  5100  from the intervertebral space. In an alternate embodiment distractor  5000  is formed as a unitary device. The distractor  5000  is sized to correspond to the baseplate footprint of the disc  160  that is to be implanted, such that, preferably, the teeth  188   a , 188   b  (or other suitable engagement features) of the disc  160  are able to travel in a corresponding guide feature (e.g., grooves  5118 ) in the ramps  5100  (as described below).  
         [0049]     Ramp  5100  has a connecting member receipt feature (e.g., channel)  5110  disposed on its proximal end for receiving a leg  5210  of c-clip  5200 . The interior side  5130  of ramp  5100 , i.e., the side that faces opposing ramp  5100 , is defined by guide features (e.g., laterally spaced grooves)  5118  disposed longitudinally on the interior side  5130  and extending along vertebral space engagement members (e.g., laterally spaced prongs)  5120  extending from the distal end of ramp  5100 . The exterior side  5140  of ramp  5100  is defined by vertebral body stop features (e.g., transversely disposed ridges)  5142  formed at the base of prongs  5120  adjacent the distal end of ramp  5100 . An instrument accommodation feature (e.g., longitudinal aperture  5150 ) is formed medially in ramp  5100  and, e.g., extends from the distal end of said ramp  5100  substantially parallel to grooves  5118  partially along the length of ramp  5100 .  
         [0050]     C-clip  5200  further comprises a fastening device for securely but removably engaging channel  5110 , such as, but not limited to, a floating ball bearing  5122  that permits a leg  5120  of the c-clip to slidably and lockably engage channel  5110 .  
         [0051]     Now further referring to  FIG. 9 , as assembled, grooves  5118  of the respective ramps  5100  face one another. In this orientation, inserter/impactor  4000  (having the disc  160  mounted thereto) is insertable between the opposing ramps  5100 , with the teeth  188   a  of the implant base plates  168   a - b  slidably engaging grooves  5118 .  
         [0052]     In practice, prongs  5120  are inserted between the vertebral endplates at the implantation site. Ridges  5142  prevent overinsertion of the prongs  5120  into the intervertebral space as the ridges  5142  confront the anterior faces of the vertebral bodies. Once the prongs  5120  are inserted, the disc  160 , already secured to the inserter/impactor  4000 , is placed onto the bottom ramp  5100  such that the teeth  188   a  “ride” in the grooves  5118  as the disc  160  is pushed forward along the length of the bottom ramp  5100 . The disc  160  is preferably oriented such that the bottom base plate  168   b  is parallel to the ramp  5100  and the top base plate  168   a  is held in a lordosed position relative to the bottom base plate  168   b  by the inserter/impactor  4000 . Also, aperture  5150  accommodates the vertebral body stops  4202  (having the ramped configuration) of a preferred embodiment of inserter/impactor  4000  (as shown in  FIGS. 5-6 ) during the forward movement of the disc  160  and inserter/impactor  4000 . (This configuration of the stop  4202  not only assists in preventing the inserter/impactor  4000  from overinserting the disc  160  (or other orthopedic device) into the intervertebral space (by the confrontation of the distal end of the stops  4202  with the anterior faces of the vertebral endplates), but also permits the inserter/impactor to  4000  to be easily withdrawn if it is necessary to remove or extract the disc  160  prior to removing the ramps  5100  from the treatment site (as the inserter/impactor  4000  is pulled backwards between the ramps  5100 , the taper of the ramped proximal portion of the stop  4202  enables the stop to not catch on the proximal end of aperture  5150 , but rather to smoothly transition from the proximal end of aperture  5150  to the remaining proximal portion of the ramp  5100 .)  
         [0053]     Continued movement of the disc  160  toward the intervertebral space is typically met with increased resistance as the space is distracted (by the wedging action of the disc  160  being pushed forward and thereby separating the prongs  5120 ) to accommodate the height of the disc  160 ; manual pressure typically overcomes this resistance. If necessary, a proximal flange  4140  on the inserter/impactor  4000  can be struck to effect any additional force required. With regard to the configuration of the prongs  5120 , the prongs  5120  are preferably dimensioned to facilitate guidance and passage of the disc  160  into the intervertebral space after leaving the distal portion of the ramps  5100  past the ridges  5142 , and out from the intervertebral space once the disc  160  is disposed therein. More particularly, the prongs  5120  are dimensioned in width to slidably fit between the convex dome  184   a , 184   b  and the teeth  188   a , 188   b  on the disc  160  baseplates, and dimensioned in length to reach far enough into the intervetebral space to provide leverage support for the wedging action. Once the disc  160  is inserted into the intervertebral space, the ramps  5100  are removed from the intervertebral space, preferably one at a time by first rotating the top ramp  5100  out from between the disc  160  and the upper vertebral endplate using the c-clip  5200  as a double-hinge. The bottom ramp  5100  may then be pulled out from between the disc  160  and the lower vertebral endplate. The inserter/impactor  4000  may then be removed from the disc  160 . Further with regard to the configuration of the prongs  5120 , the prongs&#39;  5120  dimensions preferably facilitate removal of the prongs  5120  as the ramps  5100  are pulled out (i.e., the pulling out of the ramps  5100  slides the prongs  5120  between the convex dome  184   a , 184   b  and the teeth  188   a , 188   b  of the disc  160 , to avoid damage to the disc  160  or the vertebral endplate.  
         [0054]     It should be noted that the use of the prongs  5120  and the grooves  5118  thereon, in which the teeth  188   a , 188   b  slide, avoids any possible damage to the vertebral endplates as a result of engagement of the endplate by the teeth  188   a , 188   b  prior to full insertion of the disc  160 . That is, using the above-described method, the teeth  188   a , 188   b  do not engage the endplate until after the prongs  5120  are removed, which is once the disc  160  is properly placed, and therefore the initial engagement of the endplate by the teeth  188   a , 188   b  is the final engagement. Accordingly, because no gouging or scratching of the endplate by the teeth  188   a , 188   b  occurs, the teeth  188   a , 188   b  are less likely to move from their engaged position, which provides a more secure foothold for the disc  160 .  
         [0055]     Now referring to  FIGS. 10 and 11 , a preferred embodiment of a distractor  6000  is disclosed, comprising essentially a plying device  6100  such as but not limited to a Beere-style distractor and a pair of opposing forks  6200  adapted to engage therebetween an implant such as a disc l 60 .  
         [0056]     Forks  6200  are adapted to connect to plying device  6100  using a fastening device such as but not limited to a floating ball bearing  6202  disposed on the proximal end  6210  of the fork  6200  to slidably and lockably engage a complementary portion  6102  of plying device  6100  such as but not limited to a channel. Preferably a male/female coupling arrangement is provided. Collar  6204  is preferably employed to provide a firm engagement between plying device  6100  and fork  6200 .  
         [0057]     Fork  6200  is preferably configured to engage the intervertebral space for distraction, while accommodating the passage of the disc  160  between the forks  6200  while the space is held in distraction. Accordingly, to facilitate such passage while the space is held in distraction, the forks  6200  are offset from the primary longitudinal axis of the plying device  6100 , preferably as shown, such that the plying device can be operated to open the intervertebral space, but not obstruct a line of sight or an anterior insertion of the disc  160  between the forks  6200  into the intervertebral space. More particularly, each fork  6200  comprises essentially an elongated portion  6220  terminating in a substantially U-shaped member  6230  comprising a base  6232  oriented substantially perpendicular to the elongated portion  6220  and a pair of laterally spaced tines  6234  oriented substantially perpendicular to the base  6232 . With regard to the offset nature of the forks  6200 , is it preferable that one of the tines  6234  be longitudinally aligned with the elongated portion  6220 . It is further preferable that the base  6232  of the U-shaped member have a forward ridge surface perpendicular to the tines&#39; outwardly facing surfaces, which ridge functions as a vertebral body stop to prevent the tines  6234  from being inserted too deeply into the intevertebral space.  
         [0058]     With regard to the ability of the disc  160  to pass into the intervertebral space, the U-shaped member  6230  and tines  6234  are configured to engage with or avoid certain features of the disc  160  and/or an insertion tool (e.g., the inserter/impactor  4000 ). For example, the tines  6234  are preferably dimensioned to facilitate guidance and passage of the disc  160  into the intervertebral space, and out from the intervertebral space once the disc  160  is disposed therein. More particularly, the tines  6234  are dimensioned in width to slidably fit between the convex dome  184   a , 184   b  and the teeth  188   a , 188   b  on the disc  160  baseplates, and dimensioned in length to reach far enough into the intervetebral space to provide leverage support for the distraction. Also particularly, the U-shaped member  6230  of fork  6200  has an interior side (i.e., the side facing opposite fork  6200 ) defined by a notch  6240  and curved profile  6300 , which notch allows passage of the vertebral body stops  4202  of the inserter/impactor  4000  as the disc  160  is inserted, and which curved profile permits passage of the convex dome  184   a , 184   b  of the disc  160  as the disc is inserted.  
         [0059]     In practice, the tines  6234  of forks  6200  of the distractor  6000  are placed in an intervertebral space far enough that the forward ridge surfaces of the base  6232  of the U-shaped member  6230  abut the anterior faces of the vertebral bodies. Next, the handles  6110  of plying device  6100  are squeezed together to separate the tine pairs to urge the vertebral bodies apart and create an aperture for passage of the disc  160  therethrough and into the intervertebral space. More particularly, in this position, the opposing interior sides of the U-shaped members  6230  of forks  6200 , by virtue of facing curved profiles  6300 , are positioned such that a disc  160 , in a preferred embodiment already secured to the inserter/impactor  4000 , is positionable and translatable between the U-shaped members  6230 . The curved profiles  6300  accommodate the convex domes  184   a , 184   b  of the disc  160 . Notches  6240  accommodate vertebral body stops  4202  of the inserter/impactor  4000 . The width of the tines  6234  accommodate the teeth  188   a , 188   b  and convex dome  188   a , 188   b  of baseplates  168   a - b  for passage and guidance along the tines  6234 . Once the disc  160  is situated between the forks  6200 , the inserter/impactor  4000  can be employed to manipulate the disc along the tines  6234 . After insertion of the disc  160  in the intervertebral space, the distactor  600  is removed. and the inserter/impactor  4000  is disengaged from the disc  160 . Further with regard to the configuration of the tines  6234 , the tines&#39;  6234  dimensions preferably facilitate removal of the tines  6234  as the forks  6200  are removed (i.e., the pulling out of the forks  6200  slides the tines  6234  between the convex dome  184   a , 184   b  and the teeth  188   a , 188   b  of the disc  160 , to avoid damage to the disc  160  or the vertebral endplate. Further preferably, the thickness of the extent of the tines  6234  is higher than the height of the teeth  188   a , 188   b  rising off the baseplate surfaces. Accordingly, the use of tines  6234  of at least this thickness avoids any possible damage to the vertebral endplates as a result of engagement of the endplate by the teeth  188   a , 188   b  prior to full insertion of the disc  160 . That is, using this insertion method, the teeth  188   a , 188   b  do not engage the endplate until after the tines  6234  are removed (the thickness of the tines  6234  prevents the teeth  188   a , 188   b  from engaging the endplates), which is once the disc  160  is properly placed, and therefore the initial engagement of the endplates by the teeth  188   a , 188   b  is the final engagement. Accordingly, because no gouging or scratching of the endplates by the teeth  188   a , 188   b  occurs, the teeth  188   a , 188   b  are less likely to move from their engaged position, which provides a more secure foothold for the disc  160 .  
         [0060]     While there has been described and illustrated specific embodiments of instrumentation, it will be apparent to those skilled in the art that variations and modifications are possible without deviating from the broad spirit and principle of the invention. The invention, therefore, shall not be limited to the specific embodiments discussed herein.