Patent Abstract:
The invention provides a fusion plate system, and method for installing this system upon a patient&#39;s spine. The system uses a distractor device which measures an appropriately sized fusion plate for a corpectomy or discectomy application. Once a properly sized fusion plate is selected, the distractor device compresses the vertebrae and any associated bone graft placed between the vertebrae, thereby assuring maximum contact between the vertebrae and bone graft at a corpectomy or discectomy location. Compression is maintained by the distractor device while the fusion plate is anchored upon the corpectomy or discectomy site. Furthermore, the inventive fusion plate system and method results in the fusion plate being properly centered upon a patient&#39;s spine, so that an aesthetically pleasing, as well as functional, surgical result is achieved.

Full Description:
TECHNICAL FIELD 
     This invention relates to appliances used in the stabilization and fusion of spinal vertebrae during and after spine surgery, and more specifically, relates to systems and methods for using a fusion plate for stabilizing vertebrae as part of a corpectomy or discectomy procedure to allow bone growth to occur. 
     BACKGROUND 
     Fusion plates have been in use as appliances for immobilizing and fusing adjacent spinal vertebrae following a discectomy (spinal disc removal) or for immobilizing the area surrounding a corpectomy (removal of an entire vertebral body). When these procedures are performed, a gap in the spine remains from the removed disc or vertebral body; this gap typically being closed by inserting a bone graft, usually from a cadaver. The adjacent vertebrae surrounding the discectomy or corpectomy site are then immobilized by attaching a fusion plate, usually on the anterior side of the spine, so that the vertebrae fuse to the bone graft, forming an entire fused section of the spine. Such fusing of vertebrae to the bone graft requires that the vertebrae remain immobile. Any movement during the healing process can cause a lack of fusion to occur, essentially forming a false joint in the spine at the discetomy or corpectomy site. 
     Presently, in performing a discectomy or corpectomy, a device called a “distractor” is used to spread the adjacent vertebrae so that the disc or vertebral body of interest can be removed. In use, a pair of distractor pins, which are essentially screws having a head for engaging with the distractor, are screwed into the vertebrae adjacent to the discectomy or corpectomy site. One pin is placed in the upper vertebra, and a second pin is placed in the lower vertebra, both vertebrae being directly adjacent to the discectomy or corpectomy site. The distractor tool is then coupled to the pins on the upper and lower vertebrae, above and below the site, and the vertebrae are then mechanically spread apart, for aiding in the removal of any remaining portion of the deteriorated disc or vertebral body, and also to create a gap for placing a bone graft. Once the bone graft is placed, the distractor is removed; next, the distractor pins are removed from the spine, and finally, a fusion plate is placed in a position for keeping the adjacent upper and lower vertebrae as well as the bone graft immobilized. The plate is screwed into the upper and lower vertebrae the goal of which is to provide sufficient immobility to cause fusion between the vertebrae and bone graft to occur. Examples of fusion plates presently existing in the art, which are used in the heretofore described manner, are those produced by EBI Biomet, Inc., Dupuy AcroMed, Inc., and Spinal Concepts, Inc, to name a few. 
     Two drawbacks with the present fusion plate methods and systems are: 1) the plate is often positioned off-center on the spine, during these procedures, due to the fact that there has not been a system in place to properly align the fusion plate on the spine; and 2) the above methods rely only on the natural compression of the spine (e.g. once the distractor is removed), to compress the vertebrae sufficiently against the bone graft, to allow fusion to begin. With regard to the first drawback, a fusion plate positioned off-center can result in aesthetic objections from a patient in whom a fusion plate has been implanted. This often occurs when a patient examines his spinal X-ray following surgery and the fusion plate is off-center, or crooked, leading the patient to surmise that the surgeon has performed a haphazard job. With regard to the second drawback, the failure to sufficiently compress the vertebra and bone graft together, prior to placing and anchoring the fusion plate, results in unnecessary space remaining between these components, and reduces the likelihood that fusion will occur (this can cause the “false jointing” problems noted above). 
     Therefore, a need exists for a fusion plate system and method which allows a section of spine to be compressed adequately following a corpectomy or discectomy, so that sufficient immobilization and spinal fusion can occur. Additionally, a need exists for a fusion plate system and method which allows a fusion plate to be centered properly upon a spine. 
     The foregoing reflects the state of the art of which the inventor is aware, and is tendered with a view toward discharging the inventors&#39; acknowledged duty of candor, which may be pertinent to the patentability of the present invention. It is respectfully stipulated, however, that the foregoing discussion does not teach or render obvious, singly or when considered in combination, the inventor&#39;s claimed invention. 
     SUMMARY OF THE INVENTION 
     The invention overcomes the drawbacks of the prior art by providing a modified fusion plate system, and method for installing this system upon a patient&#39;s spine. This method and system allows a desired level of compression to be applied to the adjacent vertebrae surrounding the site of a corpectomy or discectomy, prior to, and during, the anchoring of the fusion plate. Furthermore, the inventive fusion plate system and method results in the fusion plate being properly centered upon a patient&#39;s spine, so that an aesthetically pleasing, as well as functional, surgical result is achieved. 
     The inventive system and method relies upon mechanically compressing the spine to draw vertebrae together until these vertebrae are in contact with a bone graft located in the gap left by a corpectomy or discectomy. Once the spine is compressed, the fusion plate is guided to a centered positioning upon the spine over the site of the corpectomy. Finally, the fusion plate is anchored upon the spine, while the spine is still undergoing mechanical compression. The reliance of this system and method upon mechanical compression of the spine while the fusion plate is anchored, is intended to reduce spaces between the bone graft and adjacent vertebrae at the site of a corpectomy or discectomy, as much as possible, so that spinal fusion has the greatest chance of occurring. 
     In the preferred embodiment, the inventive system uses a distractor device to not only distract (e.g. spread) vertebrae, in the manner presently used, but additionally, to mechanically compress vertebrae and any bone graft located there between. Furthermore, the addition of sizing graduations to the inventive distractor device, correlating to the sizes of different fusion plates, allows a properly sized fusion plate to be selected by the surgeon for a particular application, with minimal trial and error. 
     The inventive system and method uses distractor pins to properly guide the fusion plate to a centered positioning upon a patient&#39;s spine. Once guided onto the spine, the fusion plate is anchored with bone screws. The distractor pins are centered on the spine using anatomical landmarks such as the longis colli muscles or uncinate processes. The distractor pins are also designed for having a compressing force applied to them by the distractor device such that they do not bend or disengage from the distractor device upon compressing the spine to a desired level. 
     Accordingly, the following objects and advantages of the invention apply: 
     It is an object of this invention to provide a fusion plate system and method which results in improved fusion of spinal vertebrae following a corpectomy or discectomy. 
     It is another object of this invention to provide a fusion plate system and method which causes a fusion plate to be centered upon a patient&#39;s spine. 
     Further objects and advantages of the invention will be brought out in the following portions of the specification, wherein the detailed description is for the purpose of fully disclosing preferred embodiments of the invention, without placing limitations thereon. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will be more fully understood by reference to the following drawings which are for illustrative purposes only: 
     FIG. 1 is a plan view of the C-4 and C-6 vertebrae with the C-5 vertebral body removed as in a corpectomy procedure and wherein the C-4 and C-6 vertebrae each have a centered distractor pin coupled thereto. 
     FIG. 2 is a plan view of the C-4 and C-6 vertebrae shown with a bone graft positioned in the gap left by the removal of the C-5 vertebral body, this view again showing centered distractor pins coupled to the C-4 and C-6 vertebrae. 
     FIG. 3A is a perspective view of a first preferred embodiment of the distractor pin of the inventive system, this embodiment having a slender head portion and a section that is hexagonal for mating with a surgical wrench. 
     FIG. 3B is a perspective view of a second preferred embodiment of the distractor pin of the inventive system, this embodiment having a groove located at the bottom end of the pin head portion, this groove for mating with the terminal end of a distractor device armature. 
     FIG. 3C is a perspective view of a third preferred embodiment of the distractor pin having a spring loaded, flexible portion. 
     FIG. 4 is a perspective view of a distractor device of the inventive system, this view showing the carriage body and associated armature traveling in an extended (distracted) direction. 
     FIG. 5 is a perspective view of the distractor device of FIG. 4, showing the opposite side of the distractor device shown in FIG. 4, with the carriage body and associated armature traveling in a compressed direction. 
     FIG. 6 is an end view of the carriage body of the distractor device. 
     FIG. 7 is a closeup side cutaway view of the carriage body element positioned on a section of the rack of the inventive distractor device showing a two-way toggling mechanism toggling in a position for distraction. 
     FIG. 8 is a closeup side cutaway view of the carriage body element positioned on a section of the rack of the inventive distractor device showing a two-way toggling mechanism toggling in a position for compression. 
     FIG. 9A is a closeup view of a distractor device armature and the bore of its terminal end portion showing a spring clamp coupling mechanism for coupling to the head portions of distractor pins of the type shown in FIG.  3 B. 
     FIG. 9B is a closeup cutaway view of the terminal end portion of the inventive distractor device showing the spring clamp coupling mechanism engaging the head portion of a distractor pin of the type shown in FIG.  3 B. 
     FIG. 10A is a closeup view of a section of the rack portion of the inventive distractor device having a measuring scale graduated in millimeters. 
     FIG. 10B is a closeup view of a section of the rack portion of the inventive distractor device having a measuring scale indicating an exemplary manufacturer&#39;s fusion plate model numbers. 
     FIG. 11A is a plan view of a fusion plate used for a discectomy procedure, having a cleft engagement means for snugly engaging the head of a distractor pin. 
     FIG. 11B is a perspective view of the plate shown in FIG. 11A showing the plate having a curvature for conforming to the shape of the anterior portion of a spine. 
     FIG. 11C is a plan view of the fusion plate shown in FIG. 11A showing the head portions of distractor pins snugly engaged within the cleft engagement means of the fusion plate. 
     FIG. 12A is a plan view of a fusion plate used for a corpectomy procedure. 
     FIG. 12B is a perspective view of another style of fusion plate used for a corpectomy procedure this view showing a curvature for conforming to the shape of the anterior portion of a spine. 
     FIG. 12C is a plan view of the fusion plate shown in FIG. 12B showing the head portions of distractor pins snugly engaged within the cleft portions of the plate. 
     FIG. 13 is a side view of the C-4 and C-6 vertebrae with the C-5 vertebral body removed and a gap located there between, as would occur in a corpectomy procedure. The distractor pins are aligned perpendicularly to the C-4 and C-6 vertebrae. 
     FIG. 14 is an elevated perspective view of the distractor device of FIG. 4 coupling to distractor pins in turn coupled to the C-4 and C-6 vertebrae and spreading these vertebrae apart. The C-5 vertebral body has been removed as in a corpectomy procedure and a bone graft has been placed in the gap left by the removal of the vertebral body. The spreading of the vertebrae here allows the vertebral body to be removed from the C-5 vertebrae and allows the bone graft to be placed. 
     FIG. 15 is an elevated perspective view of the distractor device of FIG. 4 coupled to distractor pins in turn coupled to the C-4 and C-6 vertebrae with a bone graft filling the gap left by the removal of the C-5 vertebral body as in a corpectomy procedure. Here the distractor device is being used to compress the C-4 and C-6 vertebrae against the bone graft. 
     FIG. 16 is an elevated perspective view of the distractor device of FIG. 4 coupled to distractor pins and compressing the C-4 and C-6 vertebrae against the bone graft while a fusion plate is positioned in a centered manner by distractor pins at the corpectomy site. 
     FIG. 17 is a closeup elevated perspective view of the terminal ends of the distractor device of FIG. 4 coupled to distractor pins and compressively holding the C-4 and C-6 vertebrae against the bone graft while a fusion plate is being anchored into place over the corpectomy site. Here a modified drill guide is used to apply the anchor screw to the fusion plate, the guide tube of drill guide being shown in cutaway with an anchor screw and screw driver placed therein. The terminal end of drill guide tube is shown seated in a chamfered region surrounding anchor holes 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 illustrates a section of cervical spine  10  with a vertebral body (not shown) removed from a fifth cervical vertebrae (C-5)  12  as would result in a standard corpectomy procedure. While the cervical section of a human spine is shown here, this is for illustrative purposes only, as this invention could be used on other vertebral sections, such as the thoracic or lumbar sections of the spine. Additionally, while a human spine is shown in the drawings, the inventive system and method could be adapted to be used on sections of animal spines. In surgery the vertebral body of the (C-5)  12  vertebrae would have been removed in sections, being careful not to damage the dura covering (not shown) of the spinal cord, thereby leaving a gap  14  having the fourth (C-4)  16  and sixth (C-6)  18  cervical vertebrae located adjacent to gap  14 . 
     In a corpectomy procedure the gap  14  is filled with a bone graft  20  that is sized and shaped to fill gap  14  snugly as is shown in FIG.  2 . Prior to placing a bone graft into gap, the bottom surface  22  of the C-4 vertebrae and the top surface  24  of the C-6 vertebrae are usually scored by the surgeon to cause bleeding. This blood flow encourages the ossification process to occur between the cervical vertebrae  16 ,  18  and the bone graft  20  placed in gap  14 , thereby causing fusion of these elements. If gravity is the only force acting on the spine to draw vertebrae  16 ,  18  in contact with the bone graft  20 , it is possible for enough space to remain between the contacting surfaces of these elements, such that fusion will not occur at all. If fusion does not occur, this may necessitate a second surgery to correct the problem. 
     As shown in FIGS. 1 and 2, first and second distractor pins  26  are placed in the (C-4)  16  and (C-6)  18  vertebrae. In the inventive method and system, distractor pins  26  are used as leverage points for the application of a distractor device  30  for purposes of both distracting, or spreading the vertebrae, and additionally, for compressing the vertebrae. Due to the application of compressive force by the inventive method and distractor device, it is preferred that distractor pins  26 , be constructed from a non-bendable material such as titanium alloy. 
     FIG. 3A illustrates a distractor pin  26  of a preferred shape to accomplish the inventive system and method. Distractor pin  26  has a head portion  32  for coupling to a distractor device and a screw portion  34  for attaching to vertebrae. Preferably, head portion  32  is tapered  36  at its top with an overall slender cylindrical profile below the tapered top having a substantially uniform cylindrical diameter. A small hexagonal section  38  for engaging with a surgical wrench aids in driving the distractor pin into the vertebra. Alternately, the head portion  32  can also be designed to be a phillips head, for example, or designed with another means for driving screw portion  34  into vertebrae. The lower section  40  of head portion  32  is cylindrical with the rest of the head portion for engaging with the fusion plate  42  in a manner described further below. 
     FIG. 3B illustrates a second embodiment of distractor pin  26  with head portion  32  having a groove  44  located above lower section  40 . This groove  44  mates with a spring clamp  106  located in the bore  104  of the armature  50 A,  50 B of distractor device  30  to form a coupling mechanism as further described below. 
     FIG. 3C illustrates a third embodiment of distractor pin  26  having a spring loaded, flexible top  52 . The flexible top allows a surgeon to bend the top  52  slightly into the bore  104  of the armature  50 A,  50 B of the distractor device  30 , thus serving as a bore-guide. Flexible top  52  is especially useful in the bloody conditions of surgery where guiding the distractor armature  50 A,  50 B onto the head portion  32  of the distractor pin  26  is often done by feel. Distractor pins  26  are preferably approximately 12-14 mm long, with the screw portion  34  comprising the majority of the length of the distractor pin in relation to the head portion  32 . The screw portion  34  can be altered in length to conform to a range of patient&#39;s bone depth and density. For example, an osteoporotic patient may require a screw portion  34  longer than normal to allow additional purchase of the distractor pin  26  in the deteriorating bone. 
     Referring again to FIGS. 1 and 2, the step in the inventive method of centering distractor pins  26  can be examined. The method described here for centering distractor pins  26  on the (C-4) and (C-6)  16 ,  18  vertebrae shown here would apply to other vertebrae located at other sections of the spine as well. The preferred method for accomplishing this step involves choosing a bilaterally symmetrical anatomical landmark such as the longis colli muscles (not shown), or the uncinate processes  54  of the vertebrae and using these landmarks for centering the distractor pins  26 . These landmarks are typically equidistant from the center of the cervical vertebra, and hence, the surgeon needs only to confirm the location of the equidistant center (demonstrated hereby arrows  130 ) and attach a distractor pin  26  to the vertebrae at that location, as shown in FIGS. 1 and 2. 
     Upon placing the distractor pins  26  in the manner heretofore described, a distractor device  30 , the preferred embodiment of which is shown in FIGS. 4 and 5 is coupled to distractor pins  26 . As shown, distractor device  30  is comprised of a carriage body  56 , a first armature  50 A coupled to carriage body  56 , a rack  60  for allowing the carriage body  56  a range of motion and a second armature  50 B coupled at an end of the rack  60 . 
     Referring also to FIGS. 6 and 7 carriage body  56  defines a chamber  64  along its length l. Chamber  64  has first and second openings  66 ,  68  at an engagement end  70  and the opposite end  72  respectively, and openings  66 ,  68  are in communication with the chamber  64 . The body  56  also defines a gear bore  74  at a location along length l, the gear bore  74  being in communication with chamber  64 . Gear bore  74  has an axis  76  which is perpendicular to length l of chamber. Gear bore  74  is preferably defined through carriage body  56  from the first side  78  to the opposite side  80  of the body  56 . 
     Referring again to FIGS. 4 and 5 and still to FIGS. 6 and 7, rack  60  is slidably disposed through first opening  66  and within the chamber  64 . Rack  60  has a first end  82  for engaging with first opening  66  and a second end  84  having a second armature  50 B coupled thereto. Rack  60  is slidable between a number of extended and compressed positions. FIG. 4 shows device  30  having rack  60  extended while FIG. 5 shows device  30  with rack being compressed to draw armatures  50 A,  50 B together. Rack  60  moves between extended and compressed positionings by engaging with gear  86  in gear bore  74 , using a number of spaced apart teeth  88  located on rack  60 . 
     Referring still to FIG.  7  and now to FIG. 8 the distractor device  30  also includes a two-way toggle switch  90  located atop carriage body  56 , toggle switch for allowing first armature  50 A coupled to carriage body  56  to alternately travel closer to, or away from, second armature  50 B. Carriage body  56  and its associated armature  50 A when traveling further from second armature  50 B causes distraction, or spreading of the vertebrae. Alternatively travel of carriage body  56  closer to second armature  50 B causes compression of vertebrae. Depending on the direction of travel desired, toggle switch  90  is switched so that the engaging member  92  located at each end of toggle switch arm  94  engages the gear teeth  88  of rack  60 . FIG. 7 shows the actuation position of toggle switch for distraction, while FIG. 8 shows the proper actuation position of toggle switch for compression. Upon switching toggle switch to a desired direction, engaging member is biased against gear teeth  88  by a spring (not shown), so that as handle  58  is turned, engaging member  92  is dragged over gear teeth  88  and locks in the valley of gear teeth. Upon locking, engaging member  92  prevents carriage body  56  from traveling in the opposite undesired direction, from which toggle switch  90  has been actuated. 
     Referring now to FIGS. 9A and 9B and still to the previous figures, the armatures  50 A,  50 B of distractor device  30  can be examined. First armature  50 A coupled to carriage body  56  is comprised of a first section  98  extending substantially perpendicularly outward from carriage body  56  and a second section  100  bent at an obtuse angle in relation to first section. Second armature  50 B is comprised of two similar sections  98 ,  100  as first armature  50 A, except that second armature is stationarilly engaged to the end  84  of rack. FIG. 9A is a closeup of the terminal end  102  of either first or second armature  50 A,  50 B showing a bore  104  axially disposed within second section  100  of armature, the bore preferably including a coupling mechanism comprised of a spring clamp  106  for receiving and releasably holding the head portion  32  of a distractor pin  26  therein. Spring clamp  106  is preferably horseshoe-shaped with the semi-circular portion  108  having a slightly smaller diameter than the head portion of distractor pin  26  of the type shown in FIG.  3 B. The ends  110  of the horseshoe shape of spring clamp  106  are flexibly anchored to the body of terminal end  102 . The top  36  of distractor pin  26  is preferably tapered, as previously discussed, to easily slide spring clamp  106  over and onto the head portion  32 . As shown in FIG. 9B, upon positioning around head portion  32 , spring wire expands into space  121  inside of bore  104  and then compresses upon reaching groove  44  of distractor pin  26 . Once inside groove  44 , spring clamp  106  prevents distractor device  30  from migrating upward and slipping off of distractor pins  26  while vertebrae are being compressed. Spring clamp  106  can be removed from distractor pins  26  by applying gentle upward pressure on armatures  50 A,  50 B until device  30  disengages from distractor pin  26 . 
     Referring now to FIGS. 10A and 10B distractor device  30  includes a measuring scale  114  located upon rack  60  which allows a surgeon to select a properly sized fusion plate  42  for attachment at the site of a corpectomy or discectomy. Measuring scale  114  corresponds to a distance between the terminal ends  102  of armatures  50 A,  50 B, this distance corresponding to a preferred fusion plate size which will most likely fit over the site of a corpectomy or discectomy. Measuring scale  114  may have standard indicia  116 , such as millimeters or inches as shown in FIG. 10A, or else correspond to a particular sizing convention associated with a particular manufacturer for the plurality of fusion plates it produces, as shown in FIG.  10 B. For example a manufacturer may designate a plate as a “No. 1 plate” a “No. 2 plate” etc., to designate different sizes. Measuring scale  114  ensures that a properly fitted plate  42  will be placed by the surgeon with minimal trial and error. 
     FIGS. 11A-C and  12 A-C illustrate exemplary fusion plates  42  which comprise the inventive system and method. Fusion plates  42  are preferably surgical quality metal, such as titanium alloy, but composite materials which are not rejected by the immune response of the human body could also be used. Additionally, fusion plates may be comprised of a synthetic absorbable material which dissolves over time. Fusion plates  42  shown here, are for cervical applications and are fashioned to be placed upon the anterior portion of the cervical spine  10 . In FIGS. 11A-C fusion plate  42  is shorter and designed for use at the site of a discectomy. In FIGS. 12A-C fusion plate  42  is elongate for purposes of spanning the site of a corpectomy. The size of a bone graft required to fill in the site of a corpectomy is greater than the size of a bone graft required to fill in a discectomy, hence the differences in the length of fusion plates adapted to each separate procedure. 
     Fusion plate  42  has an inner surface  118  and an outer surface  120 , inner surface for contacting the anterior portion of the cervical spine  10 . Inner surface  118  preferably has at least a slight curvature  122  along its longitudinal axis for conforming to a similar curvature of the section of spine to which the fusion plate  42  will attach. For cervical applications the inner surface  118  has a slight concave curvature  122  along its longitudinal axis of the plate  42 . The plate can be bent further by the surgeon if needed. The inventive system and method requires that fusion plate  42  engage distractor pins  26  for purposes of centering fusion plate  42  properly. As shown in FIGS. 11A-C and  12  A-C, cleft  124  at upper  126  and lower  128  edges located centrally along the longitudinal axis of fusion plate  42  has a width for engaging snugly with lower section  40 , of the distractor pin head portions  32 . 
     Referring again to FIGS. 1 and 2 and additionally to FIG. 13 the remainder of the inventive surgical method can be described. Prior to placing distractor pins  26  in the centered manner as previously described, a determination of bone depth and density must be performed. This can be accomplished by taking an intra-operative lateral spine x-ray. The bone depth and denisty of the vertebrae must be sufficient to anchor distractor pins  26  and bone screws. 
     Once the central location on the vertebrae is determined, the surgeon preferably positions distractor pins  26  using an alignment guide (not shown) of a type well known in the art to make sure that distractor pins are perpendicular upon the spine, as shown in FIG.  13 . Perpendicular placement of the distractor pins  26 , aids in properly engaging terminal ends  102  of the armatures  50 A,  50 B of distractor device  30 . Once aligned, distractor pins  26  are then driven into the vertebrae at the centered locations using a hexagonal surgical wrench (not shown), until the screw portion  34  of the distractor pins  26  are seated within the vertebra, at a sufficient depth for allowing compression by the distractor tool  30  to occur. 
     Next, as shown in FIG. 14, terminal ends  102  of distractor device  30  are attached to the heads  32  of distractor pins  26 . A coupling mechanism  106  of the type previously noted in FIGS. 9A and 9B engages and couples onto groove  44  of head portions  32 . The toggle switch  90  on the carriage body  56  is actuated for spreading the (C-4) and (C-6) vertebrae  16 ,  18  and handle  58  is turned to spread these vertebrae in the direction  132  shown. Next, the vertebral body (not shown) of the C-5 vertebrae  12  is removed. The engaging member  92  locks distractor  30  in a spread position, at this point, in preparation for placing a bone graft  20  between the (C-4) and (C-6) vertebrae  16 ,  18 . The bottom surface  22  of the (C-4) vertebrae and top surface  24  of the (C-6) vertebrae are cleaned and scored to promote blood flow. Next, a bone graft  20  of appropriate size and shape is placed in the gap  14  left by the removal of the (C-5) vertebral body. 
     Referring to FIGS. 15 and 16 the steps of placing the fusion plate  42  and compressing the vertebrae using the mechanical compression exerted by the distractor device  30 , are demonstrated. Distractor device  30  remains engaged upon the heads of distractor pins  26 , and toggle switch  90  is actuated to cause carriage body  56  to travel in the direction  134  resulting in compression. Handle  58  is turned in a direction so as to compress the spine  10  until the (C-4) and (C-6) vertebrae  16 ,  18  contact the bone graft  20 . Engagement member  92  locks first armature  50 A at the desired level of compression and keeps it there, thereby maintaining compression upon the bone graft  20  by the adjacent vertebrae  16 ,  18 . Once the desired level of compression is reached, the surgeon can then read the measuring scale  114  on the rack  60  of the distractor device  30  to determine the appropriately sized fusion plate  42  which should be used in a particular application. The cleft  124  located at each of the opposite ends  126 ,  128  of fusion plate  42  allows the surgeon to engage a properly sized fusion plate  42  upon the distractor pins  26  without removing the distractor device  30 . The fusion plate engages lower section  40  of head portion with cleft  124 . The clefts are preferably centered along the longitudinal axis of the fusion plate. This engagement results in the fusion plate  42  being centered upon the spine  10 , at the area of the corpectomy. The maintenance of compression on the spine  10 , while the fusion plate  42  is being placed, ensures that a minimal amount of space exists between the bone graft  20  and its adjacent vertebrae  16 ,  18 , thereby providing the best chance for fusion to occur. 
     As further shown in FIG. 17, once compressed, bone screws  136  are placed in anchor holes  138  using a drill guide  140 . Bone screws  136  may be comprised of titanium alloy, composite material or synthetic absorbable material. Anchor holes  138  are preferably placed exterior to the longitudinal axis  137  of the fusion plate  42 . However, as shown in FIG. 12A anchor holes  138  may also be placed on the longitudinal axis, as some surgeons prefer to anchor fusion plate directly in the bone graft  20 , as well as in the adjacent vertebrae  16 ,  18 . Drill guides are commonly used in spinal surgery, however the drill guide  140  shown has a wider diameter guide tube  142  to allow for a drill bit to work therein to start a pilot hole in both the patient&#39;s vertebrae  16 ,  18  and bone graft  20 . The wider diameter of guide tube  142  also allows enough space to drop a bone screw  136  down the guide tube  142  and drive it into the spine  10  with a screw driver  144 . Alternately, guide tube  142  can be used to hold bone screw  136  upright and start driving bone screw into spine  10  without first drilling a pilot hole. By using a drill guide  140  to guide bone screws  136  without using a pilot hole, bone screws are added in one step, and the frequent struggle to find a pilot hole in the middle of surgery is eliminated. Drill guide  140  is held steady during the addition of bone screws  136  by handle  145 . To further ensure the proper alignment of bone screws  136 , a furrowed region  146  surrounding anchor hole  138  allows the terminal end  148  of guide tube  142  to seat in an aligned manner upon fusion plate  42 . Additionally, anchor hole  138  includes chamfer  149  which allows bone screw  136  to seat flush with top surface  120  of fusion plate  42 . Anchor holes  138  may include locking washers (not shown) seated therein to prevent bone screws  136  from backing out. 
     Clefts  124  at each of the opposite ends  126 ,  128  preferably do not protrude beyond anchor holes  138  located at each of ends  126 ,  128 . Distractor pins  26  have been previously placed at a location on the vertebrae where bone density is adequate for strong implantation, to withstand the leveraging force on the distractor pins  26  due to compression. The region near the cleft  124 , on average, has a similar sufficient bone density for placement of the bone screws  136 . By positioning clefts  124  so that they do not protrude beyond anchor holes  138 , an increased likelihood that bone screws  136  will be inserted into a similar region of adequate bone density as the distractor pins  26 , occurs. 
     When the fusion plate  42  is fully anchored, the distractor device  30  and distractor pins  26  are removed from the patient&#39;s spine. When fusion plate  42  is anchored, bone graft  20  and its adjacent vertebrae  16 ,  18  are immobilized in a contacting manner, thereby creating the best conditions for bone fusion to occur. 
     The foregoing detailed disclosure of the inventive system and method is considered as only illustrative of the preferred embodiment of, and not a limitation upon the scope of, the invention. Those skilled in the art will envision many other possible variations of the system and method for its use as disclosed herein that nevertheless fall within the scope of the following claims. And, alternative uses for this system and method may later be realized. Accordingly, the scope of the invention should be determined with reference to the appended claims, and not by the examples which have herein been given.

Technology Classification (CPC): 0