Abstract:
An artificial replacement disc includes a pair of substantially parallel plates formed to occupy a space defined by vertebral endplates, each of the plates including a plurality of spikes on a first surface and a concave trough formed on a second surface opposite of the first surface. A mobile core includes a core rim with opposing convex surfaces extending from opposite sides of the core rim, the mobile core being capable of being disposed between the pair of plates to permit the vertebral endplates to move relative to one another. The spikes on each of the plates extend substantially away from the mobile core and the convex surfaces are formed to integrally fit within the concave trough of at least one of the plates. The core rim limits lateral movement of the mobile core relative to the parallel plates. One or more insertion tools for inserting and implanting the replacement disc are also described.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a Continuation application of U.S. patent application Ser. No. 13/893,326, filed May 13, 2013, which is a Continuation application of U.S. patent application Ser. No. 11/943,334 filed on Nov. 11, 2007 (now U.S. Pat. No. 8,535,379, issued Sep. 17, 2013), which is a Continuation-in-part of U.S. patent application Ser. No. 11/487,415, filed on Jul. 17, 2006 (now U.S. Pat. No. 7,854,766, issued Dec. 21, 2010), which is a Continuation-in-part of U.S. patent application Ser. No. 11/019,351, filed on Dec. 23, 2004 (now U.S. Pat. No. 7,083,650, issued Aug. 1, 2013), which is a Continuation-in-part application of U.S. patent application Ser. No. 10/964,633, filed on Oct. 15, 2004, and for which priority is claimed to each of the above-referenced applications under 35, U.S.C. §120; and U.S. patent application Ser. No. 11/019,351, filed on Dec. 23, 2004 (now U.S. Pat. No. 7,083,650, issued Aug. 1, 2013), and U.S. patent application Ser. No. 10/964,633, filed on Oct. 15, 2004, are Non-provisional applications of U.S. Provisional Application No. 60/788,720 filed on Apr. 4, 2006, U.S. Provisional Application No. 60/578,319 filed on Jun. 10, 2004, U.S. Provisional Application No. 60/573,346 filed on May 24, 2004, U.S. Provisional Application No. 60/572,468 filed on May 20, 2004, U.S. Provisional Application No. 60/570,837 filed on May 14, 2004, and U.S. Provisional Application No. 60/570,098 filed on May 12, 2004, for which priority is claimed under 35 U.S.C. §119(e), the entire contents of all of the above identified patent applications are hereby incorporated by reference. 
    
    
     BACKGROUND 
     This description relates to a three piece mechanical total cervical artificial disc, which includes two spiked cervical plates and a mobile core. The disc may be inserted into the cervical intervertrebral disc space using a novel disc plate insertion gun which performs sequential single plate intervertebral implantation enabling symmetric bi-disc plate alignment for inter plate mobile core placement. This cervical disc design and method of implantation avoid the cumbersome and arduous implantation techniques of many other artificial cervical disc designs improving safety, improving bone-plate insertion/integration, allowing multiple-level disc placement, preserving vertebral body integrity, eliminating the need for excessive disc space distraction, and decreasing procedure length. This description also relates to a modified application of the disc plate inserter design from copending, related applications describing posterior placed total artificial disc (PTTLAD). The modified disc plate inserter allows posterior lumbar sequential placement of two opposing disc plates rather than simultaneous two disc plate placement as outlined in our previous publication. The modified disc plate inserter enables implantation of the PTTLAD into narrower lumbar disc spaces which were not accessible with our previous lumbar disc plate inserter. 
     Cervical and lumbar discs are entering the clinical neurosurgical and orthopedic markets. The benefits of these artificial discs are well known and have been thoroughly reviewed in our prior and co-pending prosthetic disc patents, including Provisional Application 60/788,720 filed on Apr. 4, 2006, copending U.S. patent application Ser. No. 11/019,351, filed on Dec. 23, 2004 and Ser. No. 10/964,633, filed on Oct. 15, 2004, U.S. Provisional Application Nos. 60/578,319 filed on Jun. 10, 2004, 60/573,346 filed on May 24, 2004, 60/572,468 filed on May 20, 2004, 60/570,837 filed on May 14, 2004, and 60/570,098 filed on May 12, 2004, and U.S. patent application Ser. No. 11/487,415 filed on Jul. 17, 2006, the entire contents of each of which are hereby incorporated by reference. In one or more of the foregoing applications, we described four different cervical artificial disc embodiments which expanded in two or three-dimensions. This description presents an evolutionary simplification of these embodiments, e.g., with fewer small parts, which expand in only one dimension, and can be inserted very simply and efficiently. Accordingly, the advanced cervical disc design of the present application is a geometric modification of previous lumbar disc designs in one or more of the above-referenced patents, e.g., U.S. Patent Publication No. 2007/0198089 A1. 
     The cervical disc design of the present application differs from approaches of the background art which typically describe two-piece designs, e.g., as opposed to the three disc designs of the present application. In the two-piece designs, one piece consists of either an upper or lower cervical disc plate with a central trough to accommodate the opposing disc plate. The other piece, the opposing disc plate, has an incorporated dome shaped immobile core. The immobilized core is stationary and does not move. Semi-constrained artificial motion occurs as a result of the troughed plate movement against and around the immobilized core. 
     One or more of these designs are described in the following exemplary patent documents, including U.S. Pat. No. 5,314,477, filed Mar. 4, 1991 (Thierry Mamay), entitled “Prosthesis for intervertebral discs and instruments for implanting it;” U.S. Pat. No. 6,113,637 (Gill et al.), filed Oct. 22, 1998, entitled “Artificial intervertebral joint permitting translational and rotational motion; U.S. Pat. No. 6,540,785 B1 (Gill et al.) filed on Mar. 24, 2000, entitled “Artificial intervertebral joint permitting translational and rotational motion;” U.S. Pat. No. 6,899,735 B2 (Bradley J Coates et. al.) filed on Oct. 2, 2002, entitled “Modular intervertebral prosthesis system,” U.S. Pat. No. 6,908,484 B2 (Zubok et. al.) filed on Mar. 6, 2003, entitled “Cervical disc replacement.” In each of the foregoing two-piece designs of the background art, the artificial implant is implanted within the vertebral bodies either by using attached hinges, keels or some form of extension which accommodates placement of vertebral screws. 
     The present inventors have determined that one disadvantage of most of these systems is that placement of the prosthesis is arduous, and time consuming, and can destroy a substantial part of the vertebral body after insertion of the device. The designs that use screws have the potential risks of screw pull out and secondarily esophageal injury, screw breakage, and/or inability to perform multilevel disc placement. Furthermore the fact that these designs do not have a mobile core leads to substantially constrained motion. 
     Similarly, U.S. Patent Publication No. 2007/0173936 A1 (Hester) filed on Jan. 23, 2006, describes a design which includes spikes, also includes a two-piece design with an immobilized core. One or more embodiments of the present application includes a mobile core which more closely simulates natural semi-constrained motion of a healthy cervical disc. U.S. Patent Publication No. 2005/0021146 A1 (de Villiers et al.) filed May 26, 2004 consists of two separate plates placed which are inserted simultaneously as one unit, after which a mobile core is inserted in between the plates. However, the plates include keels which can damage vertebral bodies, and prevent multilevel placement. U.S. Pat. No. 6,001,130 (Bryan), filed Oct. 6, 1997, describes a one piece design. However, the one-piece design involves an arduous placement technique involving disc space distraction, and the use of hinges and screws, limiting multi-level placement. 
     SUMMARY 
     One or more of the embodiments of the present application overcome one or more of the above-described shortcomings of the background art. For example, a cervical disc design and tool for implantation of the cervical disc is an improvement over one or more of the above mentioned designs of the background art. Specifically, the spikes allow integration into the vertebral body, e.g., with relatively small spikes, without damaging the vertebral bodies. This is particularly important if future prosthetic or fusions need to be performed at that level. The cervical plates are inserted sequentially with a novel cervical plate insertion gun. The advantage of the cervical plate insertion gun is that the method of implantation is quick and efficient. No disc space distraction is needed and hence there is no fear of damaging or disarticulating posterior cervical facets. It can also be placed into narrower spaces without distraction. The mobile core of the present application also more closely approximates the natural semi-constrained motion of a healthy disc more so than the above mentioned discs. 
     Additional advantages of our posterior placed total lumbar artificial disc (PTTLAD) lumbar disc design have been fully reviewed in our co-pending patents, each of which have been incorporated by reference herein. The present lumbar disc plate inserter design offers two additional advantages over previous embodiments. First, the inserter design grasps the plates more securely. In addition, the sequential placement of the different plates allows placement of posterior artificial discs into narrower disc spaces. 
     In one general aspect, an artificial spinal disc includes a pair of substantially parallel plates formed to occupy a space defined by vertebral endplates. Each of the plates including a plurality of spikes on a first surface and a concave trough formed on a second surface opposite of the first surface. A mobile core includes a core rim with opposing convex surfaces extending from opposite sides of the core rim, the mobile core being capable of being disposed between the pair of plates to permit the vertebral endplates to move relative to one another. The spikes on each of the plates extend substantially away from the mobile core and the convex surfaces are formed to integrally fit within the concave trough of at least one of the plates. The core rim limits lateral movement of the mobile core relative to the parallel plates. 
     Implementations of this aspect may include one or more of the following features. For example, the plates and mobile core can be sized and shaped to integrally fit within a space defined by cervical vertebral endplates and/or lumbar vertebral endplates. Each trough can be disposed in a center of each respective, parallel plate. The troughs can be shaped to receive the convex surfaces of the mobile core and the core rim can be shaped to receive outer edges of the troughs with an integral fit. The substantially parallel plates can include a plurality of conically shaped spikes. 
     The mobile core rim may include at least a first substantially ring shaped member having a raised edge and a second substantially ring shaped member having a raised edge. The first and second ring shaped members may each define respective cavities where the convex surfaces are respectively positioned within and extend from. The plates can comprise an elliptical shape. 
     In another general aspect, an artificial disc insertion system includes an artificial disc having a pair of substantially parallel plates formed to occupy a space defined by vertebral endplates, each of the plates including a plurality of spikes on a first surface and a concave trough formed on a second surface opposite of the first surface. The disc includes a mobile core having a core rim with opposing convex surfaces extending from opposite sides of the core rim, the mobile core being capable of being disposed between the pair of plates to permit the vertebral endplates to move relative to one another. The spikes on each of the plates extend substantially away from the mobile core and the convex surfaces are formed to integrally fit within the concave trough of at least one of the plates. The core rim limits lateral movement of the mobile core relative to the parallel plates. The system also includes a surgical tool. 
     The surgical tool for inserting the artificial disc between vertebral endplates, the tool includes a handle portion having a trigger, an upper disc plate release button, and a lower disc plate release button. The surgical tool also includes an insertion portion extending distally away from the handle portion, the insertion portion includes an upper replacement plate releasing portion and a lower replacement plate releasing portion. The upper replacement plate releasing portion includes a release handle and a release link configured to engage and release a periphery of an upper replacement plate, e.g., to releasably secure the upper replacement plate therebetween. The lower replacement plate releasing portion includes a release handle and a release link configured to engage and release a periphery of a lower replacement plate, e.g., to releasably secure the lower replacement plate therebetween. 
     Implementations of this aspect may include one or more of the following features. For example, the mobile core and plates can be sized and shaped for a cervical disc replacement. The mobile core and the plates can be sized and shaped for a lumbar disc replacement. The mobile core rim may include at least a first substantially ring shaped member having a raised edge and a second substantially ring shaped member having a raised edge. The first and second ring shaped members may each define respective cavities where the convex surfaces are respectively positioned within and extend from. The plates can include an elliptical shape. 
     In another general aspect, a surgical tool for inserting an artificial disc between vertebral endplates includes a handle portion comprising a trigger, an upper disc plate release button, and a lower disc plate release button. The tool also includes an insertion portion extending distally away from the handle portion, the insertion portion comprising an upper replacement plate releasing portion and a lower replacement plate releasing portion. The upper replacement plate releasing portion includes a release handle and a release link configured to engage and release a periphery of an upper replacement plate, e.g., to releasably secure the upper replacement plate therebetween. The lower replacement plate releasing portion includes a release handle and a release link configured to engage a periphery of a lower replacement plate, e.g., to releasably secure the lower replacement plate therebetween. 
     Implementations of this aspect may include one or more of the following features. For example, the insertion portion may include an upper tip portion and a lower tip portion. The upper tip portion and the lower tip portion may be curved to facilitate posterior insertion of a lumbar replacement disc in a patient. At least one of the upper or lower replacement plate releasing portions can include a leaf spring, a tension cable and a wedge portion proximally disposed relative to the respective release handle and the release link. Each of the upper and lower replacement plate releasing portions can include a leaf spring, a tension cable and a wedge portion proximally disposed relative to the respective release handle and the release link. The tool can include a replacement disc plate driver portion for driving a replacement disc plate from a first, proximal position toward a second, distal position. The upper replacement plate releasing portion is configured to secure an upper replacement plate in a position opposite from and axially aligned with a center of a lower replacement plate held within the lower replacement releasing portion. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is an anterior (or posterior) view of an exemplary cervical artificial disc. 
         FIG. 1B  is an isometric view of the cervical artificial disc of  FIG. 1A . 
         FIG. 1C  is an exploded view of the cervical artificial disc of  FIG. 1A . 
         FIG. 1D  is a superior (or inferior) view of the cervical artificial disc of  FIG. 1A . 
         FIG. 2A  is a side view of an exemplary cervical artificial disc mobile core. 
         FIG. 2B  is an isometric view of the exemplary cervical artificial disc mobile core. 
         FIG. 2C  is a front (or back) view of the exemplary cervical artificial disc mobile core. 
         FIG. 3A  is a side view of an exemplary cervical artificial disc superior or inferior plate. 
         FIG. 3B  is a top oblique-trough side view of the exemplary cervical artificial disc superior or inferior plate. 
         FIG. 3C  is a top oblique-spike view of the exemplary cervical artificial disc superior or inferior plate. 
         FIG. 3D  is a front-trough side view of the exemplary cervical artificial disc superior or inferior plate. 
         FIG. 3E  is a front-spike side view of the exemplary cervical artificial disc superior or inferior plate. 
         FIG. 4A  is a cross-sectional view of a cervical disc core showing the angular movements about the x-axis of the cervical disc core with respect to the upper and lower cervical plates (lateral bending). 
         FIG. 4Bi  is a front view of later cervical disc bending. 
       FIG.  4 Bii is a side view of flexion/extension cervical artificial disc motion. 
         FIG. 4Ci  is a front view of the artificial disc showing the rotations of the mobile core between the two cervical disc plates about the x-axis (lateral bending or roll). 
       FIG.  4 Cii is a side view of the artificial disc showing the y-axis (flexion/extension or pitch). 
       FIG.  4 Ciii is a perspective view of the artificial disc showing the z-axis (rotation or yaw). 
         FIG. 5A  is a front view of a cervical disc plate insertion gun. 
         FIG. 5B  is a top view of the cervical disc plate insertion gun. 
         FIG. 5C  is a bottom view of the cervical disc plate insertion gun. 
         FIG. 6A  is a perspective, left-side, cut-away view of the cervical disc plate insertion gun. 
         FIG. 6B  is a left side, bottom angle view of the cervical disc plate insertion gun. 
         FIG. 6C  is a right side, top angle view of the cervical disc plate insertion gun. 
         FIG. 6D  is a right side, bottom angle view of the cervical disc plate insertion gun. 
         FIG. 6E  is a cut-away view of the tool tip lower cervical disc replacement plate release mechanism. 
         FIG. 7A  is a view of an outside left enclosure of the cervical disc plate insertion gun. 
         FIG. 7B  is a view of an inside left enclosure of the cervical disc plate insertion gun. 
         FIG. 7C  is a view of an outside right enclosure of the cervical disc plate insertion gun. 
         FIG. 7D  is a view of an inside right enclosure of the cervical disc plate insertion gun. 
         FIG. 8A  is a top view of inner components of the cervical plate insertion gun including the lower insertion handle. 
         FIG. 8B  is a lower insertion handle bottom view. 
         FIG. 8C  is top view of a lower insertion link. 
         FIG. 8D  is bottom view of the lower insertion link. 
         FIG. 8E  is a view of the wedge link. 
         FIG. 8F  is a top view of the upper insertion handle. 
         FIG. 8G  is a lower view of the upper insertion handle lower view. 
         FIG. 8H  is a close-up bottom view of a rear portion of the upper insertion handle. 
         FIG. 8I  is a close-up, top view of a forward portion of the upper insertion handle. 
         FIG. 8J  is a top view from left of the upper insertion release link. 
         FIG. 8K  is a top view from a right side of the upper insertion link. 
         FIG. 8L  is a view of a manual upper disc replacement plate driver. 
         FIG. 8M  is a view of a trigger spring. 
         FIG. 8N  is a view of a trigger. 
         FIG. 8O  is a view of a wedge. 
         FIG. 9A  is a perspective cut away view of an exemplary lumbar disc plat insertion gun. 
         FIG. 9B  is a cut-away view of the tool tip of the lower lumbar disc replacement plate release mechanism. 
     
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     The Medical Device of  FIG. 1-9 . 
     Referring now to  FIGS. 1-9 , the above described problems of the background art can be solved in the cervical spine (and lumbar spine) after the performance of an anterior complete cervical discectomy. The disc device  10  includes an upper cervical plate  100  and lower cervical plate  110 , one of which is inserted first by a plate insertion gun  500 . The opposite (second) cervical disc plate  110  is then inserted with the plate insertion gun  500  maintaining parallel opposition, with opposite plates  100 ,  110  and troughs  102 ,  112  perfectly aligned. A mobile core  150  is then inserted and sandwiched in-between both cervical plates  100 ,  110 . 
       FIGS. 1A-D  illustrate different views of the cervical artificial disc  10 . The disc  10  includes an upper plate  100  and a lower plate  110 . Each plate has a plurality of spikes  101 ,  111 , e.g., six spikes  101 ,  111  on each plate in a preferred embodiment, on an outer surface of the respective plate, and a centralized trough  102 ,  112  on an inner surface of each plate  100 ,  110 . 
       FIGS. 2A-C  illustrate different views of the cervical mobile core  150 . The core  150  has a centralized base rim  151  with a superior convexity  152  which interacts with the trough  102  of the upper plate  100 , and an inferior convexity  153  which interacts with the trough  112  of the lower plate  110 . 
       FIGS. 3A-E  illustrate different views of the cervical plate (superior or inferior)  100  ( 110 ). The plate  100  includes a base  114 . On an upper surface of the inferior plate  110  is a trough  112 . On a lower surface of the inferior plate  110  are 6 peripherally arranged spikes  111 . The position of the trough  112  and spikes  111  are reversed for the superior plate ( 100 ). A groove  113  is defined by the trough  112  ( 102 ) and base  114  ( 104 ) of each plate  110  ( 100 ). 
       FIG. 4A  illustrates a cross-sectional view of the cervical artificial disc  10  and the degrees of motion of the mobile core  150  movement about the x-axis with respect to the upper plate  100  and lower plate  110 . Each disc plate  100  can bend about the x axis by 4.39 degrees clockwise and counter-clockwise (lateral bending). This means that a disc plate  100 ,  110  can move − or +8.78 degrees with respect to the opposite plate  110 ,  100 . 
       FIG. 4B  illustrates a front view of lateral bending of the artificial disc  10  ( FIG. 4Bi ), and a side view illustrating flexion-extension of the cervical disc  10  about the y axis which is 4.39 degrees in either flexion or extension. 
       FIG. 4C  illustrates the rotation of the mobile core  150  between two cervical plates  100 ,  110  about the x ( FIG. 4Ci ), y (FIG.  4 Cii) and z (FIG.  4 Ciii) axes. Rotation about the x-axis is referred to as roll (alpha) which is lateral bending. Rotation about the y axis is referred to as pitch (Beta) which is flexion/extension. Rotation about the z axis is referred to as yaw (gamma) which is axial rotation. These figures display different views that show a reference frame for the disc assembly  10  with an origin O at the center of the core  150 . The axes of rotation pass through the spherical face of the core  150  which is lower than 0 but are parallel to both the x and y axes. The rotation of the disc plates  100 ,  110  about the z-axis is constrained only by the spine motions once the disc  10  is implanted. 
       FIGS. 5-8  illustrate the components of the cervical disc plate insertion gun  500 . Various opening mechanism functions will be described in greater detail hereinafter with respect to  FIGS. 5-8 . The handle  512  of the opening mechanism is made up of left and right enclosures  501 ,  502  ( FIGS. 5, 6, and 7 ).  FIG. 7  illustrates the inside and outside aspects of left and right enclosures  501 ,  502 . These enclosures  501 ,  502  are held together by five enclosure fastening screws  590  ( FIG. 6B ). The handle  512  holds the mechanism used to insert the upper disc plate  100  and lower disc plate  110  ( FIGS. 5-6 , and  FIG. 8 ) into the vertebrae. The mechanism has two functions, including: 1) Holding onto the disc plates  100 ,  110  until the user releases them, and 2) opening the tip  560  and forcing one disc plate at a time into a vertebra. 
     1. Holding onto the Discs Until User Releases them 
     The mechanism has two tips  565 ,  580  each holding a disc plate  100 ,  110 . The lower tip  580  is composed of two parts: the lower insertion release link  576  and the lower insertion release handle  551  ( FIGS. 6 and 8 ). The upper tip  565  includes two parts: the upper insertion handle  550  and the upper insertion link  575  ( FIGS. 6 and 8 ). Each tip  565 ,  580  works like a “lobster claw” that holds a disc plate by the “groove”  552  on its cylindrical extrusion. When the tip  565 ,  580  is closed the two opposing parts e.g. the lower insertion release link  576  and the lower insertion release handle  551  ( FIGS. 6 and 8 ) hold a disc plate  110  firmly. 
     A tip  580  opens to release a disc plate as follows. A lower tension cable  571  pulls on the lower insertion release link  576  ( FIGS. 6 and 8 ) that pivots about the lower release pin  598  ( FIG. 6 ) and opens up a gap big enough to loosen the grip on the disc groove  552 . The lower tension cable  571  ( FIG. 6 ) can only exert a tensile force to open the lobster claw  580 . The natural state of the lobster claw  580  is to be closed. This is ensured by pre-loading the lower insertion release link  576  with the help of a leaf spring  599  cut into the lower insertion release handle  551  ( FIGS. 6E and 8 ). The lower tension cable  571  pulls on the lower insertion release link  576  ( FIGS. 6 and 8 ) each time the user presses on the lower release button  540 . The lower tension cable  571  is clamped on one end by a lower rear crimp  592  ( FIGS. 6 and 8 ). Hence when the lower release button  540  is pressed, the tension on the lower tension cable  571  increases (in the same way the tension of a guitar string increase when one presses on the string with a finger). The tension then pulls the lower insertion release link  576  forcing it to swing open. When the user lets go of the button  540 , the tension disappears and the spring  599  carved in the lower insertion release handle  551  forces the lower insertion release link  576  to swing closed ( FIG. 6E ). 
     The upper tip  565  works in a similar fashion except that its opening is triggered by the upper release button  530 . 
     2. Opening its Tip and Forcing One Disc at a Time into a Vertebra 
     The mechanism tips  565 ,  580  open each time the user presses on trigger  510 . When the trigger  510  rotates, it pushes on the wedge link  513  which in turn pushes on the wedge part  525  ( FIG. 8 ). The wedge part  525  is wedged at its front action end that creates a gap in between the lower tool tip  580  and upper tool tip  565  forcing them to open. 
     A typical disc insertion operation starts with a lower disc plate  110  placed in the lower tip  580  and the opposing upper disc plate  100  placed on the upper side but away from the tip  565  (as shown in  FIGS. 5,6, and 8 ). A channel  553  along the upper tip  565  that is formed by the upper insertion release handle  550  and the upper insertion release link  575  which holds the second disc plate  100  in place and serves to guide it to the tip  565  when needed. 
     Once the tool tip  560  is inserted into the inter-vertebral space, the first disc plate  100  is inserted into the lower vertebra by opening the tool tip  560 . To keep alignment, the lower tool tip  585 , “lower lobster claw”, is kept closed ( FIG. 6 ), securing the disc plate just inserted. The tool  500  should be left in place. The second, upper, disc  100  initially placed in the upper tool half, away from the “upper lobster claw”  565  but away from the tip is then slid down to the end of the upper lobster claw  565  by a flexible and manually activated upper disc replacement plate driver  520  ( FIGS. 6 and 8 ). Once the second disc  100  is positioned at the tip of the upper “lobster claw”  565  ( FIG. 6 ), the tool tip  560  is opened once more, i.e., the upper tip  565  and lower lobster claw tip  580  are separated from each other, by virtue of the wedge  525  that is activated by the trigger  510 , via wedge link  513  action. Once the second, upper, disc plate  100  is inserted, the user can press on the upper release button  530  and lower release button  540  to release both discs (by opening the upper and lower “lobster claws”  565 ,  580 ) and at the same time close the tool tip  560  (by releasing the trigger  510 ). The tool tip  560  then closes while both “lobster claws”  565 ,  580  remain open, leaving both disc plates  100 ,  110  in place. The tool tip  560  can then be removed from the patient and a mobile core placed in between the two aligned disc plates  100 ,  110 . 
     This anterior cervical disc gun can be modified and enlarged for placement of anterior lumbar disc plates.  FIG. 9A  illustrates the modified posterior lumbar disc plate insertion gun  700 . The gun  700  is identical to the cervical disc plate insertion gun  500  except its tips  660  are angled to allow insertion of the specifically sized lumbar disc plates  100 ,  110  in the posterior lumbar spine underneath the thecal sac. 
       FIG. 9B  illustrates an enlarged cut-away view of the tool tip  660  of the lumbar lower disc replacement plate release mechanism  670 . The mechanism  670  is identical to that described for the cervical mechanism which is illustrated  FIG. 6E . The tips  660  of the lumbar tool are however, specifically designed and adapted for the typically bean shaped lumbar disc plates. 
     The Surgical Method 
     The method of insertion of the cervical artificial disc (or lumbar artificial disc) into the anterior cervical spine can be performed open microscopically, or closed tubularly, using endoscopic and/or fluoroscopic guidance. 
     After the adequate induction of anesthesia the patient is positioned in the supine position. Routine exposure of the anterior cervical spine is performed and the appropriate disc space is radiographically identified and exposed. A routine complete anterior cervical discectomy is performed. 
     The cervical disc plates are inserted onto the cervical disc plate insertion gun  500 . The tips  560  of the gun  500  are placed into the intervertebral space. Fluoroscopy is used to assure centrality of disc plate placement. 
     The trigger  510  of the gun  500  is depressed and the bottom plate  110  is inserted into the lower vertebrae. Once this penetrates the bone, the lower plate releasing button  540  is depressed, thereby releasing the plate from the inserter claws  580  ( FIG. 6E ). The second upper plate  100  is now manually driven into the space by the gun&#39;s manual plate driver  520 . Because of the design of the gun  500 , the upper plate  100  is perfectly aligned with the lower plate  110 . The gun trigger  510  is depressed and this drives the upper plate  100  into the upper vertebrae. The upper plate releasing button  530  is now depressed, releasing the upper plate  100  from the inserter lobster claws  565 . The gun  500  is removed from the interspace. A mobile core  150  of the appropriate height is selected and placed in between the upper and lower cervical disc plates  100 ,  110 , respectively. The patient is closed routinely. 
     The surgical method for the posterior insertion of the PPLTAD into the posterior lumbar interspace can be performed open microscopically, or closed tubularly, using endoscopic and or fluoroscopic guidance. 
     After the adequate induction of anesthesia the patient is positioned in the prone position. A midline incision is made, the appropriate unilateral lamina is radiographically identified and exposed, and a unilateral hemi-laminotomy is performed preserving facet stability. A complete discectomy is performed, and the superior and inferior endplates are exposed. The lumbar plate insertion gun  700  is placed underneath the thecal sac. Fluoroscopic guidance may be used to verify centrality of lumbar disc plate placement. The trigger of the gun  700  is depressed which leads to insertion of the lower lumbar disc plate  100  into the lower vertebra. The lower lumbar disc plate releasing button is depressed which releases the plate from the inserter claws  551  ( FIG. 9B ). The second upper plate  100  is now manually driven into the interspace by the gun&#39;s  700  manual plate driver ( 520 ). Because of the design of the gun mechanism as described above, the second plate  100  is now perfectly aligned with the first lumbar disc plate  110 . The gun trigger is depressed, and this drives the upper plate  100  into the upper vertebrae. The upper lumbar disc plate release button is now depressed and this releases the upper lumbar disc plate from the claws of the inserter gun  700 . The gun  700  is removed from the space. An appropriately sized mobile core  150  is now inserted in between upper and lower lumbar disc plates  100 ,  110 . The patient is closed routinely. 
     The current device allows safe placement of lumbar and cervical artificial discs into the spine without intervertebral distraction, and therefore places minimal tension on facet joints. The method of insertion is quick, gentle, and time efficient. The plate insertion gun could potentially be adapted for other inter-joint orthopedic devices, and further adaptations may have applications in manufacturing, toy, carpentry and other industries.