Abstract:
An expandable implant is made via a central strut having a pivotable arm on each end. The implant can be inserted into a disc space either horizontally or vertically with the arms in a closed position and then (if inserted horizontally) optionally rotated up into place. The arms are then pivoted out, thereby increasing the foot print of a horizontally inserted implant. The expanded implant can be locked in place through the use of an additional insert or ratchet that fits between the arms and locks the arms in place.

Description:
CONTINUING DATA 
       [0001]    This patent application claims priority from US provisional application U.S. Ser. No. 62/329,589, filed Apr. 29, 2016 entitled “Expandable Trials” (Bootwala et al.) (DSP5202USPSP1), and from US provisional application U.S. Ser. No. 62/239,336, filed Oct. 9, 2015 entitled “Expandable Trials” (Bootwala et al.) (DSP5202USPSP), the specifications of which are incorporated by reference in their entireties. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    The leading cause of lower back pain arises from rupture or degeneration of lumbar intervertebral discs. Pain in the lower extremities is caused by the compression of spinal nerve roots by a bulging disc, while lower back pain is caused by collapse of the disc and by the adverse effects of articulation weight through a damaged, unstable vertebral joint. One proposed method of managing these problems is to remove the problematic disc and replace it with a prosthetic disc that allows for the natural motion between the adjacent vertebrae (“a motion disc”). 
         [0003]    Prior to inserting the disc, however, the surgeon typically desires to insure that the properly sized implant has been identified for the particular patient. To this end, trial implants are commonly included within the instrument sets that allow the surgeon to temporarily insert the trial into the intervertebral disc space and assess whether the height and footprint of the trial would be appropriate for the actual implant to be inserted. Typically, a large number of trials are supplied in an instrument set, with each having a distinct height, lordotic angle and footprint. 
         [0004]    More recently, fusion cages have been redesigned to provide a small profile during insertion into the disc space and then to expand to distract the disc space. The small profile of the initial configuration allows the surgeon to operate through a smaller opening, thereby minimizing surgical trauma. With the advent of these expandable cages, there is now also a need for an expandable trial as well. 
       SUMMARY OF THE INVENTION 
       [0005]    In one embodiment, an expandable implant is made via a central strut having a pivotable arm on each end. The implant can be inserted into a disc space either horizontally or vertically with the arms in a closed position and then (if inserted horizontally) optionally rotated up into place. The arms are then pivoted out, thereby increasing the foot print of a horizontally inserted implant. The expanded implant can be locked in place through the use of an additional insert or ratchet that fits between the arms and locks the arms in place. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0006]      FIGS. 1-4  disclose a multi-plate expandable device. 
           [0007]      FIG. 5  discloses a spreader-based expandable device. 
           [0008]      FIGS. 6-14  disclose expandable devices based upon stackable blocks. 
           [0009]      FIGS. 15-20  disclose spring-based expandable designs. 
           [0010]      FIGS. 21-22  disclose an ellipse-based expandable design. 
           [0011]      FIGS. 23-28  disclose an expandable device based upon floating blades. 
           [0012]      FIGS. 29-31  disclose an expandable device based upon gears. 
           [0013]      FIGS. 32-38  disclose an expandable design based upon a box chisel. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0014]    In accordance with  FIGS. 1-4 , there is provided an intervertebral device, comprising:
       a) a first strut  1  comprising i) an upper portion  3  forming an upper surface  5  having teeth  7  adapted for gripping an upper natural endplate and ii) a lower portion  9  forming a lower surface  11  comprising teeth  13  adapted for gripping a lower natural endplate,   b) an upper arm  15  pivotally connected to the upper portion of the first strut and having an upper surface  17  having teeth  18  adapted for gripping an upper natural endplate, and   c) a lower arm  19  pivotally connected to the lower portion of the first strut and having a lower surface  21  having teeth  23  adapted for gripping a lower natural endplate,   wherein the upper surface of the first strut and the upper surface of the upper arm are substantially co-planar in an expanded condition,   wherein the lower surface of the first strut and the lower surface of the lower arm are substantially co-planar in an expanded condition.
           Preferably, the pivotal connections between first strut and each arm each form a ratchet connection  25  adapted to lock the device in the expanded condition.   
               
 
         [0021]    In some embodiments, the device further comprises:
       d) a second strut  27  extending between a lower surface of the upper arm and an upper surface of the lower arm to lock the device in the expanded condition.
           Preferably, each of the lower surface of the upper arm and the upper surface of the lower arm comprises a recess  29  adapted for reception of a respective end of the second strut.   
           Preferably, each arm has a first endface  31  opposite its pivotal connection, and the first endfaces are substantially opposed in an unexpanded condition.       
 
         [0025]    Also in accordance with  FIGS. 1-4 , there is provided: a method of using an intervertebral device, comprising the steps of:
       a) inserting the intervertebral device of claim  1  into a disc space in its unexpanded condition,   b) moving each arm so that the device adopts its expanded condition,   c) locking the device in its expanded condition.       
 
       Footprint/Spreader 
       [0029]    In a  FIG. 5  embodiment, there is provided a spreader trial in which a U-shaped element houses a spreader having a substantially rectangular axial cross-section, wherein the height of the cross-section is less than its width. The spreader is rotatably coupled to the apex of the U-shaped element. These two elements are inserted into the disc space as one piece, with a rotatable shaft carrying the spreader and coupled to the apex of the U-shaped element. The U-shaped element is inserted so that each leg of the U-shaped is substantially parallel to the adjacent vertebral endplates (i.e., the U-shaped spreader cross-section provides a minimum height), while the spreader is inserted so that its height is extending between the endplates and a minimum height is established. Once inserted, the shaft is rotated about 90 degrees so that the spreader width is now extending between the endplates so that the spreader displays its maximum height. This condition preferably produces distraction of the disc space. Bone filler can then be added around the spreader within the U-shaped element. 
         [0030]    In accordance with  FIG. 5 , there is provided an intervertebral device comprising:
       a) a substantially U-shaped element  33  comprising a substantially C-shaped portion  35  and a pair of arms  37  extending therefrom, an upper surface  39  adapted for gripping a natural endplate, a lower surface  41  adapted for gripping a natural endplate, and an inner surface  43  including a concave surface  45 , the concave surface having a first threaded coupling extending therein, wherein the inner surface defines a cavity, wherein a first distance between the upper and lower surfaces defines a first height, and wherein a second distance between the inner surfaces of the arms defines a width of the cavity,   b) a spreader element  51  having i) a block  53  having a first end  55  having a second threaded coupling  57  that mates with the first threaded coupling, a second end  59 , a second height and a width, wherein the height is less than the width, ii) a shaft  61  extending from the second end of the block and iii) a handle (not shown) connected to the shaft,
 
wherein the first and second threaded couplings threadably mate,
 
wherein the width of the block is less than the width of the cavity so that the block of the spreader element is received in the cavity of the U-shaped element.
       
 
         [0033]    Also in accordance with  FIG. 5 , there is provided a method of preparing a disc space between opposed vertebral endplates, comprising the steps of: 
         [0000]    a) inserting the intervertebral device of  FIG. 5  into a disc space wherein the block is oriented so that the height of the block spans the opposed vertebral endplates
 
b) rotating the block by about 90 degrees so that the width of the block spans the opposed vertebral endplates, thereby distracting the disc space.
 
         [0034]    Preferably, this method further comprises the steps of:
       c) disengaging the spreader from the U-shaped element, and   d) removing the block from the disc space.       
 
         [0037]    Also preferably, this method further comprises the steps of:
       e) contacting the U-shaped element with an implant material.       
 
       Stackable Blocks 
       [0039]    In a  FIGS. 6-9  embodiment, a plurality of stackable spacers are inserted in sequence to build an implant of a desired height and preferably width. Preferably, the spacers are designed so that the subsequent spacers can be added both in the vertical and lateral directions. Preferably, endcap spaced are also utilized that cap off the vertical dimension and provide lordosis. In one embodiments, the endcaps have vertical throughholes and legs extending towards each other that are designed to mate, so that once the endcaps are placed and mated, the intermediate spacers can be removed and a hollow fusion cage results. 
         [0040]    In accordance with  FIGS. 6-9 , there is provided an intervertebral device comprising:
       a) a base block  65  having an upper surface  67  having a first mating feature  69 , a lower surface  71  and a first side surface  73  having a second mating feature  75  therebetween,   b) a first upper spacer  77  having a lower surface  79  having a third mating feature  81 , and an upper surface  83  having a fourth mating feature  85 , and a side surface  87  therebetween   c) a first lateral spacer  89  having an inner side surface  91  having a fifth mating feature  93 , an outer side surface  95  having a sixth mating surface  97  therebetween, and an upper surface  99  therebetween,
 
wherein the first mating feature of the base block slidably mates with the third mating feature of the first upper spacer, and
 
wherein the second mating feature of the base block slidably mates with the fifth mating feature of the first lateral spacer.
       
 
         [0044]    In some embodiments, each mating feature is a dovetail feature. 
         [0045]    Preferably, the device further comprises:
       d) a second upper spacer  101  having a lower surface  103  having a seventh mating feature  105 , and an upper surface  107  having a eighth mating feature  109 , and a side surface  111  therebetween   e) a second lateral spacer  113  having an inner side surface  115  having a ninth mating feature  117 , an outer side surface  119  having a tenth mating surface  121  therebetween, and an upper surface  123  therebetween,
 
wherein the fourth mating feature of the first upper spacer slidably mates with the seventh mating feature of the second upper spacer, and
 
wherein the sixth mating feature of the first lateral spacer slidably mates with the ninth mating feature of the second lateral spacer.
       
 
         [0048]    Preferably, the device further comprises:
       f) a third upper spacer having a lower surface having an eleventh mating feature, an upper surface disposed at an angle to its lower surface, and a side surface therebetween,   wherein the third upper spacer is disposed above the second vertical spacer.       
 
         [0051]    Preferably, the eleventh mating feature of the third vertical spacer is located substantially directly above the eighth mating surface of the second vertical spacer. 
         [0052]      FIG. 10  discloses a central insert  65  within the stackable blocks. 
         [0053]    Also in accordance with  FIGS. 11-12 , there is provided other stackable designs with various inserts  65 . 
         [0054]    In a  FIG. 13 a   - 14  embodiment, there is an intervertebral device comprising:
       a) an upper shell  171  having an upper surface  173  having a throughhole  175  therethrough and opposed sidewalls,   b) a lower shell  177  having a lower surface  179  having a throughhole  181  therethrough and opposed sidewalls,   c) a plurality of stacked spacers disposed between the upper shell and the lower shell, wherein each spacer shares with its adjacent spacer a mating interface comprising a pair of mating features,   wherein the opposed sidewalls of the upper shell mate with the opposed sidewalls of the lower shell.       
 
         [0059]    In some embodiments, there is a method of building a fusion cage comprising:
       inserting into a disc space a plurality of stacked spacers, wherein each spacer shares with its adjacent spacer a mating interface comprising a pair of mating features, the plurality having an uppermost spacer having an upper mating feature and a lowermost spacer having a lower mating feature,   attaching to the uppermost spacer an upper shell having an upper surface having a throughhole therethrough, a lower surface having a lower mating feature and opposed sidewalls, wherein the upper mating feature of the uppermost spacer mates with the lower mating feature of the upper shell,   attaching to the lowermost spacer a lower shell having an lower surface having a throughhole therethrough, an upper surface having an upper mating feature and opposed sidewalls, wherein the lower mating feature of the lowermost spacer mates with the upper mating feature of the lower shell,   attaching the sidewalls of the upper shell to the sidewalls of the lower shell,   removing the plurality of stacked spacers from the disc space to create a void between the upper and lower shells, and   filling the void with a bone filler.       
 
         [0066]      FIG. 14  discloses trial heights sections with the links section  178 . As the clinician pushes the trial sections forward, they will ride up the ramps of each other with the aid of link sections holding them all together. As the trail sections are stacked, this will determine the disc height for the appropriate implant. 
       Spring 
       [0067]    In the  FIG. 15  embodiment, a torsion spring is provided between implant endplates in a collapsed configuration having a height H 1 . Once the tension in the spring is released, the spring expands, thereby increasing the height between the endplates to an expanded height H 2 . The torsion spring could also be made from one or more nitinol leaf springs that expand through temperature change or mechanical means. Once the implant is expanded, the spaced between the endplates can be filled with bone graft or a monolithic insert. 
         [0068]    In accordance with  FIG. 15 , there is provided:
       an intervertebral device comprising;   a) a first endplate  201  having an outer surface  203  adapted for gripping a first natural endplate and an inner surface  205 ,   b) a second endplate  207  having an outer surface  209  adapted for gripping a second opposed natural endplate and an inner surface  211 ,   c) a torsion spring  213  having a first portion  215  contacting the inner surface of the first endplate and a second portion  217  contacting the inner surface of the second endplate,
 
the device having an unexpanded state and an expanded state,
 
wherein the torsion spring is tensioned in the unexpanded state and released in the expanded state.
       
 
         [0073]    Also in accordance with  FIG. 16 , there is provided an intervertebral device comprising;
       a) a first endplate  219  having an outer surface  221  adapted for gripping a first natural endplate and an inner surface  223 ,   b) a second endplate  225  having an outer surface  227  adapted for gripping a second opposed natural endplate and an inner surface  229 ,   c) a memory metal leaf spring  231  having end portions contacting the inner surface of the first endplate and an intermediate portion  233  contacting the inner surface of the second endplate,
 
the device having an unexpanded state and an expanded state,
 
wherein the leaf spring is under force in the unexpanded state and released in the expanded state.
       
 
         [0077]    In a  FIG. 17-18  embodiment, tethers are used to hold a coil spring in a collapsed state so that an implant has a collapsed height H 1 . The tethers can be cut or removed after insertion, thereby allowing the implant to expand under spring tension to a height H 2 . The space between the endplates can be filled with bone graft or a monolithic insert. The tension of the spring can be adjusted by using different springs. 
         [0078]    In one embodiment, three springs increasing force are provided sequentially between endplates. The release of the varying tensions in the springs produces lordosis. Additionally, the expanded endplates can be held open in all of these spring embodiments through a mechanical means such as a cam locking mechanism. 
         [0079]    In accordance with  FIGS. 17-18 , there is provided an intervertebral device comprising;
       a) an upper endplate  235  having an upper surface  237  adapted for gripping an upper natural endplate and a lower surface  238 ,   b) a lower endplate  239  having a lower surface  241  adapted for gripping a lower natural endplate and an upper surface  243 ,   c) a coil spring  245  having a first endportion  247  contacting the lower surface of the upper endplate and a second endportion  249  contacting the upper surface of the lower endplate,   d) a tether  251  having a first endportion  253  contacting the lower surface of the upper endplate and a second endportion  255  contacting the upper surface of the lower endplate,
 
the device having an unexpanded state and an expanded state,
 
wherein the coil spring is tensioned in the unexpanded state and released in the expanded state,
 
wherein the tether is tensioned in the unexpanded state and severed in the expanded state.
       
 
         [0084]    In accordance with  FIGS. 19-20 , there is provided an intervertebral device comprising;
       a) A first endplate  261  having an outer surface  263  adapted for gripping a first natural endplate, an inner surface  265 , an anterior end  267  and a posterior end  269 ,   b) a second endplate  271  having an outer surface  273  adapted for gripping a second opposed natural endplate, a lower surface  275 , an anterior end  277  and a posterior end  279 ,   c) a first coil spring  281  having a first endportion  283  contacting the inner surface of the first endplate and a second endportion  285  contacting the inner surface of the second endplate,   d) a second coil spring  287  having a first endportion  289  contacting the inner surface of the first endplate and a second endportion  291  contacting the inner surface of the second endplate,
 
wherein a first distance between the outer surfaces at the anterior ends of each endplate constitutes an anterior height, and wherein a second distance between the outer surfaces at the posterior ends of each endplate constitutes a posterior height, and
 
the device having an unexpanded state and an expanded state,
 
wherein each coil spring is tensioned in the unexpanded state and released in the expanded state,
 
wherein the first and second coil spring provide varying tensions so that, in the released state, the anterior height is smaller than the posterior height.
       
 
       Ellipse 
       [0089]    This  FIGS. 21-22  embodiment has an elliptical body housed between two endplates. The ellipse has two opposed arcuate slots on its face that mate with a pair of pins placed substantially in the center of each endplate. A pair of springs are also provided between the two endplates on either side of the ellipse. These springs are compressed in the collapsed state of the implant. When the springs are release, they push the endplates apart and the ellipse rotates in accordance with the travel of the pins in the slots, thereby producing an expanded state for the implant. 
         [0090]    In accordance with  FIGS. 21-22 , there is provided an intervertebral device comprising:
       a) an upper endplate  301  having an upper surface  303  and an upper pin  305  extending therefrom in a direction substantially parallel to the upper surface,   b) a lower endplate  307  having a lower surface  309  and a lower pin  311  extending therefrom in a direction substantially parallel to the lower surface,   c) first and second compression springs  313 , each spring having an upper endportion  315  attached to the upper endplate and a lower endportion  317  attached to the lower endplate,   d) a substantially elliptical body  319  disposed between the upper and lower endplates and between the first and second springs, the body having:
           i) a first dimension defining a height, a second dimension perpendicular thereto defining a width, wherein the height is greater than the width, a center, and a perimeter,   ii) an upper arcuate slot  321  therethrough and a lower arcuate slot  323  therethrough, and   iii) an actuation element  327  for rotating the body,   
           wherein the upper pin is slidingly received in the upper arcuate slot and the upper pin is slidingly received in the upper arcuate slot,   wherein the device has a collapsed state and an expanded state,   wherein, when the device is the collapsed state, the body extends between the endplates substantially in the second dimension and the springs are in compressed states, and   wherein, when the device is the expanded state, the body extends between the endplates substantially in the first dimension and the springs are in expanded states.
           Preferably, the actuation element is a projection disposed substantially in the center of the substantially elliptical body.   Preferably, the actuation element is a recess disposed substantially in the center of the substantially elliptical body.   Preferably, the actuation element has a hexagonal shape and is disposed substantially in the center of the substantially elliptical body.   Preferably, the upper endplate has an upper pawl  329  and the body has an upper ratchet  331  upon its perimeter, wherein the upper pawl is engaged with the upper ratchet. preferably, the lower endplate has a lower pawl  333  and the body has a lower ratchet  335  upon its perimeter, wherein the lower pawl is engaged with the lower ratchet,   Preferably, the upper and lower pins extend substantially in the same direction.   Preferably, the upper and lower pins each extend substantially in the same direction.   Preferably, each endplate has first  336  and second  337  ends and each pin is located approximately halfway between the first and second ends.   
               
 
       Squid 
       [0109]    In this  FIG. 23-25   d  embodiment, an inserter having upper and lower flexible blades is provided. A shaft with a pusher at its end is advanced between the blades. The pusher has an acicular cross-section so that its height is less than its width. Rotation of the pusher causes the larger width of the pusher to extend between the endplates thereby distracting the disc space. An indicator is built in to the inserter that measures the amount of distraction and thus the height. 
         [0110]    In some embodiments, the shaft can be retracted and an implant loaded in front of the pusher. The shaft can then be advanced to act as an inserter.
       In accordance with  FIGS. 23-25   d , there is provided an intervertebral implant inserter, comprising:   a) a elongated central body  341  having a distal end  343 , a proximal end, an outer surface, and a longitudinal throughbore  349  therethrough,   b) upper  351  and lower  353  blades, each blade having a distal end portion  355  and a base portion  357 , the base portion of each blade pivotally coupled to the elongated central body,   c) a shaft  359  having a longitudinal axis, wherein the shaft is advanceable within the throughbore and rotatable about the longitudinal axis, the shaft having a distal end  361  forming a pusher  363  having an acicular transverse cross-section,   d) upper  365  and lower  367  endplates respectively detachably connected to the distal end portion of a respective blade.       
 
         [0116]    Preferably, each endplate has an upper surface  369 , a lower surface  371 , and a central throughhole  373  extending from the upper surface to the lower surface. 
         [0117]    Preferably, the inserter further comprises: 
         [0000]    e) a height indicator  375  attached to the elongated central body. 
         [0118]    In some embodiments, there is an intervertebral assembly comprising: 
         [0000]    a) the inserter of  FIG. 23 , and
 
b) a spacer disposed between the endplates and having an upper surface, a lower surface, and vertical throughhole extending between its upper and lower surfaces.
 
         [0119]    Preferably, the upper surface of the spacer is substantially uniplanar with the upper surface of the upper endplate, and the lower surface of the spacer is substantially uniplanar with the lower surface of the lower endplate.
       Preferably, the vertical throughhole of the spacer substantially aligns with the central throughhole of each endplate.       
 
         [0121]    In some embodiments, there is provided an intervertebral assembly comprising:
       a) the inserter of  FIG. 23 , and   b) a spacer disposed distal of and in contact with the pusher, the spacer having an upper surface, a lower surface, and vertical throughhole extending between its upper and lower surfaces.       
 
       Reverse Squid 
       [0124]    In the  FIG. 26-28  embodiment, a core is provided between two ramped surfaces and caused to move between them, thereby increasing the distance between the two ramped surfaces. As the knob of the device is turned, the knob pulls the cable proximally, thereby pulling wedged core proximally as well. An indicator on the cable indicates the height achieved by the activity. In some embodiments, a second core is provided that indicates the angle of lordosis. In some embodiments, the ramped surfaces have indents or other such markings that provide height increments. In some embodiments, a spring is wrapped around the distal end portion of the cable, thereby allowing retraction of the core and bring the device back to its collapsed state.
       In other embodiments, a wedged core is advanced forward instead of being retracted to allow for indications of height and lordotic angle.       
 
         [0126]    In accordance with  FIGS. 26-28 , there is provided, an intervertebral trial, comprising;
       a) an upper endplate  381  having a proximal end portion  383 , a distal end portion  385 , an upper surface  387  and a lower surface  389  disposed at an acute angle from the upper surface,   b) a lower endplate  391  having a proximal end portion  393 , a distal end portion  395 , a lower surface  397  and an upper surface  399  disposed at an acute angle from the lower surface,   c) a tube  401  having a throughbore  403 , a proximal end portion  405 , and a distal end portion  407  pivotally attached to the proximal end of each endplate   d) a spacer  409  disposed between a the distal end portions of the endplates and biased against the lower surface of the upper endplate and the upper surface of the lower endplate,   e) a cable  411  having a distal end portion  412  attached to the spacer, an intermediate portion  413  disposed within the throughbore of the tube, and a proximal end portion  415 ,   f) a knob  417  threadably attached to the proximal end portion of the tube and connected to the proximal end portion of the cable,   g) an indicator  419  extending from the cable, and   h) a first indicia of distance  421  attached to the tube and adapted to measure changes of position of the indicator.
 
wherein proximal movement of the cable causes the spacer to move proximally, thereby causing the upper surface of the upper endplate and lower surface of the lower endplate to move apart a distance that is conveyed by the viewing the indicator against the first indicia of distance.
       
 
         [0135]    Preferably, the trial further comprises:
       i) a spring  423  disposed about the distal end portion of the cable.   Preferably, at least one of the lower surface of the upper endplate and the upper surface of the lower endplate comprises a second indicia of distance.   Preferably, the upper surface of the upper endplate and the lower surface of the lower endplate are substantially parallel.       
 
         [0139]    Now referring to  FIG. 27 , as the ball  409  is pulled back, the ball will rest in the indents  400  within the trail arms. The small indents are spaced apart for different trail heights. The ball position will indicate the heights on the disk space. 
       Gears 
       [0140]    Now referring to  FIGS. 29-31 , there is provided an expandable intervertebral device in which two sets of parallel flanges are pivoted from a collapsed configuration in opposite directions about 90 degrees to produce an expanded configuration capable of distracting a disc space. In some embodiments, the sets of flanges are attached on opposite sides of a fixed carriage. The opposite pivoting of the flanges (i.e., clockwise and counterclockwise) is accomplished by rotating a pair of interlocked gears respectively connected to the first and second flanges. The rotation can be accomplished by inserting a driver into a driving connection on one of the gears and rotating the driver to cause opposed rotation of the gears and thereby opposed pivoting of the sets of flanges. The pivoting can be stopped and locked after the desired amount of distraction is achieved. 
         [0141]    In some embodiments, the device is used as a trial to measure the amount of distraction, preferably as a prelude to inserting an expandable cage. The amount of distraction can be measured by measuring the amount of gear rotation. If the expandable cage has a lordotic feature, then the ratio of the gear diameters can be less than one to provide the required lordosis. Accordingly, the amount of angle produced can also be measured by measuring the extent of rotation in these different diameter gears. 
         [0142]    In some embodiments, both gears can operate independently of each other by the use of a toggle switch in order to obtain precise angulation of the spacer. 
         [0143]    In accordance with  FIGS. 29-31 , there is provided: an intervertebral device comprising:
       a) a first elongate flange  431  having a first end portion  433 , a second end portion  435  and a pair of lateral sidewalls  437 ,   b) a second elongate flange  439  having a first end portion  441 , a second end portion  443  and a pair of lateral sidewalls  445 ,   c) a first gear  447  connected to the first flange by a first pin  449 , the first gear having a plurality of teeth  451  and a driving connection  453 ,   d) a second gear  455  connected to the second flange by a second pin  457 , the second gear having a plurality of teeth  459 ,   e) a carriage  461  comprising a proximal wall  463  having first and second throughholes extending in the proximal-distal direction, a distal wall  469  and a bottom wall  471  connecting the proximal and distal walls, wherein the bottom wall has a bottom surface  473 ,   wherein the teeth of the first and second gears are interlocked,   wherein the first and second pins respectively pass through the first and second throughholes and respectively connect to the first end portions of the first and second flanges,   wherein the device has a collapsed configuration in which the sidewalls of the elongate flanges are substantially parallel to the bottom surface,   wherein rotation of the gears in the collapsed configuration produces in the device an expanded configuration in which the sidewalls of the elongate flanges are substantially perpendicular to the bottom surface.   Preferably, the device further comprises:   f) a third elongate flange  475  having a first end portion  477 , a second end portion  479  and a pair of lateral sidewalls  481 ,   g) a fourth elongate flange  483  having a first end portion  485 , a second end portion  487  and a pair of lateral sidewalls  489 ,
 
wherein the first and second pins respectively pass through the first and second flanges and respectively connect to the first end portions of the third and fourth flanges, thereby respectively connecting the first and second pins to the third and fourth flanges,
 
wherein the first and third elongate flanges are substantially parallel in the collapsed and expanded configurations,
 
wherein the second and fourth elongate flanges are substantially parallel in the collapsed and expanded configurations,
   Preferably, each flange has a second end and wherein, in an expanded configuration, a distance between the bottom surface of the bottom wall of the carriage and the second end of each flange corresponds substantially to the height of a disc space.   Preferably, each flange comprises a narrowed intermediate section  493  between the first and second end portions.       
 
       Box Chisel 
       [0158]    In the  FIG. 32-38  embodiment, a four-sided osteotome is modified to house a pair of endplates connected by an expansion mechanism. In use, the osteotome is used as a box chisel to shape the disc space, and then the expansion mechanism is actuated to eject the endplates away from the rest of the osteotome, thereby providing a basis for an implant.
       In accordance with  FIGS. 32-38 , there is providedan expandable intervertebral box chisel, comprising;   a) a four-sided osteotome  501  comprising i) an upper wall  503  having a vertical throughhole  505  and a sharpened distal edge  507  and ii) a lower wall  509  having a vertical throughhole and a sharpened distal edge  513 , and iii) opposed sidewalls  515  connected the upper and lower walls,   b) a shaft  517  having a proximal end portion  519  and a distal end portion  521  connected to the osteotome,   c) a handle  523  connected to the proximal end portion of the shaft, and   d) upper  525  and lower endplates disposed in the respective vertical throughholes and connected by an expansion mechanism  529 ,
 
wherein the chisel has a collapsed configuration in which the endplates are disposed in the throughholes and separated by a first distance and an expanded configuration in which the endplates are moved further apart and out of the throughholes, and are separated by a second distance greater than the first distance.
   Preferably, the expansion mechanism comprises a spring.   Preferably, the expansion mechanism comprises a ratchet.   Preferably, the upper and lower walls are pivotally attached at a first pivot junction proximal to the osteotome.