Abstract:
A fracture reduction implant for treating a vertebral compression fracture and instruments and methods for implanting the fracture reduction device utilizing a minimally invasive lateral approach are described. The implant may be inserted into a fractured vertebra through a T-shaped cut formed in the vertebral wall. The T-shaped cut may be formed in the lateral aspect of the wall. After insertion, a portion of the implant may be elevated within the vertebral body to reduce the fracture. The implant may include a base assembly with an elevator plate and a support column. The support column may be configured for guided insertion into the base assembly. The support column may be locked to the base assembly after insertion.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a non-provisional patent application claiming the benefit of priority from U.S. Provisional Patent Application Ser. No. 61/365,108, filed on Jul. 16, 2010, (incorporated by reference in its entirety herein) and U.S. Provisional Patent Application Ser. No. 61/365,122, filed on Jul. 16, 2010, (incorporated by reference in its entirety herein). 
    
    
     FIELD 
     The present application describes implants, instruments, and methods for treating bone fractures of the human spine. 
     BACKGROUND 
     Vertebral compression fractures are crushing injuries to one or more vertebrae and are most commonly associated with osteoporosis. Bones weakened by osteoporosis can collapse and the resulting decrease in vertebral body height can lead to back pain, development of neurological conditions, or exacerbation of preexisting neurologic conditions. Trauma and metastatic cancer are also causes of vertebral compression fractures. 
     Non-surgical treatment for vertebral compression fractures includes short term bed rest, analgesics, calcium and vitamin D supplements, external bracing, and other conservative measures. If non-surgical treatment does not alleviate the painful symptoms of the fracture, surgical intervention may be required. Typical compression fracture patients are elderly and often do not tolerate open surgical procedures well. For these reasons, minimally invasive surgical techniques for treating these fractures have been developed. One such technique is percutaneous vertebroplasty which involves injecting bone cement under pressure into the fractured vertebra to provide stabilization. A second technique is balloon kyphoplasty which uses two balloons that are introduced into the vertebra to reduce the fracture. The balloons are then deflated and removed, and bone cement is placed in the void. While these techniques have seen an increase in popularity, neither consistently elevates the vertebral body end plates sufficiently to fully restore lost bone height for all indications. The present invention is directed at overcoming, or at least improving upon, the disadvantages of the prior art. 
     SUMMARY 
     This application describes an implant assembly and methods for restoring bone height after a vertebral compression fracture. The implant may be used in the cervical, thoracic, and lumbar spine. According to one embodiment, the implant assembly includes a base plate, an elevator plate, and a support column. One or more locking mechanisms may also be provided. The implant components are available in multiple lengths, widths, and heights to tailor to the size requirements of each fracture. 
     The implant is preferably composed of a surgical-grade metal material, including, but not necessarily limited to, titanium, stainless steel, and cobalt chrome. Alternatively, the implant may be composed of a carbon fiber reinforced plastic (CFRP), epoxy, polyester, vinyl ester, nylon, or poly-ether-ether-ketone (PEEK), and/or ceramic-reinforced PEEK, alone or in combination with a surgical-grade metal material. 
     When implanting within the lumbar and thoracic spine, access to the operative site is accomplished via a lateral approach. In the lumber spine, the approach is preferably a neurophysiology-guided transpsoas approach in the lumbar spine. This approach provides a large access window to permit introduction of a robust implant better suited for fully restoring the vertebral height while still achieving advantages of a minimally invasive approach such that it is generally well tolerated by elderly patients. According to one example, the neurophysiology guided trans-psoas approach to the lumbar spine is performed as follows. The skin is incised at the appropriate lateral location. Blunt finger dissection through the muscle layers allows safe access into the retroperitoneal space. The finger is used to guide an initial instrument to the surface of the psoas muscle through the retroperitoneal space. Once the initial instrument is safely guided to the surface of the psoas muscle, it is attached to a neurophysiologic monitoring system which is used to guide the direction of the approach away from nearby nerves. Using neurophysiologic guidance, the initial instrument is gently advanced through the psoas muscle. The neurophysiologic monitoring system confirms location of nerves near the distal end of the instrument. Fluoroscopy may be used simultaneously to assure correct targeting of the vertebral fracture. Once the instrument is docked on the target vertebra in the desired position, the position is secured with a k-wire. An operative corridor is thereafter created using a series of sequential dilators and a retractor assembly. 
     Following creation of the operative corridor, a cavity is created in the vertebral body to receive the implant. The cavity is upside down T-shaped and may be created using a single box T-shaped cutter, or, using separate horizontal and vertical cutters (among other options). Multiple tamp-sizers can be used to dilate the T-shaped cut to the appropriate size, if necessary. As the T-shaped cut is formed, cancellous bone is impacted outwards toward the cortical bone. Once the cavity is formed an implant may be inserted. The implant may include a base assembly with an elevator plate and support column. An appropriately sized base assembly is selected based on the size requirements of the patient. The base assembly is introduced into the vertebral body through the T-shaped cut. Insertion of the implant may be guided by a guide rod. The implant is advanced all the way across the vertebral space and positioned so that there is a small overhang over the cortical, lateral aspects of the vertebral body to help stabilize the implant and prevent subsidence in the softer cancellous bone. 
     The elevator plate is raised from the base plate using multiple distraction shims. The use of multiple distraction shims includes, inserting a small shim which distracts the elevator plate a certain height, removing the small shim and then repeating this process with progressively larger shims until the desired height is reached. Once the elevator plate is elevated to the final height and the vertebral fracture is fully reduced, the final distraction shim is removed. The support column is inserted into the base assembly through a slotted passageway in the support strut. The support column is then locked to the base plate. After implant placement, bone growth material may be used to fill the voids in the vertebra. Following successful implantation, the retractor assembly and all of the surgical instruments are removed and the operative corridor is closed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Many advantages of the present invention will be apparent to those skilled in the art with a reading of this specification in conjunction with the attached drawings, wherein like reference numerals are applied to like elements and wherein: 
         FIG. 1  is a perspective view of a fracture reduction implant assembly for treatment of a vertebral compression, the implant assembly including a base assembly and a support column, according to one example embodiment; 
         FIG. 2  is an exploded view of the implant assembly of  FIG. 1 ; 
         FIG. 3  is a perspective view of the base assembly of  FIG. 1 ; 
         FIG. 4  is a perspective proximal view of the base assembly  FIG. 1 ; 
         FIG. 5  is a perspective view of the support column of  FIG. 1 ; 
         FIG. 6  is a side view of the support column of  FIG. 1 , coupled to a support column inserter; 
         FIG. 7  is an illustration depicting a vertebral compression fracture that may be treated with the implant assembly of  FIG. 1 ; 
         FIG. 8  is a flow chart outlining the steps according to one example method for preparing a target vertebral body for receiving the implant assembly of  FIG. 1 ; 
         FIG. 9  is a perspective view of a cutter template used during the preparation of a fractured vertebral body to receive the implant assembly of  FIG. 1 ; 
         FIG. 10  is a cut-away proximal view of the cutter template of  FIG. 9 ; 
         FIG. 11  is an anterior view of a spine with the cutter template secured to a lateral aspect of the a target vertebral body of the spine and a guide wire secured to the target vertebral body through the cutter template; 
         FIG. 12  is a side view of a notched guide wire, according to one example embodiment; 
         FIG. 13  is a anterior of the spine of  FIG. 11  with the cutter template removed and a depth gauge deployed over the guide wire; 
         FIG. 14  is a perspective view of a horizontal cutter; according to one example embodiment; 
         FIG. 15  is an antero-lateral view of the spine of  FIG. 13  with the depth gauge removed and a horizontal cutter deployed over the guide wire; 
         FIG. 16  is a lateral view of a spine with a horizontal cut formed by the cutter of  FIG. 14  in the target vertebral body; 
         FIG. 17  is a side view of a vertical cutter according to one example embodiment; 
         FIG. 18  is a lateral view of a spine with a vertical cut formed by the cutter of  FIG. 17  connecting with the horizontal cut of  FIG. 16  to make a T-cut cavity in the target vertebral body, according to one example embodiment; 
         FIG. 19  is a flowchart outlining the steps according to one example method for implanting the implant assembly of  FIG. 1  in order to reduce a vertebral compression fracture; 
         FIG. 20  is a perspective view of the base assembly of  FIG. 3  with a pair of rod extensions coupled to base assembly; 
         FIG. 21  is a perspective view of the base assembly of  FIG. 20  with an elevator retainer inserted over one of the rod extensions; 
         FIG. 22  is an anterior view of a spine showing the base assembly with attached rod extensions and elevator retainer positioned in a target vertebral body; 
         FIG. 23A  is a perspective view of a blocker, according to a first example embodiment; 
         FIG. 23  B is a perspective view of a blocker, according to a second example embodiment; 
         FIG. 24  is an antero-lateral view of the spine of  FIG. 22  with a blocker advanced over one of the rod extensions and contacting the exterior of the vertebral body; 
         FIG. 25A  is a lateral view of the blocker of  FIG. 23A  positioned adjacent to the target vertebral body; 
         FIG. 25B  is a lateral view of the blocker of  FIG. 23B  positioned adjacent to the target vertebral body; 
         FIG. 26  is an anterior view of the spine and blocker of  FIG. 25A ; 
         FIG. 27  is a perspective view of a shim for elevating the elevator plate above the base assembly, according to one example embodiment; 
         FIG. 28  is a side view of a the shim of  FIG. 27  inserted into the base assembly; 
         FIG. 29  is an anterior view of a spine with a shim inserted into the base assembly implanted in the vertebral body; 
         FIG. 30A  is a perspective view of the base assembly of  FIG. 3  with the elevator plate in a partially elevated position; 
         FIG. 30B  is a proximal view of the base assembly of  FIG. 3  with the elevator plate in a partially elevated position; 
         FIG. 31A  is a perspective view of the base assembly of  FIG. 3  with the elevator plate in a fully elevated position; 
         FIG. 31B  is a proximal view of the base assembly of  FIG. 3  with the elevator plate in a fully elevated position; 
         FIG. 32  is an anterior view of the spine of  FIG. 26  with the blocking plate being removed after the elevator plate has reached the appropriate elevated position; 
         FIG. 33  is an anterior view of the spine of  FIG. 26  blocker removed and the support column being inserted into the base assembly; 
         FIG. 34  is a perspective view of the implant assembly of  FIG. 1  with the elevator plate fully raised and the support column being inserted; 
         FIG. 35  is a perspective view of the implant assembly of  FIG. 1  with the support column fully inserted; 
         FIG. 36  is a perspective antero-lateral view of a spine with the implant assembly of  FIG. 1  fully deployed in the target vertebral body and with a locking screw being engaged to lock the support column to the base assembly; 
         FIG. 37  is a perspective view of the implant assembly of  FIG. 1 , with the support column fully inserted and affixed to the base assembly with a locking screw; 
         FIG. 38  is an anterior view of a spine with the implant assembly of  FIG. 1  implanted in the target vertebral body; and 
         FIG. 39  is a lateral view of a spine with the implant assembly of  FIG. 1  implanted in the target vertebral body. 
     
    
    
     DETAILED DESCRIPTION 
     Illustrative embodiments of the invention are described below. In the interest of clarity, not all features of an actual implementation are described in this specification. It will of course be appreciated that in the development of any such actual embodiment, numerous implementation-specific decisions must be made to achieve the developers&#39; specific goals, such as compliance with system-related and business-related constraints, which will vary from one implementation to another. Moreover, it will be appreciated that such a development effort might be complex and time-consuming, but would nevertheless be a routine undertaking for those of ordinary skill in the art having the benefit of this disclosure. The vertebral compression fracture reduction implant and methods for use disclosed herein boasts a variety of inventive features and components that warrant patent protection, both individually and in combination. 
       FIGS. 1-2  illustrate one example embodiment of a fracture reduction implant  10  for treating a vertebral fracture. In use the implant  10  is inserted into a cavity formed in the fractured (target) vertebral body where it is expanded to restore the height of the vertebra and prevent recollapse in the future. The implant is optimized for insertion from a lateral access approach to the spine. The implant  10  may be used in any of the cervical, thoracic, and lumbar spine and may be sized accordingly. The implant  10  includes a base assembly  12  and a support column  14 . A lock, for example, the locking screw  16  may also be provided to lock the support column  14  to the base assembly  12 . 
     As illustrated in  FIG. 3 , the base assembly  12  includes a base plate  18 , a support strut  20  extending generally perpendicularly from the base plate  18 , and an elevator plate  22 . The base plate  18  has (by way of example) a generally rectangular footprint dimensioned to allow positioning across the vertebral body from a lateral insertion approach. The length of the base plate  18  extends from a distal or leading end  24  to a proximal or trailing end  26 . The length of the base plate  18  is preferably such that the base plate  18  spans the length of the vertebral body when inserted such that the proximal end  24  and distal end  26  extends to the cortical outer wall of the vertebral body, providing a solid base for the implant  10 . By way of example, the base plate  18  length may be in the range of 45 mm to 60 mm. The base plate may have a width in the range of 14 mm to 26 mm. The height of the base assembly  12 , including the base plate  20  and the support strut  20 , may be in the range of 12 mm to 22 mm. According to one example, multiple base assemblies according to different size configurations are provided in order to match the implant  10  to the particular patient anatomy. By way of example, base assemblies may be provided with length dimensions increasing in 5 mm increments from 45 mm to 60 mm, width dimensions of 14 mm and 18 mm, and height dimensions increasing in 2 mm increments from 12 mm to 22 mm. The support strut  20  extends from the base plate  18  and includes a includes an upper surface  30 , a first side wall  32 , and second side wall  34 , such that a slot  36  is formed which extends from the base plate  18 . The slot  36  is dimensioned to receive the support column  14  therethrough. Viewing windows  35  in the form of vertical slots are situated in the center of each of the first side wall  32  and second side wall  34 . The viewing windows  35  are recognizable in an A/P (Anterior/Posterior) fluoroscopy image to aid with implant positioning during insertion. A longitudinal channel  37  extends along the upper surface of the base plate  18 . The longitudinal channel  37  is aligned with the slot  36  in the support strut  20  and extends from and opening in the proximal end  26  to a position short of the distal end  24  but beyond the support strut  20 . The longitudinal channel  37  has a width dimension to accommodate the support column  14  which slides into position through the longitudinal channel  37  and slot  36 . The upper surface of the base plate  18  also includes a recess  39  in which the elevator plate  22  rests such that it is flush with the base plate  18  when in the fully lowered, insertion position. 
     The elevator plate  22  has (by way of example) a generally rectangular shape to match the rectangular shape of the base plate  18 . The width of the elevator plate  22  is approximately equal to the width of the base plate  18 , and, as previously indicated sits flush with the exterior surfaces of the base plate  18  by virtue of the recess  39  in which the elevator plate is received. A pair of slits  38  extend longitudinally through the interior of the elevator plate  18 . The first side wall  32  and the second side wall  34  of the support strut  20  extend through the slits  38  such that the elevator plate  22  may move vertically along the support strut  20  from the base plate  18  to the upper surface  30  of the support strut  20 . 
       FIG. 4  illustrates the proximal end  26  of base plate  18  which includes two receptacles  28 . The receptacles  28  are configured for removable coupling with instruments used to facilitate insertion of the implant  10 , including for example, a guide rod  50  and blocker rod  140  ( FIG. 20 ). Receptacles  28  are also each configured such that they can receive and engage a lock screw  16 . The lock screws  16  may be used to lock the support t column  14  to the base assembly  12 . 
     With reference to  FIG. 5 , the support column  14  includes a body  40  having a distal end  41  and a proximal end  42 , a neck  44  extending proximally from the bottom of the proximal end  42 , and an elongated end face  45  situated at the end of the neck  44 . The body  40  is inserted through the support strut  20 , supporting and maintain the elevator plate  22  in the elevated position. The proximal end  42  of body  40  contains an insertion aperture  43  configured to threadedly couple with a support column inserter  55 , as illustrated in  FIG. 6 . The length of the body  40  matches approximately the length of the elevator plate  22  and the length of the neck is matches approximately the length of the base plate  18  from the proximal end  26  to the start of the elevator plate  18  such that when the support column  14  is fully inserted, the end face  45  rests flush against the proximal end  26  of the base plate. A pair of guide holes  46  in the end face  45  align with the receptacles  28  of the base plate distal end  26  ( FIG. 35 ). The guide holes  46  are dimensioned such that they are capable of slidably passing over various instruments, including, but not limited to the guide rod  50  and the blocking rod  140  as shown in  FIG. 19 . These guide holes  46  are also dimensioned to permit passage of the shaft of locking screw  16  but not the head of the locking screw  16 , such that the locking screw may engage one of the base plate receptacles through a guide hole to lock the support column  14  to the base assembly  12  ( FIG. 36 ). 
       FIG. 7  is an illustration of a fractured vertebra  52  in the human patients spine for which the implant  10  may be deployed for treatment.  FIG. 8  sets forth steps, which are depicted in FIGS.  9 - 18 , utilized according to one example method for preparing a target vertebra  52  within the spine to receive the implant  10 . At step  54 , and operative corridor to the vertebral body  56  is achieved via a lateral approach (e.g. a neurophysiology-guided transpsoas approach). At step  56 , a cutter template  64  corresponding to the desired width and height of the implant  10  is chosen. As shown in  FIGS. 9-10 , the cutter template  64  has a head  65  that matches the shape of the T-cut which is to be created in the vertebral body. The head includes at least one, and preferably 3, small securing spikes  66  extending distally from the head. The head  65  also includes a viewing slot  69  formed therethrough to help ensure proper orientation with A/P fluoroscopy. A cannulated shaft  67  extends proximally from the head  65  and connects with an aperture  68  extending through the head  65 . Together, the cannulated shaft  67  and aperture  68  are configured to permit passage of a guide wire. A/P and lateral fluoroscopy views may be utilized to place the template  64  in the desired position and orientation on the target fractured vertebral body  52 . Also at step  56 , the template  64  is secured to the vertebral body  52  by impacting the shaft  67  to penetrate the securing spikes  66  into the vertebral body  52 . Once the template  64  is secured to vertebral body  52 , at step  58  a guide wire  70  may be advanced into the vertebral body through the cannulated shaft  67  ( FIG. 11 ). The cannulated shaft guides the guide wire into the correct position and supports the guide wire to prevent excessive bending as the wire is driven into the vertebral body  52 . By way of example only, the tip  72  of the guide wire  70  may be a trocar tip or a blunt tip. The guide wire  70  directs the cutter instruments and is also used to determine the width of the vertebral body  52 , and hence the length of the implant  10  to be implanted. 
     According to one example embodiment, shown in  FIG. 12 , the guide wire  70  may include notched depth markings  74  such that the depth of the guide wire  70  may be read directly off of the guide wire  70 . For example, the notches may be formed at 45 mm, 50 mm, 55 mm, and 60 mm (corresponding to the implant lengths provided according to a preferred example) from the tip of the guide wire  70 . Thus, with the guide wire properly advanced to the contralateral margin the appropriate length implant can be determined using A/P fluoroscopy. Alternatively, a depth gauge  75  may be used to determine the width of the vertebral body  52  (and length of the implant  10  to be implanted). As illustrated in  FIG. 13 , the depth gauge  75  includes a cannulated distal end  76  which can be advanced over the guide wire  70  until it rests on the vertebral body  52 . The guide wire  70  extends out of the cannulated distal end  76  along a handle having depth markings  77  that correspond to the length of wire extending distally beyond the distal end  76  of the depth gauge (i.e. the length of wire penetrated into the vertebral body). 
     At step  60 , as highlighted in  FIGS. 14-16 , a first, horizontal cut  98  is made in the fractured vertebral body  52  using a horizontal cutter  78 . The horizontal cutter  78  includes serrations  85  around the distal cutting end  84  for cutting through the vertebral body  52 . A shoulder  88  adjacent to the proximal end  80  prevents advancement of the cutter  78  through the vertebral body into the contralateral tissues. The cutter may be provided in multiple lengths corresponding to the length options of the implant  10 . A threaded member  82  at the proximal end  80  permits coupling to a handle, such as the cutter holder  92 . The proximal end  80  includes a cannulated aperture  90  extending into the interior of the cutter body such that the horizontal cutter  78  may be introduced over the guide wire  70 . The horizontal cutter  78  includes viewing slots, including distal viewing slot  85  and proximal viewing slot  86  that are visible under A/P fluoroscopy. The viewing slots  86  and  87  are spaced to correspond to implant length. The distal slot  86  indicates how far the cutter needs to be advanced to reach the contralateral margin of the vertebral body  52 . 
     To facilitate advancement of the horizontal cutter  78  through the vertebral body  52 , the cutter holder  92  may be further coupled to a handle outfitted with a strike plate (for example, the cannulated T-handle  94  of  FIG. 15 ). A forked mallet  96  (or similar instrument suited for striking the T-handle  94  around the guide wire  70 ) may be used to drive the horizontal cutter  78  into the fractured vertebral body  52 . The horizontal cutter  98  should be advanced until a horizontal cut  98  has been made through the contralateral cortical margin  100 , as indicated by the distal viewing slot  86 . It is to be appreciated that once the horizontal cut  98  has been started, the guide wire  70  may be removed and the horizontal cut  98  and vertical cut  116  can be finished without the guide wire  70 , preventing inadvertent advancement of the guide wire  70  into the contralateral tissues. Once the desired horizontal cut  98  has been made, the horizontal cutter  78 , along with the cutter holder  92  and cannulated T-handle  94 , may be removed ( FIG. 16 ). 
     At step  62 , a second, vertical cut  116  is made through the fractured vertebral body  52  using a vertical cutter  102 . The horizontal cut  98  acts as a guide for the vertical cutter  102 , illustrated in  FIG. 17 . The vertical cutter  102  includes a sled  108 , dimensioned to be received into the horizontal cut  98 , with a tapered distal end  109  for easy insertion through the horizontal cut  98  as the vertical cutter  102  is advanced into the fractured vertebral body  52 . The sled also includes a distal viewing slot  110  that is visible under A/P fluoroscopy. The vertical cutter  116  also includes serrated edges  112  perpendicular to the distal end  108 , a shoulder  114  adjacent to the proximal end  104  for preventing inadvertent advancement into the contralateral tissues, and a threaded member  106  at the proximal or trailing end  104  for threadably receiving the cutter holder  92 . 
     The vertical cutter  102  is assembled to the cutter holder  92  via the threaded member  106  at the proximal end  104  of the vertical cutter  102 . The cutter holder  92  may be further coupled to a handle outfitted with a strike plate (for example, the cannulated T-handle  94  of  FIG. 15 ) which can be impacted to drive the cutter. The vertical cutter  102  may then be advanced through the vertebral body  52  until it has aligned with the contralateral cortical margin  100  of the vertebral body  52 , as indicated by the distal viewing slot  110 . Once the desired vertical cut  116  has been made, the vertical cutter  102 , cutter holder  92 , and cannulated T-handle  94 , may be removed, leaving a T-cut cavity  117 , and any remaining bony debris left inside the T-cut  117  may be removed using a small curette or other suitable surgical instrument.  FIG. 18  depicts the vertebral body  52  with T-cut  117  formed there in. 
       FIG. 19  sets forth steps, which are depicted in  FIGS. 19-36 , utilized according to one example method for deploying the implant into the target vertebral body  52 . As illustrated in  FIG. 20 , at step  118  the guide rod  50  is inserted into one receptacle  28  on the base plate  18 . The guide rod  50  will be used to insert the implant into the T-cut  117  and later, as a guide for inserting distraction shims. The guide rod  50  includes a quick connect proximal end (e.g. male Hudson connector) which can be attached to a handle to aid in threading the guide rod  50  into the receptacle  28 . At step  120   m , the blocker rod  150  is inserted into the second receptacle  28  on the base plate  18 . The blocker rod  140  will be used to guide positioning of a blocker  146  which prevents the implant  10  from advancing distally during shim insertion to elevate the elevation plate  22 . The blocker rod  140  may also have a quick connect proximal end which can be attached to a handle to aid in threaded coupling to the receptacle  28 . To differentiate the blocker rod  140  and the guide rod  50 , the blocker rod  140  may be shorter than the guide rod  50  and/or may be of different color than the guide rod  50 . An elevator plate retainer  142  ( FIG. 21 ) may be employed to prevent the elevator plate  22  from lifting off the base plate  18  during implantation of the base assembly  12 . The elevator plate retainer  142  includes a cannulated shaft  143 , dimensioned to pass over the guide rod  50 , and a head  144  including an elongate extension that sits above base plate  18  and elevator plate  22  to prevent the elevator plate  22  from moving. At step  122 , the elevator plate retainer is introduced over the guide rod  50  until the elongate extension of the head  1844  passes into the slot  36  in the support strut  20 . With the elevator plate  22  secure, the implant base assembly  12  is inserted into the T-cut cavity  117  (step  124 ), as shown in  FIG. 22 . 
       FIGS. 23A and 23B  illustrate a pair of example embodiments of blocker  146 . The blocker  146  includes a blocker plate  148  situated at the distal end of a cannulated shaft  147 . The blocker plate  148  includes a cutout region  149  that facilitates slidable insertion of distraction shims and the support column  14  past the blocker plate  148  and into the base plate assembly  12 . A set screw  152  encroaches into the cannulation  150  of the shaft  147  to secure the blocker  146  to the blocker rod  140 , which in turn is secured to the base plate  18  (thus preventing the base assembly  12  from further advancement). The blocker shown in  FIG. 23A  has a metallic (e.g. titanium) mesh blocker plate that provides a large footprint for maximum contact with the vertebral body. The blocker shown in  FIG. 23B  includes a polymer (e.g. PEEK) blocker plate with a small (and radiolucent) foot print maximum visualization. At step  126 , illustrated in  FIG. 24 , the blocker  146  is introduced over the blocker rod  140  until the blocker plate  148  contacts the vertebral body  52 . The blocker  146  is then secured to the blocker rod  140  with the set screw  152 . 
     At step  130 , a plurality of shims  156  are successively inserted to raise the elevator plate  22  to the selected height. With reference to  FIG. 27 , the distraction shims  156  have a tapered distal end  158  that facilitates lifting of the elevator plate  22  as the shim is inserted down the longitudinal channel  37  and through the slot  36  in the support strut  20 . A guide tube  162  along the side of the shim  156  is dimensioned to permit passage of the guide rod  52  such that the shim is easily guided into and along the channel  37  and slot  36 . A shaft  160  extends proximally from the shim  156  to facilitate insertion of the shim. The end of the shaft  160  includes a knob  168  that facilitates removal of the shim (for example using the forked mallet  96 . A viewing slot  166  situated near the distal end of the shim is viewable under A/P fluoroscopy to monitor shim advancement. As a first (smallest) shim  156  is inserted, the elevator plate  22  is lifted upward such that the cancellous bone above it is compressed toward the cortical endplate. The shim  156  is advanced until the view slot  166  is viewable past the distal end of the support strut  20 . The small shim  156  may then be removed and a second larger shim  156  may be inserted such that the elevator plate  22  is lifted further upward compressing the cancellous bone and lifting the cortical endplate.  FIGS. 30A-B  depict the base plate  18  and elevator plate  22  after partial elevation of the elevator plate  22 . Insertion of sequentially larger shims  156  continues until the elevator plate is fully raised to the selected height. With the elevator plate  22  raised to the final position, the blocker plate  146  and blocker rod  140  are removed (step  132 ) in preparation for insertion of the support column. 
     At step  134 , the support column  14  is inserted into the base plate assembly  14  as shown in  FIGS. 33-35 . To accomplish this, the support column  14  is coupled to the support column inserter  54  which is threaded into the hole  43  in the body  40  of the support column. The support column inserter  54  may have a quick connect proximal end which can be attached to a handle to aid in threaded coupling to the hole  43 . A guide hole  46  of the support column end face  45  is advanced over the guide rod  52  in order to guide the support column into position. The support column  14  is advanced through the longitudinal channel  37  and slot  36  until the end face  45  rests flush against the distal end  28  of the base plate  20 . A locking screw  16  is then passed through the second guide hole  46  with a screw driver  170  (having a length greater than the guide rod  52  and support column insertion rod  54  such that it is not interfered with) and secured into the open receptacle  28  of base plate to secure the support column (step  136 ). The guide rod  52  and support column inserter  54  are then removed, and if desired, a second locking screw  16  may be secured into the open receptacle  28  through the now open guide hole  46 .  FIGS. 38-39  show the final implantation configuration of the implant  10  in the reduced vertebra  172 . Materials such as bone growth promoting materials or cement may be packed into the void created by the elevation of the elevation plate  22 . 
     While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof have been described herein and shown drawings by way of example in the. It should be understood, however, that the description herein of specific embodiments is not intended to limit the invention to the particular forms disclosed, but on the contrary, the invention is to cover all modifications, equivalents and alternatives falling within the spirit and cope of the invention as defined by the e appended claims. By way of example, it should be appreciated that while the present embodiment includes a single support strut, it is contemplated that more than one (for example, anywhere from two to six) support struts could be used. It is further contemplated that the footprint of the base plate and/or elevator plate may be oval or D-shaped.