Abstract:
The apparatus of the invention is an adjustable intervertebral shaver with a handle portion and a blade portion that adjusts width while remaining in the disc space. The invention also includes methods using the adjustable intervertebral shaver to surgically prepare the intervertebral space. By changing the width of the blade portion, the surgeon adjusts the aggressiveness of the curetting and also determines the appropriate size for an intervertebral graft. By remaining in the disc space, this decreases the time it may take to appropriately prepare the disc space. In addition, since the blade portion remains in the disc space it reduces the number of times an instrument must be passed adjacent to nerves and neural elements, thus decreasing the likelihood of damage to these structures. The width of the blade portion adjusts via an adjustment knob on the handle portion of the adjustable intervertebral shaver.

Description:
CROSS REFERENCE TO OTHER APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Application number 61/226,595, filed on Jul. 17, 2009, which is incorporated by reference in its entirety. 
     
    
     TECHNICAL FIELD 
       [0002]    The invention relates to apparatus and methods for preparation of the intervertebral disc space as performed during surgery to fuse vertebrae. Vertebrae are fused in an attempt to alleviate pain and restore neurologic function associated with disease that affects the cervical, thoracic, and lumbar discs and their adjacent vertebra. The technology also applies to all circumstances in which intervertebral bony arthrodesis may be desired. 
       BACKGROUND OF THE INVENTION 
       [0003]    Degenerative disc disease is a condition related to the degenerative of intervertebral discs and the adjacent vertebrae. These discs normally serve as cushions between vertebrae and allow for some degree of motion of the vertebrae. In the setting of degeneration, bone spurs may form which may be the source of pain. Further, disc material may herniate into the spinal canal causing neurologic injury. A common treatment for degenerative disc disease is to remove the degenerated disc and/or bone spurs and to fuse the vertebra together. This is often done with the use of instrumentation, namely titanium screws/plates to hold the vertebra in correct position until the fusion takes place. Bone is usually placed in the intervertebral space after removing the disc. Often synthetic intervertebral spaces, or cages, are used to restore disc height and allow a space for fusion to occur. These cages are commonly made of titanium, stainless steel, polyetheretherketone (PEEK), graphite, or carbon fiber. In order to prepare the intervertebral space for arthrodesis, the intervertebral contents must be removed. This is often done with the assistance of curettes, shavers, rongeurs, high-speed drill, and other tissue removing devices. This device facilitates the preparation of the disc space for arthrodesis (spinal fusion) or for arthroplasty (placement of an artificial disc). 
       SUMMARY OF THE INVENTION 
       [0004]    The apparatus of the invention is an adjustable intervertebral or interbody shaver with a handle portion and a blade portion that adjusts width while remaining in the disc space. The invention also includes methods using the adjustable intervertebral shaver to surgically prepare the intervertebral space. By changing the width of the blade portion, the surgeon adjusts the aggressiveness of the curetting and also determines the appropriate size for an intervertebral graft. By remaining in the disc space, this decreases the time it may take to appropriately prepare the disc space. In addition, since the shaver remains in the disc space it reduces the number of times an instrument must be passed adjacent to nerves and neural elements, thus decreasing the likelihood of damage to these structures. The width of the blade portion adjusts via an adjustment knob on the handle portion of the adjustable intervertebral shaver. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0005]      FIG. 1  is a side view of the adjustable intervertebral shaver of the present invention shown in a contracted or unexpanded position. 
           [0006]      FIG. 2  is an end view of the adjustable intervertebral shaver of  FIG. 1  in the contracted or unexpanded position. 
           [0007]      FIG. 3  is a side view of the adjustable intervertebral shaver of  FIG. 1  shown in an expanded position. 
           [0008]      FIG. 4  is an end view of the adjustable intervertebral shaver of  FIG. 3  in the expanded position. 
           [0009]      FIG. 5  illustrates the adjustable intervertebral shaver of  FIGS. 1-4  in use for surgically preparing an intervertebral space. 
           [0010]      FIG. 6  is a cut-away side view of an adjustable intervertebral shaver with a screw-type expansion mechanism shown in an unexpanded position. 
           [0011]      FIG. 7  is a cut-away end view of the adjustable intervertebral shaver of  FIG. 6  in the unexpanded position. 
           [0012]      FIG. 8  is a cut-away side view of the adjustable intervertebral shaver of  FIG. 6  in an expanded position. 
           [0013]      FIG. 9  is a cut-away end view of the adjustable intervertebral shaver of  FIG. 8  in the expanded position. 
           [0014]      FIG. 10  is a cut-away side view of an adjustable intervertebral shaver with a scissor-type expansion mechanism shown in an unexpanded position. 
           [0015]      FIG. 11  is a cut-away end view of the adjustable intervertebral shaver of  FIG. 10  in the unexpanded position. 
           [0016]      FIG. 12  is a cut-away side view of the adjustable intervertebral shaver of  FIG. 10  in an expanded position. 
           [0017]      FIG. 13  is a cut-away end view of the adjustable intervertebral shaver of  FIG. 12  in the expanded position. 
           [0018]      FIG. 14  is a cut-away side view of another adjustable intervertebral shaver with a scissor-type expansion mechanism shown in an unexpanded position. 
           [0019]      FIG. 15  is a cut-away end view of the adjustable intervertebral shaver of  FIG. 14  in the unexpanded position. 
           [0020]      FIG. 16  is a cut-away side view of the adjustable intervertebral shaver of  FIG. 14  in an expanded position. 
           [0021]      FIG. 17  is a cut-away end view of the adjustable intervertebral shaver of  FIG. 16  in the expanded position. 
           [0022]      FIG. 18  is a cut-away side view of an adjustable intervertebral shaver with a rack-and-pinion expansion mechanism shown in an unexpanded position. 
           [0023]      FIG. 19  is a cut-away end view of the adjustable intervertebral shaver of  FIG. 18  in the unexpanded position. 
           [0024]      FIG. 20  is a cut-away side view of the adjustable intervertebral shaver of  FIG. 18  in an expanded position. 
           [0025]      FIG. 21  is a cut-away end view of the adjustable intervertebral shaver of  FIG. 20  in the expanded position. 
           [0026]      FIG. 22  is a cut-away side view of another adjustable intervertebral shaver with a rack-and-pinion expansion mechanism shown in an unexpanded position. 
           [0027]      FIG. 23  is a cut-away end view of the adjustable intervertebral shaver of  FIG. 21  in the unexpanded position. 
           [0028]      FIG. 24  is a cut-away side view of the adjustable intervertebral shaver of  FIG. 21  in an expanded position. 
           [0029]      FIG. 25  is a cut-away end view of the adjustable intervertebral shaver of  FIG. 23  in the expanded position. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0030]      FIG. 1  is a side view and  FIG. 2  is an end view of the adjustable intervertebral shaver  100  of the present invention shown in a contracted or unexpanded position.  FIG. 3  is a side view and  FIG. 4  is an end view of the adjustable intervertebral shaver of  FIG. 1  shown in an expanded position. The intervertebral shaver  100  has a distal blade portion  102  that is connected to a proximal handle portion  104 . Preferably, the blade portion  102  has a flat, paddle-shaped configuration with a thickness that is generally less than its width. The width of the blade portion  102  is incrementally adjustable from the contracted or unexpanded position ( FIGS. 1-2 ) to the expanded position ( FIGS. 3-4 ). In the embodiment shown in  FIGS. 1-4 , the blade portion  102  includes a pair of wings  106 ,  108  that extend and retract from the lateral sides of a central housing  116  of the blade portion  102  in response to an expansion mechanism enclosed within the intervertebral shaver  100 . The lateral edges  107 ,  109  of the wings  106 ,  108  provide scraping or cutting surfaces that may be configured as straight or convex surfaces. Other geometries of scraping or cutting surfaces known in the industry may also be applied to the lateral edges  107 ,  109  of the wings  106 ,  108 . Preferably, the width of the blade portion  102  will have an expansion ratio of approximately 2 times from a fully contracted position to a fully expanded position, however different expansion mechanisms may provide different expansion ratios. Preferably, the width of the blade portion  102  will be incrementally adjustable from approximately 6-7 mm up to approximately 12-14 mm. The thickness of the blade portion  102  will preferably be approximately 1-3 mm, most preferably approximately 1.5 mm. The length of the blade portion  102  will preferably be approximately 20-40 mm. 
         [0031]    The handle portion  104  includes a shaft  110  and a T-handle  112  that are connected to the blade portion  102 . The T-handle  112  is preferably aligned with the width of the blade portion  102  to provide a visual indication of the position of the blade portion  102  during use. The length of the shaft  110  will typically be approximately 25-35 cm. The typically of the T-handle  112  will preferably be approximately 10-12 cm. An adjustment knob  114  is provided on the handle portion  104  for operating the expansion mechanism for the blade portion  102 . Preferably, the adjustment knob  114  will be marked to provide a visual indication of the width that the blade portion  102  has been adjusted to. 
         [0032]      FIG. 5  illustrates the adjustable intervertebral shaver  100  of  FIGS. 1-4  in use for surgically preparing an intervertebral space prior to arthrodesis or arthroplasty. The blade portion  102  of the intervertebral shaver  100  is adjusted to its smallest size and then inserted in a flat orientation into the intervertebral space between two vertebral bodies V after an incision is made in the disc D with a knife or other instrument. Using the adjustment knob  114 , the blade portion  102  of the intervertebral shaver  100  is adjusted to the desired width and the intervertebral shaver  100  is rotated or oscillated (either clockwise and/or counterclockwise) with the T-handle  112  to remove disc material and scrape the cartilaginous vertebral endplates. If desired, the width of the blade portion  102  can be increased without removing it from the disc space and the process can be repeated until a sufficient amount of disc material has been broken up. Typically, these steps are repeated 3-4 times. The blade portion  102  of the intervertebral shaver  100  is then collapsed to its smallest size and withdrawn through the incision. The broken up disc material can be removed from the disc D with the assistance of rongeurs, suction devices or other instruments. 
         [0033]    The adjustable width of the intervertebral shaver  100  allows it to do the work of several different sizes of standard intervertebral shavers without the need for repeated insertions and withdrawals of multiple instruments. This will reduce the time needed for preparing the intervertebral space and it will improve the safety of the procedure because fewer instruments will have to be inserted or withdrawn past the nerves and other sensitive structures close to the spine. If necessary, the intervertebral shaver  100  can be reinserted into the disc D and the process repeated. Even if the intervertebral shaver  100  must be reinserted, the fact that it can be contracted to a smaller size before insertion or withdrawal will improve the safety of the procedure. 
         [0034]    Various expansion mechanisms can be used for extending and retracting the wings  106 ,  108  of the blade portion  102  of the intervertebral shaver  100 .  FIG. 6  is a cut-away side view and  FIG. 7  is a cut-away end view of an adjustable intervertebral shaver  100  with a screw-type expansion mechanism shown in an unexpanded position.  FIG. 8  is a cut-away side view and  FIG. 9  is a cut-away end view of the adjustable intervertebral shaver  100  of  FIG. 6  in an expanded position. 
         [0035]    The wings  106 ,  108  are configured for a sliding fit within a central housing  116  of the blade portion  102 . Optionally, the central housing  116  may be contoured (e.g. rounded or tapered) on the proximal  118  and distal  120  ends of the blade portion  102 . A pair of threaded holes  122  &amp;  124 ,  126  &amp;  128 , are located in each of the wings  106 ,  108 . The holes  122  &amp;  124  in the first wing  106  are threaded in the opposite direction from the holes  126  &amp;  128  in the second wing  108 . Two threaded rods  130 ,  132  engage the threaded holes  122  &amp;  124 ,  126  &amp;  128 , in each of the wings  106 ,  108 . The threaded rods  130 ,  132  are threaded in opposite directions on opposite ends of the threaded rods  130 ,  132 . A pinion gear  134 ,  136  is attached at the center of each of the threaded rods  130 ,  132 . A worm gear  138  attached to a rotating inner shaft  140  engages each of the pinion gears  134 ,  136 . One long worm gear  138  can be used, as shown, or, alternatively, a pair of smaller worm gears may be used. The inner shaft  140  is connected to the adjustment knob  114  on the handle portion  104  (See  FIG. 1 ). 
         [0036]    When the adjustment knob  114  is rotated in a first direction, the inner shaft  140  rotates the worm gear  138 , which causes of each of the pinion gears  134 ,  136  and therefore the threaded rods  130 ,  132  to rotate, moving the wings  106 ,  108  apart to increase the width of the blade portion  102 , as shown in  FIGS. 8 and 9 . When the adjustment knob  114  is rotated in the opposite direction, the inner shaft  140  rotates the worm gear  138 , which causes of each of the pinion gears  134 ,  136  and therefore the threaded rods  130 ,  132  to rotate in the opposite direction, moving the wings  106 ,  108  together to decrease the width of the blade portion  102 , as shown in  FIGS. 6 and 7 . Stops may be provided to prevent the wings  106 ,  108  from overextending and becoming disengaged from the threaded rods  130 ,  132 . 
         [0037]    The embodiment of the intervertebral shaver  100  shown in  FIGS. 6-9  utilizes two threaded rods  130 ,  132  to assure stable and parallel motion of the wings  106 ,  108 . The same could also be accomplished using a single, centrally positioned threaded rod and a pair of guide rods or tracks to assure stable and parallel motion of the wings  106 ,  108 . 
         [0038]      FIG. 10  is a cut-away side view and  FIG. 11  is a cut-away end view of an adjustable intervertebral shaver  100  with a scissor-type expansion mechanism shown in an unexpanded position.  FIG. 12  is a cut-away side view and  FIG. 13  is a cut-away end view of the adjustable intervertebral shaver  100  of  FIG. 10  in an expanded position. The wings  106 ,  108  are configured for a sliding fit within a central housing  116  of the blade portion  102 . In this embodiment, the wings  106 ,  108  of the blade portion  102  are constructed with a hollow configuration to allow additional room for the components of the expansion mechanism. A pair of scissor mechanisms  150 ,  152  are connected between the first and second wings  106 ,  108 . Each of the scissor mechanisms  150 ,  152  is made up of eight bars that are pivotally connected to form three diamond-shaped units. The pivot points between the bars can be provided by hinge pins, by flexible, living hinges or by a combination of the two. Other known configurations of scissor mechanisms may also be used. 
         [0039]    The opposite sides of the central diamond-shaped unit are connected a pair of push/pull rods  154 ,  156 . When the push/pull rods  154 ,  156  are moved to decrease the proximal-to-distal length of the central diamond-shaped units in the scissor mechanisms  150 ,  152 , the lateral width of the scissor mechanisms  150 ,  152  increases, moving the wings  106 ,  108  apart to increase the width of the blade portion  102 , as shown in  FIGS. 12 and 13 . When the push/pull rods  154 ,  156  are moved to increase the proximal-to-distal length of the central diamond-shaped units in the scissor mechanisms  150 ,  152 , the lateral width of the scissor mechanisms  150 ,  152  decreases, moving the wings  106 ,  108  together to decrease the width of the blade portion  102 , as shown in  FIGS. 10 and 11 . The adjustment knob  114  may actuate the push/pull rods  154 ,  156  through screw threads, cams, levers or other mechanisms. Stops may be provided to prevent the wings  106 ,  108  from overextending. 
         [0040]    The embodiment of the intervertebral shaver  100  shown in  FIGS. 10-13  utilizes two scissor mechanisms  150 ,  152  to assure stable and parallel motion of the wings  106 ,  108 . The same could also be accomplished using a single, centrally positioned scissor mechanism and a pair of guide rods or tracks to assure stable and parallel motion of the wings  106 ,  108 . 
         [0041]      FIG. 14  is a cut-away side view and  FIG. 15  is a cut-away end view of another adjustable intervertebral shaver  100  with a scissor-type expansion mechanism shown in an unexpanded position.  FIG. 16  is a cut-away side view and  FIG. 17  is a cut-away end view of the adjustable intervertebral shaver  100  of  FIG. 14  in an expanded position. The scissor-type expansion mechanism operates similarly to the mechanism described above in connection with  FIGS. 10-13 , however the blade portion  102  of the intervertebral shaver  100  is configured differently. There is no central housing, instead the first wing  106  is configured to slide telescopically within the second wing  108 . Slots or openings  142 ,  144  in the proximal faces of the wings  106 ,  108  are provided for the push/pull rods  154 ,  156 . The slots  142 ,  144  are covered by a contoured proximal part  118  of the blade portion  102  so that the interior of the blade portion  102  and the expansion mechanism will not be open to tissue or bodily fluids. Optionally, a contoured distal part  120  of the blade portion  102  may be attached to the second wing  108 . 
         [0042]    As in  FIGS. 10-13 , when the push/pull rods  154 ,  156  are moved to decrease the proximal-to-distal length of the central diamond-shaped units in the scissor mechanisms  150 ,  152 , the lateral width of the scissor mechanisms  150 ,  152  increases, telescopically sliding the wings  106 ,  108  apart to increase the width of the blade portion  102 , as shown in  FIGS. 16 and 17 . When the push/pull rods  154 ,  156  are moved to increase the proximal-to-distal length of the central diamond-shaped units in the scissor mechanisms  150 ,  152 , the lateral width of the scissor mechanisms  150 ,  152  decreases, telescopically sliding the wings  106 ,  108  together to decrease the width of the blade portion  102 , as shown in  FIGS. 14 and 15 . Stops may be provided to prevent the wings  106 ,  108  from overextending. 
         [0043]    The embodiment of the intervertebral shaver  100  shown in  FIGS. 14-17  also utilizes two scissor mechanisms  150 ,  152  to assure stable and parallel motion of the wings  106 ,  108 . The same could also be accomplished using a single, centrally positioned scissor mechanism and a pair of guide rods or tracks to assure stable and parallel motion of the wings  106 ,  108 . 
         [0044]      FIG. 18  is a cut-away side view and  FIG. 19  is a cut-away end view of an adjustable intervertebral shaver  100  with a rack-and-pinion expansion mechanism shown in an unexpanded position.  FIG. 20  is a cut-away side view and  FIG. 21  is a cut-away end view of the adjustable intervertebral shaver of  FIG. 18  in an expanded position. The wings  106 ,  108  are configured for a sliding fit within a central housing  116  of the blade portion  102 . In this embodiment, the wings  106 ,  108  may be hollow or solid, as desired. A rack-type gear  160 ,  162  is attached to each of the wings  106 ,  108 . Each rack gear  160 ,  162  is engaged by a pinion gear  164  on a rotating inner shaft  166 . The inner shaft  166  is connected to the adjustment knob  114  on the handle portion  104  (See  FIG. 1 ). 
         [0045]    When the adjustment knob  114  is rotated in a first direction, the inner shaft  166  rotates the pinion gear  164 , which causes of each of the rack gears  160 ,  162  and therefore the wings  106 ,  108  to move outward to increase the width of the blade portion  102 , as shown in  FIGS. 20 and 21 . When the adjustment knob  114  is rotated in the opposite direction, the inner shaft  166  rotates the pinion gear  164  in the opposite direction, which causes of each of the rack gears  160 ,  162  and therefore the wings  106 ,  108  to move inward to decrease the width of the blade portion  102 , as shown in  FIGS. 18 and 19 . Stops may be provided to prevent the wings  106 ,  108  from overextending and to keep the rack gears  160 ,  162  from becoming disengaged from the pinion gear  164 . 
         [0046]    The embodiment of the intervertebral shaver  100  shown in  FIGS. 18-21  utilizes a very wide rack-and-pinion gearset to assure stable and parallel motion of the wings  106 ,  108 . The same could also be accomplished using a pair of narrower, spaced apart rack-and-pinion gearsets that act in synchrony to assure stable and parallel motion of the wings  106 ,  108 . 
         [0047]      FIG. 22  is a cut-away side view and  FIG. 23  is a cut-away end view of another adjustable intervertebral shaver with a rack-and-pinion expansion mechanism shown in an unexpanded position.  FIG. 24  is a cut-away side view and  FIG. 25  is a cut-away end view of the adjustable intervertebral shaver of  FIG. 22  in an expanded position. The rack-and-pinion expansion mechanism operates similarly to the mechanism described above in connection with  FIGS. 18-21 , however, the blade portion  102  of the intervertebral shaver  100  is configured differently. There is no central housing, instead the first wing  106  is configured to slide telescopically within the second wing  108 . Slots or openings  142 ,  144  in the proximal faces of the wings  106 ,  108  are provided for the inner shaft  166 . The slots  142 ,  144  are covered by a contoured proximal part  118  of the blade portion  102  so that the interior of the blade portion  102  and the expansion mechanism will not be open to tissue or bodily fluids. Optionally, a contoured distal part  120  of the blade portion  102  may be attached to the second wing  108 . 
         [0048]    When the adjustment knob  114  is rotated in a first direction, the inner shaft  166  rotates the pinion gear  164 , which causes of each of the rack gears  160 ,  162  to move outward, telescopically sliding the wings  106 ,  108  apart to increase the width of the blade portion  102 , as shown in  FIGS. 24 and 25 . When the adjustment knob  114  is rotated in the opposite direction, the inner shaft  166  rotates the pinion gear  164  in the opposite direction, which causes of each of the rack gears  160 ,  162  to move inward, telescopically sliding the wings  106 ,  108  together to decrease the width of the blade portion  102 , as shown in  FIGS. 22 and 23 . Stops may be provided to prevent the wings  106 ,  108  from overextending and to keep the rack gears  160 ,  162  from becoming disengaged from the pinion gear  164 . 
         [0049]    The embodiment of the intervertebral shaver  100  shown in  FIGS. 22-25  also utilizes a very wide rack-and-pinion gearset to assure stable and parallel motion of the wings  106 ,  108 . The same could also be accomplished using a pair of narrower, spaced apart rack-and-pinion gearsets that act in synchrony to assure stable and parallel motion of the wings  106 ,  108 . 
         [0050]    In each of the embodiments of the adjustable intervertebral shaver  100  described herein, the various components of the device can be fabricated from metals, such as stainless steel, titanium or cobalt-chromium alloys, or from high-strength polymers or fiber reinforced polymer composites or from a combination of these materials. The adjustable intervertebral shaver  100  may be constructed to be reusable, using materials that will stand up to repeated sterilization and use. Alternatively, the adjustable intervertebral shaver  100  may be constructed for one-time use, using economical materials and construction methods that would allow the device to be disposable. In either case, the device may optionally be packaged sterile and ready for use. 
         [0051]    While the present invention has been described herein with respect to the exemplary embodiments and the best mode for practicing the invention, it will be apparent to one of ordinary skill in the art that many modifications, improvements and subcombinations of the various features and embodiments, adaptations and variations can be made to the invention without departing from the spirit and scope thereof.