Abstract:
A pivoting wedge expandable spinal implant. An upper portion and a lower portion are pivotally connected together. The implant, in a collapsed position, is inserted into a disc space. A driving screw engages and applies a force to a pushing portion, driving the pushing portion toward the implant&#39;s distal end. The pushing portion engages and drives a wedge toward the implant&#39;s distal end. The wedge pivots upward against an inner surface of the lower portion. The wedge continues to pivot along an inner surface of the upper portion, translating the force to the upper portion, pivoting and expanding the upper portion to an expanded position.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    Field of the Invention 
         [0002]    The present invention relates to a spinal implant. More particularly, the invention relates to an expandable spinal implant having a pivoting wedge, configured to expand within a patient&#39;s disc space between two adjacent vertebral bodies, from a collapsed position to an expanded position. 
         [0003]    Description of the Related Art 
         [0004]    Expandable spinal implants are known in the art. Such expandable implants can be configured to have lordotic, tapered configurations to assist in the restoration or enhancement of spinal lordosis. The expandability of such implants allows placement of the implant, while in a collapsed position, through a relatively small opening in a patient&#39;s body, into a corresponding surgically-enhanced disc space between two adjacent vertebral bodies. Thereafter, expansion of the implant within the disc space increases the height between the two adjacent vertebral bodies, assisting in the restoration or enhancement of spinal lordosis. 
         [0005]    The related art expandable implants typically have two components, pivotally held together by a pivot pin. During expansion of the implant to the expanded position, the pin, in some cases, may be incapable of withstanding all of the forces generated between the two components, resulting in damage to, and inoperabilty of, the implant. 
       SUMMARY OF THE INVENTION 
       [0006]    It is an object of the present invention to provide an expandable spinal implant which obviates one or more of the shortcomings of the related art. 
         [0007]    It is another object of the present invention to provide a pivoting wedge expandable spinal implant for insertion into a patient&#39;s disc space between an upper vertebral body and a lower vertebral body. The implant has a proximal end and a distal end defining a mid-longitudinal axis. The implant is expandable between a collapsed position and an expanded position. The implant includes an upper portion. The upper portion has a proximal end and a distal end. The upper portion also has an inner surface and an outer surface. The outer surface is configured to engage a vertebral endplate of the upper vertebral body. The inner surface has an upper ramp surface. 
         [0008]    The implant further includes a lower portion. The lower portion is pivotally engaged with the upper portion, and has a proximal end and a distal end. The proximal end includes a threaded proximal end opening. The lower portion also has an inner surface and an outer surface. The outer surface is configured to engage a vertebral endplate of the lower vertebral body. The inner surface includes a lower ramp surface. The lower ramp surface and the upper ramp surface define an internal pocket therebetween. 
         [0009]    A force application device is configured to be inserted into the proximal end threaded opening. The force application device includes a distal end. 
         [0010]    A pushing portion is defined in the proximal end of the implant. The pushing portion has a proximal end and a distal end. The proximal end of the pushing portion is configured to come into contact with the distal end of the force application device. 
         [0011]    A wedge is defined in the distal end of the implant. The wedge has a proximal end and a distal end. The proximal end of the wedge is configured to be in contact with the distal end of the pushing portion. The distal end of the wedge is configured to be positioned, when the implant is in the collapsed position, within the internal pocket defined by the upper ramp surface and the lower ramp surface. The distal end of the wedge is further configured, when force is applied by the force application device to the pushing portion, forcing the pushing portion to move in the direction of the distal end of the implant, to be moved, by the pushing portion, up along the lower ramp surface and into contact with the upper ramp surface, translating the motion to the upper ramp surface, thereby and moving the upper ramp portion away from the lower ramp portion. The distal end of the wedge further moves up along the upper ramp surface, further expanding the implant until it reaches the expanded position. 
         [0012]    It is a further object of the present invention to provide a method of inserting the expandable spinal implant as described above into a patient&#39;s disc space between an upper vertebral body and a lower vertebral body. 
         [0013]    The method includes surgically preparing a disc space between a lower vertebral body and an upper vertebral body, inserting the implant described above, in the collapsed position, into the disc space, with the force application device applying a force to the pushing portion, thereby pushing the pushing portion toward the distal end of the implant, pushing the wedge toward the distal end of the implant, up the lower ramp surface and into contact with at least a portion of the upper ramp surface, translating the force to the upper ramp surface, moving the upper ramp portion away from the lower ramp portion, pushing the distal end of the wedge up the upper ramp surface, and expanding the implant to the expanded position. 
         [0014]    These and other objects of the present invention will be apparent from review of the following specification and the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]      FIG. 1  is a lower perspective view of a pivoting wedge expandable spinal implant in accordance with the invention; 
           [0016]      FIG. 2  is an upper perspective view of a pivoting wedge expandable spinal implant in accordance with the invention; 
           [0017]      FIG. 3  is an exploded parts view of a pivoting wedge expandable spinal implant in accordance with the invention; 
           [0018]      FIG. 3A  is a perspective view of an upper portion of the pivoting wedge expandable spinal implant in accordance with the invention, flipped over to depict an interior configuration of the upper portion, including an upper ramp portion; 
           [0019]      FIG. 4  is a side view of a pivoting wedge expandable spinal implant in accordance with the invention in the collapsed position; 
           [0020]      FIG. 5  is a side cross-sectional view of a pivoting wedge expandable spinal implant in accordance with the invention in the collapsed position; 
           [0021]      FIG. 6  is a lower perspective view of a pivoting wedge expandable spinal implant in accordance with the invention in the process of expanding to the expanded position; 
           [0022]      FIG. 7  is an upper perspective view of a pivoting wedge expandable spinal implant in accordance with the invention in the process of expanding to the expanded position; 
           [0023]      FIG. 8  is a side view of a pivoting wedge expandable spinal implant in accordance with the invention in the process of expanding to the expanded position; 
           [0024]      FIG. 9  is a side cross-sectional view a pivoting wedge expandable spinal implant in accordance with the invention expanded to the 100% expanded position; 
           [0025]      FIG. 10  is a side cross-sectional view of a pivoting wedge expandable spinal implant in accordance with another embodiment of the invention; 
           [0026]      FIG. 11  is a side cross-sectional view of a pivoting wedge expandable spinal implant in accordance with the invention, expanded to the 20% expanded position; 
           [0027]      FIG. 12  is a side cross-sectional view of a pivoting wedge expandable spinal implant in accordance with the invention, expanded to the 40% expanded position; 
           [0028]      FIG. 13  is a side cross-sectional view of a pivoting wedge expandable spinal implant in accordance with the invention, expanded to the 60% expanded position; 
           [0029]      FIG. 14  is a side cross-sectional view of a pivoting wedge expandable spinal implant in accordance with the invention, expanded to the 80% expanded position; 
           [0030]      FIG. 15  is a lower perspective cross-sectional view of a pivoting wedge expandable spinal implant in accordance with the invention, without a pushing portion, and with a distal end of the force application device configured to contact a proximal end of the wedge, expanded to an 80% expanded position; 
           [0031]      FIG. 16  is a side cross-sectional view of the pivotal wedge expandable spinal implant depicted in  FIG. 15 , in the collapsed position; 
           [0032]      FIG. 17  is a lower perspective cross-sectional view of the pivoting wedge expandable spinal implant depicted in  FIG. 15 , expanded to a 40% expanded position; 
           [0033]      FIG. 18  is an upper perspective view of a threaded force application device; used in the pivotal wedge expandable spinal implant depicted in  FIG. 15 ; and 
           [0034]      FIG. 19  is an upper perspective view of a wedge, used in the pivotal wedge expandable spinal implant depicted in  FIG. 15 . 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0035]    In accordance with the invention, and as depicted in  FIGS. 1-15 , a pivoting wedge expandable spinal implant  10  is provided, configured to be inserted in a surgically-enhanced disc space between an upper vertebral body and a lower vertebral body (not shown). The implant includes a proximal end  12  and a distal end  14 , defining a mid-longitudinal axis L-L therebetween. 
         [0036]    In accordance with the invention, the implant includes an upper portion  16 . The upper portion  16  includes a proximal end  18 , a distal end  20 , an inner surface  22 , and an outer surface  24 . 
         [0037]    In accordance with the invention, and as depicted in  FIG. 2 , the distal end  14  is preferably tapered, for simplicity of access to the disc space. 
         [0038]    The outer surface  24  includes one or more raised ridges  26 , for engaging a vertebral endplate of the upper vertebral body. 
         [0039]    In accordance with the invention, and as depicted in  FIGS. 3, 3A, and 15 , the inner surface  22  defines an upper ramp surface  28 . The upper ramp surface  28  extends from a first position  30  intermediate the proximal end  18  and the distal end  20 , to a second position  32  proximate the distal end  14  of the implant  10 . A first planar surface  34  extends from the second position  32  to the distal end  14  of the implant  10 . The upper ramp surface  28  includes an arcuate portion  36  proximate the second position  32 . The arcuate portion  36  intersects with the first planar surface  34  at a first transition point  40 . The invention is not limited to the configuration of the upper ramp surface  28  described above. Additional configurations for the upper ramp surface  28  are conceivable and within the scope of the invention, including, but not limited to, a substantially planar surface parallel to the longitudinal axis. 
         [0040]    In accordance with a preferred embodiment of the invention, the implant includes a lower portion  46 . The lower portion  46  includes a proximal end  48 , a distal end  50 , an inner surface  52 , and an outer surface  54 . The outer surface  54  includes one or more raised ridges  56 , for engaging a vertebral endplate of the lower vertebral body. The inner surface  52  defines a lower ramp surface  58 . 
         [0041]    In accordance with the invention, and as depicted in  FIGS. 3 and 15 , the lower ramp surface  58  extends from a first position  60  intermediate the proximal end  48  and the distal end  50  to a second position  62  proximate the distal end  14  of the implant  10 . A first planar surface  64  extends from the second position  62  to the distal end  14  of the implant  10 . The lower ramp surface  58  includes an arcuate portion  66  proximate the second position  62 . The arcuate portion  66  intersects with the first planar surface  64  at a second transition point  70 . The lower portion  46  further includes, at the proximal end  48 , a threaded proximal aperture  44 . The invention is not limited to the configuration of the lower ramp surface  58  described above, and depicted in  FIGS. 3, 3A and 15 . Additional configurations for the lower ramp surface  58  are conceivable and within the scope of the invention, including, but not limited to, a substantially planar surface proximate the first position  60 , which ramps upward transverse to the mid-longitudinal axis, defining the ramp surface  58 , to the arcuate position  66  proximate the second position  62 . The lower ramp surface  58  combines with the upper ramp surface  28  to define an internal pocket  74 , internal to the implant  10 . 
         [0042]    In accordance with a preferred embodiment of the invention, and as depicted in  FIG. 4 , the upper portion  16  is pivotally connected to the lower portion  46  via a hinge  76  defined at the proximal end  12  of the implant  10 . 
         [0043]    In accordance with a preferred embodiment of the invention, a force application device  80  is provided. As depicted in  FIGS. 1-8 , force application device  80  is a screw, having a shaft  82 . Shaft  82  includes threads  84 , a T-shaped distal end  86 , and a distal surface  85  that is perpendicular to the mid-longitudinal axis. In the embodiment of  FIG. 5 , distal surface  85  includes a distal thread. The invention, however, is not limited to use of a screw as the force application device  80 , nor is the invention limited to use of a distal thread as the distal surface  85 . 
         [0044]    In accordance with one embodiment of the invention, a pushing portion  90  is defined in the proximal end  12  of the implant  10 . As depicted in  FIGS. 5-9 , pushing portion  90  includes a proximal end pocket  92 . The proximal end pocket  92  includes an opening  94  defined in the proximal end of the proximal end pocket  92 . A vertical wall  96  is defined on the pushing portion  90  adjacent the proximal end pocket  92 . The pushing portion  90  further includes a hook-shaped projection  98 . As depicted in  FIG. 5 , when the implant  10  is in the collapsed position, the hook-shaped projection  98  engages a locking portion  95  on the upper portion  16  to hold the implant  10  in the collapsed position. As depicted in  FIG. 8 , however, when the implant  10  is being moved to the expanded position, the force application device is moved through the proximal aperture  44 . The hook-shaped projection  98  is pushed away from the locking portion  95  to allow the implant  10  to expand. The T-shaped distal end  86  of the force application device  80  is configured to insert through the opening  94 , and move into the proximal end pocket  92  of the pushing portion  90 , where it is held in place via a pin  93 . The distal surface  85  comes into contact with the vertical wall  96  adjacent the proximal end pocket  92 , moving the pushing portion  90  towards the distal end  14  of the implant  10 . The motion is then translated by the pushing portion  90 , moving the pushing portion  90  toward the distal end  14  of the implant  10 . 
         [0045]    In accordance with another preferred embodiment of the invention, as depicted in  FIG. 8 , the pushing portion  90  also includes a distal end pocket  99 . 
         [0046]    In accordance with a preferred embodiment of the invention, a wedge  100  is provided proximate the distal end  14  of the implant  10 . The wedge  100  includes a proximal end  102  and an arcuate distal end  104 . The proximal end  102  of the wedge  100  is connected to the pushing portion  90 . In one embodiment of the invention, as depicted in  FIG. 5 , the proximal end  102  of the wedge  100  is attached to the pushing portion  90  with a pin  108 . As depicted in  FIG. 8 , the proximal end  102  of the wedge  100  also can be configured to be engaged to the pushing portion  90  by contact with the distal end pocket  99 . 
         [0047]    In accordance with another embodiment of the invention, the outer surface  24  of the upper portion  16 , and the outer surface  54  of the lower portion  46  are each configured with upper and lower apertures  110 ,  112 , respectively. The upper and lower apertures  110  and  112  provide openings to the internal pocket  74 . In addition, the sides of the implant  10  in this embodiment define side apertures  114 . In this embodiment of the invention, after the implant  10  is in place in the disc space, bone-growth material packed into the internal pocket  74  of the implant  10  can grow through the respective openings  110 ,  112 , and  114 . Suitable bone graft material is well-known in the art. In particular, the side apertures  114  allow the implant  10  to be packed with bone graft material after the implant  10  has been inserted into the disc space. 
         [0048]    In accordance with a preferred embodiment of the invention, the implant  10  is configured, such that, commencing in the collapsed position, as depicted in  FIG. 5 , upon translation of the motion from the force application device  80  to the pushing portion  90 , subsequent distal motion of the pushing portion  90  is translated to the proximal end  102  of the wedge  100 . As depicted in  FIG. 11 , the arcuate distal end  104  of the wedge  100  moves out of the internal pocket  74 , and moves up along the arcuate portion  66  of the lower ramp surface  58  towards the second transition point  70 . At this point, as depicted in  FIG. 11 , the implant  10  is approximately 20% open. As depicted in  FIGS. 11 and 12 , the wedge  100  moves past the first transition point  40  of the upper ramp surface  28 . As depicted in  FIG. 12 , the implant is approximately 40% open. Subsequently, as depicted in  FIGS. 13 and 14 , the external radius  106  of the arcuate distal end  104 , moves along the internal upper ramp surface  28 . In this manner, the force applied to the pushing portion  90  by the force application device  80  is translated into movement of the upper portion  16 , thereby pivoting the upper portion  16  on hinge  76 , and moving the upper portion  16  away from, the lower portion  46 . As depicted in  FIG. 13 , the implant  10  is approximately 60% open. As depicted in  FIG. 14 , the implant  10  is approximately 80% open. Movement of the upper portion  16  will continue until the implant  10  achieves the expanded position (i.e., approximately 100% expanded, as depicted in  FIG. 9 ). 
         [0049]    In accordance with another embodiment of the invention, as depicted in  FIG. 10 , the implant  10  may include an arcuate posterior ramp portion  116  defined on the pushing portion  90 . As depicted in  FIG. 10 , the proximal end  18  of the upper portion  16  includes an arcuate portion  118 . The arcuate posterior ramp portion  116  has a radius which is larger than a radius of the arcuate posterior ramp portion  118 . Alternatively, the posterior ramp portions may have straight inclines, or multiple curves. Interaction between these two arcuate components further moves the upper portion  16  of the implant  10  away from the lower portion  46  of the implant  10 . 
         [0050]    In accordance with another embodiment of the invention, as depicted in  FIG. 10 , the distal end  14  of the implant  10  may include distal end projecting pins  120  projecting from the upper portion  16  and the lower portion  46 . An elastic member  122  may be wrapped around the distal end projecting pins  120 . Upon translation of the force application device from the distal end of the implant, the elastic member  122  assists pulling the upper portion  16  and the lower portion  46  back together in the collapsed position. 
         [0051]    In accordance with a preferred embodiment of the invention, a disc space of a patient between an upper vertebral body and a lower vertebral body is surgically prepared. An implant  10 , having the configuration of the invention as described above, is inserted into the disc space, either via a posterior approach, or via a lateral approach. The implant  10  is inserted into the disc space in the collapsed position. The ridges  26  on the outer surface  24  of the upper portion  16  engage a vertebral endplate of the upper vertebral body. Likewise, the ridges  56  on the outer surface  54  of the lower portion  46  engage a vertebral endplate of the lower vertebral body. As depicted in  FIG. 5 , the hook-shaped projection  98  on the pushing portion  90  is engaged with the locking portion  95  of the upper portion  16 , assisting in holding the upper portion  16  in place over the lower portion  46 , assisting in keeping the implant  10  in the collapsed position. 
         [0052]    In accordance with a preferred embodiment of the invention, the force application device  80 , preferably in the form of a threaded screw, is moved in the threaded proximal aperture  44  toward the distal end  20  of the implant  10 . The T-shaped distal end  86  is held in place in the proximal end pocket  92  by the pin  93 . The distal surface  85  contacts the vertical wall  96  adjacent the proximal end pocket  92 , translating motion of the force application device  80  to the pushing portion  90 . The pushing portion  90  moves toward the distal end  14  of the implant  10 . This motion causes the hook-shaped projection  98  to be disengaged from the locking portion  95  on the upper portion  16 . 
         [0053]    In accordance with a preferred embodiment of the invention, and as depicted in  FIGS. 5-7 , the motion of the pushing portion  90  is subsequently translated to the proximal end  12  of the wedge  100 . The wedge  100  moves toward the distal end  14  of the implant  10 , while the pin  108  may or may not remain unloaded. The arcuate distal end  104  of the wedge  100  is pushed out of the internal pocket  74 , and up the lower ramp surface  58 , past the second transition point  70 , and into contact with the first transition point  40  on the upper portion  16 . Motion translated to the upper portion  16 , causes the upper portion  16  to rotate upward on hinge  76 , away from lower portion  46 . 
         [0054]    In accordance with a preferred embodiment of the invention, as the upper portion  16  commences to move the arcuate distal end  104  of the wedge  100  moves along the upper ramp surface  28 , moving the upper portion away from the lower portion. The arcuate distal end  104  of the wedge  100  continues to move up the upper ramp surface  28  until the implant  10  has reached the expanded position. 
         [0055]    In accordance with the invention, in the process of being expanded from the collapsed position to the expanded position, the wedge  100  both pivots and engages two ramps, while the pin  108  may or may not remain unloaded. The internal pocket  74  between the upper ramp surface  28  and the lower ramp surface  58  carries the majority of all of the force between the pushing portion  90  and the components of the wedge  100 . The resulting degree of expansion in the expanded position of the implant  10  is significantly increased when compared to a non-pivoting wedge. The increased degree of expansion of the implant  10  in the expended position results in an increased angle between the lower portion  46  and the upper portion  16 . This increased angle results in increased lordosis between the upper and lower vertebral bodies. 
         [0056]    In accordance with another preferred embodiment of the invention, as depicted in  FIGS. 17-19 , the implant  10  does not include a pushing portion  90 . In this embodiment, a stem  112  of the T-shaped distal end  86  of the force application device  80  fits into a notch  124  defined in the proximal end  102  of the wedge  100 . With this configuration the force application device  80  is positioned to translate motion directly to the proximal end  102  of the wedge  100 . Rotation of the threaded force application device  80  in the threaded proximal aperture  44  moves the force application device  80  toward the distal end  14  of the implant  10 . Contact between the distal surface  85  of the force application device  80  with the distal end  102  of the wedge  100  translates the motion of the force application device  80  directly to the wedge  100 , thereby moving the wedge  100  toward the distal end  14  of the implant  10 . The wedge  100  is moved along the lower ramp surface  58  into contact with the upper ramp surface  28 . The wedge  100  moves along the upper ramp surface  28 , rotating the upper ramp surface  28 , on the hinge  76 , away from the lower ramp surface  58 , until the implant  10  reaches the expanded position. 
         [0057]    Other embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. For example, and not by way of limitation, a modular upper portion  16  can be removed, e.g., by disconnecting the modular upper portion  16  from the lower portion  46  at the hinge  76 , and replacing the removed modular upper portion with another modular upper portion  16 , which may have different dimensions, in addition, all of the components described above as being associated with the upper portion, and all of the components described above as being associated with the lower portion can be switched, i.e., the upper and lower portions can be entirely reversed in orientation, and the resultant implant would still fall within the spirit and scope of the present invention. The specification and examples are to be considered as exemplary only, with a true scope and spirit of the invention being indicated by the following claims.