Patent Publication Number: US-11638650-B2

Title: Standalone anterior cervical interbody spacer

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application No. 62/905,381 filed Sep. 24, 2019, which is incorporated herein by reference. 
    
    
     FIELD 
     The present invention relates generally to the field of surgery, and more specifically, to an anterior cervical interbody spacer for placement in intervertebral space between adjacent vertebrae during anterior cervical spinal fixation. 
     BACKGROUND 
     A spinal disc can become damaged as a result of degeneration, dysfunction, disease and/or trauma. Conservative treatment can include non-operative treatment through exercise and/or pain relievers to deal with the pain. Operative treatment options include disc removal and replacement using an interbody spacers such as anterior cervical interbody fusion (ACIF), anterior lumbar interbody fusion (ALIF), direct lateral interbody fusion (DLIF) (also known as XLIF), posterior lumbar interbody fusion (PLIF), and transforaminal lumbar interbody fusion (TLIF). 
     The spacers are placed in the interdiscal space between adjacent vertebrae of the spine, resulting in spinal fusion of the adjacent vertebra wherein two or more vertebrae are joined together (fused) by way of interbody spacers, sometimes with bone grafting, to form a single bone. The current standard of care for interbody fusion requires surgical removal of all or a portion of the intervertebral disc. After removal of the intervertebral disc, the interbody spacer is inserted in the space between the adjacent vertebrae. 
     Ideally, the interbody spacer should stabilize the intervertebral space and allow fusion of the adjacent vertebrae. Moreover, during the time it takes for fusion to occur, the interbody spacer body should have sufficient structural integrity to withstand the stress of maintaining the space without substantially degrading or deforming and have sufficient stability to remain securely in place prior to actual bone ingrowth fusion. 
     The interbody spacers are typically one piece that are assembled at the manufacturing stage. Many different sizes are made, which results in a large inventory of plate/spacer body combinations, as well as large sterilization/shipping caddies to facilitate transfer of spacers large interbody spacers. In addition, typical interbody spacers require a secondary element to install the plate in-situ to inhibit fixation screw migration. This secondary action is time consuming and cumbersome when the surgical procedure is time sensitive. 
     Some prior art designs utilized titanium arms for distraction, this places a large amount of force on the PEEK spacer body, potentially damaging the spacer during assembly. This increased distraction force requires a large assembly tool to overcome the titanium arms and makes disassembly difficult. 
     It would be desirable to provide an interbody spacer with modularity and functionality to decreased inventory size. 
     SUMMARY 
     Disclosed is a standalone anterior cervical interbody spacer that includes a spacer body and cervical plate with a unique locking system rigidly couple the spacer body and cervical plate via two flexible locking pins. 
     The locking system include locking features designed to engage with one or more flexible locking pins to lock the spacer body and cervical plate together. The locking features are part of the engagement arm or engagement protrusion with a locking pin engagement surface having distraction geometry and lock geometry. The distraction geometry includes an inclined or ramped portion and the lock geometry includes a pin engagement recess or pocket. The distraction geometry is such that as the spacer body and cervical plate are coupled, the inclined or ramped portion will engage and force the flexible pin to deform and slide on the surface. Once the cervical plate and spacer body are completely joined, the flexible pin reaches the lock geometry recess or pocket, allowing the flexible pin to return to its original form in the recess or pocket, thereby locking the spacer body and cervical plate. The pin engaging the recess may provide an audible click sound the let the user know that the parts are joined and locked together. 
     In some embodiments the flexible locking pins are positioned within the spacer body. 
     In some embodiments the flexible locking pins are positioned within the cervical plate. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    shows various configurations or variations of a modular cervical interbody spacer having a cervical spacer body coupled with different cervical plates. 
         FIG.  2    shows various configurations or variations of a cervical interbody spacer with different cervical spacer body footprints or configurations coupled with a cervical plate. 
         FIG.  3    shows an exploded perspective view showing one embodiment of a cervical interbody spacer 
         FIG.  4    shows a proximal view of the spacer body showing locking geometry 
         FIG.  5    shows a sectional view at A-A of the spacer body shown in  FIG.  4   . 
         FIG.  6    shows a top view of the cervical plate. 
         FIG.  7    shows a proximal view of the spacer body 
         FIG.  8    shows a side view of the spacer body. 
         FIG.  9    shows a perspective view of spacer body that is shown as transparent. 
         FIG.  10    shows a perspective view of the cervical plate. 
         FIG.  11    shows a top view of the cervical plate. 
         FIG.  12    shows an exploded perspective view showing another embodiment of a cervical interbody spacer 
         FIG.  13    shows a proximal view of the cervical plate. 
         FIG.  14    shows a sectional view at B-B of the cervical plate shown in  FIG.  13   . 
         FIG.  15    shows a top view of the spacer body. 
         FIG.  16    shows a perspective view of cervical plate that is shown as transparent. 
         FIG.  17    shows a perspective view of the spacer body and cervical plate, shown as transparent. 
         FIG.  18    shows a top view of the spacer body and cervical plate, shown as transparent. 
         FIG.  19    shows a side view of the spacer body and cervical plate, shown as transparent. 
     
    
    
     DETAILED DESCRIPTION 
     The invention is direct to an anterior cervical interbody spacer that is a modular two piece design comprising a cervical spacer body and cervical plate that are designed to lock together via two flexible locking pins. With this design, each of the components are provided in various sizes and configurations so that the surgeon can pick or choose the desired spacer body configuration and size. The surgeon can then select the desired cervical plate configuration and join the two together. The spacer body and cervical plate have engagement features that are configured to rigidly couple them together via the flexible locking pins to form the cervical interbody spacer. 
       FIG.  1    shows three configurations or variations of a modular cervical interbody spacer  100  comprising a cervical spacer body  102  coupled with three different cervical plate configurations or profile options: Zero  104   a , Half  104   b , Full  104   c.    
       FIG.  2    shows three configurations or variations of a cervical interbody spacer comprising a three different cervical spacer body footprints or configurations coupled with a cervical plate. The spacer body configurations may include various footprints having different widths W, depths D, heights and sagittal profiles. For example, spacer body  102   a  may be 14×12 mm,  102   b  may be 16×14 mm, and  102   c  may be 18×15 mm, the heights of the spacer body may include seven heights from 5 mm-12 mm @1 mm increments, and two sagittal profiles, 7°, 10°. 
     1 st  Embodiment—Flexible Locking Pins Positioned in the Spacer Body 
       FIG.  3    is an exploded perspective view showing one embodiment of a cervical interbody spacer  100  comprising a spacer body  102  and a cervical plate  104  having coupling features to rigidly affixed the spacer body  102  to the cervical plate  104 . 
     The spacer body  102  is u-shape having a closed distal end  106  and open proximal ends  108   a ,  108   b  connected by lateral sides  110 ,  112  with a central opening  114 . The spacer body further includes an upper surface  118  and lower surface  120 . The upper and lower surfaces  118 ,  120  may include teeth  122 . The proximal end  108   a ,  108   b  of the spacer body  102  includes one or more bores or slots  144  and one or more slots  146  in the proximal portion of the right and left sides  130 ,  132 . The spacer body  102  may also include a marker pin  124  for locating the spacer  100  on x-ray. The cervical plate is made of PEEK or titanium (TI). 
     The cervical plate  104  includes a proximal end  126 , a distal end  128  and right and left sides  130 ,  132 . The cervical plate further includes an upper surface  134  and lower surface  136 . The upper and lower surfaces  134 ,  136  may include teeth  138 . The distal end  128  includes one or more protrusions  140  configured to engage and to slide into the one or more bores or slots  144  and engagement arms  142  configured to engage and to slide into the one or more slots  146 . The cervical plate is made of a rigid material, such as titanium (TI). The engagement arms  142  are design not to flex. 
       FIG.  4    is a proximal view of the spacer body  102  showing locking geometry, including the one or more bores or slots  144  and the one or more slots  146  in the proximal portion of the right and left sides  130 ,  132 . 
       FIG.  5    is a sectional view at A-A of the spacer body  102  showing flexible locking pins  148  positioned in the slots  146 . There are also pin distraction pockets  150  proximate the flexible locking pins  148  that are sized for the pin  148  to flex into during insertion of the engagement arms  142  of the cervical plate  104 . 
       FIG.  6    is a top view of the cervical plate  104  showing the one or more protrusions  140  and engagement arms  142  configured to slide into the one or more bores or slots  144  and one or more slots  146  during joining of the spacer body  102  and cervical plate  104 . The engagement arms  142  having features designed to engage with the flexible locking pins  148  to lock the spacer body  102  and cervical plate  104  together. The engagement arms  142  features may include distraction geometry  152  and lock geometry  154 . The distraction geometry  152  includes an inclined or ramped portion  156  and the lock geometry  154  includes a pin engagement recess or pocket  158 . The distraction geometry  152  is such that as the engagement arms  142  are slid into the slots  146 , the inclined or ramped portions  156  engage flexible locking pins  148 . Since the engagement arms  142  do not flex, the engagement forces the flexible locking pins  148  to deform or flex into the pin distraction pockets  150 . Once the cervical plate  102  and spacer body  104  are completely joined, the flexible locking pins  148  reach the lock geometry recess or pockets  158 , allowing the flexible locking pins  148  to return to their original form in the slot  146 , thereby locking the spacer body  102  and cervical plate  104 . The flexible locking pins  148  engaging the recess may provide an audible click sound the let the user know that the parts are joined and locked together. 
       FIG.  7    is a proximal view and  FIG.  8    is a side view of the spacer body  102  showing the one or more bores or slots  144  and slots  146  and flexible locking pins  148 . 
       FIG.  9    is a perspective view of spacer body  102  that is shown as transparent showing the locations of the locking pins  148 . The flexible locking pins  148  are press-fit into holes  149  of the spacer body  102 . 
       FIG.  10    is a perspective view and  FIG.  11    is a top view of the cervical plate  140  and flexible locking pins  148  in the locked position. The flexible locking pins  148  are positioned within the recess or pocket  158  of the engagement arms  142 . 
     In some embodiments, the spacer  100  will utilize a PEEK or titanium (TI) spacer body  102  in conjunction with a TI cervical plate  104  that can be assembled on the back table in the operating room. The cervical plate  104  will be rigidly affixed to the spacer body  102  via two flexible locking pins  148  press fit into the PEEK or TI spacer body and distraction/lock geometry present on the plate engagement arms  142 . 
     While assembling the cervical plate  104  to the spacer body  102  the geometry of the cervical plate  104  is such that it will force the flexible locking pins  148  to deform into a relief pocket  150  present on the spacer body  102 . Once the cervical plate  104  has been sufficiently inserted into the spacer body  102  the lock geometry on the cervical plate  104  will allow for the flexible locking pins  148  to return to its original form, thereby rigidly locking the cervical plate  104  to the spacer body  102 . 
     The locking features of the present invention only requires relatively small amounts of assembly force due to the elasticity of the flexible locking pins, in addition, the flexible locking pins can be easily distracted utilizing a secondary instrument, allowing for simple and fast spacer disassembly. 
     2 nd  Embodiment—Flexible Locking Pins Positioned in the Cervical Plate 
       FIG.  12    is an exploded perspective view showing another embodiment cervical interbody spacer  200  comprising a spacer body  202  and a cervical plate  204  having coupling features to rigidly affixed the spacer body  202  to the cervical plate  204 . The spacer body  202  and cervical plate  204  are similar to spacer  102  and cervical plate  104  discussed above, but the spacer body  202  includes attachment arms and the flexible locking pins are located in the cervical plate  204 . 
     The spacer body  202  is u-shape having a closed distal end  206  and open proximal ends  208   a ,  208   b  connected by lateral sides  210 ,  212  with a central opening  214 . The spacer body further includes an upper surface  218  and lower surface  220 . The upper and lower surfaces  218 ,  220  may include teeth  222 . The proximal end  208   a ,  208   b  of the spacer body  202  includes engagement arms  242  configured to engage and lock the spacer body  202  to the cervical plate  204  and side slots  246  (discussed below). The spacer body  202  may also include a marker or locating pin  224  for locating the spacer  200  on x-ray. 
     The cervical plate  204  includes a proximal end  226 , a distal end  228  and right and left sides  230 ,  232 . The cervical plate further includes an upper surface  234  and lower surface  236 . The upper and lower surfaces  234 ,  236  may include teeth  238 . The distal end  228  includes one or more alignment tabs  240  configured to couple with the slots  246 . 
       FIG.  13    is a proximal view and  FIG.  14    is a sectional view at B-B of the cervical plate  204  showing the flexible locking pins  248  positioned in the slots  246 . There are also pin distraction pockets  250  proximate the flexible locking pins  248  that are sized for the pin  248  to flex into during insertion of the engagement arms  242  of the spacer body  202 . 
       FIG.  15    is a top view of the spacer body  202  showing the engagement arms  242  having features designed to engage with the flexible locking pins  248  to lock the spacer body and cervical plate together. The engagement arms  242  features may include distraction geometry  252  and lock geometry  254 . The distraction geometry includes an inclined or ramped portion  256  and the lock geometry includes a pin engagement recess or pocket  258 . The distraction geometry  252  is such that as the engagement arms  242  are slid into the slots  246 , the inclined or ramped portion  256  engages and forces the flexible pin  248  to deform or flex into the pin distraction pockets  258 . Once the cervical plate and spacer body are completely joined, the flexible pin  248  reaches the lock geometry recess or pocket  258 , allowing the flexible pin  248  to return to its original form in the slot  246 , thereby locking the spacer body and cervical plate. The flexible locking pins  248  engaging the recess may provide an audible click sound the let the user know that the parts are joined and locked together. 
       FIG.  16    is a perspective view of cervical plate  204  that is shown as transparent showing the locations of the flexible locking pins  248 . The flexible locking pins  248  are inserted into holes  249  of the cervical plate  204 . 
       FIG.  17    is a perspective view,  FIG.  18    is a top view and  FIG.  19    is a side view of the spacer body  202  and cervical plate  204 , shown as transparent, showing the locking features. The flexible locking pins  248  are positioned within the recess or pocket  258  of the engagement arms  242 . 
     In some embodiments, the spacer  200  will utilize PEEK or TI spacer body  202  in conjunction with a TI cervical plate  204  that will be assembled on the back table in the OR. The cervical plate  204  will be rigidly affixed to the spacer body  202  via two flexible locking pins  248  slip fit into holes  249  in the TI cervical plate  204  and swaged to retain. The spacer body  202  contains distraction/lock geometry for the flexible locking pins  248 . 
     While assembling the cervical plate  204  to the spacer body  202  the geometry of the spacer body  202  is such that it will force the flexible locking pins  248  to deform into a relief pocket  250  present on the cervical plate  204 . Once the cervical plate  204  has been sufficiently inserted into the spacer body  202  the lock geometry on the spacer body  202  will allow for the flexible locking pins  248  to return to its original form, thereby locking the cervical plate  204  to the spacer body  202 . 
     As described above, the locking features of the spacer are designed to engage with one or more flexible locking pins to lock the spacer body and cervical plate together. The locking features are part of the engagement arm or engagement protrusion with a locking pin engagement surface having distraction geometry and lock geometry. The distraction geometry includes an inclined or ramped portion and the lock geometry includes a pin engagement recess or pocket. The distraction geometry of the locking pin engagement surface is such that as the spacer body and cervical plate are coupled, the inclined or ramped portion will engage and force the flexible pin to deform and slide on the surface. Once the cervical plate and spacer body are completely joined, the flexible pin reaches the lock geometry recess or pocket, allowing the flexible locking pins to return to its original form in the recess or pocket, thereby locking the spacer body and cervical plate. The flexible pin engaging the recess may provide an audible click sound the let the user know that the parts are joined and locked together. 
     Referring back to  FIG.  1   , the cervical plate  104 ,  204  includes two more fastener holes sized to receive bone engagement fasteners (not shown) configured to anchor the spacer  100  between two vertebrae of the spine. The cervical plates may also include a bone fastener locking feature to prevent the bone fastener from withdrawing from the fastener holes. 
     Cervical plate  104   a  includes two fastener holes, one fastener hole is tilted at an upward angle so that the engagement fastener engages the vertebra above the spacer and the other fastener hole is tilted at a downward angle so that the bone engagement fastener engages the vertebra below the spacer. Cervical plate  104   b  includes three fastener holes, a center fastener hole tilted at a downward angle so that the bone engagement fastener engages the vertebra below the spacer and two outer holes are tilted at an upward angle so that the engagement fasteners engage the vertebra above the spacer. Cervical plate  104   c  includes four fastener holes, an upper pair of fastener holes tilted at an upward angle so that the engagement fasteners engage the vertebra above the spacer and a lower pair of fastener holes tilted at a downward angle so that the bone engagement fasteners engage the vertebra below the spacer. 
     Example embodiments of the methods and systems of the present invention have been described herein. As noted elsewhere, these example embodiments have been described for illustrative purposes only and are not limiting. Other embodiments are possible and are covered by the invention. Such embodiments will be apparent to persons skilled in the relevant art(s) based on the teachings contained herein. Thus, the breadth and scope of the present invention should not be limited by any of the above-described exemplary embodiments but should be defined only in accordance with the following claims and their equivalents.