Spinal fusion implant

Abstract

The present invention relates to spacers that are configured to promote fusion. Windows or openings in the sidewalls of the fusion spacers may be provided to allow a physician to view the treated area to confirm that fusion has occurred or to check on the progress of treatment. Fusion spacers of the invention may have two or more pairs of openings or windows that allow viewing of the treated area from different perspectives.

1 . An intervertebral fusion cage for implantation in a treated area of an intervertebral space between vertebral bodies of a spine, wherein said fusion cage comprises: 
 a spacer body comprising an inferior surface and a superior surface, 
 wherein the inferior and superior surfaces each have a contact area capable of engaging with anatomy in the treated area, and  
 wherein said inferior and superior surfaces define a through-hole extending through the spacer body;  
   a sidewall disposed between the inferior surface and the superior surface of the spacer body, wherein the sidewall defines at least a portion of an outer perimeter of the spacer;    a first window having a first area formed in said sidewall, 
 wherein the first window extends from a first side of said spacer body to a second side along a first window axis, thereby forming a second window having a second area in the second side,  
 wherein the first and second windows are capable of permitting confirmation that the vertebral bodies in the treated area are fusing together, and  
 wherein when viewing the spacer body along the first window axis the first window area is about 20 percent or more of the visible area of the first side when viewed from the first window axis;  
   a leading edge for insertion of the spacer into the treated area, wherein the leading edge is substantially free of protrusions, and    wherein the spacer body has a leading end that is inserted first into the treated area, said leading end having a leading end profile;    wherein the superior surface further comprises a first channel formed therein;    wherein the inferior surface further comprises a second channel formed therein; and    wherein said first and second channels are capable of receiving instrumentation for positioning the spacer in the treated area without increasing the leading end profile.    
   
   
       2 . The intervertebral fusion cage of  claim 1 , wherein said first window axis extends laterally through said body.  
   
   
       3 . The intervertebral fusion cage of  claim 1 , wherein the outer perimeter of said fusion cage is generally tear-drop shaped.  
   
   
       4 . The intervertebral fusion cage of  claim 1 , wherein the outer perimeter of said fusion cage is generally trapezoidal in shape.  
   
   
       5 . The intervertebral fusion cage of  claim 1  further comprising: 
 a third window having a third area formed in the spacer body, 
 wherein the third window extends from a third side of the spacer body to a fourth side along a second window axis, thereby forming a fourth window in the fourth side,  
 wherein the third and fourth windows are capable of permitting confirmation that the vertebral bodies in the treated area are fusing together.  
   
   
   
       6 . The intervertebral fusion cage of  claim 5 , wherein when viewing the spacer body along the second window axis the third window area is about 20 percent or more of the visible area of the third side when viewed from the second window axis.  
   
   
       7 . An intervertebral fusion cage for implantation in a treated area of an intervertebral space between vertebral bodies of a spine, wherein said fusion cage comprises: 
 a spacer body comprising an inferior surface and a superior surface, 
 wherein the inferior and superior surfaces each have a contact area capable of engaging with anatomy in the treated area, and  
 wherein said inferior and superior surfaces define a through-hole extending through the spacer body;  
   a sidewall disposed between the inferior surface and the inferior surface of the spacer body, wherein the sidewall defines at least a portion of an outer perimeter of the spacer;    a first window having a first area formed in said sidewall, 
 wherein the first window extends from a first side of said spacer body to a second side along a first window axis, thereby forming a second window having a second area in the second side,  
 wherein the first and second windows are capable of permitting confirmation that the vertebral bodies in the treated area are fusing together, and  
 wherein when viewing the spacer body along the first window axis the first window has a width of about  6  mm or more when viewed from the first window axis;  
   a leading edge for insertion of the spacer into the treated area, wherein the leading edge is substantially free of protrusions.    
   
   
       8 . The intervertebral fusion cage of  claim 7 , wherein said first window axis extends approximately in an anterior-posterior direction.  
   
   
       9 . The intervertebral fusion cage of  claim 7 , further comprising a second leading edge that is substantially free of protrusions.  
   
   
       10 . The intervertebral fusion cage of  claim 7 , wherein the outer perimeter of said fusion cage is generally arch shaped.