Apparatus and method for spinal stabilization

Abstract

A surgical method and apparatus for implanting a spinal fusion implant includes a rigid centering guide having a distal end sized to be inserted into the disc space with the guide extending along a longitudinal axis from a distal end to a proximal end. The guide includes a first external guide surface which extends at least partially between the distal end and the proximal end. The external guide surface is shaped complimentary to an external guided surface of a drill guide. The external guide surface and the guided surface are nested such that the guided surface slides against the external guide surface along a path of travel parallel to the longitudinal axis.

What is claimed is:  
     
         1 . A surgical method for implanting a spinal fusion implant into a disc space separating a first vertebra and a second vertebra, said method comprising: 
 inserting a distal end of a rigid centering guide into said disc space with said guide extending along a longitudinal axis from said distal end to a proximal end exterior of said disc space and with said guide having a first external guide surface of predetermined geometry;    placing an implement against said centering guide with said implement having an external guided surface shaped complementary to said first external guide surface for said first external guide surface and said guided surface to be nested with said guided surface sliding against said first guide surface along a path, of travel parallel to said longitudinal axis;    sliding said implement toward said vertebrae with said first guide surface and said guided surface maintaining movement of said implement along said path of travel.    
     
     
         2 . A method according to  claim 1  comprising selecting said distal end to be sized to distract said disc space upon insertion of said distal end into said disc space and distracting said disc space by insertion of said distal end into said disc space.  
     
     
         3 . A method according to  claim 2  comprising inserting said distal end from an anterior approach and selecting said distal end to have opposite side edges defining an angle approximate to a desired angle of lordosis between said disc space.  
     
     
         4 . A method according to  claim 2  comprising inserting said distal end from a posterior approach and selecting said distal end to have opposite side edges defining an angle approximate to a desired angle of lordosis between said disc space, said distal end inserted by first inserting said distal end into said disc space with said side edges rotated to oppose said disc space and subsequently rotating said distal end within said disc space for said side edges to oppose and distract said vertebra.  
     
     
         5 . A method according to  claim 1  wherein said guide includes said first external guide surface and a second external guide surface, said first and second external guide surfaces positioned on opposite sides of said longitudinal axis with each of said first and second external guide surfaces shaped complementary to said external guided surface of said implement for a selected one of said first and second external guide surfaces to nest with said guided surface for said guided surface to slide against said selected one along said path of travel, and wherein said implement is a drill guide adapted to axially guide a drill, said method further comprising: 
 sliding said drill guide toward said vertebrae against said first guide surface;  
 inserting a drill through said drill guide and boring a first bore;  
 inserting an implant into said first bore;  
 sliding a drill guide toward said vertebrae against said second guide surface;  
 inserting a drill through said drill guide and boring a second bore; and  
 inserting an implant into said second bore.  
 
     
     
         6 . A method according to  claim 1  wherein said guide includes an external second surface on a side of said longitudinal axis opposite said first guide surface, said second surface being convex to present a smooth surface opposing a dura, said method including: 
 retracting a dura before inserting said distal end into said disc space; and  
 placing said distal end into said disc space with said second surface opposing said dura.  
 
     
     
         7 . An apparatus for use in implanting a spinal fusion implant into a disc space separating a first vertebra and a second vertebra, said apparatus comprising: 
 a rigid centering guide having a distal end sized to be inserted into said disc space with said guide extending along a longitudinal axis from said distal end to a proximal end exterior of said disc space;    a first external guide surface extending at least partially between said distal end and said proximal end; and    said external guide surface shaped complementary to an external guided surface of an implement for said first external guide surface and said guided surface to be nested with said guided surface sliding against said first guide surface along a path of travel parallel to said longitudinal axis.    
     
     
         8 . An apparatus according to  claim 7  wherein said distal end is sized to distract said disc space upon insertion of said distal end into said disc space.  
     
     
         9 . An apparatus according to  claim 8  wherein said distal end includes side edges spaced apart by a desired distraction and with said side edges defining an angle approximate to a desired lordosis angle between said first and second vertebrae.  
     
     
         10 . An apparatus according to  claim 9  wherein said angle is selected for an anterior approach with said distal end having a narrowest spacing between said side edges at said distal end.  
     
     
         11 . An apparatus according to  claim 9  wherein said angle is selected for a posterior approach with said distal end having a narrowest spacing between said side edges at a location spaced rearwardly from said distal end.  
     
     
         12 . An apparatus according to  claim 7  wherein said guide includes said first external guide surface and a second external guide surface, said first and second external guide surfaces positioned on opposite sides of said longitudinal axis with each of said first and second external guide surfaces shaped complementary to said external guided surface of said implement for a selected one of said first and second external guide surfaces to nest with said guided surface for said guided surface to slide against said selected one along said path of travel.  
     
     
         13 . An apparatus according to  claim 7  wherein said guide includes an external second surface on a side of said longitudinal axis opposite said first guide surface, said second surface being convex to present a smooth surface opposing a dura.  
     
     
         15 . An apparatus according to  claim 7  wherein said guide includes a plurality of x-ray detectable indicia at a plurality of positions at said distal end.  
     
     
         16 . An apparatus according to  claim 7  wherein said drill guide is cylindrical and said first external guide surface is a convex arc taken in cross-section orthogonal to said longitudinal axis and having a radius of curvature approximate to an external radius of said implement.