Tapered bone fusion cages or blocks, implantation means and method

Abstract

Methods for fusion inside a forward widely tapering human disc space. A stabilizing/guiding system is driven into and against the disc space. The device is further stabilized by spreading and gripping means inside both vertebral end plates. Rod retaining members hold calibrated rod units whose adapted tips perform reaming and threading of the disc space. Subsequently, the tapered cage or implant can be inserted by a free-hand method under direct vision into the prepared and tapered bed. Rod unit divergent angulation is set to match that of the disc space as well as the implants so they obtain optimal distributed purchase of vertebral bone. In one embodiment, inserts are confluent with parallel medial walls rather than their long axes, increasing torsional or lateral translational stability and simplifying placement of additional bone chips. No tubular guide means are required.

1 . A method of implanting a pair of fusion cages or similar fusion-inducing devices in a spinal disc space, the method comprising:
 providing an implantation system including a guide body and first and second rod retaining members positioned at opposite sides of the guide body, respectively;   securing a distal end of the guide body to the disc space;   preparing a first intradiscal bed in the disc space via at least one rod unit selectively maintained by the first rod retaining member;   preparing a second intradiscal bed in the disc space via at least one rod unit selectively maintained by the second rod retaining member;   inserting a first fusion-inducing device into the first intradiscal bed; and   inserting a second fusion-inducing device into the second intradiscal bed;   wherein the implantation system is configured to form the intradiscal beds such that upon insertion, the first and second fusion-inducing devices are angularly oriented relative to one another in that corresponding distal ends of the inserted devices are more closely spaced as compared to corresponding proximal ends.   
     
     
         2 . The method of  claim 1 , wherein the method is performed on an L5-S1 disc space. 
     
     
         3 . The method of  claim 1 , wherein the fusion-inducing devices are tapered fusion cages. 
     
     
         4 . The method of  claim 3 , wherein an angle of the intradiscal beds relative to a centerline of the disc space approximates a taper of the fusion cages. 
     
     
         5 . The method of  claim 1 , wherein preparing a first intradiscal bed includes manipulating the first rod retaining member to orient a guide axis defined by the first rod retaining member to a desired position relative to a central axis defined by the guide body. 
     
     
         6 . The method of  claim 1 , wherein inserting a first fusion-inducing device includes free hand implantation of the first fusion-inducing device. 
     
     
         7 . The method of  claim 1 , wherein the steps of preparing first and second intradiscal beds occur while the distal end of the guide body is secured to the disc space. 
     
     
         8 . The method of  claim 1 , wherein preparing a first intradiscal bed includes:
 assembling a first rod unit including an elongate rod and a distal reaming member to the first rod retaining member such that the rod extends along a guide axis defined by the first rod retaining member;   manipulating the first rod unit along the guide axis such that the reaming member reams a passage into the disc space;   removing the first rod unit from the first rod retaining member;   assembling a second rod unit including an elongate rod and a distal working member differing from the distal reaming member to the first rod retaining member such that the rod of the second rod unit extends along the guide axis; and   manipulating the second rod unit along the guide axis such that the distal working member modifies the passage.   
     
     
         9 . The method of  claim 8 , wherein the distal working member forms a threaded surface and manipulating the second rod unit includes tapping a surface of the passage. 
     
     
         10 . The method of  claim 8 , wherein preparing a second intradiscal bed includes:
 assembling a third rod unit including an elongate rod and a distal reaming member to the second rod retaining member such that the rod of the third rod unit extends along a guide axis defined by the second rod retaining member;   manipulating the third rod unit along the guide axis of the second rod retaining member to ream a second passage into the disc space;   removing the third rod unit from the second rod retaining member;   assembling a fourth rod unit including an elongate rod and a distal working member to the second rod retaining member such that the rod of the fourth rod unit extends along the guide axis of the second rod retaining member; and   manipulating the fourth rod unit along the guide axis of the second rod retaining member such to modify the second passage.   
     
     
         11 . The method of  claim 1 , wherein the first and second rod retaining members each form a guide axis, and further wherein the guide axis intersect a central axis of the guide body distal the distal end of the guide body. 
     
     
         12 . The method of  claim 1 , wherein the distal end of the guide body includes an expandable tip expandable from the first state to a second state, and further wherein securing a distal end of the guide body to the disc space includes:
 inserting the expandable tip in the first state into the disc space; and   expanding the expandable tip toward the second state to rigidly mount the guide body to the disc space.   
     
     
         13 . The method of  claim 12 , wherein the expandable tip includes opposing, first and second tip bodies pivotably connected to the guide body and each defining an engagement surface, and further wherein expanding the expandable tip includes:
 pivoting the first tip body relative to the guide body such that the engagement surface of the first tip body is forced into a superior end plate of the disc space; and   pivoting the second tip body relative to the guide body such that the engagement surface of the second tip body is forced into an inferior end plate of the disc space.   
     
     
         14 . The method of  claim 13 , wherein the steps of pivoting the first and second tip bodies occurs simultaneously. 
     
     
         15 . The method of  claim 14 , wherein the steps of pivoting the first and second tip bodies includes proximally retracting a wedge between the tip bodies. 
     
     
         16 . The method of  claim 12 , wherein expansion of the tip from the first state toward the second state occurs in a plane perpendicular to a common plane defined by guide axes of the rod retaining members.