Anterior spinal instrumentation and method for implantation and revision

Abstract

A system and method for anterior fixation of the spine utilizes a cylindrical implant engaged in the intradiscal space at the cephalad and caudal ends of the construct. The implants are cylindrical fusion devices (10) filled with bone material to promote bone ingrowth and fusion of the disc space. An attachment member (40) is connected to each of the fusion devices (10) and a spinal rod (50) is connected to each of the attachment members using an eyebolt assembly (53, 54, 55). In a further inventive method, a revision of the construct is achieved by removing the fusion devices. Each fusion device is engaged by an elongated guide member (62) over which a cylindrical trephine (70) is advanced. The trephine (70) is used to extract a core (84) of bone material around the fusion implant, while the guide member (62) is used to remove the bone core (84) containing the fusion implant (10). In another aspect of the invention, a removal insert (90, 90') is provided that engages an implanted fusion device (10). The removal insert (90, 90') can be used to guide the trephine (70) around the fusion device, and is connected to a removal tool (100) once the bone core is created. The removal tool (100) includes a shaft (101) attached to the removal insert (90, 90'), and a slap hammer (104) slidably mounted on the shaft.

What is claimed is: 
     
       1. An apparatus for removal of a fusion implant in the disc space between adjacent vertebrae, comprising: a guide member having an elongated shaft and an engagement end having means for engaging the fusion implant within the disc space to permit removal of the implant from the disc space by the guide member; and   a cylindrical trephine concentrically disposed about said guide member, said trephine having a cutting end adjacent said engagement end of said guide member, said cutting end defining teeth for cutting a core of bone from the the adjacent vertebrae surrounding the fusion implant.   
     
     
       2. The apparatus for removal of a fusion implant of claim 1, wherein said cylindrical trephine includes depth markings defined on an outer surface of said trephine for gauging a depth of insertion of said cutting end into the adjacent vertebrae. 
     
     
       3. The apparatus for removal of a fusion implant of claim 1, wherein said trephine includes a clamp for engaging said shaft of said guide member. 
     
     
       4. The apparatus for removal of a fusion implant of claim 1 further comprising: a contact surface associated with said guide member disposed apart from said engagement end; and   a slap hammer slidably disposed on said shaft between said engagement end and said contact surface, said slap hammer operable to strike said contact surface when said guide member is engaged to said fusion implant to dislodge the device from the disc space.   
     
     
       5. The apparatus for removal of a fusion implant of claim 4 further comprising a stop attached to said shaft between said contact surface and said engagement end to restrict movement of said slap hammer along said shaft toward said engagement end. 
     
     
       6. An apparatus for removal of a device disposed within bone, comprising: a guide member having a body with conical portion at one end and an engagement portion at an opposite end configured to engage the device disposed within bone to permit removal of the device from the bone by the guide member;   cylindrical trephine concentrically disposed about said guide member, said trephine having a cutting end adjacent said engagement end of said guide, member, said cutting end defining teeth for cutting a core of bone surrounding the device.   
     
     
       7. The apparatus for removal of a device disposed within bone of claim 6, wherein said cylindrical trephine includes depth markings defined on an outer surface of said trephine for gauging a depth of insertion of said cutting end into the bone. 
     
     
       8. The apparatus for removal of a device disposed within bone of claim 6, wherein said guide member has an outer diameter that is substantially equal to an outer diameter of the device disposed within bone. 
     
     
       9. The apparatus for removal of a device disposed within bone of claim 8, wherein said trephine has an inner diameter sized for a close running fit over said outer diameter of said guide member. 
     
     
       10. The apparatus for removal of a device disposed within bone of claim 6 further comprising: an elongated shaft having an engagement end configured to engage said guide member and a contact surface disposed apart from said engagement end; and   a slap hammer slidably disposed on said shaft between said engagement end and said contact surface, said slap hammer operable to strike said contact surface when said guide member is engaged to the device to dislodge the device from the disc space.   
     
     
       11. The apparatus for removal of a fusion implant of claim 10 further comprising a stop attached to said shaft between said contact surface and said engagement end to restrict movement of said slap hammer along said shaft toward said engagement end. 
     
     
       12. A removal insert for engagement between a device disposed within bone and a removal tool, said insert comprising: a body having a substantially cylindrical portion with a first end and an opposite second end;   a conical portion attached to said body at said first end; and   an engagement portion attached to said body at said second end, said engagement portion configured to engage the device disposed within bone.   
     
     
       13. The removal insert of claim 12, wherein said engagement portion includes a threaded post adapted to engage a threaded bore in the device disposed within bone. 
     
     
       14. The removal insert of claim 12, wherein said engagement portion includes: a ring sized to be received within an opening in an end of the device disposed within bone; and   at least one engagement tab projecting outwardly from said ring.   
     
     
       15. The removal insert of claim 12, in which the removal tool includes a threaded post and wherein said conical portion defines a threaded bore for threaded engagement with the post of the removal tool.