Linked Bilateral Spinal Facet Implants and Methods of Use

Abstract

Superior and/or inferior facets of one or more facet joints may be replaced by superior and/or inferior facet joint prostheses. In one embodiment, a kit of superior or inferior prostheses is provided, in which the prostheses have at least two dimensions that vary among members of the kit independently of each other. Each prosthesis may have a bone engaging surface having a surface that is polyaxially rotatable against a corresponding resection of a vertebra. Each prosthesis may also have an articulating surface shaped such that, after attachment to the spine, the replaced or partially replaced facet joints provide a larger medial-lateral range of motion when the spine is flexed than when the spine is extended. Crosslinks may be used to connect left and right prosthesis together in such a manner that they are stabilized in a position in which they are seated directly against the vertebra.

What is claimed is: 
     
         1 . An implantable system comprising:
 a superior member attachable to a bone member via a first fixation member;   an inferior member attachable to a bone member via a second fixation member, wherein the superior member and the inferior member are configured to articulate relative to one another; and   a flexible link extending a length of the inferior member and configured to attach to opposing ends of the inferior member.   
     
     
         2 . The system of  claim 1 , wherein the inferior member comprises a ball-and-socket joint. 
     
     
         3 . The system of  claim 1 , wherein the first fixation member comprises an oval shaped cross-section that is wider in a first direction than in a second direction. 
     
     
         4 . The system of  claim 1 , wherein the first fixation member comprises a square cross-section design with four substantially perpendicular sides. 
     
     
         5 . The system of  claim 1 , wherein the first fixation member comprises a triangular cross-section with three sides. 
     
     
         6 . The system of  claim 1 , wherein the superior member comprises a bone ingrowth surface. 
     
     
         7 . The system of  claim 6 , wherein the bone ingrowth surface comprises a porous coating of beads or meshes. 
     
     
         8 . The system of  claim 6 , wherein the bone ingrowth surface comprises electrochemically etched shapes. 
     
     
         9 . The system of  claim 6 , wherein the bone ingrowth surface comprises porous pads pressed onto the superior member composed of tantalum. 
     
     
         10 . An implantable system comprising:
 a superior member attachable to a bone member via a first fixation member;   an inferior member attachable to a bone member via a second fixation member, wherein the superior member and the inferior member are configured to articulate relative to one another; and   a flexible link extending a length of the inferior member and configured to attach to opposing ends of the inferior member,   wherein the superior member comprises a curved articulating surface with an opening formed therethrough.   
     
     
         11 . The system of  claim 10 , wherein the first fixation member comprises longitudinal fins. 
     
     
         12 . The system of  claim 10 , wherein the first fixation member comprises an oval shaped cross-section that is wider in a first direction than in a second direction. 
     
     
         13 . The system of  claim 10 , wherein the first fixation member comprises a square cross-section design with four substantially perpendicular sides. 
     
     
         14 . The system of  claim 10 , wherein the first fixation member comprises a triangular cross-section with three sides. 
     
     
         15 . The system of  claim 10 , wherein the superior member comprises a bone ingrowth surface. 
     
     
         16 . The system of  claim 15 , wherein the bone ingrowth surface comprises a porous coating of beads or meshes. 
     
     
         17 . The system of  claim 15 , wherein the bone ingrowth surface comprises electrochemically etched shapes. 
     
     
         18 . The system of  claim 15 , wherein the bone ingrowth surface comprises porous pads pressed onto the superior member composed of tantalum.