Facet arthroplasty devices and methods

Abstract

A prosthesis assembly replaces a cephalad portion of a left natural facet joint (i.e., a left inferior articular process) on a vertebral body and a cephalad portion of a right natural facet joint (i.e., a right inferior articular process) on a vertebral body. The prosthesis assembly has a left prosthesis body accommodating fixation to the vertebral body at or near a left pedicle and without support by a lamina. An artificial left facet joint structure carried by the left prosthesis body and is adapted and configured to replace a cephalad portion of the left natural facet joint. The prosthesis assembly further has a right prosthesis body accommodating fixation to the vertebral body at or near a left pedicle and without support by a lamina. An artificial right facet joint structure is carried by the right prosthesis body and is adapted and configured to replace a cephalad portion of the right natural facet joint.

1 . A spine stabilization device, comprising: a brace adapted to span between a first bone anchor and a second bone anchor, the brace including: a first joint; and a second joint; wherein the brace allows for movement between the first joint and the second joint such that the movement of the second joint with respect to the first joint is generally restricted to vertical and horizontal movement along a three dimensional curved path surface having a substantially constant radius about a center of rotation wherein the center of rotation is positioned outside of the brace.  
     
     
         2 . The spine stabilization device of  claim 1 , further comprising a distracting mechanism coupled to the first joint and the second joint to exert a force between the first joint and second joint.  
     
     
         3 . The spine stabilization device of  claim 1 , wherein the center of rotation is substantially positioned within a spine disc space when the device is implanted between two vertebrae.  
     
     
         4 . The spine stabilization device of  claim 1 , wherein the brace further comprises: a third joint; a first link coupled to the first joint and the third joint; and a second link coupled to the second joint and the third joint.  
     
     
         5 . The spine stabilization device of  claim 4 , wherein movement of the third joint is generally restricted to a generally curved path having the constant radius about the center of rotation. 
 axis which intersects the center of rotation.    
     
     
         6 . The spine stabilization device of  claim 1  wherein the first joint is coupled to a first member and the second joint is coupled to a second member.  
     
     
         7 . The spine stabilization device of  claim 6  further comprising a means for creating a force between the first member and the second member.  
     
     
         8 . A spine stabilization system comprising: a first bone anchor; a second bone anchor; a brace spanning between the first bone anchor and the second bone anchor, the brace including: a first member coupled to the first bone anchor; a second member coupled to the second bone anchor, wherein the first member and the second member are slideably mated along a portion of their longitudinal lengths such that the movement of the second member with respect to the first member is generally restricted to vertical and horizontal movement along a three dimensional curved path surface having a substantially constant radius about a center of rotation, wherein the center of rotation is positioned outside of the brace.  
     
     
         9 . The spine stabilization system of  claim 8  wherein the first and second bone anchors are anchors adapted to attach to a spinous process of a vertebra.  
     
     
         10 . The spine stabilization system of  claim 8  wherein the brace further comprises a means for creating a force between the first member and the second member.  
     
     
         11 . A method for spine stabilization comprising: inserting a first bone anchor into a first vertebra; inserting a second bone anchor into a second vertebra; attaching a first joint to the first bone anchor; attaching a second joint to the second bone anchor; and interconnecting the first joint and the second joint to create a brace that spans the first bone anchor and the second bone anchor, such that the first joint and the second joint are slideably mated along a portion of their longitudinal lengths; wherein the brace allows for movement between the first joint and the second joint such that the movement of the first joint with respect to the second joint is generally restricted to vertical and horizontal movement along a three dimensional curved path surface having a substantially constant radius about a center of rotation, wherein the center of rotation is positioned outside of the brace.  
     
     
         12 . The method of  claim 11  wherein the step of interconnecting the first joint and the second joint further comprises: interconnecting a third joint to the first joint with a first link; and interconnecting the third joint to the second joint with a second link; wherein the third joint is generally restricted to a generally curved path having the constant radius about the center of rotation.