Facet joint replacement

Abstract

A prosthesis for the replacement of at least a portion of the bone of a facet located on a mammalian vertebra, comprising: an articulating surface that articulates with another facet; a bone contacting surface that contacts a surface of the vertebra, the articulating surface being connected to the bone contacting surface; and a fixation element that attaches the bone contacting surface to the vertebra, the fixation element being adapted for implantation into an interior bone space of a pedicle of the vertebra; wherein the prosthesis is configured so that no portion of the prosthesis contacts the posterior arch of the vertebra.

What is claimed is: 
     
         1 . A fixation element comprising:
 a head member; and   a bone stabilization member connected to the head member,   wherein the bone stabilization member has a non-circular cross-section to resist torsion when implanted in a vertebra.   
     
     
         2 . The fixation element of  claim 1 , wherein the head member includes a threaded connection feature and the bone stabilization member includes a complementary bone threaded connection feature, and the head member is driven onto the bone stabilization member by turning the head member. 
     
     
         3 . The fixation element  claim 1 , wherein the head member is monolithically formed with the bone stabilization member. 
     
     
         4 . The fixation element of  claim 1 , wherein the cross-section of the bone stabilization member is generally cruciate. 
     
     
         5 . The fixation element of  claim 1 , wherein the cross-section of the bone stabilization member is generally oval with a first diameter that is larger than a second diameter, the first and second diameters being orthogonal to each other. 
     
     
         6 . The fixation element of  claim 1 , wherein the cross-section of the bone stabilization member includes four sides. 
     
     
         7 . The fixation element of  claim 1 , wherein the cross-section of the bone stabilization member includes three sides. 
     
     
         8 . The fixation element of  claim 4 , wherein the bone stabilization portion further includes a plurality of fins extending from the bone stabilization member. 
     
     
         9 . The fixation element of  claim 1 , further comprising a plurality of deformable barbs. 
     
     
         10 . A fixation element comprising:
 a central element; and   an expandable expansion sleeve, the expandable sleeve configured and dimensioned to receive at least a portion of the central element,   wherein the expansion sleeve moves from an unexpanded position to a radially expanded position upon movement of the central element with respect to the central sleeve.   
     
     
         11 . The fixation element of  claim 10 , wherein the central element further comprises a proximal post and a mandrel. 
     
     
         12 . The fixation element of  claim 11 , wherein the expandable expansion sleeve further comprises a plurality of fingers. 
     
     
         13 . The fixation element of  claim 12 , wherein the mandrel engages with an inner side of the fingers of the expandable sleeve to push the fingers radially outwardly. 
     
     
         14 . The fixation element of  claim 1 , wherein the fixation element further comprises a cross pin element that obliquely engages the bone fixation element.