Anti-Rotation Fixation Element for Spinal Prostheses

Abstract

Prostheses, systems, and methods are provided for replacement of natural facet joints between adjacent vertebrae with vertebral prostheses. A portion of the vertebral prosthesis includes anti-rotation and/or anti-pullout elements to prevent or reduce prosthesis fastener rotation or pull out as a result of torques applied to the prosthesis. Various tools and methods aid the process of surgically adding the vertebral prosthesis to a patient's vertebra.

1 . A system for vertebral implantation, comprising:
 a first vertebral prosthesis comprising a first fixation element adapted to be inserted into a first hole formed in a vertebra, the first fixation element having a first longitudinal axis;   a second vertebral prosthesis comprising a second fixation element adapted to be inserted into a second hole formed in the vertebra, the second fixation element having a second longitudinal axis; and   a cross-bar connecting the first vertebral prosthesis and the second vertebral prosthesis;   wherein the first vertebral prosthesis comprises an anti-rotational element extending along the first fixation element of the first vertebral prosthesis, wherein the anti-rotational element is configured to resist a rotational force that would cause rotation of the first fixation element in the first hole of the vertebra.   
     
     
         2 . The system of  claim 1 , wherein the first fixation element comprises a tapered section. 
     
     
         3 . The system of  claim 1 , wherein the anti-rotational element comprises a longitudinal depression. 
     
     
         4 . The system of  claim 3 , wherein the longitudinal depression is helical. 
     
     
         5 . The system of  claim 1 , wherein the first vertebral prosthesis further comprises a bearing surface. 
     
     
         6 . The system of  claim 1 , wherein the first vertebral prosthesis comprises a socket element for attachment to a vertebral prosthesis. 
     
     
         7 . The system of  claim 1 , wherein the cross-bar is inserted into openings in the first vertebral prosthesis and the second vertebral prosthesis. 
     
     
         8 . A system for vertebral implantation, comprising:
 a first vertebral prosthesis comprising a first proximal shaft having a longitudinal axis and a first distal shaft having a longitudinal axis that differs from the longitudinal axis of the proximal shaft, wherein the first distal shaft is configured to be inserted into a first hole formed in a vertebra;   a second vertebral prosthesis comprising a second proximal shaft and a second distal shaft, wherein the second distal shaft is configured to be inserted into a second hole formed in the vertebra; and   a cross-bar connecting the first vertebral prosthesis and the second vertebral prosthesis;   wherein the first vertebral prosthesis comprises one or more anti-rotational elements extending along the first distal shaft of the first vertebral prosthesis, wherein the one or more anti-rotational elements are configured to resist a rotational force that would cause rotation of the first distal shaft in the first hole of the vertebra.   
     
     
         9 . The system of  claim 8 , wherein the first distal shaft of the first vertebral prosthesis is tapered. 
     
     
         10 . The system of  claim 8 , wherein the anti-rotational elements comprise longitudinal depressions. 
     
     
         11 . The system of  claim 10 , wherein the longitudinal depressions are helical. 
     
     
         12 . The system of  claim 8 , wherein the first proximal shaft has a different diameter from the first distal shaft of the first vertebral prosthesis. 
     
     
         13 . The system of  claim 8 , wherein the first proximal shaft transitions into the first distal shaft via a bend. 
     
     
         14 . The system of  claim 8 , wherein the proximal shaft includes a socket element. 
     
     
         15 . A system for vertebral implantation, comprising:
 a first vertebral prosthesis comprising a first proximal shaft having a longitudinal axis and a first distal shaft having a longitudinal axis that differs from the longitudinal axis of the proximal shaft, wherein the first proximal shaft transitions into the first distal shaft via a bend;   a second vertebral prosthesis comprising a second proximal shaft and a second distal shaft, wherein the second proximal shaft transitions into the second distal shaft via a bend; and   a cross-bar connecting the first vertebral prosthesis and the second vertebral prosthesis;   wherein the first vertebral prosthesis comprises one or more anti-rotational elements extending along a length of the first vertebral prosthesis.   
     
     
         16 . The system of  claim 15 , wherein the anti-rotational elements comprises depressions. 
     
     
         17 . The system of  claim 15 , wherein the first proximal shaft has a different diameter from the first distal shaft. 
     
     
         18 . The system of  claim 15 , wherein the first distal shaft is tapered and configured to fit into a first hole of a first vertebra. 
     
     
         19 . The system of  claim 15 , wherein the first proximal shaft comprises a socket element. 
     
     
         20 . The system of  claim 15 , wherein the first proximal shaft comprises a bearing surface for slidably engaging a corresponding bearing surface of another prosthesis.