Artificial intervertebral disc

Abstract

The instant invention proposes an artificial intervertebral disc providing for angular displacements between adjacent vertebrae wherein these displacements are accommodated by internal shear in an elastomeric layered element residing between the upper and lower bases attached, respectively, to the upper and lower adjacent vertebrae, without sliding.

1 . An artificial intervertebral disc, comprising: 
 lower and upper bases, each made from a rigid material and each attached, respectively, to the lower and upper adjacent vertebras,    said lower and upper bases having relative mobilities in three angular coordinate directions,    with all these relative mobilities resulting from shear deformations within at least one elastomeric layered element attached to said lower and upper bases,    wherein both of said rigid lower and upper bases have co-axial concave spherical sockets, and an intermediate rigid element is inserted between said lower and upper bases, said intermediate rigid element having on its opposing lower and upper sides, respectively adjacent to said lower and upper bases, convex co-axial spherical protrusions, these protrusions being co-axial with the concave spherical sockets on the lower and upper bases, with center points of said spherical protrusion on the upper side of said intermediate rigid element and said spherical socket on the upper base approximately coinciding, with center points of said spherical protrusion on the lower side of said intermediate rigid element and said spherical socket on the lower base approximately coinciding, with the lower part of elastomeric layered element residing between and attached to said concave spherical socket on said lower base and said convex spherical protrusion on the upper side of said intermediate element, and with the upper part of elastomeric layered element residing between and attached to said concave spherical socket on the upper base and said convex spherical protrusion on the upper side of said intermediate element.    
     
     
         2 . The artificial intervertebral disc of  claim 1 , wherein both of said rigid lower and upper bases have co-axial convex spherical protrusions, and an intermediate rigid element is inserted between said lower and upper bases, said intermediate rigid element having on its opposing lower and upper sides, respectively adjacent to said lower and upper bases, concave co-axial spherical sockets, these sockets being co-axial with the convex spherical protrusions on the lower and upper bases, with center points of said spherical socket on the upper side of said intermediate rigid element and said spherical protrusion on the upper base approximately coinciding, with center points of said spherical socket on the lower side of said intermediate rigid element and said spherical protrusion on the lower base approximately coinciding, with the lower part of elastomeric layered element residing between and attached to said spherical protrusion on said lower base and said spherical socket on the upper side of said intermediate element, and with the upper part of the elastomeric layered element residing between and attached to said spherical protrusion on the upper base and said spherical socket on the upper side of said intermediate element.  
     
     
         3 . The artificial intervertebral disc of  claim 1 , wherein each of said upper and lower elastomeric layered elements comprise one layer of an elastomeric material.  
     
     
         4 . The artificial intervertebral disc of  claim 2 , wherein each of said upper and lower elastomeric layered elements comprise one layer of an elastomeric material.  
     
     
         5 . The artificial intervertebral disc of  claim 1 , wherein said upper and lower elastomeric layered elements are preloaded in compression before insertion between the vertebras.  
     
     
         6 . The artificial intervertebral disc of  claim 2 , wherein said upper and lower elastomeric layered elements are preloaded in compression before insertion between the vertebras.