Intervertebral prosthesis

Abstract

An intervertebral prosthesis for insertion between adjacent vertebrae includes upper and lower prosthesis plates locatable against respective vertebrae and having opposing, concavely curved recesses therein, and a core located between the plates. The core has opposed, convexly curved surfaces received in the recesses of the plates to allow the plates to slide in articulated manner over the core. The opposed surfaces of the core and the recesses of the plates have cooperating spherical curvatures. The recess of each plate surrounds a locating peg projecting centrally from the base of the recess and is bounded by an annular rim, such that the annular rims of the plates are arranged to contact one another at a predetermined limit of sliding movement of the plates over the core. The peg locates loosely in an opening located centrally in a curved surface of the core, whereby the plates can slide over the core in all directions while the peg holds the core captive.

1 .- 17 . (canceled) 
   
   
       18 . An intervertebral prosthesis for insertion between adjacent vertebrae, the prosthesis comprising:
 upper and lower prosthesis plates locatable against respective vertebrae and having opposing recesses therein;   a core located between the plates, the core having opposed bearing surfaces received in the recesses of the plates to allow the plates to slide in articulated manner over the core;   wherein the opposed bearing surfaces of the core and the recesses of the plates comprise cooperating curvatures; and   wherein the core is formed with angularly spaced, radial passages accommodating radially oriented pins serving as the radiographic markers.   
   
   
       19 . A prosthesis according to  claim 18 , wherein the core is transparent to X-radiation. 
   
   
       20 . A prosthesis according to  claim 19 , wherein the core is formed of a low friction plastic. 
   
   
       21 . A prosthesis according to  claim 18 , wherein the pins are titanium pins. 
   
   
       22 . A prosthesis according to  claim 18 , wherein the core is movable with respect to both the upper and lower prosthesis plates. 
   
   
       23 . An intervertebral prosthesis for insertion between adjacent vertebrae, the prosthesis comprising:
 upper and lower prosthesis plates locatable against respective vertebrae and having opposing recesses therein;   a core located between the plates, the core having opposed bearing surfaces received in the recesses of the plates to allow the plates to slide in articulated manner over the core;   wherein the opposed bearing surfaces of the core and the recesses of the plates comprise cooperating curvatures; and   wherein the core is transparent to X-radiation and is formed with one or more radial passages accommodating pins serving as radiographic markers.   
   
   
       24 . A prosthesis according to  claim 23 , wherein the core is formed of a low friction plastic. 
   
   
       25 . A prosthesis according to  claim 23 , wherein the pins are titanium pins. 
   
   
       26 . A prosthesis according to  claim 23 , wherein the core is movable with respect to both the upper and lower prosthesis plates. 
   
   
       27 . An intervertebral prosthesis for insertion between adjacent vertebrae, the prosthesis comprising:
 upper and lower prosthesis plates locatable against respective vertebrae and having opposing, concavely curved recesses therein;   a core located between the plates, the core having opposed, convexly curved surfaces received in the recesses of the plates to allow the plates to slide in articulated manner over the core;   wherein the opposed surfaces of the core and the recesses of the plates comprise cooperating curvatures;   wherein each plate and is bounded by an annular rim, such that the annular rims are arranged to contact one another at a predetermined limit of sliding movement of the plates over the core;   wherein the core is transparent to X-radiation and carries radiographic markers; and   wherein the core is formed with angularly spaced, radial passages accommodating radially oriented pins serving as the radiographic markers.   
   
   
       28 . A prosthesis according to  claim 27 , wherein the core is formed of a low friction plastic. 
   
   
       29 . A prosthesis according to  claim 27 , wherein the pins are titanium pins. 
   
   
       30 . A prosthesis according to  claim 27 , wherein the core is movable with respect to both the upper and lower prosthesis plates.