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 . A method for implanting an intervertebral prosthesis between adjacent vertebrae, the method comprising:
 providing a prosthesis comprising,
 upper and lower prosthesis plates having at least one upstanding elongate fin, at least one of the upper and lower prosthesis plates having a concavely curved, spherical bearing surface therein, 
 a movable core having at least one convexly curved, spherical surface configured to cooperate with the concavely curved surface of the upper or lower plate, and 
 a protrusion on at least one of the plates and corresponding opening on the core which hold the core captive and prevent the core from slipping out sideways from between the plates; 
   placing the upper and lower plates into place between adjacent vertebrae with the at least one fin entering a slot cut in an associated vertebral surface; and   inserting the movable core between the plates, wherein the upper and lower plates are able to both translate and rotate with respect to each other and with respect to the core.   
   
   
       19 . A method according to  claim 18 , wherein a maximum articulation between the upper and lower plates after implantation is 12 degrees. 
   
   
       20 . A method according to  claim 18 , wherein the protrusion and the corresponding opening are located at a center of the movable core and the at least one plate. 
   
   
       21 . A method according to  claim 18 , wherein the at least one upstanding elongate fin includes a plurality of holes formed transversely through the fins. 
   
   
       22 . A method according to  claim 18 , wherein the plates have coarse surfaces adjacent to the fin, the coarse surfaces comprising machined serrated finishes. 
   
   
       23 . A method according to  claim 18 , wherein the plates each have a concavely curved, spherical bearing surfaces therein which are opposed to one another. 
   
   
       24 . A method according to  claim 18 , wherein a radius of curvature of the bearing surface is about 18 mm.