Intervertebral prosthetic disc

Abstract

A prosthetic disc for insertion between adjacent vertebrae includes upper and lower plates, a core disposed between the plates, and at least one projection extending from at least one of the upper and lower curved surfaces of the core into at least one recess of one of the inner surfaces of the plates. The recess is oversize with respect to the projection to allow sliding movement of the plate over the core while retaining the core between the plates during such sliding movement. The projection(s) may include a rod extending through an axial hole in the core, multiple surface features of the core, or the like.

1 . An intervertebral prosthetic disc for insertion between adjacent vertebrae, the disc comprising:
 upper and lower plates having upper and lower inner bearing surfaces, respectively;   a core between the plates, the core having upper and lower surfaces complementary in shape to the upper and lower inner bearing surfaces, respectively, and a lateral surface between the upper and lower surfaces; and   a core retainer for holding the core captive between the plates, the core retainer comprising two projecting portions that project from the lateral surface of the core at two points, respectively, only in diametrically opposite directions.   
     
     
         2 . The prosthetic disc of  claim 1 , comprising a central axis extending between upper and lower poles of the core on the upper and lower surfaces, respectively, an axis between the two projecting portions extending perpendicularly to the central axis. 
     
     
         3 . The prosthetic disc of  claim 1 , comprising a plane between the upper and lower surfaces, an axis between the two projecting portions lying on the plane. 
     
     
         4 . The prosthetic disc of  claim 1 , wherein the upper and lower surfaces are symmetrical about a plane of symmetry between the upper and lower surfaces, and an axis between the two projecting portions lies on the plane of symmetry. 
     
     
         5 . The prosthetic disc of  claim 1 , wherein the upper and lower surfaces are each continuous surfaces. 
     
     
         6 . The prosthetic disc of  claim 1 , wherein the upper and lower surfaces intersect with the lateral surface, and each of the upper and lower surfaces are continuous surfaces to at least where they intersect with the lateral surface. 
     
     
         7 . The prosthetic disc of  claim 6 , wherein the lateral surface is discontinuous with the upper and lower surfaces. 
     
     
         8 . The prosthetic disc of  claim 1 , wherein the lateral surface is cylindrical. 
     
     
         9 . The prosthetic disc of  claim 8 , wherein the lateral surface is circularly cylindrical. 
     
     
         10 . The prosthetic disc of  claim 1 , comprising a central axis extending between upper and lower poles of the core on the upper and lower surfaces, respectively, wherein a cross-sectional shape of the core taken perpendicular to the central axis substantially defines an oval or an ellipse, and a major axis of the oval or ellipse extends through the lateral surface. 
     
     
         11 . The prosthetic disc of  claim 1 , wherein the upper and lower surfaces define a majority of a total surface area of the core. 
     
     
         12 . The prosthetic disc of  claim 1 , wherein the core retainer extends into a channel in the core between the upper and lower surfaces. 
     
     
         13 . The prosthetic disc of  claim 12 , wherein the channel is tapered with the channel being wider at the lateral surface of the core. 
     
     
         14 . The prosthetic disc of  claim 1 , wherein the core retainer extends through the core through a channel in the core between the upper and lower surfaces. 
     
     
         15 . The prosthetic disc of  claim 1 , comprising fasteners carried by one of the plates to fasten the core retainer on the plate. 
     
     
         16 . The prosthetic disc of  claim 15 , wherein the fasteners fasten the core retainer on diametrically opposite regions of the plate. 
     
     
         17 . The prosthetic disc of  claim 1 , wherein the fasteners are imbedded within one of the plates. 
     
     
         18 . The prosthetic disc of  claim 1 , wherein the core retainer comprises a cable. 
     
     
         19 . A method of retaining a core in a prosthetic disc, comprising:
 providing upper and lower plates having upper and lower inner bearing surfaces, respectively;   positioning the a core between the plates; and   holding the core captive between the plates with a core retainer comprising two projecting portions that project from the lateral surface of the core at two points, respectively, only in diametrically opposite directions, and with fasteners carried by one of the plates to fasten the core retainer on the plate.   
     
     
         20 . The method of  claim 19 , comprising extending a portion of the core retainer through a channel through the core.