Elastomeric intervertebral disc prosthesis

Abstract

An intervertebral disc prosthesis includes upper and lower rigid endplates and an elastomeric core structure located between the endplates and attached thereto, wherein the elastomeric core structure has a centroid positioned posterior to a centroid of at least one of the endplates.

1 - 12 . (canceled) 
   
   
       13 . An intervertebral disc prosthesis for implanting between adjacent vertebrae in a spinal motion segment, comprising:
 an upper rigid prosthesis endplate for fixation to an adjacent upper vertebra, and having a periphery, an anteroposterior dimension, and a transverse dimension,   a lower rigid prosthesis endplate for fixation to an adjacent lower vertebra, and having a periphery, an anteroposterior dimension, and a transverse dimension, and   an elastomeric core structure located between said prosthesis endplates and attached to said endplates,   said elastomeric core structure including at least one elastomeric core member and having a total cross-sectional area in a horizontal plane and durometer hardness effective to provide sufficient compressive strength to support physiological axial loads,   wherein said elastomeric core structure has a centroid positioned posterior to a centroid of at least one of said upper prosthesis endplate and said lower prosthesis endplate.   
   
   
       14 . The intervertebral disc prosthesis of  claim 13 , wherein said core structure has an antero-posterior dimension not greater than three times an axial height dimension of said core structure. 
   
   
       15 . The intervertebral disc prosthesis of  claim 13 , wherein said core member has an antero-posterior dimension not greater than three times an axial height dimension of said core structure. 
   
   
       16 . The intervertebral disc prosthesis of  claim 13 , wherein said elastomeric core member has a generally peanut shell-shaped cross section. 
   
   
       17 . The intervertebral disc prosthesis of  claim 13 , wherein said elastomeric core structure has at least an average antero-posterior dimension sufficiently less than at least one of said upper prosthesis endplate antero-posterior dimension and said lower prosthesis endplate antero-posterior dimension, such that said elastomeric core structure does not protrude beyond the periphery of said at least one of said prosthesis endplates during normal flexion and extension of said spinal motion segment. 
   
   
       18 . The intervertebral disc prosthesis of  claim 13 , wherein said elastomeric core structure includes a first elastomeric core member and a second elastomeric core member disposed outside an outer periphery of said first elastomeric core member, said first elastomeric core member having a durometer hardness greater than that of said second elastomeric core member. 
   
   
       19 . The intervertebral disc prosthesis of  claim 18 , wherein said core structure has an antero-posterior dimension not greater than three times an axial height dimension of said core structure. 
   
   
       20 . The intervertebral disc prosthesis of  claim 18 , wherein said core structure has a minimum antero-posterior dimension in a horizontal plane located axially between said endplates, said minimum antero-posterior dimension being not greater than three times an axial height dimension of said core member. 
   
   
       21 . The intervertebral disc prosthesis of  claim 18 , wherein said first elastomeric core member has a generally peanut shell-shaped cross-section.