Artificial Disc Replacements With Natural Kinematics

Abstract

This invention improves upon prior art total disc replacements (TDRs) by more closely replicating the kinematics of a natural disc. The preferred embodiments feature two or more fixed centers of rotation (CORs) and an optional variable COR (VCOR) as the artificial disk replacement (ADR) translates from a fixed posterior COR that lies posterior to the COR of the TDR to facilitate normal disc motion. The use of two or more CORs allows more flexion and more extension than permitted by the facet joints and the artificial facet (AF). AF joint-like components may also be incorporated into the design to restrict excessive translation, rotation, and/or lateral bending.

1 . An artificial disc replacement (ADR), comprising:
 a superior component having an upper contacting portion having a first bone contacting surface for contacting an endplate of a superior vertebra and a lower articulating portion having a lowermost surface and a first concave surface extending upward from the lowermost surface; and   an inferior component having a lower bone contacting portion having a second bone contacting surface for contacting an endplate of an inferior vertebra and an upper articulating portion having an uppermost surface and second concave surface extending downward from the uppermost surface,   wherein the superior and inferior components are articulable about first and second centers of rotation (CORs), the first COR being disposed above the lowermost of the superior component, and the second COR being disposed below the uppermost surface of the inferior component.   
     
     
         2 . The ADR of  claim 1 , wherein first and second bone contacting surfaces include keels extending therefrom. 
     
     
         3 . The ADR of  claim 2 , wherein the keels have a plurality of holes extending therethrough. 
     
     
         4 . The ADR of  claim 1 , wherein the superior and inferior component defined an anterior edge of the ADR, and the first COR is positioned closer to the anterior edge than the second COR. 
     
     
         5 . The ADR of  claim 4 , wherein the second concave surface is positioned closer to the anterior edge of the ADR than the first concave surface. 
     
     
         6 . The ADR of  claim 1 , the second concave surface includes a toroidal and spherical region. 
     
     
         7 . The ADR of  claim 1 , wherein the lowermost and uppermost surfaces are planar. 
     
     
         8 . An artificial disc replacement (ADR), comprising:
 a superior component having an upper contacting portion having a first bone contacting surface for contacting an endplate of a superior vertebra and a lower articulating portion having a first concave surface and a first perimeter surface extending at least partially about a perimeter of the first concave surface; and   an inferior component having a lower bone contacting portion having a second bone contacting surface for contacting an endplate of an inferior vertebra and an upper articulating portion having a second concave surface and a second perimeter surface extending at least partially about a perimeter of the second concave surface,   wherein the superior and inferior components are rotatable relative to each other about first and second centers of rotation (CORs), the first COR being disposed below the second perimeter surface of the inferior component, and the second COR being disposed above the second perimeter surface of the superior component.   
     
     
         9 . The ADR of  claim 8 , wherein the first and second perimeter surfaces are planar. 
     
     
         10 . The ADR of  claim 8 , wherein the first and second perimeter surfaces interface only a portion of the perimeter of the first and second concave surfaces, respectively. 
     
     
         11 . The ADR of  claim 8 , wherein the first COR is positioned above the first bone contacting surface, and the second COR is positioned below the second bone contacting surface. 
     
     
         12 . The ADR of  claim 8 , wherein the superior and inferior components directly articulate with each other about the CORs. 
     
     
         13 . The ADR of  claim 8 , wherein first and second bone contacting surfaces include keels extending therefrom. 
     
     
         14 . The ADR of  claim 8 , wherein the keels have a plurality of holes extending therethrough. 
     
     
         15 . An artificial disc replacement (ADR), comprising:
 a superior component having an upper contacting portion having a first bone contacting surface for contacting an endplate of a superior vertebra and a lower articulating portion having a first concave surface extending into a first perimeter surface of the superior component, the first concave surface defining a first center of rotation (COR), the first perimeter surface at least partially defining a perimeter of the first concave surface; and   an inferior component having a lower bone contacting portion having a second bone contacting surface for contacting an endplate of an inferior vertebra and an upper articulating portion having a second concave surface extending into a second perimeter surface of the inferior component, the second concave surface defining a second COR, the second perimeter surface at least partially about a perimeter of the second concave surface,   wherein the superior and inferior components are respectively articulable about the first and second CORs, the first COR being disposed below the second perimeter surface of the inferior component, and the second COR being disposed above the first perimeter surface of the superior component.   
     
     
         16 . The ADR of  claim 15 , wherein the first perimeter surface of the superior component and the second perimeter surface of the inferior component are planar. 
     
     
         17 . The ADR of  claim 16 , wherein the first perimeter surface defines only a portion of a perimeter of the first concave surface. 
     
     
         18 . The ADR of  claim 15 , wherein the lower articulating portion of the superior component includes a convex surface for articulation with the second concave surface of the inferior component. 
     
     
         19 . The ADR of  claim 18 , wherein the first perimeter surface at least partially defines the convex surface.