Patent ID: 6908484

Claim:
An articulating joint implant for use in a spinal column comprising: a first element having an upper surface for seating against an endplate of a superior vertebral body and a lower articulating surface, the entirety of said lower articulating surface being a single saddle surface that is defined by a concave arc having a substantially constant radius of curvature A about a first axis perpendicular to an anterior-posterior plane of the spinal column, and a convex arc having a substantially constant radius of curvature B about a first axis perpendicular to a lateral plane of the spinal column; and a second element having a lower surface for seating against an endplate of an inferior vertebral body and an upper articulating surface, the entirety of said upper articulating surface being a single saddle surface that is defined by a convex arc having a substantially constant radius of curvature C about a second axis perpendicular to the anterior-posterior plane of the spinal column, and a concave arc having a substantially constant radius of curvature D about a second axis perpendicular to the lateral plane of the spinal column, said constant radius of curvature A being greater than said constant radius of curvature C and said constant radius of curvature B being less than said constant radius of curvature D; wherein the saddle surface of the first element and the saddle surface of the second element are nestable with one another and articulatable against one another in flexion/extension in an anterior-posterior plane of the spinal column and in lateral bending in a lateral plane of the spinal column.