Patent ID: 7637955

Claim:
An intervertebral implant comprising: a first member for engaging a first vertebra, the first member comprising a concave first surface, the concave first surface having a substantially constant first radius of curvature; a second member for engaging a second vertebra, the second member comprising a convex second surface and a tapered surface extending outwardly from the convex second surface, the convex second surface having a substantially constant second radius of curvature, the second radius of curvature being smaller than the first radius of curvature; and a center member positioned at least partially between the first member and the second member and in sliding articulating engagement with the first and second members, the center member comprising: a convex third surface for articulating with the concave first surface of the first member, the third surface having a substantially constant third radius of curvature substantially similar to the first radius of curvature, a concave fourth surface for articulating with the convex second surface of the second member, the concave fourth surface having a substantially constant fourth radius of curvature substantially similar to the second radius of curvature, a convex fifth surface extending substantially around the concave fourth surface, the convex fifth surface having a substantially constant fifth radius of curvature substantially equal to the first radius of curvature, the convex fifth surface configured for articulating with the tapered surface of the second member, the convex fifth surface being spaced from the tapered surface in a neutral position and in contact with the tapered surface in an articulation position, and a sidewall extending between the convex third surface and the convex fifth surface, the sidewall having a substantially circular outer profile; wherein the first member and the second member are formed of a relatively rigid biocompatible material and wherein the third and fourth surfaces of the center member are formed of an outer material that is harder than an inner material closer to a core of the center member.