Patent ID: 8062371

Claim:
A prosthetic disc for insertion between adjacent vertebrae, the prosthetic disc comprising: a metallic core having upper and lower metallic bearing surfaces; first and second metallic plates, each plate having an outer surface which engages a vertebra and an inner bearing surface which slides and translates over the corresponding bearing surface of the core, wherein a center of rotation of the core is free to move relative to the upper and lower metallic plates; and a peripheral restraining structure on at least one of the first and second plates configured to hold the core against the bearing surface of at least one of the plates during sliding movement of the plates over the core, the peripheral restraining structure comprising a peripheral structure extending over at least a portion of the periphery of the core and a projecting structure on one of the first and second plates, which projecting structure engages and retains the peripheral structure, wherein the core does not extend radially outside of the projecting structure on the at least one of the first or second plates.