Patent ID: 8002835

Claim:
An intervertebral disc prosthesis comprising at least three pieces including a first plate, a second plate, and a core, the core mobile at least in rotation, at least with respect to one of the plates, the core having a curved surface in contact with at least a part of a complementary curved surface of the first plate, and a substantially flat surface in contact with at least a part of a substantially flat surface of the second plate, male and female co-operation means situated near the periphery of the second plate and of the core allowing to limit or prevent the movements in translation of the core in relation to the second plate to along an axis substantially parallel to the substantially flat surfaces, and allowing to limit or prevent the movements in rotation of the core in relation to the second plate, about an axis substantially perpendicular to the substantially flat surfaces, wherein the top of the curved surface of the core is off center, in at least one direction, in relation to the geometric center of this curved surface of the core, wherein the rest position of the core is shifted in the opposite direction to that of the off-center top of the curved surface of the core, thanks to the fact that the axes of symmetry of the first and second plates are aligned when the plates are anchored on the vertebrae and that the curved surface of the first plate, complementary with the curved surface of the core, induces the aligning of the off-center top of this curved surface of the core with the axes of symmetry of the plates and therefore a shifting of the core in the opposite direction to that of the off-centre top of its curved surface, which provokes a bringing together of the co-operation means present on the core and those present on the second plate, this bringing together consequently limiting the displacement of the core in the opposite direction to that of the off centre top of its curved surface.