Patent ID: 7326250

Claim:
An intervertebral disc prosthesis for replacement of a fibrocartilaginous disc between adjacent elements of a spinal column, comprising: an upper plate comprising an internal face and an external face adapted to support one of the adjacent elements of the spinal column; a lower plate comprising an internal face and an external face adapted to support the other of the adjacent elements of the spinal column; a nucleus displaceable in translation or rotation or both with respect to the upper plate and the lower plate, the nucleus comprising an upper face, a lower face, and a perimeter surface; loadbearing sliding surfaces comprising a contact surface disposed on the internal face of the lower plate and a complementary contact surface disposed on the lower face of the nucleus each shaped as part of a sphere and a contact surface disposed on the internal face of the upper plate and a complementary contact surface disposed on the upper face of the nucleus each shaped as part of a sphere having a radius less than the radius of the contact surface disposed on the internal face of the lower plate and the complementary contact surface disposed on the lower face of the nucleus; and a stop comprising plural parts including a peripheral part of the nucleus disposed along the perimeter surface of the nucleus and a stop surface protruding from at least one of the upper plate and the lower plate, said plural parts of the stop being arranged to limit the displacement of the nucleus in translation or rotation or both with respect to at least one of the upper plate and the lower plate.