Patent ID: 8172904

Claim:
A nucleus for an artificial disc for replacing the natural disc of a human spine having superior and inferior surfaces and anterior/posterior and medial/lateral sides and being adapted to fit between and move relative to upper and lower end plates that are attached to adjacent vertebrae, comprising: a. a nucleus body having a superior side and an inferior side opposite the superior side, the superior side having a superior bearing surface for engaging a cooperating bearing surface formed on the upper end plate, and the inferior side having an inferior bearing surface for engaging a cooperating bearing surface formed on the lower end plate; b. said superior bearing surface having an anterior section and a posterior section, and adapted to engage a cooperating bearing surface on said upper end plate and allow for anterior/posterior translation between the nucleus and said upper end plate; c. said superior bearing surface having a straight section extending between the anterior section and the posterior section, the nucleus body at the anterior end of the straight section having a greater height measured between the superior side and the inferior side normal to the straight section than the height of the nucleus body at the posterior end of the straight section measured between the superior side and the inferior side normal to the straight section, to correct lordosis; and d. an anterior nucleus portion projecting anteriorly from the anterior portion of the superior bearing surface, the projecting anterior nucleus portion having a planar superior side and a planar inferior side.