Patent ID: 8231677

Claim:
An artificial disc replacement system, comprising: a pair of end plates, wherein each end plate comprises a bone-contacting surface, an inner surface opposite the bone-contacting surface, and a perimeter surface that extends around the end plate between the bone-contacting surface and the inner surface; a single keel protruding from a first one of the bone-contacting surfaces; a pair of keels protruding from a second one of the bone-contacting surfaces; a trough in a first one of the inner surfaces, wherein an end of the trough opens through the perimeter surface; and a nucleus comprising a flat surface, wherein the flat surface is received in the trough, wherein the nucleus further comprises a convex surface opposite the flat surface, wherein the convex surface forms a joint with a complementary concave surface in a second one of the inner surfaces, wherein the concave surface comprises chromium and a selected one of the bone-contacting surfaces comprises titanium, and wherein the concave surface and the selected bone-contacting surface are carried by a single one of the end plates.