Patent ID: 8715364

Claim:
A prosthetic device comprising: a cup including a concave cup surface, the concave cup surface defined by at least one radius of curvature R C ; a head configured to fit within the cup, the head including a convex head surface configured to engage the concave cup surface, the convex head surface defined by at least one radius of curvature R H ; an articulation zone provided upon the convex head surface, the head surface configured to engage the cup surface in the articulation zone, wherein R C differs from R H in the articulation zone by a first amount that is no greater than forty microns; and a peripheral zone provided on the convex head surface outside of the articulation zone, wherein R C differs from R H in the peripheral zone by a second amount that is greater than the first amount but is no greater than fifty microns, and wherein the peripheral zone extends over an area subtended by a peripheral zone angle of at least 10°, the peripheral zone angle having a vertex at a center of the head.