Patent ID: 8029572

Claim:
A liner comprising: an outer surface; an inner surface defining a cavity; a lip comprising an inner edge defining a cavity opening, wherein the inner edge comprises: a first substantially arcuate portion having a first end and a second end, wherein the first substantially arcuate portion is defined as a portion of a first circle, a second substantially arcuate portion having a third end and a fourth end, wherein the second substantially arcuate portion is defined as a portion of a second circle that is concentric with the first circle and radially offset from the first circle, and a first connecting portion and a second connecting portion, wherein the first connecting portion connects the first end of the first substantially arcuate portion to the third end of the second substantially arcuate portion, the second connecting portion connects the second end of the first substantially arcuate portion to the fourth end of the second substantially arcuate portion, and neither the first connecting portion nor the second connecting portion extends along either the first circle or the second circle, and wherein the liner is adapted to receive within the cavity an implant stem head having a generally spherical body with a surface that corresponds to at least the first connecting portion and wherein, after rotation, the implant stem head is restrained within the cavity by a femoral stem component attached to the implant stem head.