US Patent 6869448 Prosthesis

A tibial prosthesis has a metal tray component (1) comprising a transverse member (3) with a peripheral upstanding rim (6) and a projecting stem (4). The upstanding rim (6) includes a posterior rim portion with an undercut lip forming a pair of recesses (7, 8) and an anterior rim portion with an open angled posterior surface portion (9) and a posteriorly projecting barbed portion (10). The prosthesis also includes a tibia insert (2) made of a plastics material which fits on the tibial implant (1) within the upstanding rim (6) and has on a posterior portion thereof a shaped contour (14, 15) adapted in use to fit snugly under the undercut lip and on an anterior portion thereof an anterior surface (13) having a taper angle substantially corresponding to the angle of the open angled posterior surface portion.