Stem for tibia part of a knee joint endoprosthesis

Claim 1

A knee joint endoprosthesis which comprises a elongated shaft for introduction into a prepared medullary cavity, said shaft extending out of one side of a plate, and a stem extending out of the other side of said plate in alignment with a longitudinal axis passing through said shaft, wherein, when the prosthesis is implanted, it is inserted in a space prepared in the medullary bone cavity in the tibia, wherein the cross-sections along the length portions of the stems of both left and right tibias of a patient comprise posterior rounded configurations and planar anterior surfaces terminating in apices pointed in a common direction, the improvement consisting in that the cross-section along the length of said stem is substantially anatomically matched to the cross-sectional shape of the medullary cavity of both left and right tibias, said stem having over its entire length, a posterior surface having a substantially semicircular cross-sectional configuration to match said posterior rounded configuration of said tibias, and an anterior surface having an angular configuration defined by a pair of planar surfaces extending from said posterior surface and angled toward each other to define a continuous medial ridge, said medial ridge being receivable in either of said apices in the right and left tibias.