Multiple-cam, posterior-stabilized knee prosthesis

Abstract

A distal femoral knee-replacement component provides additional points of cam action to facilitate a more normal rollback while inhibiting initial translation which could lead to increased wear and sub-optimal patella femoral mechanics. The inventive component preferably includes additional points of cam action, useable separately or together, to prevent early translation at the initiation of flexion, and a distinct point of cam action to prevent a dislocation of the femoral component over the tibial post which often occurs in cruciate-substituting designs. The preferred embodiment includes three distinct point of cam action. The first is preferably located substantially where existing cams are found, namely, at a point spaced apart a slight distance posteriorly relative to the post in full extension. A second point of cam action is located immediately adjacent the posterior aspect of the superior post to minimize and, ideally, prevent anterior translation at the initiation of flexion. The third point of cam action is preferably located more posteriorly to allow enhanced flexion without a dislocation of the cams over the post. The points of cam action may be implemented using any member or combination of elements operative to provide distinct stages of cooperation with the posterior aspect of the superior post. For example, transverse bars may be used which bridge, or partially bridge, the intercondylar space. The members or elements need not be straight across, but may instead be curved, with the post being curved to allows for a rotation, if so desired. The cam structures according to the invention may also be connected to one another forming points of contact as opposed to complete transverse elements such as distinct bars.