Application of a novel design method for knee replacements to achieve normal mechanics

The purpose of this study was to utilize a novel method for the design of total knee replacements for use in the absence of the cruciate ligaments, with the design criteria of reproducing the medial stability and lateral mobility characteristics of the normal anatomic knee.

The starting point was a femoral component with surfaces approximating anatomic. This surface was moved into multiple positions describing a neutral path of motion and laxity about the neutral path. The distal part of the femoral composite was then used to define the tibial surface. By varying the femoral design, different tibial surfaces were produced. The reference design featured a dished medial tibial surface and a shallow lateral tibial surface, but this provided limited motion guidance. To provide further guidance, two types of design were generated, one using intercondylar guide surfaces, the other providing guidance from the condylar surfaces themselves.

The design method was capable of generating a range of total knee surfaces which could potentially return the arthritic knee to more normal function.