Influence of total knee replacement (TKR) design on screw-home movement: Comparison of five designs for total knee replacement prostheses

We evaluated the effect of surface geometry and retention of the posterior cruciate ligament (PCL) on screw-home movement in the knees of patients fitted with total knee replacement prostheses of five different designs (Miller/Galante Zimmer, Warsaw, IN, USA], Mark II Mizuho, Tokyo, Japan], Genesis PCL retaining, and cruciate substituting Smith & Nephew/Richards, Memphis, TN, USA], and Yoshino/Shoji II Biomet, Wiltshire, UK]). Three-dimensional motion was measured with a six-degree-of-freedom electrogoniometer (our original) during active flexion and extension of the knee. The Genesis-PCL retaining design, which has symmetric femoral and asymmetric tibial components, exhibited a pattern of screw-home movement closest to that in a normal control group (continuous external rotation between 30° flexion and extension). The implants with symmetric tibial components and the Genesis PCL-substituting design, with its asymmetric tibial articulating surface, did not replicate the screw-home movement. An asymmetric tibial articulating surface and retention of the PCL in total knee replacement may be important factors in allowing screw-home movement to occur.