Evaluation of the Tibiofemoral Contact Characteristics of a Customized Surface-Guided Knee Implant

A surface-guided total knee replacement (TKR) aims to achieve close to normal kinematics through specially shaped tibiofemoral articulating surfaces. The resulting geometry of the TKR components affects the tibiofemoral contact mechanics. Therefore, evaluation of the contact characteristics of the implant is critical, as the tibiofemoral contact stress influences the short-term and long-term performance and durability of the implants. In this study, the contact behavior at the tibiofemoral articulating interface for a customized surface-guided TKR was studied. The contact area and mean contact stress at specific flexion angles were measured mechanically by pressure sensitive films to validate the outcomes from finite element analysis (FEA) under similar load conditions. Two activities of daily living were studied; lunging and squatting. As expected, FEA predicted larger contact areas at various flexion angles due to the limited sensitivity range of the pressure sensitive films. During lunging and squatting, the contact area increased as the flexion angle reached 90 degrees, and decreased as the knee was flexed to higher angles. The mean contact pressure was less than 10MPa at 120 degrees of flexion under squatting load. The outcomes revealed that a high range of motion can be achieved, while the mean contact pressure remains below the material limits of the tibial polyethylene insert.