Effect of components mal-alignment on biomechanics in fixed unicompartmental knee arthroplasty using multi-body dynamics model during a walking cycle

Aberrant knee biomechanical environment caused by the component mal-alignment of unicompartmental knee arthroplasty (UKA) could lead to knee pain and even early prosthetic failure. This study aims at quantifying the effects of the coronal mal-alignment of femoral and tibial components on biomechanics of knee joint during walking. A subject-specific musculoskeletal multibody model of UKA was established based on a model validated in our previous study. In this model, both of femoral and tibial components were re-aligned with the coronal angle ranging from 9 degrees of varus to 9 degrees of valgus at 3 degrees increment, respectively. It was shown that the valgus mal-alignment of femoral component and the varus mal-alignment of tibial component caused a clearly increased trend in the contact force and valgus rotation of tibiofemoral joint, and in the medial collateral ligament and anterior cruciate ligament force, with the most remarkable alterations in the 9 degrees condition. However, component mal-alignment had no effect on the biomechanical environment of patellofemoral joint. It is then advisable that surgeons should be concerned with coronal component position on UKA because of adverse biomechanical effects. Specifically, more than 9 degrees of mal-alignment could lead to more detrimental effects.