Flexed femoral component improves kinematics and biomechanical effect in posterior stabilized total knee arthroplasty.

The kinematics and biomechanics of the knee joint are important in ensuring patient satisfaction and functional ability after total knee arthroplasty (TKA). There has been no study on knee joint mechanics with regard to the sagittal alignment of the femoral component. The objective of this study is to determine the extent of the impact of the femoral component's sagittal alignment on kinematics and biomechanics. A validated computational TKA model was used. The femoral component was simulated at - 3°, 0°, 5°, and 7° of flexion in the sagittal plane. This study evaluated the tibiofemoral (TF) joint kinematics, contact point, quadriceps force, and contact stress on the patellofemoral (PF) joint under a deep-knee-bend condition. The kinematics of the TF joint in the posterior direction increased with the flexion of the femoral component position. For all tasks, the overall posterior locations of the TF contact points were observed in the medial and lateral compartments as the femoral component flexion angle increased. The quadriceps force and contact stress on the PF joint decreased with the femoral component flexion. This study found that the femoral component sagittal position is an important factor in knee joint mechanics. In this study, the flexion of femoral component showed a stable reconstruction of the knee extensors' mechanism. Surgeons may consider neutral-to-mild flexed femoral component position, without concerns of anterior notching of the femoral cortex.