As most knee replacement patients reach maximum flexion when femoro-tibial impingement occurs, the 3DKnee insert sulcus is positioned 5mm posterior to the AP center, encouraging rollback and delaying ROM-limiting impingement [1]. A posterior based technique allows for maintenance of the posterior condylar offset of the femur [2]. The femoral condyles are designed to maintain area contact in deep flexion, and to provide maximum posterior clearance to avoid impingement. In vivo fluoroscopic studies in the U.S.A. [10] and Japan [11] demonstrate greater posterior condylar translation and greater weight-bearing knee flexion than has been observed in traditional posterior cruciate retaining designs.
