Tibiofemoral contact behavior is improved in high-flexion cruciate retaining TKA

Recently, total knee arthroplasty (TKA) designs have been modified to prevent edge loading on the posterior tibial articular surface and increase the tibiofemoral contact area at high degrees of flexion. The expected improvement in contact behavior of high-flexion TKA over conventional design is not well documented. We ascertained peak contact locations and contact areas of a conventional and a high-flexion cruciate-retaining TKA design. Both TKAs showed similar kinematics throughout the range of flexion although their contact behaviors differed: the peak contact point for the high-flexion TKA was located more anteriorly than the conventional TKA for flexion angles greater than 90 degrees. The tibiofemoral contact of both TKAs reached the polyethylene posterior edge at 150 degrees. The contact on conventional TKA reached the polyethylene posterior edge approximately 15 degrees to 30 degrees before the high-flexion TKA. The high flexion TKA exhibited similar contact areas to conventional TKA. While the clinical relevance is unclear, these data suggest high flexion TKA might improve tibiofemoral contact biomechanics if high flexion is achievable.