Kinematics in Total Knee Arthroplasty

Total knee arthroplasty (TKA) continues to be a successful procedure for the past 50 years. We investigated the kinematics after under- and overstuffing the joint space with the polyethylene (PE) insert in both cruciate-retaining (CR) TKA and posterior-stabilized (PS) TKA. We compared CR and PS designs to evaluate their respective kinematic differences. This study employed a hybrid computational-experimental joint motion simulation on a 6 degrees of freedom joint motion simulator. Physical prototypes of a virtually performed TKA based on cadaveric CT scans and a virtual ligament model were utilized. We demonstrated understuffing decreases stability and the joint compressive forces, with the inverse occurring with overstuffing. In isolation, understuffing did not result in instability during activities of daily living in CR-TKA. Notably, a 2 mm increase or decrease in PE thickness altered the post-cam mechanism engagement. The PS design demonstrated greater stability, but overall, the kinematics between CR and PS designs were similar. This study demonstrates the ability of a hybrid model to further the understanding of kinematics in TKA.