In Vivo Kinematic Analysis of a High-Flexion, Posterior-Stabilized, Mobile-Bearing Knee Prosthesis in Deep Knee Bending Motion

The objective of this study was to evaluate the kinematics of a high-flexion, posterior-stabilized, mobile-bearing total knee arthroplasty (TKA) in weight-bearing, deep knee bending motion. Thirteen patients implanted with the Legacy Posterior Stabilized Flex (Zimmer, Warsaw, IN) mobile-bearing TKA were examined during a deep knee bending motion using fluoroscopy. Femorotibial motion was determined using a 2-dimensional to 3-dimensional registration technique, which used computer-assisted design models to reproduce the position of metallic implants from single-view fluoroscopic images. The average flexion range of motion between the metallic implants was 116°. The average rotation of the femoral component was 9.3° external rotation. The mean kinematic pathway was early rollback, lateral pivot with external rotation, and bicondylar rollback. We found that the kinematic pattern of the Legacy Posterior Stabilized Flex mobile-bearing TKA was different than normal knee kinematics.