IN VIVO KINEMATICS OF HIGH FLEX POSTERIOR STABILIZED TOTAL ARTHROPLASTY IN WEIGHT-BEARING DEEP KNEE BENDING –COMPARISON OF THREE DIFFERENT PROSTHESIS DESIGNS

Abstract

The objective of this study was to evaluate the kinematics of a high-flexion, posterior-stabilized total knee arthroplasty (TKA) in weight-bearing, deep knee bending motion. Fifteen patients implanted with the Legacy Posterior Stabilized Flex (8; mobile bearing and 7; fixed bearing), 18 patients with Scorpio NRG, and 8 patients with PFC sigma RP-F 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 flex-ion ranges of motion between the metallic implants were 120° with Legacy Flex, 125° with NRG and 121° with RP-F. The average rotation of the femoral component was 11° external rotation (ER) with Legacy Flex, 12° with NRG and 11° with RP-F. The mean kinematic pathways were early rollback, lateral pivot with ER, and bicondylar rollback with Legacy Flex, medial pivot with ER and bicondylar rollback with NRG and central pivot with ER and bicondylar rollback with RP-F. The in vivo kinematics was different due to the prosthesis designs to obtain weight-bearing deep knee bending motion.