Optimal knee joint function obviously requires a delicate balance between the osseous anatomy and the surrounding soft tissues, which is distorted in the case of joint line elevation (JLE). Although several studies have found no correlation between JLE and outcome, others have linked JLE to inferior results. The purpose of this in vitro investigation was to evaluate the effect of JLE on tibiofemoral kinematics and collateral ligament strains. Six cadaver knees were equipped with reflective markers on femur and tibia and CT scans were made. A total knee arthroplasty (TKA) was performed preserving the native joint level. The knees were then tested in passive flexion-extension and squatting in a knee kinematics simulator while marker positions were recorded with an optical system. During squatting quadriceps forces were measured as well as tibio-femoral contact pressures. Finally, a revision TKA was performed with JLE by 4 mm. The femoral component was downsized and a thicker insert was used. The knees were again tested as before. Based on the bony landmarks identified in the CT scans and the measured trajectories of the markers, relative tibiofemoral kinematics could be calculated as well as distance changes between insertions of the collateral ligaments. Statistical tests were carried out to detect significant differences in kinematic patterns, ligaments elongation, tibiofemoral contact pressures and quadriceps forces between the primary TKA and after JLE.Introduction
Materials and Methods
