The purpose of this study is to examine the joint component gap and its relationship with post-operative flexion angles in posterior cruciate-retaining (CR) total knee arthroplasty (TKA). In posterior-stabilized (PS) TKA, an inverse correlation between the joint component gap and the post-operative flexion angle was reported. However, the kinematics of the joint component gap has a different pattern in PS and CR TKA. It was hypothesised that CR TKA has a different correlation between the joint component gap and the post-operative flexion angle compared to PS TKA.
The joint component gap was measured with an offset-type tensor. The joint component gaps were measured at 0°, 10°, 30°, 60°, 90° and 120° knee flexion angle and various values of the change in the joint component gap were calculated; 10°-0°, 30°-0°, 60°-0°, 90°-0° and 120°-0°. Multivariate regression analysis was used to determine the influencing of these parameters to post-operative knee flexion angle.
The post-operative flexion angle was positively correlated with a joint component gap of 90° and 120° and the values of the change in the joint component gap of 90°-0° and 120°-0°. Multivariate regression analysis demonstrated pre-operative knee flexion angle, and the values of the change in the joint component gap of 90°-0° had a significant independent factor of post-operative knee flexion angle.
IV.
Post-operative flexion angle is multi-factorial. However, it is important to avoid flexion component gap tightness as well as excessive flexion component gap looseness for acquisition of better flexion angle in CR TKA.