Introduction: The importance of soft tissue balance in total knee arthroplasty (TKA) has been documented, and several authors have documented operative procedure of soft tissue release for soft tissue balancing. However, the quantity of change of soft tissue balance in each procedure has not been reported in detail, and the importance of each procedure of soft tissue release has not been well argued. This study is a quantitative evaluation of the effect of soft tissue release on soft tissue balance in TKA.

Materials and methods: Forty-five varus knees in 42 patients with a preoperative femorotibial angle (FTA) of more than 180°underwent TKAs from 1996 to 2000, and these knees were evaluated in this study. The mean age of the subject was 70.1 years (from 33 to 87 years), including 5 knees in male and 40 knees in female. The extension and flexion gap of the knee joint was measured by the instrument applying the force of the moment of 50kg& #65381;cm to each medial and lateral joints. We decided the procedure of soft tissue balancing as follows and the extension and flexion gap were measured in each steps. The procedure were 1) exposure of posterior medial aspects of the tibia with release of the attachment of semimembranosis, 2) removal of osteophytes from the medial distal femur and proximal tibia, 3) resection of the posterior cruciate ligament (if necessary), 4) release of the superficial medial collateral ligament (MCL), 5) resection of the superficial MCL (if necessary).

Results: The results of the change of the extension and flexion gap in each procedure were shown as below. Final gap was calculated as the difference against medial extension gaps.

Procedure: The change of extension gap The change of flexion gap medial lateral medial lateral 1) (n=45) 1.2 ± 1.4 1.2 ± 1.2 1.9 ± 2.2 1.7 ± 2.6 2) (n=36) 1.9 ± 2.5 0.7 ± 1.2 1.7 ± 1.6 1.3 ± 2.0 3) (n=19) 1.8 ± 1.5 1.9 ± 1.8 2.7 ± 2.0 2.9 ± 2.2 4) (n=18) 2.0 ± 1.9 0.3 ± 0.5 2.4 ± 1.7 0.9 ± 1.1 5) (n=4) 2.8 ± 2.3 0.4 ± 0.8 4.1 ± 1.5 1.5 ± 1.4 Final gap 0 3.4 ± 2.6 0.5 ± 3.1 3.1 ± 3.4

Discussion: The change of soft tissue balance in each soft tissue procedure in TKA was evaluated quantitatively in this study. The amount of the changes in each steps were few and differed with cases. The procedure for medial osteophytes and MCL had a tendency of efficacy to medial tightness against lateral in knees with varus deformity.