Soft-tissue balancing in total knee arthroplasty: cruciate-retaining versus posterior-stabilised, and measured-resection versus gap technique

Purpose The purpose of this study was to prove the hypothesis that soft tissues are well balanced using the gap technique with a navigation system in cruciate-retaining (CR) and posterior-stabilised (PS) total knee arthroplasty (TKA), leading to better clinical outcomes compared with the measured-resection technique. Methods One hundred and thirty-five TKAs (90 CR and 45 PS) were performed in patients with varus-type osteoarthritis using the gap technique guided by the offset-type tensor and a navigation system. Soft-tissue balance (joint-component gap and ligament balance) were intraoperatively assessed with the tensor under 40 lb of joint-distraction force. The achievement in the equalised rectangular gap at extension and flexion was assessed and retrospectively compared with the previous series in which the measured-resection technique was used (20 CR and 100 PS TKAs). In addition, clinical outcomes, including range of motion and Knee Society Score were assessed at a minimum two year follow-up. Results In achieving equalised rectangular gaps at extension and flexion, CRTKAs met criteria in more cases [66.7% (64/90) vs. 44.4 % (20/45) of PS TKA] with the gap technique, which was superior to that with the measured-resection technique [ 50.0 % (10/20) of CRTKA and 28.0% (28/100) of PS TKA]. However, clinical outcomes showed no significant differences among groups at minimum two year follow-up. Conclusions The superiority of CR TKA with the gap technique in achieving equalised rectangular gaps at extension and flexion does not directly reflect two year postoperative clinical outcomes.