The computer-assisted sequential lateral soft-tissue release in total knee arthroplasty for valgus knees

Soft-tissue management is a critical factor in total knee arthroplasty, especially in valgus knees. The stepwise release has been based upon surgeon's experience. Computer-assisted surgery has gained increasing scientific interest in recent times and allows the intraoperative measurement of leg axis and gap size in extension and flexion. We therefore aimed to analyse the effect of sequential lateral soft-tissue release and the resulting change in the a.p. limb axis on the one hand and the tibiofemoral gaps on the other hand in extension as well as in flexion in eight cadaveric knees. Measurements were obtained using a CT-free navigation system. In extension the highest increase compared to the previous release step was found for the first (iliotibial band, P=0.002), second (popliteus muscle, P=0.0003), third (LCL, 0.007) and the sixth (entire PCL, P=0.001) release step. In 90 degrees flexion all differences of the lateral release steps were statistically significant (P<0.004). Massive progression of the lateral gap in flexion was found after the second (popliteus muscle, P=0.004) and third (LCL, 0.007) release step. Computer-assisted surgery allows measurement of the effect of each release step of the sequential lateral release sequence and helps the surgeon to better assess the result.