Quantification of the Effect of Vertical Bone Resection of the Medial Proximal Tibia for Achieving Soft Tissue Balancing in Total Knee Arthroplasty.

BACKGROUND Degenerative osteoarthritis of the knee usually shows arthritic change in the medial tibiofemoral joint with severe varus deformity. In total knee arthroplasty (TKA), the medial release technique is often used for achieving mediolateral balancing. But, in a more severe varus knee, there are more difficult technical problems. Bony resection of the medial proximal tibia (MPT) as an alternative technique for achieving soft tissue balancing was assessed in terms of its effectiveness and possibility of quantification. METHODS TKAs were performed in 78 knees (60 patients) with vertical bone resection of the MPT for soft tissue balancing from September 2011 to March 2013. During operation, the medial and lateral gaps were measured before and after the bony resection technique. First, the correlation between the measured thickness of the resected bone and the change in medial and lateral gaps was analyzed. Second, the possibility of quantification of each parameter was evaluated by linear regression and the coefficient ratio was obtained. RESULTS A significant correlation was identified between alteration in the medial gap change in extension and the measured thickness of the vertically resected MPT (r = 0.695, p = 0.000). In the medial gap change in flexion, there was no statistical significance (r = 0.214, p = 0.059). When the MPT was resected at an average thickness of 8.25 ± 1.92 mm, the medial gap in extension was increased by 2.94 ± 0.87 mm. In simple linear regression, it was predictable that MPT resection at a thickness of 2.80 mm was required to increase the medial gap by 1.00 mm in knee extension. CONCLUSIONS The method of bone resection of the MPT can be considered effective with a predictable result for achieving soft tissue balancing in terms of quantification during TKA.