Insufficient correction and preoperative medial tightness increases the risk of varus recurrence in open wedge high tibial osteotomy.

PURPOSE To assess serial changes of the limb alignment after open wedge high tibial osteotomy (HTO) using the weight-bearing line (WBL) ratio in the midterm, with a focus on varus recurrence. METHODS Patients undergoing open wedge HTO between January 2010 and December 2016 were retrospectively reviewed. Those who did not take serial postoperative weight-bearing long-leg alignment films, those who showed remained varus alignment after osteotomy, and those who had 67%, overcorrection. To determine risk factors for varus recurrence (WBL ratio <50%), immediate postoperative WBL ratio category and preoperative valgus and varus stress angles, which represented medial and lateral tightness of the joint respectively, were investigated using logistic regression analysis, taking other related factors into account. Clinical outcomes according to varus recurrence were measured using the Hospital for Special Surgery (HSS) scores. RESULTS A total of 148 cases were included. Varus recurrence was noted in 40 out of 148 cases (27.0%) with a mean follow-up of 49.7 ± 21.8 months (range, 24-102 months). The incidence of varus recurrence was different according to WBL ratio category: 10/10 (100.0%) in undercorrection; 16/33 (48.5%) in insufficient correction; 13/58 (22.4%) in planned correction; and 1/47 (2.1%) in overcorrection. Based on the logistic regression analysis, insufficient correction and preoperative valgus stress angle were found to be significant risk factors (P =.038, and .008, respectively). With valgus stress angle <2°, 7 of 10 insufficient correction cases showed varus recurrence (P =.005). However, HSS scores did not differ according to varus recurrence (P =.363). CONCLUSION Insufficient correction and preoperative medial tightness increased the risk of varus recurrence. Especially in cases where preoperative valgus stress angle was <2°, insufficient correction was strongly associated with varus recurrence. However, no significant differences in clinical outcomes were observed according to varus recurrence in the midterm.