Postoperative Joint Line Convergence Angle (JLCA) following high tibial osteotomy is affected not only by preoperative JLCA but also by postoperative hip-knee-ankle angle.

Abstract

Accurate preoperative planning for high tibial osteotomy (HTO) requires understanding the factors influencing postoperative joint line convergence angle (JLCA). This study aimed to identify independent predictors of postoperative absolute JLCA and its change from preoperative values (ΔJLCA). Radiological assessments were performed on 113 knees from 109 patients who underwent inverted V-shaped high tibial osteotomy (iV-HTO), both preoperatively and 1 year postoperatively, using radiographs taken in standing and supine positions. Prior to univariate and multiple regression analyses, the knees were divided into two Groups S (preoperative JLCA ≤ 2°) and G (preoperative JLCA > 2°). To explore affecting factors, first, univariate regression analysis was performed to assess the correlation between each of the demographic and radiographic parameters and each of the postoperative JLCA and ΔJLCA. Then, multiple regression analyses were performed separately for postoperative JLCA and ΔJLCA, using the significant parameters identified in the univariate regression analysis as explanatory variables. In Group G, the postoperative JLCA (mean, 2.5°) was significantly reduced (<i>p</i> < 0.0001) compared to the preoperative JLCA (4.4°), while there was no significant difference between the preoperative (1.5°) and postoperative JLCA (1.3°) values in Group S. In Group G, the postoperative JLCA was significantly affected by the preoperative JLCA (<i>p</i> < 0.001) and the postoperative HKA (<i>p</i> = 0.032). The following multiple regression equation with significant usefulness (<i>p</i> < 0.001), the adjusted <i>R</i> ² of which was 0.342, was yielded. On the other hand, the postoperative ΔJLCA was significantly affected by the preoperative laxity of the lateral soft tissues (<i>p</i> < 0.001) and the preoperative JLCA (<i>p</i> = 0.004). The postoperative absolute JLCA was significantly affected not only by the preoperative JLCA but also by the postoperative HKA. In HTO for OA knees with a large JLCA, maximal JLCA reduction requires a preoperative plan aiming at the greatest clinically acceptable valgus HKA and a suitable surgical procedure. Level II, cohort study.