Knee ankle joint line angle: a critical value at 10。for decompensated knee joint line obliquity in medial opening wedge osteotomy

Background: Medial opening wedge high tibial osteotomy (MOWHTO) changes the knee joint inclination in the coronal plane, which can be compensated by the ankle joint. Once there is a decompensated knee joint obliquity, it can induce excessive shear force on the articular cartilage. This study aimed to investigate the capacity of the compensation by analyzing the correlation of the knee-ankle joint line angle (KAJA) and the knee joint line obliquity (KJLO). Methods: The correlations between postoperative KJLO and body mass index (BMI), correction amount, KAJA, mechanical lateral distal femoral angle (mLDFA), preoperative medial proximal tibia angle (MPTA), ankle joint line obliquity (AJLO), KJLO and mechanical hip-knee-ankle angle (mHKA) were analyzed using Pearson correlation coefficient. The contribution of significant factors was further analyzed using multiple linear regression. The KJLO between ≦ 5º, 5º-10º And ≧ 10º KAJA groups were compared using Kruskal-Wallis test. Results: Postoperative KAJA and preoperative KJLO moderately correlated to postoperative KJLO. Preoperative MPTA, mHKA, AJLO weakly correlated to postoperative KJLO. After multiple linear regression, only postoperative KAJA, preoperative MPTA and mHKA still showed significant contribution, while preoperative KAJA made the greatest contribution. The KJLO was substantial higher in the ≧ 10º KAJA group with a high rate (68%) of high-degree KJLO. Conclusions: 10̊postoperative KAJA is a critical value for decompensated KJLO. The results suggest us carefully assess the KAJA intraoperatively. Double osteotomy should be considered if ideal alignment cannot be achieved when the KAJA reach 10º © 2020, CC BY.