Changes in ankle and hip joints following medial opening‐wedge high tibial osteotomy affect knee joint line obliquity

Abstract

Purpose This study aimed to measure the change in knee joint line obliquity (KJLO) and the changes in radiologic parameters of the ankle and hip joints after medial opening-wedge high tibial osteotomy (MOWHTO), and to evaluate the correlation and causal relationship between these parameters. Methods This study evaluated 109 patients who underwent MOWHTO between April 2015 and December 2021. Radiologic parameters, including KJLO, medial proximal tibial angle (MPTA), ankle joint line obliquity (AJLO), and hip abduction angle (HAA), were analysed before and 1 year after MOWHTO. Multiple linear regression analysis was used to identify independent variables that significantly affected the change in KJLO after MOWHTO. Receiver operating characteristic (ROC) analysis was used to evaluate the cutoff value for a change in KJLO that exceeded 5° postoperatively, and the predicting values of radiologic parameters. Results Multiple linear regression analysis showed that changes in MPTA, AJLO, and HAA (β = 0.440, P < 0.001; β = − 0.310, P < 0.001; β = 0.164, P = 0.035, respectively) were predictors of the change in KJLO after MOWHTO. ROC analysis showed that the threshold value for a change in KJLO which exceeded 5° postoperatively was 4.6° (66.7% sensitivity, 63.8% specificity, P = 0.025). Moreover, ROC curves for predicting a change in KJLO of > 4.6° showed that the AUC was significantly higher for the change in MPTA than that of the other two parameters (P = 0.011 for AJLO and P < 0.001 for HAA). Conclusion MOWHTO increases the KJLO by valgization of the proximal tibia and causes hip adduction and ankle valgization. The postoperative ankle valgization after MOWHTO could reduce the increase in KJLO, counteracting the effects of proximal tibial valgization and hip adduction. Therefore, the effects of the hip and ankle joints should be considered to achieve an optimal KJLO and satisfactory clinical outcomes after MOWHTO. Level of studyCohort study, IV. Keywords Knee • Medial opening-wedge high tibial osteotomy • Knee joint line obliquity • Hip abduction angle • Ankle joint line obliquity Sang-Gyun Kim and June-Bum Jun contributed equally to this work and should be considered as co-first authors.

Osteotomy around the painful degenerative varus knee has broader indications than conventionally described but must follow a strict planning process: ESSKA Formal Consensus Part I

“…A brace test for instance may help to identify these patients [24]. Another point to note is the ankle joint alignment which is reported, following MOWH-TO, to improve from preoperative valgus malalignment to postoperative neutral [15] Additionally, a recent study reported that MOWHTO increases knee joint line obliquity and results in hip adduction and ankle valgisation [16]. Furthermore, the postoperative ankle joint alignment angle was reported to significantly contribute to increased knee joint line obliquity following MOWHTO, hence should be accounted for in the preoperative planning [33].…”

Joint line and knee osteotomy

“…This is mainly due to a compensatory effect provided by the change in orientation in the ankle joint relative to the ground, facilitated by subtalar joint mobility (60,61). Following the valgus osteotomy of the proximal tibia, the ankle JLO also transitions from varus to a neutral alignment (62).…”

“…However, it has a less strong effect compared to changes in ankle loading. This is likely due to the distance from the knee and the correction of JLCA, which mitigates femoral adduction (62).…”