Distal femoral varus deformity becomes a cause of undercorrection in open wedge high tibial osteotomy.

Purpose: To evaluate whether a high lateral distal femoral angle (LDFA) contributes to undercorrection of lower-limb alignment following medial open wedge high tibial osteotomy (MOWHTO), and to determine the LDFA threshold above which tibial correction alone may be insufficient. Methods: This retrospective study analysed 68 patients who underwent MOWHTO at our hospital between 2020 and 2022. Based on their postoperative mechanical axis (MA), patients were categorised into two groups: the acceptable correction group (A-group; MA 57%-67%) and the undercorrection group (U-group; MA ≤ 56%). Radiographic parameters before and after surgery were compared between the two groups. Simple and multiple regression analyses were used to identify factors affecting postoperative MA. A receiver operating characteristic (ROC) curve was utilised to identify the LDFA cut-off value associated with undercorrection. Results: A total of 54 patients met the inclusion criteria (A-group, Conclusions: A high LDFA (≥89.2°) is associated with an increased risk of undercorrection after MOWHTO, despite accurate tibial correction. These findings suggest that in cases with significant distal femoral varus, isolated tibial osteotomy may be insufficient. Double-level osteotomy, including femoral correction, should be considered in such cases to achieve optimal alignment. Level of Evidence: Level Ⅳ, retrospective comparative study.