Ankle Alignment Changes After High Tibial Osteotomy due to Valgus-Shaped Distal Tibia

Purpose Medial open-wedge high tibial osteotomy (MOW-HTO) is effective for correcting varus knee deformity but may unintentionally affect ankle joint alignment. This study investigated radiographic factors associated with postoperative ankle alignment changes following valgus-producing MOW-HTO. Methods A retrospective analysis was conducted on a prospective cohort of 50 knees in 49 patients (mean age 46.3 ± 8.2 years). Patients were included if they underwent MOW-HTO between 2016 and 2024, were enrolled in the hospital knee registry, and had both pre-and postoperative whole-leg radiographs available. These weight-bearing long-leg radiographs were used to assess tibial bone deformity and ankle joint alignment. Postoperative ankle alignment was classified as deviating closer to neutral or further from neutral. Correlation analyses and within- and between-group comparisons were performed, with significance set at p < 0.05. Results After MOW-HTO in varus-shaped knees, all alignment parameters shifted toward valgus. Tibial deformity predominantly originated from the distal tibia, with a medial center of rotation of angulation (CORA), reflecting an overall valgus-shaped tibia. Distal tibial valgus showed a strong correlation with talar orientation relative to the ground (ρ = 0.81, p < 0.001). Patients deviating further from neutral had nearly 5° more distal tibial valgus than those deviating closer to neutral (p < 0.001), and more frequently showed an overall valgus-shaped tibia (p < 0.01). Additionally, larger correction angles were moderately associated with greater valgus shift of the ankle (ρ = −0.44, p < 0.001). Conclusion MOW-HTO results in a valgus shift of the talar orientation, particularly in patients with preoperative distal tibial valgus, an overall valgus-shaped tibia, and larger correction angles. Thorough preoperative assessment of tibial morphology is essential to better anticipate postoperative ankle alignment changes.