Mid-term effects of opening wedge high tibial osteotomy on coronal alignment and osteoarthritis progression in the ankle joint: a comparison with total knee arthroplasty

This study aimed to investigate whether knee alignment changes after opening wedge high tibial osteotomy (OWHTO) affect ankle alignment and ankle osteoarthritis (OA) progression, compared to total knee arthroplasty (TKA) in the mid-term. This retrospective study included 72 knees (65 patients) treated with OWHTO and 74 knees (52 patients) treated with TKA, each with a minimum follow-up of 5 years. An a priori sample size calculation was performed, and measurement reliability was evaluated using intraclass correlation coefficients and weighted kappa coefficients. Radiographic parameters included the hip–knee–ankle angle (HKAA), medial proximal tibial angle (MPTA), knee joint line obliquity (KJLO), and ankle joint line obliquity (AJLO). Ankle OA stage was classified using the modified Takakura–Tanaka classification and assessed preoperatively, 1 year postoperatively, and at final follow-up. Statistical comparisons were made between groups and correlations between knee and ankle alignment changes were analyzed. Progression of ankle OA stage was assessed. No significant difference in ankle OA stage progression at final follow-up was observed between OWHTO (5.6%) and TKA (4.1%). OWHTO led to greater increases in MPTA and KJLO; however, postoperative AJLO and the degree of change in AJLO were significantly greater with TKA. OWHTO significantly alters ankle alignment, but no significant difference in the mid-term progression of ankle OA was detected compared with TKA. The study may have been underpowered to detect small between-group differences because the achieved sample size was smaller than planned. In addition, ankle-specific functional outcomes were not assessed.