Changes in clinical outcomes and alignment of the ipsilateral knee and ankle after supramalleolar osteotomy in patients with varus osteoarthritis of the ankle: a short-term follow-up study

Purpose: The purpose of this study was to investigate the changes in clinical outcomes and alignment of the ipsilateral knee and ankle in patients with varus ankle osteoarthritis after supramalleolar osteotomy (SMO).Methods: We retrospectively reviewed 23 patients (24 ankles) with Takakura II, IIIa and IIIb ankle osteoarthritis treated with SMO between May 2017 and March 2022. The radiologic parameters of ankles contained medial distal tibial angle (TAS), tibiotalar angle (TT), tibial lateral surface (TLS), tibial plafond inclination (TPI) and talar inclination (TI). The radiologic parameters of knees contained medial proximal tibial angle (MPTA), joint line convergence angle (JLCA), the knee joint line orientation relative to ground (G-KJLO) and WBL. Hip-knee-ankle angle (HKA) was also collected. The Takakura system was used for evaluating the ankle osteoarthritis and the Kellgren-Lawrence (KL) system was used for evaluating the knee osteoarthritis. Clinical evaluation of the ankle joints contained American Orthopedic Foot and Ankle Society (AOFAS), range of motion (ROM) and visual analogue scale (VAS). Clinical evaluation of the knee joints contained Japanese Orthopaedic Association Scores (JOA), ROM, VAS.Results: The mean follow-up times were 20.3 +/- 7.3 months (range 12-38). According to the radiologic evaluation, the TAS increased from preoperative 84.7 degrees +/- 2.0 degrees to 91.2 degrees +/- 1.8 degrees at the last follow-up (P < 0.001). The TPI and TI decreased from 4.4 degrees +/- 4.2 degrees and 11.0 degrees +/- 5.2 degrees to 0.1 degrees +/- 4.7 degrees and 4.1 degrees +/- 4.8 degrees (P < 0.001 for both). The TT angel improved from 9.5 degrees +/- 4.1 degrees to 4.9 degrees +/- 3.3 degrees (P < 0.001). No significant differences were found regarding MPTA, JLCA, G-KJLO, knee WBL and HKA (P > 0.05 for all). The Takakura stage improved after SMO (P < 0.001) whilst the KL stage maintains the similar lever (P > 0.05). According to the clinical evaluation, the AOFAS significantly increased from 67.5 +/- 10.6 to 88.5 +/- 9.3 and the VAS of the ankle decreased from 4.7 +/- 1.6 to 1.2 +/- 1.1, whilst there were no changes on VAS and even the JOA and knee ROM after SMO (P > 0.05 for all).Conclusions: SMO can alleviate the symptoms of varus ankle osteoarthritis and delay the time for ankle replacement or arthrodesis by redistributing the abnormal stress of the ankle and restoring the congruence of the tibiotalar joint. In addition, it did not induce the clinical symptoms of knee without compromising lower limb alignment or knee joint line orientation in the short term.