Background: Medial opening wedge high tibial osteotomy (MOWHTO) is an effective treatment for varus osteoarthritic
knee. Alteration of knee alignment after MOWHTO may affect ankle biomechanics.
Objective: To evaluate the coronal alignment change of the ankle after MOWHTO.
Material and Method: Thirty-five patients who underwent 40 MOWHTO procedures were retrospectively reviewed. Preoperative and 6 to 12 month postoperative standing hip-to-ankle films were assessed. Differences in the anatomical femorotibial angle (FTA) and the talar tilt angle (TTA) were measured and the correlations were analyzed.
Results: The mean differences in FTA and TTA were 14.06+4.89 degrees and 0.48+1.27 degrees, respectively. Increased FTA difference was found to correlate with increased TTA (p<0.001). According to ROC analysis, an FTA correction of more than 14 degrees results in a 50% chance of altering ankle coronal alignment.
Conclusion: An FTA correction of more than 14 degrees may alter ankle coronal alignment. Other factors may affect talar tilt; therefore, further study is required.

Keywords: Ankle coronal alignment, High tibial osteotomy