Category: Ankle Arthritis; Ankle Introduction/Purpose: Supramalleolar osteotomy is a considerable technique for medial compartment ankle arthritis as a joint preservation and has been shown to be effective in several studies The indication for supramalleolar osteotomy is generally presented as early and mid-stage arthritis (Takakura stage 2 or 3A), and there is much arguments about the application of stage 3B. This study analyzes the results of suprmalleolar osteotomy performed in patients with Takakura stage 3B arthritis and seeks to identify factors that influence clinical outcomes. Methods: From August 2007 to May 2021, a total of 67 cases in which tibio-fibula osteotomy were performed for medial compartment arthritis of the ankle joint. We analyzed 67 cases and 19 cases of 3B stage before surgery which were possible for at least on year follow-up. Clinical assessments assessed VAS score, AOFAS score, and ROM, and radiological assessment assessed TAS angle, TLS angle, Talar tilt, and Contact surface percentage. Results: VAS pain scores improved from 6.6(3-9) to 2.3(0-6), AOFAS scores improved from 56.6(20-87) to 85.1(66-100), and ROM DF/PF improved from 15.3/30.6 to 16.7/34.6 degrees, which was not significantly different from the Takakura stage 2 or 3A group performed in this center at the same time. The preoperative and final follow-up TAS angle was 2.5 degrees overcorrection, from 84.7 to 97.2, and the TLS angle changed from 77.6 to 81.5. The talus tilt improved from 9.1 to 6.8 degrees, which was higher than in the Takakura stage 2 or 3A patient group. Except one case, All cases obtained bone union, with an average duration of 7.5 (3-12) months. And we found contact surface percentage help us anticipate possibility of correction and clinical outcomes. Conclusion: Compared to stage 2 or 3A, the results of supramalleolar osteotomy in Takakura stage 3B patients showed radiologically TAS overcorrection and higher talar tilt angles, but clinically there was no significant difference and showed good results. Therefore, it is believed that even in advanced medial compartment ankle arthritis at stage 3B, it may be a selectively good indication for supralleolar osteotomy.