• Yasushi Akamatsu, Shuntaro Nejima, Masaki Tsuji, Hideo Kobayashi, and Shuntaro Muramatsu.
• Department of Joint Surgery, Fureai Yokohama Hospital, 2-3-3, Bandai-cho, Naka-ku, Yokohama, 231-0031, Japan. yakamatsu@live.jp.
• Arch Orthop Trauma Surg. 2021 Apr 1; 141 (4): 645-653.

IntroductionPreoperative supine joint line convergence angle (JLCA) correlates with postoperative standing JLCA. Here, we compared the radiographic and clinical outcomes of knees with preoperative JLCAs of ≥ 4° and < 4° in open-wedge high tibial osteotomy (OWHTO). We hypothesized that the postoperative coronal alignment in both groups would not be affected by a change in JLCA if this change could predict before surgery.Materials And MethodsEighty-four patients with medial knee osteoarthritis who underwent OWHTO were enrolled retrospectively. A weight-bearing line (WBL) ratio of 62% and a JCLA equivalent to the preoperative supine JLCA were anticipated in preoperative planning. These were intraoperatively set using an alignment rod and a radiolucent protractor under fluoroscopy. Soft tissue correction was defined as correction angle minus bone correction. The participants with preoperative JLCAs of < 4° (low-JLCA group) and ≥ 4° (high-JLCA group) were compared.ResultsNo significant difference in the coronal alignment was found between the groups after OWHTO. No significant differences in correction angle or bone correction were found between the groups, but the soft tissue correction in the high-JLCA group was higher than that in the low-JLCA group after OWHTO (p = 0.013).ConclusionsWhen we controlled intraoperative JLCA, the postoperative coronal alignment was not affected by the change in JLCA and the differences in soft tissue correction between the low-JLCA and high-JLCA groups. However, overcorrection compared with the target coronal alignment remained in both groups.Level Of EvidenceLevel III, retrospective comparative study.

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