• Shu Takagawa, Naomi Kobayashi, Yohei Yukizawa, Takayuki Oishi, Masaki Tsuji, and Yutaka Inaba.
• Department of Orthopaedic Surgery, Yokohama City University Medical Center, 4-57 Urafune-cho, Minami-ku, Yokohama, 232-0024, Japan.
• Knee Surg Sports Traumatol Arthrosc. 2020 Sep 1; 28 (9): 3022-3030.

PurposeThis study aimed to assess the effect of soft tissue correction due to knee joint laxity, which induces alignment error after hybrid closed-wedge high tibial osteotomy (CWHTO). In addition, to verify whether postoperative soft tissue correction can be predicted from preoperative radiographic parameters.MethodsA retrospective evaluation of data from patients treated by CWHTO in 2016-2019 was performed. Standing full-length anteroposterior radiograph measurement was performed pre- and post-surgery, and short anteroposterior radiographs of the knee under maximal manual varus and valgus stress were taken preoperatively. The weight-bearing line, hip-knee-ankle angle (HKA), medial proximal tibial angle (MPTA), and joint line convergence angle (JLCA) were measured, in addition to JLCA under varus or valgus conditions. Soft tissue correction was defined as ΔHKA minus ΔMPTA. Multiple regression analysis was performed to evaluate preoperative factors that could influence soft tissue correction.ResultsData from 49 knees were included in the analysis. The mean soft tissue correction was 3.2°, which indicates an over-correction. Multiple regression analysis revealed that JLCA (β = 0.642; p < 0.001) and valgus JLCA (β = - 0.422; p = 0.001) were significantly associated with postoperative soft tissue correction. The final model of the regression formula was described by the following equation: postoperative soft tissue correction = 0.691 × JLCA - 0.411 × valgus JLCA - 0.399.ConclusionPreoperative values for JLCA and JLCA under valgus stress are associated with soft tissue correction. Surgeons should, therefore, consider these measurements to achieve postoperative limb alignment.

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