Gap Volume Based on Computed Tomography Measurement Is a Strong Risk Factor for Delayed Gap Healing After Open-Wedge High Tibial Osteotomy.

ABSTRACT

PURPOSE: To identify factors that affect delayed gap healing after open-wedge high tibial osteotomy (OWHTO) and to determine whether large gap volume is a predictor of delayed gap healing. METHODS: This retrospective study analyzed biplane OWHTO performed between 2019 and 2023 for knee osteoarthritis or osteonecrosis. The minimum follow-up period was 1 year. Delayed gap healing was defined when the medial half of the osteotomy gap area had not reached the consolidation phase by 6 months after surgery based on anteroposterior knee radiographs. Gap volume was calculated from computed tomography images. Logistic regression was performed using body height, smoking, correction angle, hinge fracture, flange thickness, and gap volume. A gap volume cutoff value for delayed gap healing was determined with receiver operating characteristic curve analysis. Gap volume was predicted with multiple linear regression. RESULTS: There were 80 knees in 71 patients (36 men and 44 women). The mean gap volume was 7.6 cm3. Gap healing rates at 3, 6, 9, and 12 months after surgery were 26%, 65%, 89%, and 100%, respectively. There were 25 knees with delayed gap healing. Male sex was not a significant risk factor when adjusted for body height. Multivariate logistic regression revealed that only larger gap volume was a significant risk factor (odds ratio, 1.45; P = .006). The gap volume cutoff value was 7.6 cm3, with an area under the curve of 0.74. Tall body height and a large correction angle (both P < .001) were associated with a significantly larger gap volume (R2 = 0.73). CONCLUSIONS: Large gap volume is the most important risk factor for delayed gap healing after OWHTO. Gap volume can be predicted based on body height and correction angle. When OWHTO with substantial correction is planned for tall men, surgeons should be aware of possibly delayed gap healing. LEVEL OF EVIDENCE Level IV, retrospective case-control study.