Change in leg length after open-wedge high tibial osteotomy can be predicted from the opening width: A three-dimensional analysis

Background: The purpose of this study was to evaluate true change in leg length after open-wedge high tibial osteotomy (OWHTO) using three-dimensional (3D) assessments, exam-ine the factors that influence leg lengthening and verify their validity in clinical practice. Methods: Study 1: a retrospective case series simulation study, included 46 patients (55 knees) that underwent knee arthroplasty or HTO. OWHTO was simulated from preopera-tive computed tomography using 3D preoperative planning software. Uni-and multivari-ate regression analyses were conducted to identify predictors related to change in leg length. Study 2: a retrospective case series study, included 53 patients (55 knees) that underwent OWHTO in another institution. Change in leg length was measured preopera-tively and 1 year postoperatively and was compared with the predicted change in leg length calculated using the formula obtained from Study 1. Results: Study 1: the true change in leg length significantly increased and showed a strong correlation with the opening width. The change in leg length was predicted using the formula "change in leg length = opening width x 0.75-1.5." Study 2: the predicted change in leg length showed no significant difference from the change in leg length 1 year postoperatively and a strong correlation with the measured change. Conclusions: The true change in leg length after OWHTO was predicted using the formula obtained from the 3D model. Predicting the change in leg length preoperatively can be a basis to consider other HTOs. (c) 2021 Elsevier B.V. All rights reserved.