Predicting the knee adduction moment after high tibial osteotomy in patients with medial knee osteoarthritis using dynamic simulations Cynthia Fantini Pagani a, ⁎, Johannes Funken a , Kai Heinrich a , Andree Ellermann b , Rüdiger Schmidt-Wiethoff b , Wolfgang Potthast a,b a Institute of Biomechanics and Orthopaedics, German Sport University Cologne, Am Sportpark Müngersdorf 6, 50933 Cologne, Germany b ARCUS Clinics Pforzheim, Rastatter Str. 17-19, 75179 Pforzheim, Germany article info abstract Article history: Received 25 April 2019 Received in revised form 24 July 2019 Accepted 7 August 2019 Background: High tibial osteotomy (HTO) is a surgical treatment for knee osteoarthritis, which alters the load distribution in the tibiofemoral joint. To date, all surgical planning methods are based on radiographs, which do not consider the loading characteristics during ambulation. This study aimed to develop and validate a simulation tool for predicting the knee adduction moment (KAM) expected after a HTO using the patient pre-operative gait analysis data and dy- namic simulations. Methods: Ten patients selected for a HTO underwent a gait analysis before surgery. Pre- operative gait data along with the planned correction angle were used for simulation of the KAM expected after leg realignment. After surgery, the same procedures of gait analysis were performed and post-operative KAM was compared to the simulation results. Results: Significant reductions of the KAM were observed after surgery. During gait at 1.2 m/s, means of the 1st peak KAM were 3.19 ± 1.03 (standard deviation), 1.21 ± 0.80 and 1.21 ± 0.71% BW × Ht for the conditions pre-operative, post-operative and simulation, respectively. Mean root-mean-square error for the KAM was 0.45% BW × Ht (range: 0.23–0.78% BW × Ht) and Lin's concordance coefficient for the 1st peak KAM was 0.813. An individual analysis showed high agreement for several patients and lower agreement for others. Possible changes in gait pattern after surgery may explain this variability. Conclusion: A novel approach for surgical planning based on dynamic loading of the knee dur- ing ambulation is presented. The simulation tool is based on patient-specific gait characteristics and may improve the surgical planning procedures used to date. © 2019 Elsevier B.V. All rights reserved. Keywords: High tibial osteotomy Knee adduction moment Surgical planning Knee dynamic loading Valgus malalignment Dynamic model simulation 1. Introduction High tibial osteotomy (HTO) is a commonly used surgical procedure aiming at altering the load distribution in the tibiofemoral joint during ambulation in cases of medial knee osteoarthritis (OA) [1,2]. In order to correct a varus alignment, the weight-bearing axis is moved laterally, but, its ideal position is not known and the target correction angle is discussed controversially in the lit- The Knee 27 (2020) 61–70 ⁎ Corresponding author at: Institute of Biomechanics and Orthopaedics, German Sport University Cologne, Am Sportpark Müngersdorf 6, 50933 Köln, Germany. E-mail addresses: c.fantini@dshs-koeln.de (C. Fantini Pagani), j.funken@dshs-koeln.de (J. Funken), heinrich@applied-biomechanics.com (K. Heinrich), ellermann@sportklinik.de (A. Ellermann), schmidt-wiethoff@sportklinik.de (R. Schmidt-Wiethoff), potthast@dshs-koeln.de. (W. Potthast). https://doi.org/10.1016/j.knee.2019.08.003 0968-0160/© 2019 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect The Knee