Finite Element Analysis of the Influence of Hinge Fractures on the Mechanical Stability of Medial Open Wedge Tibial High Osteotomy

Li Bing; Lai Zhimin; Zhang Qiaona; Chen Jiao; Zhao Fengnian; Yue Ju'an; Sun Qiang; Wang Randong; Liu Wangyan

Abstract：Objective Hinge fracture is a common complication of medial open wedge high tibial osteotomy(MOWHTO).This study aims to explore the changes in mechanical stability of the osteotomy site after hinge fracture through finite element model analysis,so as to provide a reference for formulating treatment and rehabilitation plans.Methods CT scans were performed on the lower extremities of an adult male patient with knee osteoarthritis to obtain bone data.Finite element models of MOWHTO with intact hinge,as well as Takeuchi type Ⅰ,Ⅱ,and Ⅲ hinge fractures fixed with TomoFix plates and screws,were established.Loads were applied to different models to simulate the plate stress changes,displacement of the medial osteotomy site,and displacement around the lateral hinge under sitting-up state,walking state,and torsional load.Results In the sitting-up state,compared with the intact hinge model,the maximum plate stress in the type Ⅰ,Ⅱ,and Ⅲ hinge fracture models increased by 118.3％,178.3％,and 85.5％respectively;the maximum displacement of the medial osteotomy site increased by 27.2％,33.2％,and 6.0％respectively;the maximum displacement around the lateral hinge increased by 35.2％,51.0％,and 15.8％respectively.In the walking state,compared with the intact hinge model,the maximum plate stress in the type Ⅰ,Ⅱ,and Ⅲ hinge fracture models increased by 56.6％,113.1％,and 62.8％respectively;the maximum displacement of the medial osteotomy site increased by-3.4％,17.2％,and-3.4％respectively;the maximum displacement around the lateral hinge increased by 40.4％,389.4％,and 106.4％respectively.Under torsional load,compared with the intact hinge model,the maximum plate stress in the type Ⅰ,Ⅱ,and Ⅲ hinge fracture models increased by 154.2％,261.4％,and 25.5％respectively;the maximum displacement of the medial osteotomy site increased by 307.5％,362.6％,and 16.8％respectively;the maximum displacement around the lateral hinge increased by 286.0％,338.8％,and 8.5％respectively.Conclusion Hinge fractures can lead to increased plate stress at the MOWHTO osteotomy site and decreased mechanical stability.Among them,type Ⅰ hinge fracture has a minor impact,but the influence of torsional stress should be avoided as much as possible after surgery.Type Ⅱ hinge fracture has a significant impact;therefore,it is necessary to enhance the stability of the osteotomy site during surgery and delay full weight-bearing after surgery to reduce the incidence of internal fixation failure,postoperative loss of target alignment,and nonunion of the osteotomy site.The impact of type Ⅲ hinge fracture on stability is mainly reflected at the fracture site of the lateral tibial plateau;if necessary,fixation from lateral to medial can be added during surgery,and weight-bearing should be delayed after surgery to ensure the healing of the tibial plateau fracture.Sitting-up stress and torsional stress have the greatest impact on the stability of the osteotomy site.Therefore,in the early rehabilitation process of MOWHTO patients with hinge fractures,sitting-up and torsional movements should be avoided or performed under protection to reduce the occurrence of complications.The above research provides a reference for the treatment and rehabilitation of MOWHTO patients with hinge fractures,but further biomechanical studies are still needed for confirmation.