Investigation of biomechanical models for treatment of syndesmotic injury of ankle joint by finite element analysis and gray relational analysis methods

Abstract

Ankle injuries, especially in young people and athletes are more frequent and may cause permanent disability if not treated properly. About 10% of ankle injuries consist of syndesmotic ligament injuries. Screw fixation is often used in surgical treatment. Screw fixation is made with various pieces, diameter and length screws. In this study, we aimed to determine the optimal position and diameter of the pedicle screw in ankle injuries by finite element analysis. Computed tomography (CT) images are modeled using the MIMICS (version 10.01) program as a three-dimensional (3D) solid model of the lower extremity (tibia, fibula, talus, and calcaneus) of a normal human. Cortical screw Ø 3.5 mm, Ø 4.5 mm diameter is modeled in Solidworks program. The screws are placed at three or four cortices and perpendicular to the sagittal plane to the lower extremity model. The obtained models are transferred to the ANSYS program and the loads coming to the lower extremity were applied in the normal posture position. Ti-6AL-4V titanium properties and S-N graph obtained from literature as screw material are entered into ANSYS (Version 19.0) program. The mean stress and fatigue behavior of the screw are compared. Then, the obtained values are evaluated in the Gray Relational Analysis method. As a result of finite element analysis, the maximum stresses and life span of screws of each diameter and length were calculated. It is found that the region with the least life span has the closest region of the screw where the maximum stress value is calculated. In addition, the best model is determined by Gray Relational Analysis method. The findings are similar to the position of the screw failure mentioned in the literature. This study is carried out in order to prevent postoperative complications related to the insertion of screws by surgeons. Screw that Ø4,5 mm diameter, two screws and three cortex fixation the most appropriate model. For this reason, surgeons' placement of screw counts, positions and diameters will affect the success of the operation. For this reason, it is thought that the surgeons will affect the success of the surgery by considering screw counts, position and diameter.