Predicting ankle joint syndesmotic screw lifetime using finite element and fatigue analysis

After recovery and loading on the patient’s leg, syndesmotic screws mounted on an injured ankle may fail. The main subject of this study is to estimate the lifetime of screws considering the patient’s weight and physical activity. Method: A 3D finite element model of the bone and implemented screws were provided assigning the mechanical properties of ligaments, bones, and screws. Considering axial and tangential physiological loads during the walking phase, the stress and fatigue analyses were performed. Results: The stress distribution had an identical pattern in the screws and all of them experienced the maximum stress during 60–70% of the walking phase. Conclusion: The results of analyses show that body weight has a significant effect on the mounted screw lifetime. Patients with a weight of more than 100  kg should prevent applying body load on the operated leg. Conversely, no worry about a patient having less than 73  kg body weight.