Preliminary Finite Element Analysis Of Anterior Inferior Tibiofibular Syndesmosis Injuries Treated With Screw And Tight-Rope Fixation

Objective:To establish finite element models of anterior inferior tibiofibular syndesmosis injuries(AITSI),screw fixation,Tight-rope(TR)fixation and totally inferior tibiofibular syndesmosis injuries,and to compare its force and displacement,so as provide evidence for clinical diagnosis and treatment.Methods: A three-dimensional model of a healthy ankle complex was developed by computed tomography(CT)images,then anterior inferior tibiofibular syndesmosis injuries(AITSI)model and totally inferior tibiofibular syndesmosis injuries were established,then a screw was inserted into AITSI model to obtain a screw fixation model,and a Tight-rope system was put into AITSI model to obtain a TR model.Simulated loads were applied under three conditions:neutral position with single-foot standing,internal and external rotation of the ankle.The focus was on the stress of distal tibia,distal fibula and talus articular surface,and displacement of distal tibia and fibula.Results: Inferior tibiofibular syndesmosis injuries increased the stress of distal tibia,distal fibula and talus articular surface,which also increased the displacement of distal tibia and fibula.when AITSI existing,either a screw or TR could restrict excessive displacement of distal tibia and fibula.However,screw fixation severely limited normal physiological activity of ankle,and increased the force of distal tibia,distal fibula and articular surface of talus.The forces were concentrated on the screw.In the screw fixation model,the maximum force of tibia and fibula was more than 1.3 times that of TR model,and the contact force of talus articular surface was about 1.8 times.In the screw fixation model,the displacement of tibial attachment point of anterior tibiofibular ligaments was approximately 0.6 times that of the normal model.While the data in the TR model is about 1.1 times,but TR has poor control of the displacement of fibula.Conclusion:Severe anterior inferior tibiofibular syndesmosis injuries could cause stress and displacement distribution of ankle joint to change ankle instability and should be treated with internal fixation.Both of the screw and TR could be effective for AITSI.Tight-rope has advantages over screw fixation in terms of skeletal force,activity of ankle joint,and internal fixation fracture,but Tight-rope has disadvantage in fibular rotation.Patients with Weber type C ankle fractures and obesity are more suitable for screw fixation.