Objective To analyze the effects of 2 different screw positions on the ankle motion by means of three-dimensional finite element models of inferior tibiofibular syndesmosis injury fixated by screws.Methods Helical CT scan images of right foot from a 30 year-old male volunteer were obtained.Using Mimics 10.01 and SolidWorks 2009,three-dimensional structures of the foot bones were reconstructed,ligamentous connection was simulated and contact pair between each joint was generated.Next,3 three-dimensional finite element models were established of normal ankle,tibiofibular syndesmosis injury fixated with screws placed 2.5 cm and 5.0 cm above the tibiotalar joint respectively.Neutral position with single foot standing,internal rotation and external rotation of the ankle were simulated for solution.Results Movements of the distal tibia and fibula decreased significantly in the anterior/posterior and medial/lateral directions after screw fixation at both positions,but the absolute displacements were both less than 0.3 mm between the distal tibia and fibula.After screw fixation at both positions,the relative rotation angles of the tibiotalar joint were 1.75° and 1.65° respectively at internal rotation of the ankle,and 0.60° and 0.54° respectively at external rotation of the ankle.Conclusions Screw fixation of the tibiofibular syndesmosis at the 2 positions is reliable but decrease the displacement of each bone and rotational motion range of the ankle.There is no significant difference between the 2 screw positions regarding the effects on the ankle motion.