Finite Element Study On Biomechanical Properties Of Fixed Inferior Tibiofibular Screw With Different Screw Angles

Objective:There are still many controversies in screw placement after tibiofibular syndesmosis injury,and the angle of screw placement is rarely studied.With the gradual development of computer technology,finite element method has been continuously applied in the field of orthopedics,and the reliability of this technology has been greatly improved.By establishing a finite element model of the ankle joint,the biomechanical characteristics of different angle fixation of the tibiofibular syndesmosis with a single tibiofibular syndesmosis screw were studied,providing a theoretical basis for the diagnosis and treatment of the tibiofibular syndesmosis injury with the angle fixation.Methods: Based on the CT image,Mimics software and Geomagic Studio software were used to establish the ankle joint model and verify its validity.The model was imported into Solidworks software.The finite element model of fixing the inferior tibiofibular joints with screws at six different angles(Model a: 15°forward,10°upward,model b: 15°forward,15°upward,model c:15°forward,20°upward,model d: 25°forward,10°upward,model e: 25°forward,15°upward,model f: 25°forward,20°upward)was established to simulate the force mode of the ankle joint when the human body stood on one foot in neutral position.The maximum stress distribution and the maximum displacement of screws with different angle fixing methods were compared.Results:Under internal rotation and external rotation loads,the maximum stress point of the screw was between the tibia and fibula near the tibia.Under internal rotation load,the maximum stresses of models a,b,c,d,e,and f were 53.38,52.05,52.63,54.39,53.85 and 52.83 MPa,respectively.Under external rotation load,the maximum stresses of models a,b,c,d,e,and f screw were 73.75,71.62,66.81,77.96,75.31,and 74.60 MPa,respectively.Under internal rotation load,the maximum displacements of models a,b,c,d,e,and f were 3.27,3.25,3.2,2.83,2.99 and 2.98 mm,respectively.Under external rotation load,the maximum displacements of models a,b,c,d,e,and f screw were 2.69,2.71,2.75,2.41,2.53 and 2.55 mm.Conclusion: Under the action of the same force,the displacement values of the forward 25°fixation are all smaller than those of the forward 15° fixation.It can be judged that the forward25° fixation is superior to the forward 15° fixation and has stronger biomechanical stability.Whether the screw fixation at 20° upward is better than that at 10° upward and 15°upward is to be further verified because the difference of stress values between each group is small.