BACKGROUND:Different fixtures can be used for the internal fixation treatment of patients with posterior ankle fractures in clinic, however, different internal fixation methods wil produce different biomechanical effect. OBJECTIVE:To compare and analyze the biomechanical properties of mini steel plate internal fixation and tension screw internal fixation in the treatment of posterior ankle fracture. METHODS:The clinical data of 95 patients with posterior ankle fractures were retrospectively analyzed. Al patients were treated with internal fixation. Mini steel plate group (n=48 cases) and tension screw group (n=47 cases) were divided according to the internal fixation methods. RESULTS AND CONCLUSION:The fixation effect of these two groups was simulated and analyzed using three-dimensional finite element model. The results showed that when the posterior ankle joint fracture block spreaded to the distal tibial articular surface of more than 25%, the mean pressure of internal fixation failure of tension screw group was significantly less than that of the mini steel plate group (P<0.05). When the posterior ankle joint fracture block spreaded to the distal tibial articular surface of 25%or less, the mean pressures of internal fixation failure of tension screw group was significantly greater than that of the mini steel plate group (P<0.05). The excel ent and good rate of ankle joint internal fixation of tension screw group was significantly higher than that of the mini steel plate group (P<0.05). In these two groups, there were no internal fixation material related adverse events during the treatment. These results demonstrate that the clinical effect of tension screw internal fixation for the treatment of posterior ankle fractures was better than that of the mini steel plate internal fixation, but the use of mini steel plate for internal fixation was more appropriate when the posterior ankle joint fracture block spreaded to the distal tibial articular surface of more than 25%.