BACKGROUND:The morphological and mechanical transfers of unstable intertrochanteric fractures were complicated, so it is difficult to analyze the biomechanical characteristicsof the common experimental methods in a comprehensive way. Moreover, the high cost, long cycle and poor repeatability of common tests limit its application in biomechanics. OBJECTIVE:To analyze the biomechanical characteristics of unstable intertrochanteric fracture in different fixation ways by three-dimensional finite element analysis. METHODS:Intertrochanteric fracture locking dynamic hip fixation model (C1), Gamma nail fixation model (C2) and proximal femoral anatomical locking plate model (C3) were established. The distal end of the femur was fixed, and subjected to the hip reaction force of 2800 N and abduction muscle strength of 1 200 N. Three-dimensional finite element analysis was used to analyze the stress distribution, stress concentration and maximum displacement of unstable intertrochanteric fracture in three different fixation ways. RESULTS AND CONCLUSION:(1) Stress: the anterolateral stress and anteromedial stress of C3 were the maximum. Posterolateral stress and posteromedial stress ofC3 were the minimum. There were significant differences among the three groups (alP< 0.05). (2) Stress of fracture space: significant differences in anterolateral stress, anteromedial stress, posterolateral stress and posteromedial stress were determined in C1, C2 and C3 (P< 0.05). Anterolateral stress of C3 was significantly less than anterolateral stresses of C1 and C2 (P< 0.05). Anteromedial stress of C3 was significantly less than that of C1 and C2 (P< 0.05). Posterolateral stress of C1 was significantly larger than that of C2 and C3 (P<0.05). Posteromedial stress of C1 was significantly larger than that of C2 (P< 0.05). Posteromedial stress of C3 was significantly less than that of C1 and C2 (P< 0.05). (3) Significant differences in bone stress around the screw top were detected among the three groups (P< 0.05). Bone stress around the screw top of C3 was significantly larger than that of C1 and C2 (P< 0.05). (4) Thus, locking dynamic hip screw, Gamma nail and proximal femoral anatomical locking plate have their advantages and disadvantages for treatment of unstable intertrochanteric fracture of the femur. The appropriate internal fixation device should be selected according to the need.