BACKGROUND:Intertrochanteric fracture is one of the common fracture, and accompanied by osteoporosis and high energy injury. The fracture line often descended, and induced A3 intertrochanteric fracture. This type of fracture is difficult to treat. Common intramedulary fixation includes proximal femoral nail anti-rotation and InterTan, which have high stability, are minimaly invasive, and have been extensively used. OBJECTIVE: To compare the biomechanical stability of A3 intertrochanteric fracture fixed with proximal femoral nail anti-rotation and InterTan by finite element analysis. METHODS:Three three-dimensional finite element models of the AO3.1, AO3.2 and AO3.3 intertrochanteric fracture fixed with proximal femoral nail anti-rotation and InterTan were established. Fixation was completed according to the requirement of Department of Orthopedics. Stress distribution of femur and fixator of different models was observed. Stress peak at different areas was compared in femur and fixation models. Biomechanical stability was analyzed. RESULTS AND CONCLUSION: The maximum pressure concentration area in AO3.1 intertrochanteric fracture with proximal femoral nail anti-rotation was located in the lateral proximal femur, and with Intertan was located in the medial proximal femur. The AO3.2 had little differences between two types of nails. The AO3.3 intertrochanteric fracture with proximal femoral nail anti-rotation was located in the medial proximal femur and the medial distal implant. There was no significant pressure concentration with InterTan. The von Mises pressure of six models was concentrated in the medial distal implant, and higher maximum von Mises pressure was found in the proximal femoral nail anti-rotation. There was significant difference of von Mises distribution between the lateral and medial implant with proximal femoral nail anti-rotation. Except the AO3.3 intertrochanteric fracture with proximal femoral nail anti-rotation, the maximum pressures of remaining models were located in the main nail and interlocking nail infal. These results concluded that the fracture fixed with InterTan exhibited fine fixation stability in the AO3.1 and AO3.3 intertrochanteric fracture. There was no significant difference of fixation stability between proximal femoral nail anti-rotation and InterTan in AO3.2. The von Mises distribution of InterTan for intertrochanteric fracture is more reasonable.