Biomechanical comparison of internal fixations in osteoporotic intertrochanteric fracture. A finite element analysis

OBJECTIVE: To compare the biomechanical characteristics of dynamic hip screw (DHS) and proximal femoral nail anti-rotation (PFNA) for the treatment of 3 types of osteoporotic femoral intertrochanteric fracture (OFIF) by modeling, and virtual reduction with finite element analysis, and to provide some theoretical basis and reference to select the best internal fixation for clinical treatment of OFIF.

METHODS: The experiment was conducted at the Laboratory of Biomechanics, Shanghai Institute of Orthopedics and Traumatology, Shanghai Jiaotong University School of Medicine, Shanghai, People's Republic of China from February to December 2011. The CT scan was performed in 3 cases with different types of OFIF (Evans-Jensen II, III, and IV). Upon validation, fracture models with different internal fixations were developed to simulate and analyze. Under the conditions of 7 different apparent bone densities and 3 different loads, the Von Mises stresses, and the failure rates were calculated, and the stress distribution patterns were compared.

RESULTS: The PFNA internal fixation system has better stress distribution than DHS. The former has smaller maximum Von Mises stress of femur and internal fixation, and the femoral element failure rate, as well. The safety range of osteoporosis in PFNA is wider than the DHS.

CONCLUSION: The experiment verifies, from the view of biomechanics, that PFNA should be taken into consideration firstly for OFIF (Evans-Jensen II, III, and IV).