Analysis of a subtrochanteric fracture of human proximal femur

Investigation of the fracture behavior of human proximal femurs under various loading orientations has valuable theoretical and clinical applications in the analysis of bone injuries and the related pathologic and forensic studies. The characterization of these fractures requires accurate and reliable methods for the stress analysis of proximal femur, which is a challenging task because of the complex geometry, inhomogeneous mechanical properties, and the variations in the loading conditions of human femur.  This paper reports the results of an experimental/computational investigation of crack initiation and growth in subtrochanteric fractures of human proximal femur.  A combination of mechanical testing and Quantitative Computed Tomography (QCT) voxel-based finite element (FE) simulations were used to analyze the subtrochanteric fractures of two fresh frozen human femurs.  The crack initiation and growth behaviors were successfully simulated through a novel implementation of the cohesive elements within the re-meshed crack paths and a nonlinear FE analysis scheme.  The cohesive properties of the cortical bone were obtained from a series of experimental tests on different types of specimens excised from femoral diaphysis.  The simulation results, along with the mechanical properties of the cortical tissue, were used to analyze the specific fracture paths on different anatomic regions of the femoral shaft.  In general, the locations and patterns of crack initiation, the sequences of crack growth on different paths, and the compatibility of growth increments were in very good agreement with the observed specifications of the experimental fracture paths.  Also, very good agreements were achieved between the measured and simulated fracture loads.