Femoral neck fracture prediction by anisotropic yield criteria

Osteoporosis is a bone disease related to age, it weakens bone structure by deterioration of the trabecular architecture and decreases the cortical envelop width and increases its porosity. Hip fractures are the more recurrent consequences of osteoporosis, and are the cause of morbidity and increase the rate of mortality. The fracture risk due to osteoporosis, is undertaken with Dual-Energy X-ray Absorptiometry (DEXA) which is an average of bone mineral density measurement, without taking into account the bone structure. The objective of this study was an experimental test to solicit the human proximal femurs by a physiological configuration (one leg stance phase of walking) to retrieve the clinical osteoporosis fractures and analysis the contribution of both cortical envelop and trabecular bone in the strength of femur structure. For this, transversely isotropic finite element models were developed from CT scan acquisition. The failure load assessment was insured by anisotropic yield behaviour criteria based on distortion energy criterion (Hill’s criterion) and taking into account the difference between tension and compression yield properties (Tsai– Wu’s criterion). The results found in this study showed the significance part of anisotropic yield behaviour of bone on proximal femur. The difference between compression and tension behaviour of human cortical bone, taken into account in the Tsai–Wu’s criterion, hold possible to predict the failure load. KEY-WORDS: 3Dreconstruction, finite element model, anisotropic yield behaviour.