An Investigation of the Femoral Neck Susceptibility to Fracture Incorporating the Effects of Age-remodelling and Stress Reduction

Age-related bone remodeling causes fragility of the femoral neck, increasing fracture risk in elderly populations. We investigated the effects of age-remodeling and stress-reduction on femoral neck regions using the Finite Strip Method (FSM), verifying the possibility that the femoral neck is likely to undergo fracture through two mechanisms: yielding and local buckling. We hypothesized that femoral necks of young subjects are more prone to fracture by yielding, whereas those of elderly subjects are more susceptible to local buckling. Slices from CT-scans of 8 subjects corresponding to lowest area moment of inertia were segregated into cortex and trabeculae. Geometric properties for each strip were obtained from the CT-scans. The FSM was implemented on models comprising both cortex and trabeculae that incorporated the effects of age-related bone remodeling, and reduction in physiological stress on bone (due to weight loss). Comparisons were made with FS analyses performed on only the cortex, in order to ascertain the contributions of the trabeculae to femoral neck strength. Femoral neck models of simulated young subjects manifested a predisposition to yielding, whereas femoral neck models of simulated elderly subjects were prone to buckling. Trabecular degradation and cortical thinning during aging render the femoral neck susceptible to buckling failure.