Hip geometry on femoral neck bone strength; a review article

Low bone strength of the hip, which depends on both bone mass and bone geometry, leads to risk for fragility hip fracture. Anatomical adaptations of the proximal femoral structure are important to maintain higher bone strength because they predict the fracture risk independent of bone mass. Therefore, it is crucial to evaluate the bone strength of proximal femur to predict the likelihood of fragility fracture risk based on both bone mass and geometric adaptations, as well as the biomechanical strength of femoral neck (FN). Aim: To discuss the literature on geometric indices and biomechanical indices of the proximal femur to estimate FN strength. Material and methods: Dual energy xray absorptiometry (DXA) based hip structural analysis (HSA) technique derived indices of FN geometric adaptations and biomechanical strength at FN and their impact on FN bone strength were explored using the existing literature. Bone mineral content (BMC, gram) and areal bone mineral density (aBMD, g/cm2) can be measured using the HAS technique. The simple hip geometric indices such as hip axis length (HAL), femoral neck length (FNL), neck shaft angle (NSA), FN diameters, FN width and biomechanical indices such as cross-sectional moment of inertia (CSMI, cm4), section modulus (Z, cm3) and cross-sectional area (CSA, cm2) can be estimated using the HSA technique to estimate FN bone strength. Conclusion: Estimation of FN bone strength by HSA based geometric adaptations and biomechanical strength indices provides better understanding of bone strength at FN. HAL and FN bone size with BMD provide better hip fracture predictability.