Ex Vivo Evaluation of Hip Fracture Risk by Proximal Femur Geometry and Bone Mineral Density in Elderly Chinese Women

Abstract

BACKGROUND The incidence of hip fracture is steadily increasing. We aimed to establish a creative approach to precisely estimate the risk of hip fracture by exploring the relationship between hip fracture and bone mineral density (BMD)/femur geometry. MATERIAL AND METHODS Sixteen samples of cadaveric female proximal femora were randomly selected. Experiments were performed experimental measurement of the femoral neck BMD and geometric parameters (including neck length, neck diameter, head diameter, and neck-shaft angle). In addition, the experimental measurements contain the failure load, which represents the mechanical strength of the femoral neck, and we calculated the correlation coefficient among BMD, geometric parameters, and failure load. RESULTS Significant correlations were discovered between femoral mechanical properties and femoral neck BMD (r=0.792, r²=0.628, P<0.001), trochanteric BMD (r=0.749, r²=0.560, P=0.001), and head diameter (r=0.706, r²=0.499, P=0.002). Multiple linear regression analyses indicated that the best predictor of hip fracture was the combination of femoral neck BMD, head diameter, and neck diameter (r²=0.844, P<0.001). CONCLUSIONS The results confirmed that, compared with BMD alone, the combination of BMD and geometric parameters of proximal femur is a better estimation of hip fracture. The geometry of the proximal femur played an important role in assessing the biomechanical strength of femur. This method greatly assists in predicting the risk of hip fracture in clinical trials and will assist studies on why the incidence of hip fracture varies among races.

Figure 1

Geometry of proximal femur; A, B – Femoral neck axis length from the external side of the trochanter to the inner pelvic brim; C, D – Femoral neck diameter orthogonally to the hip axis at the narrow portion of the femoral neck; E, F – Femoral head diameter orthogonally to the hip axis at the wide portion of the femoral head; α – Neck-shaft angle between the femoral neck and shaft axis; G, H – femoral shaft axis.

Figure 2

DXA scans of the femora were obtained using a standard narrow-angle fan-beam scanner (GE Lunar Prodigy, GE Lunar Corporation, Madison, WI, USA), the proximal femur specimens being placed in the same position.