The application of DXA-based strength analysis of the hip geometric structure in clinical femoral neck fracture

GONG Jian; LI Yan-xia; LI Ying-xin; XU Hao

doi:10.3969/j.issn.1001-9448.2017.15.010

Abstract：Objective Using dual energy X-ray absorptiometry (DXA) to study the differences of hip geometric structural strength between osteoporotic femoral neck fracture patients and healthy control subjects, thus to investigate the correlations between the structural parameters and fracture risk.Methods Paired t test was applied for comparison of bilateral femur DXA measurement parameters in 100 healthy subjects, including femoral neck bone mineral density (FN BMD) and bone geometric structure strength parameters (cross-sectional moment of inertia (CSMI), cross-sectional area (CSA), section modulus (SM), endocortical diameters (ED), outer diameter (OD), cortical thickness (CT), femoral neck-shaft angle (NSA), hip axis length (HAL) and hip strength index (SI)).The femoral DXA measurement parameters of 59 patients with femoral neck fracture were compared with those of age matched healthy controls.The DXA geometric parameters of hip were taken as the risk factors of femoral neck fracture and analyzed by conditional logistic regression.The relative risks of femoral neck fractures were calculated by these geometric strength parameters.Results There was high positive correlation (r=0.847~0.998, P<0.05) between the left and right DXA femoral measurement parameters.There was no significant difference in FN BMD, CSMI, CSA, NSA, or SI parameters between left and right hips in healthy controls, though there were small but significant differences in SM, OD, ED, CT, and HAL between left and right hips.In women with fractures, FN BMD, CSMI, CSA, SM, CT and SI were significantly lower than those in controls.In men with fractures, FN BMD, CSMI, CSA, SM and SI were significantly lower than those in controls.After adjusting for height, weight and FN BMD, the CSMI and SM in females with fracture were significantly lower than controls, as the SM in males with the fracture was significantly lower than controls.HAL was the only risk factor for femoral neck fracture in both males and females, with the OR values of 1.385 and 1.269, respectively.Conclusion Differences in hip geometric strength parameters between fractured and healthy controls can explain the reduction of proximal femoral bone strength in patients with femoral neck fractured.HAL obtained with DXA is the risk factor of hip fracture in both men and women.