The Cortical Bone Factor For Fragile Fracture Of Femoral Neck

Objective: To study the importance of the cortical change in fragile fracture of femoral neck.Methods: The proximal femur was examined with CT scan and DEXA for 60 patients. There were 29 patients with fragile fracture of femoral neck in fracture group including 10 males and 19 females(mean age 73.6±9.9yrs, range 53-88yr). There were 31 patients in non-fracture group including 11 males and 20 females(mean age 64.2±9.3yrs, range 50-82yr).The parameters of femur neck geometry were measured in the topviews of CT scan ,the thickness of cortical bone and the ratio of cortex thickness was measured in the cross-sectional images of CT scan.Results: Compared with those in non-fracture group, the cortex was thinner appranently and the ratio of cortex thickness was decreased markedly in femoral neck of fracture group(P<0.05). The cortex thickness,the ratio of cortex thickness and BMD were negative correlated with the change of age from 50yr to 90yr . The cortex thickness and the ratio of cortex thickness was decreased appranently with increased age from 66yr to 90yr. The BMD was decreased markedly with increased age from 50yr to 65yr. There were no statistically significant differences in BMD of the femoral neck between fracture group and non-fracture group with age from 66yr to 90yr(P>0.05). There were no statistically significant differences in BMD of the femoral neck between 66-80yr age group and 81-90yr age group(P>0.05). There were statistically significant differences between the two groups with the longer femoral neck length(FNL),greater femoral neck-shaft angle(NSA),decreased ratio of FNW/FNAL,increased ratio of FNL/FNAL and increased ratio of FNL/FNW in the fracture group(P<0.05). There were no statistically significant differences in the measurements of the femoral neck axis length(FNAL),femoral neck width(FNW) and femoral medullary cavity width(FMCW) between the two groups(P>0.05). Conclusion: the thinner cortex and the decreasd ratio of the cortex thickness are important factors in fragile fracture of femoral neck. The patients in the 50-65yr age, especially postmenopausal women, lost more trabecular than cortical; after age 65 years, most bone lost was cortical ,not trabecular. The BMD and femoral neck geometry parameters have a limitation for predicting the risk of fragile fracture of femoral neck. After age 65 years, the cortex thickness and the ratio of cortex thickness are important indicators for predicting the risk of fragile fracture of femoral neck.