Proximal femur geometry to detect and distinguish femoral neck fractures from trochanteric fractures in postmenopausal women.

Abstract

Some proximal femur geometry (PFG) parameters, measured by dual-energy X-ray absorptiometry (DXA), have been reported to discriminate subjects with hip fracture. Relatively few studies have tested their ability to discriminate femoral neck fractures from those of the trochanter. To this end we performed a cross-sectional study in a population of 547 menopausal women over 69 years of age with femoral neck fractures (n = 88), trochanteric fractures (n = 93) or controls (n = 366). Hip axis length (HAL), neck-shaft angle (NSA), femoral neck diameter (FND) and femoral shaft diameter (FSD) were measured by DXA, as well as the bone mineral density (BMD) of the nonfractured hip at the femoral neck, trochanter and Ward's triangle. In fractured subjects, BMD was lower at each measurement site. HAL was longer and NSA wider in those with femoral neck fractures. With logistic regression the age-adjusted odds ratio (OR) for a 1 standard deviation (SD) decrease in BMD was significantly associated at each measurement site with femoral neck fracture (femoral neck BMD: OR 1.9, 95% confidence interval (95% CI): 1.4-2.5; trochanter BMD: OR 1.6, 95% CI 1.2-2.0; Ward's triangle BMD: OR 1.7, 95% CI 1.3-2.2) and trochanteric fracture (femoral neck BMD: OR 2.6, 95% CI 1.9-3.6; trochanter BMD: OR 3.0, 95% CI 2.2-4.1; Ward's triangle BMD: OR 1.8, 95% CI 1.4-2.3). Age-adjusted OR for 1 SD increases in NSA (OR 2.2, 95% CI 1.7-2.8) and HAL (OR 1.3, 95% CI 1.1-1.6) was significantly associated with the fracture risk only for femoral neck fracture. In the best predictive model the strongest predictors were site-matched BMD for both fracture types and NSA for neck fracture. Trochanteric BMD had the greatest area (0.78, standard error (SE) 0.02) under the receiver operating characteristic curve in trochanteric fractures, whereas for NSA (0.72, SE 0.03) this area was greatest in femoral neck fractures. These results confirm the association of BMD with proximal femur fracture and support the evidence that PFG plays a significant role only in neck fracture prediction, since NSA is the best predictive parameter among those tested.