Combination of bone mineral density and upper femur geometry improves the prediction of hip fracture

Abstract

Bone mineral density (BMD) measured by dual-energy X-ray absorptiometry (DXA) is the main determinant of the clinical evaluation of hip fracture risk. However, it has been shown that BMD is not the only predictive factor for hip fracture, but that bone geometry is also important. We studied whether the combination of bone geometry and BMD could further improve the determination of hip fracture risk and fracture type. Seventy-four postmenopausal females (mean age 74 years) with a non-pathologic cervical or trochanteric hip fracture without previous hip fracture or hip surgery constituted the study group. Forty-nine had a cervical fracture (mean age 73 years) and 25 had a trochanteric fracture (mean age 76 years). The control group consisted of 40 age-matched females (mean age 74 years). The geometrical parameters were defined from plain anteroposterior radiographs, and the potential sources of inaccuracy were eliminated as far as possible by using a standardized patient position and calibrated dimension measurements with digital image analysis. BMD was measured at the femoral neck (FEBMD), Ward's triangle (WABMD), and the trochanter (TRBMD). Stepwise linear regression analysis showed that the best predictor of hip fracture was the combination of medial calcar femoral cortex width (CFC), TRBMD, neck/shaft angle (NSA), and WABMD ( r=0.72, r(2)=0.52, P<0.001). The area under the receiver operating characteristic curve (ROC) for this model was 0.93, while the area under ROC for TRBMD alone was 0.81. At a specificity of 80%, sensitivity improved from 52.5% to 92.5% with this combination compared with TRBMD alone. The combined predictors of cervical and trochanteric fracture differed, being NSA, CFC, TRBMD, and WABMD for cervical and TRBMD and femoral shaft cortical thickness for trochanteric fracture. In addition, we found a statistically significant correlation between FEBMD and femoral shaft and femoral neck cortex width ( r=0.40, P<0.01 and r=0.30, P<0.01, respectively). The results confirm that the combination of BMD and radiological measures of upper femur geometry improve the assessment of the risk of hip fracture and fracture type compared to BMD alone, and that bone geometry plays an important role in the evaluation of bone strength.

In vivo discrimination of hip fracture with quantitative computed tomography: Results from the prospective European Femur Fracture Study (EFFECT)

“…(49) Trochanteric fractures also have been shown to be associated with increased mortality when compared with cervical fractures, and this could not be explained by differences in age or comorbidity. (4) Since there is evidence in both in vitro (14,15,42,47,50) and in vivo (3,30) studies that cervical and trochanteric fractures have different risk factors, we compared densitometric and geometric variables between the two subgroups and analyzed hip fracture discrimination separately for each subgroup. Compared with cervical fracture cases, we found lower DXA aBMD and QCT BMD values in trochanteric fracture cases, but differences were not statistically significant.…”

“…These results are in agreement with current knowledge that women with trochanteric fractures have a more severe and generalized low bone density involving particularly the trabecular component, with lower aBMD in the trochanteric region and lumbar spine. (51) Cervical fractures seem to depend more on proximal femur or pelvic geometry (such as a larger femoral neck shaft angle or a longer hip axis length in cervical fractures (2,3,30,50) ) combined with focal bone loss. (51) In the EPIDOS study, aBMD values of novel upper and lower femoral neck subregions were lower in trochanteric fractures than in controls, but prediction of cervical fractures was improved by measuring aBMD only in the upper subregion of the femoral neck.…”

“…(3) It is well established that bone density measurements made at the specific fracture site provide stronger fracture risk prediction. (2,17,18,30,51) Using statistical parametric mapping, Li and colleagues (45) demonstrated recently the existence of a small region between the femoral neck and head with significantly lower BMD values in cervical compared with trochanteric fracture cases. Also, a small region of the trochanter was shown to contain voxels with lower BMD values in trochanteric fractures.…”

“…(27) Currently, only a few in vivo quantitative computed tomographic (QCT) studies investigating hip fractures exist. (30)(31)(32) Owing to technical limitations of the QCT techniques applied, in particular, to assess cortical bone in the different compartments of the proximal femur, the ability of these studies to identify predictors of femoral fracture also is limited, despite the fact that QCT provides separate assessments of cortical and trabecular bone and measurement of 3D geometry. Therefore, in this 2-year case-control prospective in vivo study we aimed to identify QCT parameters that best discriminate hip fracture in postmenopausal women using an advanced image analysis software for 3D QCT images of the proximal femur that has already been used in in vivo (33) and in vitro (14) studies.…”

Bone mineral density changes on androgen deprivation therapy for prostate cancer and response to antiresorptive therapy

“…22 The predictors of femoral neck fractures are neck/shaft angle (NSA), medial calcar femoral cortex width (CFC), the trochanter (TRBMD), and Ward's triangle (WABMD). 23 On followup at 12-15 months, we noted a significant interval change compared to that of baseline (Table 3). At 12-15 months follow-up significant loss of BMD is noted in those who are not antiresorptive therapy, whereas significant improvement in BMD is noted in the group on antiresorptive therapy.…”