Differences in hip quantitative computed tomography (QCT) measurements of bone mineral density and bone strength between glucocorticoid-treated and glucocorticoid-naive postmenopausal women

Abstract

Chronic treatment with glucocorticoids (GCs) leads to significant bone loss and increased risk of fractures. In chronically GC-treated patients, hip fracture risk is nearly 50%. The purpose of this investigation was to determine if there are differences in the quantities of trabecular and cortical bone and bone strength of the hip between GC-treated osteoporotic patients and controls.

Methods: Study subjects were GC-treated osteoporotic postmenopausal women, and controls were postmenopausal women, recruited for separate clinical trials. Quantitative computed tomography (QCT) and dual-energy X-ray absorptiometry (DXA) of the hip were obtained from all subjects. QCT outcome variables measured included total, cortical, and trabecular BMD of hip subregions (femoral neck and trochanter) and total hip. In addition, finite element modeling (FEM) was performed on a subset of 19 cases and 38 controls, matched on age (+/- 5 years), weight (+/- 5 kg), and history of hormone replacement (> 1 year use) to assess failure load in stance and fall loading conditions. Generalized linear models were used to adjust the QCT variables for covariates between groups. Multiple regression was performed to identify independent predictors of bone strength from the QCT variables.

Results: Compared with controls, GC-treated subjects were significantly (p < 0.05) younger, weighed less, and had more years of hormone replacement. QCT of the hip in GC-treated subjects for total femoral integral, cortical, and trabecular BMD averaged 4.9-23.2% (p < 0.002) less than controls, and similar results were seen by hip subregion including the trochanter and femoral neck. DXA of the total hip was 17% lower in GC subjects than controls (p < 0.05). Compared with controls, FEM failure load in GC subjects was 15% (p<0.05) and 16% (p = 0.07) lower for stance and fall loading conditions, respectively. Multiple regression analysis demonstrated that a combination of QCT measures was correlated with bone strength as measured by FEM.

Conclusions: Chronic GC treatment in postmenopausal women resulted in significantly decreased BMD of the hip, measured by QCT, with loss of both trabecular and cortical bone. In addition, GC treatment decreased bone strength as determined by FEM. The reduced cortical and trabecular bone mass in the hip may contribute to the disproportionately high hip fracture rates observed in GC-treated subjects.