Fracture History of Healthy Premenopausal Women is Associated with a Reduction of Cortical Microstructural Components at the Distal Radius.

Chevalley T , Bonjour JP , van Rietbergen B , Ferrari S , Rizzoli R
OBJECTIVES: To determine in healthy premenopausal women with a history of fracture which bone structural components of distal radius, are the most closely associated with a risk of fracture. METHODS AND PARTICIPANTS: Measurement of radial areal bone mineral density (aBMD) by DXA, microstructural components by high-resolution quantitative peripheral computerized tomography (HR-pQCT) and strength variables by micro Finite Element Analysis (μFEA) in 196 healthy premenopausal women aged 45.9±3.7 (±SD) years with (FX, n=96) and without (NO-FX, n=100) a history of fracture. Evaluation: differences in T-scores between FX and NO-FX; risk of fracture by Odds ratios (OR with 95% confidence intervals, CI) per one SD decrease, using logistic regression analysis after adjustment for age, height, weight, menarcheal age, calcium and protein intakes, and physical activity. RESULTS: In the whole group the mean radial metaphysis aBMD T-Score was not significantly different from zero. In the FX as compared to the NO-FX group, the differences in T-Scores were for: radial metaphysis aBMD, -0.24 (P=0.005); for distal radius microstructure components: cortical volumetric BMD, -0.38 (P=0.0009); cortical thickness, -0.37 (P=0.0001); cross-sectional area (CSA), +0.24 (P=0.034); endosteal perimeter, +0.28 (P=0.032); for strength estimates: stiffness: -0.15 (P=0.030); failure load: -0.14 (P=0.044); apparent modulus: -0.28 (P=0.006). T-scores of trabecular volumetric BMD and thickness did not significantly differed between the FX and the NO-FX group. Accordingly, the risk of fracture (OR, 95% CI) for 1 SD decrease in radius bone parameters was as follows: radial metaphysis aBMD: 1.70 (1.18-2.44), P=0.004; cortical volumetric BMD: 1.86 (1.28-2.71), P=0.001; cortical thickness 2.36 (1.53-3.63), P=0.0001. The corresponding fracture risk for the strength estimates was: stiffness 1.66 (1.06-2.61), P=0.028; failure load 1.59 (1.02-2.47), P=0.041; apparent modulus 1.76 (1.17-2.64), P=0.006. CONCLUSIONS: In healthy premenopausal women, a history of fracture is associated with reduced T-Scores in the distal radius, the cortical components showing the greatest deficit. A reduction of one SD in cortical thickness is associated with a nearly three-fold increased risk of fracture. This finding strengthens the notion that, in healthy women, a certain degree of bone structural fragility contributes to fractures before the menopause and therefore should be taken into consideration in the individual prevention strategy of postmenopausal osteoporosis.

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