Fracture history of healthy premenopausal women is associated with a reduction of cortical microstructural components at the distal radius.

OBJECTIVES: The objective of this study is to determine in healthy premenopausal women with a history of fracture which bone structural components of the distal radius are the most closely associated with a risk of fracture.

METHODS AND PARTICIPANTS: The method was as follows: 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. We evaluated differences in T-scores between FX and NO-FX and 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 as follows: 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); and endosteal perimeter, +0.28 (P = 0.032); and for strength estimates: stiffness, -0.15 (P = 0.030); failure load, -0.14 (P = 0.044); and apparent modulus, -0.28 (P = 0.006). T-scores of trabecular volumetric BMD and thickness did not significantly differ 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; and cortical thickness: 2.36 (1.53-3.63), P = 0.0001. The corresponding fracture risk for the strength estimates was as follows: stiffness: 1.66 (1.06-2.61), P = 0.028; failure load: 1.59 (1.02-2.47), P = 0.041; and 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, with 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.