Postmenopausal women with normal BMD who have fracture have deteriorated bone microarchitecture: A prospective analysis from the OFELY study.

Most postmenopausal women who sustain fragility fracture (Fx) have their areal bone mineral density (aBMD) above the osteoporosis threshold. A sizeable proportion of them have normal aBMD. The aim of this study was to prospectively investigate the association of fragility Fx with bone microarchitecture (MA) assessed by high resolution peripheral computed tomography (HR-pQCT) in postmenopausal women without low BMD. At the 14th annual follow-up of the OFELY study, we have measured bone MA at the distal radius and tibia with HR-pQCT in addition to areal BMD with DXA, in 586 postmenopausal women. Among them, 166 (29 %) women, mean (SD) age 65 (8) yr, had normal BMD defined as a T score ≥ -1 at the lumbar spine, femoral neck and total hip. During a median [IQR] 15 [14-15] yr of follow-up, 46 of those women sustained incident fragility Fx, including 19 women with a major osteoporotic Fx (clinical spine, forearm, proximal humerus, hip). Women who sustained Fx did not differ for age, BMI, tobacco and alcohol use, diabetes, falls, FRAX®, aBMD and TBS compared with women without incident Fx. In contrast, they had significant impairment of volumetric densities, cortical area (Ct.Ar) and thickness (Ct.Th), stiffness (K) and estimated failure load (FL) at the radius compared with women without incident Fx. At the radius, each SD decrease of volumetric densities, Ct.Ar, Ct.Th, K and estimated FL was significantly associated with an increased risk of all fragility fractures with hazard ratios (HR) from 1.44 to 1.56 and of major osteoporotic fractures (HR from 1.66 to 2.57). Lesser impairment of bone MA was seen at the tibia. We conclude that even in women with normal areal BMD fragility fractures are associated with deterioration of bone microarchitecture.