January 26, 2018
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Peak bone mass, not rate of bone loss, predicts incident fragility fracture in postmenopausal women

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In white, postmenopausal women, peak bone mass, and not rate of change in bone quality, is associated with incident fragility fractures, according to findings published in the Journal of Bone and Mineral Research.

“Although DXA classifies individuals as being osteoporotic, less than half of all nonvertebral fractures occur in postmenopausal women with an osteoporotic T-score, indicating something other than, or in addition to, [areal bone mineral density] contributes to fracture risk,” Lauren A. Burt, PhD, senior scientist in the department of radiology at the Cumming School of Medicine, University of Calgary, Canada, and colleagues wrote.

Previous cross-sectional studies that employed machine learning have shown that high-resolution peripheral quantitative CT (HR-pQCT) outperforms DXA in fracture discrimination, the researchers wrote, suggesting that the structural bone parameters measured by HR-pQCT have a “unique, biomechanical interaction” contributing to diminished bone strength and predisposing individuals to fracture.

Burt and colleagues analyzed data from 163 postmenopausal women participating in the Calgary cohort of the population-based Canadian Multicenter Osteoporosis study, who were aged at least 60 years at the time of follow-up (97% white). During a mean follow-up of 5 years, participants completed annual questionnaires on fracture history, medical and health information, and nutrition and lifestyle habits. New incident fractures were confirmed by X-ray reports. Participants underwent DXA measurements of the total hip, left femoral neck and lumbar spine, and underwent HR-pQCT scanning to assess total and trabecular volumetric BMD, trabecular number, thickness and separation, as well as total cross-sectional area, cortical volumetric BMD, cortical thickness and cortical porosity. Researchers used t tests and chi-square analyses to compare differences between groups at baseline and the percent difference between incident fracture (n = 22) and nonfracture (n = 127) groups, and calculated ORs of fracture status per standard deviation change.

In assessing baseline HR-pQCT measurements of the radius, researchers found that women who sustained a fracture had a 19% lower total trabecular BMD, a 25% lower trabecular BMD and a 14% lower trabecular number with 19% higher trabecular separation vs. women who did not sustain a fracture.

At the tibia, women with incident fracture had a 15% lower total trabecular BMD, 12% lower trabecular volumetric BMD, 14% lower cortical thickness, 12% lower cortical area and 10% lower failure load, according to researchers, as well as a 7% higher total area and 10% higher trabecular area vs. women who did not sustain a fracture.

At the radius, every 1 standard deviation decrease in total BMD, trabecular volumetric BMD and trabecular number was associated with an increased OR for fragility fracture (OR = 2.1 for total BMD; OR = 2 for trabecular volumetric BMD; OR = 1.7 for trabecular number). At the tibia, every 1 standard deviation decrease in total BMD, trabecular volumetric BMD, cortical thickness, cortical area and failure load was associated with an increased OR for fragility fracture, with ORs of 2.1 for total BMD, 1.7 for trabecular volumetric BMD, 2.2 for cortical thickness, 1.9 for cortical area and 1.7 for failure load.

The annualized percent rate of bone loss was not different between fracture groups, regardless of scanning modality, according to researchers.

“In our Calgary cohort, we found baseline impairment of bone quality predicts incident fragility fracture over 5 years at both the radius and tibia,” the researchers wrote. “There were no differences in rate of change for any DXA, HR-pQCT or finite element bone parameter between women who fractured and those who did not fracture. Our conclusions suggest peak bone mass and density play an important role in fragility fractures and is more relevant than rate of bone loss.” – by Regina Schaffer

Disclosures: The authors report no relevant financial disclosures.