A new fracture prediction model based on CT measures of bone microstructural deterioration can outperform the current BMD and FRAX-based approaches that miss the majority of fractures in older women, research shows.

The model developed by Professor Ego Seeman of Austin Health, Melbourne, uses high resolution peripheral quantitative CT  (HR-pQCT) to obtain a structural fragility score (SFS) from distal radial images in postmenopausal women.

Working in collaboration with French researchers, Prof Seeman has shown in a study that SFS detected two‐to three-fold more postmenopausal women having fractures than current BMD or FRAX methods.

In one cohort (QUALYOR), 1539 women with an average age of 67 years were followed for 4 years, while in another (OFELY) 561 women with an average age of 68 years followed for eight years after having baseline imaging done by HR-pQCT.

As expected, most fractures (80%) occurred in women with osteopenia or normal BMD rather than those with osteoporosis (defined as a BMD T-score of −2.5 SD or lower).

They also occurred disproportionately in women over 70 years of age, who comprised 29% of the cohort, but accounted for up to 62% of fractures depending on increasing follow‐up duration.

Using SFS scores of over 70 to define microstructural deterioration, the study showed that for each BMD category (osteoporosis, osteopenia and ‘normal’ BMD), fracture incidence was two to three times higher in women with SFS scores over 70 compared to those with under 70.

In multivariable analyses, SFS remained associated with fracture after accounting for BMD, whereas BMD was no longer, or weakly, associated with fractures after accounting for SFS.

Published in Journal of Bone and Mineral Research, the study showed that for women with osteopenia/normal BMD, an excess SFS score conferred an odds ratio for fracture of 2.69 to 5.19 for women of any age and 4.98 to 12.2 for women ≥70 years.

The study authors said SFS would be particularly valuable for identifying postmenopausal women with with an imminent risk of fragility fracture who would benefit from prompt therapy such as an anabolic agent. For women 70 years and over with osteopenia or normal BMD, the SFS had a 82.3% sensitivity and 72.5% specificity for fragility fractures within two years, compared to 5.88% and 94.7%, respectively for FRAX.

They acknowledged the high cost of CT scans for imaging of bone microarchitecture, but even with the current costs of USD$210 per SFS they calculated that it would be cost effective for fracture prevention.

Targeting women aged ≥70 years with osteopenia indicated that treating 25% using SFS to allocate treatment conferred a cost‐effectiveness ratio < USD $21,000/QALY saved, they estimated.

“Including a measurement of microstructural deterioration complements the used of BMD by identifying women at imminent, intermediate, and long-term risk for fragility fracture who otherwise remain undetected by measurement of BMD alone,” they concluded.

Professor Seeman and other authors declared a financial interest in StraxCorp, which is commercialising SFS technology into a marketed medical device.