Introduction: Fractures have immediate morbidity, cost, reduce longevity; consequences that can be averted by preemptive immediate treatment provided women at risk of imminent fracture can be identified before the event. Neither bone densitometry nor FRAX assessment address this need. As increased cortical porosity and reduced trabecular density predispose to fracture, we hypothesized that measurement of microstructural deterioration will identify patients at risk of imminent fracture (with ~ 2 years of assessment) and will do so with greater sensitivity and specificity than BMD or FRAX.
Methods We tested this hypothesis in a prospective cohort of 589 women aged 42 to 94 years (The OFELY cohort). Distal radius microstructure was acquired using high resolution peripheral quantitative computed tomography (HRpQCT, Scanco Medical, Switzerland) and processed using StrAx1.0 (StraxCorp, Melbourne, Australia). Microstructural deterioration was expressed on a continuous scale as a Structural Fragility Score which captures the increment in cortical porosity and deficit in trabecular density relative to young normal women. Hip BMD was measured and FRAX scores calculated.
Results Of the 589 women, 33 (5.6%) sustained a fracture within 2 years of assessment. Sensitivity and specificity were 61% and 75% for the SFS, 18% and 95% for BMD; and 22% and 90% for FRAX. In a multivariate model, the SFS predicted imminent fractures independently of BMD and FRAX. The 9 out of 33 (i.e., 27.3%) individuals with imminent fractures captured by both BMD and FRAX were all captured by SFS.
Conclusion This the first prospective study showing that a measure of microstructural deterioration identifies women before an imminent fracture, and does so better than BMD and FRAX. Measurement of microstructure is likely to improve identification of women in need of immediate treatment.