FRAX model predicts major osteoporotic fractures (MOF) ignoring sites other than the hip, spine, proximal humerus, and distal forearm. This study aims to quantify the contribution of non-major osteoporotic fractures (Non-MOF) to adverse outcomes and propose an alternative fracture classification based on anatomical site.
The study included 10,934 participants (69% females) aged 60+ from 2 longitudinal population-based cohorts: the Dubbo Osteoporosis Epidemiology Study and the Canadian Multicentre Osteoporosis Study. Fractures were classified as MOF (hip, vertebral, humerus, and forearm) and Non-MOF (remaining fractures except digits and skull) for aim 1, and as hip, vertebral, proximal (sites above elbow and above knee) and distal fracture (remaining sites except digits) for aim 2. Refracture and mortality risks were quantified using sex-specific multivariable-adjusted Cox models.
There were 1998 initial fractures (38% Non-MOF), 605 refractures (38% post Non-MOF) and 556 deaths (29% post Non-MOF) during 9551 person-years in females and 484 initial fractures (48% Non-MOF), 97 refractures (48% post Non-MOF) and 196 deaths (38% post Non-MOF) during 2230 person-years in males. Non-MOFs were associated with increased refracture risk of 69% in females (HR: 1.69; 95% CI: 1.47-1.95) and over 2-fold in males (2.06; 1.52-2.80), and over 33% excess mortality risk in both sexes (females: 1.37; 1.16-1.60, males: 1.33; 1.03-1.72) (Figure). MOFs were associated with higher but not significantly different risks of these adverse outcomes. The anatomical site classification, which incorporated more sites, showed incremental increase in the risk of refracture from distal, to proximal, vertebral and hip fractures which was significant for all groups. A similar pattern was observed for mortality. All groups were significantly associated with excess mortality except distal in males.
Non-MOF have significant consequences. Anatomical classification provides a more informative assessment of fracture severity than MOF classification and should be considered for the assessment of fracture risk and its outcomes.