Metacarpal radiographic indices in the assessment of bone strength and fracture risk.

Osteoporotic fractures are associated with morbidity and increased
mortality, and treating fractures is an increasing expenditure for national
health systems. Targeting fracture preventative measures appropriately
starts with finding those at risk of fracture, services for which can be
expensive and poorly available. Metacarpal morphometry can potentially
be an inexpensive and widely available method of skeletal strength
assessment. In this study a semi-automated metacarpal morphometry
(SMCM) technique and a fully automated digital x-ray radiogrammetry
(OXR) technique were studied for fracture prediction ability.
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OXR was studied in a nested case-control setting with hip fracture patients
and controls (Hip fracture Prevention Study, HIPS), and OXR bone mineral
density (BMO) and OXR metacarpal index (MCI) were found to predict hip
fracture risk (odds ratio, OR 1.79 and 1.72 respectively for 1 standard
deviation (SO) decrease in measurement). OXR was also studied in a
prospective setting for vertebral fracture prediction (Vertebral Osteoporosis
Trial), and OXR-BMO and OXR-MCI were found to predict vertebral
fracture risk (OR 1.56 and 1.81 respectively). SMCM was studied in a
prospective setting (HIPS), and average MCI of 6 metacarpals (AMCI) was
found to predict all fracture risk and hip fracture risk (OR 1.30 and 1.42
respectively), but not clinical vertebral fracture risk. In all these settings
however, hip, spinal and forearm OXA measures had similar or higher
point estimates for the respective fracture risk predictions. There was a
trend for disproportionately greater bone loss with age at the metacarpals
by MCM measures, compared to hip or forearm OXA measures, especially
when associated with other medical conditions such as rheumatoid
arthritis.
Although MCM measures were not superior to OXA measures in fracture
risk prediction, there may be a useful role for them in epidemiological
studies or providing a clinical service where access to OXA is limited.