Metacarpal morphometry using a semi-automated technique in the assessment of osteoporosis and vertebral fracture risk

Metacarpal morphometry represents a potentially cheap and widely available non-invasive assessment of skeletal status. In two cross-sectional studies, we compared the performance characteristics of a semi-automated technique (the Teijin Bonalyzer) with an in-house manual measurement, and with measures of skeletal strength at other sites. The metacarpal cortical index (mCI) was measured on hand radiographs of 178 osteoporotic women using both the Teijin Bonalyzer and a digitizing tablet. Measurements on the latter were consistently lower than with the Bonalyzer except for mCI (0.443 +/- 0.080 vs 0.364 +/- 0.060, p<0.001), although correlation coefficients between these two methods were highly significant (r = 0.62-0.83, p<0.001). The reproducibility errors of metacarpal bone mineral density (mBMD) were constant (1.1-1.2%) whilst those for mCI showed a marked operator-dependency (2.0-7.9%). In 379 elderly community-dwelling women, Bonalyzer mCI and mBMD showed a significant decline with age (r = -0.30 and -0.27 respectively, p<0.05). Both mCI and mBMD correlated significantly with forearm BMD (r = 0.50 and 0.57 respectively, p<0.001) and hip BMD (r = 0.48 and 0.53 respectively, p<0.001). After adjustment for age and weight, hip BMD demonstrated the best: discrimination for prevalent vertebral fractures as judged by the gradient of risk for a 1 SD decrease in measurement (odds ratio (OR) 2.17, 95% CI 1.56-3.01). Similar but smaller gradients of risk were shown by Bonalyzer mCI (OR 1.32, 95% CI 1.00-1.75), mBMD (OR 1.35, 95% CI 1.02-1.78) and forearm BMD (OR 1.39, 95% CI 1.08-1.80). MCI, and in particular mBMD, may be useful assessments of bone mass and fracture risk. In our study, it is comparable to peripheral assessment of skeletal status by forearm densitometry.