EVALUATION OF VERTEBRAL VOLUMETRIC VS AREAL BONE-MINERAL DENSITY DURING GROWTH

Bone mineral ''density'' (BMD) measured by dual-energy X-ray absorptio metry (DEXA) does not represent the volumetric density (grams per cubi c centimeter), but rather the areal density (grams per square centimet er), This distinction is important during growth, The purpose of this study was to measure vertebral dimensions in cadavers of young pigtail macaques (Macaca nemestrina), and to derive equations to predict the volumetric bone density from noninvasive measurements, We measured the areal bone density by DEXA, vertebral volume by underwater weighing, mineral content by ashing, dimensions of lumbar vertebrae by calipers, and dimensions of vertebrae by radiography, Somatometric measurements of the female lumbar vertebral bodies showed that the shape changed d uring growth, The bone mineral content from the densitometer correlate d significantly with the ash weight (r = 0.99, error 8.7%), The correl ation coefficient between the volumetric bone mineral density and area l BMD measurement was significant (r = 0.68, p < 0.0001) with a 9.5% e rror; this improved significantly to 0.82 (7.2% error) when the BMD wa s divided by the vertebral depth from the radiograph. Areal BMD showed a strong correlation with age (r = 0.82, p < 0.0001), with an average increase of 7.4%/year. In contrast, volumetric mineral density showed a weak relationship with age (r = 0.43, p < 0.01), for an average inc rease of 1.5%/year, When studying bone mineral density during growth, the differences between volumetric and areal bone mineral density shou ld be taken into consideration. (C) 1997 by Elsevier Science Inc.