Imaging to Evaluate Bone Health
Bone mineral density (BMD) measurements by dual-energy x-ray absorptiometry (DXA) are an important part of a bone health assessment, and DXA scans of the lumbar spine and whole body are recommended for adolescents. Bone mineral content (BMC) and BMD are expressed as age-, sex-, and ancestry-specific Z-scores. As a two-dimensional technique, DXA measures areal BMD (aBMD), which is influenced by bone size. Adjustments of aBMD Z-scores are needed in patients with growth delay to prevent erroneous interpretation of results. The most promising adjustment approaches include calculation of bone mineral apparent density (BMAD) and correction using height-for-age-adjusted Z-scores. In select clinical circumstances, a bone age adjustment can be helpful as well. Follow-up DXA scans to aid clinical management should be performed every 1–2 years, at most. Vertebral fractures may be evident on DXA spine scans and invalidate aBMD results. Suspicion of vertebral fracture on a DXA scan warrants radiological follow-up. A special software for vertebral fracture assessment (VFA) by DXA has recently been found to be as good as conventional radiography in identifying moderate to severe vertebral fractures in children and adolescents. Several types of quantitative computed tomography (QCT) have been used to characterize bone, but they remain research tools in pediatrics owing to lack of standardization and reference ranges.
KeywordsBone mineral content Bone mineral density Bone mineral apparent density BMAD Bone fragility Delayed growth Dual-energy x-ray absorptiometry DXA Height-for-age Peripheral QCT Vertebral fracture
- 5.NCRP, National Council on Radiation Protection and Measurements. Limitation of exposure to ionizing radiation. National Council on Radiation Protection and Measurements, Bethesda; 1993; NCRP report no. 116.Google Scholar
- 21.Zemel BS, Kalkwarf HJ, Gilsanz V, Lappe JM, Oberfield S, Shepherd JA, et al. Revised reference curves for bone mineral content and areal bone mineral density according to age and sex for black and non-black children: results of the bone mineral density in childhood study. J Clin Endocrinol Metab. 2011;96(10):3160–9.CrossRefPubMedPubMedCentralGoogle Scholar
- 32.Wren TA, Kalkwarf HJ, Zemel BS, Lappe JM, Oberfield S, Shepherd JA, et al. Longitudinal tracking of dual-energy X-ray absorptiometry bone measures over 6 years in children and adolescents: persistence of low bone mass to maturity. J Pediatr. 2014;164(6):1280–5.e2.CrossRefPubMedPubMedCentralGoogle Scholar
- 34.LeBlanc CMA, Ma J, Taljaard M, Roth J, Scuccimarri R, Meiettunen P, et al. Incident vertebral fractures and risk factors in the first three years following glucocorticoid initiation among pediatric patients with rheumatic disorders. J Bone Miner Res. 2015;30(9):1667–75.CrossRefPubMedPubMedCentralGoogle Scholar