Aortic calcification contributing to bone densitometry measurement

A 75-yr-old glucocorticoid-dependent asthmatic male had a bone mineral density study to assess possible osteoporosis prior to initiating therapy. A radiograph of the lumbar spine revealed an asymmetrical compression of the second lumbar vertebra, marked scoliosis, vertebral osteopenia, and a highly calcified abdominal aorta. Bone mineral density (dual X-ray absolptiometry [DXA]) revealed low bone mass in L2-L4 and a markedly abnonrnal pattern, with a linear central density representing a calcified aorta. Posterior-anterior measurements of the midlumbar region with and without the overlying aorta indicated that the calcified vessel contributed up to 33% of the measured density. This was a far higher contribution than reported in other studies. Lateral DXA measurements of the L2 vertebra and the overlying aorta were performed to validate this finding. The density of the L2 vertebra was 0.215 g/cm(2), and that of the overlying calcified aorta was 0. 210 g/cm(2). This case suggests that aortic calcifications may contribute sign)ficantly to overall lumbar bone density and, unless recognized, can inadvertently lead to misclassification of osteoporosis.