Assessment of the bone mineral density in the lumbar vertebrae of newborns by quantitative computed tomography

To assess the true mineral density (BMD, in g/cm3) of the lumbar spine in newborns.

A postmortem analysis of five infants with gestational ages ranging from 35 to 40 weeks, and birth weights from 2765 to 3200 g, was conducted using dual-energy quantitative computed tomography (QCT; Siemens Somatom DR). A 2 or 4 mm thick slice was obtained for each lumbar vertebra from L1 to L4. The density measured in these vertebrae was corrected by reference to a solid phantom (Osteo-CT) measured simultaneously. A three-dimensional image of the spine (Elscint CT Twin), as well as a photomicrograph of histological preparation from L2 vertebra, were also obtained in another term baby for comparison with the CT results.

In the range of values studied, the vertebral densities were not dependent on birth weight. BMD values measured in L2, L3 and L4 were not significantly different, but were 10% lower than in L1 in four of five infants. The spatial resolution of the QCT protocol used (0.4 mm) did not permit the differentiation of trabecular and cortical bone, and the vertebral bodies appeared very homogeneous and dense, with a mean density value of 210 +/- 30 mg Ca/cm3, which is 2.5 times higher than the mean maximum value found in young normal adults. These preliminary results highlight the potential of QCT in neonatology. Special protocols will, however, need to be developed for in vivo measurements in this particular paediatric field.