The relationship between bone mineral density, vertebral body shape and spinal curvature in the elderly thoracolumbar spine: an in vitro study.

Vertebral body geometry, defined by the anterior/posterior (A/P) and mid/posterior (M/P) vertebral body height ratios, was measured in 18 vertebral columns (T1-L5) from sagittal computed tomography scans. For each vertebra, the trabecular density (VTD) and bone mineral density (BMD) were measured using quantitative computed tomography (QCT) and dual-energy X-ray absorptiometry (DXA), respectively. Lateral view radiographs were digitized to measure the thoracic curvature. The segmental correlations between vertebral shape and bone density were poor (r = 0.01-0.31). The mean thoracic BMD and VTD and the mean lumbar VTD were significantly correlated with the mean thoracic A/P ratio (r = 0.55-0.69). The thoracic curvature was significantly correlated with both the mean thoracic and the mean lumbar VTD and BMD (r = 0.55-0.73). In summary, the extent of vertebral wedging and thoracic curvature was moderately indicative of the mean BMD of the thoracic vertebrae, and lumbar spine densitometry is useful to assess the relative severity of osteopenia in individuals with thoracic vertebral deformities.