Regional variations in trabecular architecture of the lumbar vertebra: associations with age, disc degeneration and disc space narrowing.

Previous studies suggest that age and disc degeneration are associated with variations in vertebral trabecular architecture. In particular, disc space narrowing, a severe form of disc degeneration, may predispose the anterior portion of a vertebra to fracture. We studied 150 lumbar vertebrae and 209 intervertebral discs from 48 cadaveric lumbar spines of middle-aged men to investigate regional trabecular differences in relation to age, disc degeneration and disc narrowing. The degrees of disc degeneration and narrowing were evaluated using radiography and discography. The vertebrae were dried and scanned on a μCT system. The μCT images of each vertebral body were processed to include only vertebral trabeculae, which were first divided into superior and inferior regions, and further into central and peripheral regions, and then anterior and posterior regions. Structural analyses were performed to obtain trabecular microarchitecture measurements for each vertebral region. On average, the peripheral region had 12-15% greater trabecular bone volume fraction and trabecular thickness than the central region (p<0.01). Greater age was associated with better trabecular structure in the peripheral region relative to the central region. Moderate and severe disc degeneration were associated with higher trabecular thickness in the peripheral region of the vertebral trabeculae (p<0.05). The anterior region was of lower bone quality than the posterior region, which was not associated with age. Slight to moderate narrowing was associated with greater trabecular bone volume fraction in the anterior region of the inferior vertebra (p<0.05). Similarly, greater disc narrowing was associated with higher trabecular thickness in the anterior region (p<0.05). Better architecture of peripheral trabeculae relative to central trabeculae was associated with both age and disc degeneration. In contrast to the previous view that disc narrowing stress-shields the anterior vertebra, disc narrowing tended to associate with better trabecular architecture in the anterior region, as opposed to the posterior region.