Failure load of thoracic vertebrae correlates with lumbar bone mineral density measured by DXA.

Fractures of the thoracic spine account for a large portion of vertebral fractures in the elderly, yet noninvasive measurements of bone mineral properties are limited to the L2-L4 vertebral bodies. The purpose of this investigation was to determine whether bone mineral properties of the lumbar spine correlate with the failure properties of thoracic vertebrae. Cadaveric lumbar segments were scanned using dual-energy x-ray absorptiometry (DXA) from both the lateral and anteroposterior projections. Three-body segments L1-L3 and T10-T12 were then compressed to create crush fractures in the L2 and T11 vertebral bodies, and linear correlation analyses were performed to compare each DXA measure with the failure properties of L2 and T11. Lumbar BMD from the lateral view correlated significantly with T11 ultimate load (r = 0.94, P < 0.001), as did lumbar BMD from the anteroposterior projection (r = 0.83, P = 0.001). Significant correlations were also found between both lumbar BMD and BMC and the stiffness and energy to failure of T11. Furthermore, BMD and BMC measured at L2 correlated significantly with L2 ultimate load, stiffness, and energy to failure. We conclude that bone mineral properties measured at the lumbar spine provide a valid assessment of the compressive strength of both thoracic and lumbar vertebrae. Lumbar BMD may therefore be used to derive an index for the prediction of thoracolumbar fractures to aid in the early intervention of vertebral fractures.