In-vitro relationships between vertebral body density, size, and compressive strength the elderly thoracolumbar spine.

The bone density of thoracolumbar vertebral columns (T1-L2) from 12 individuals having a mean age of 73 years was examined using quantitative computed tomography and dual energy X-ray absorptiometry. Spinal units, comprising three vertebrae, from different regions were then tested for compressive strength in a materials test device. Results showed segmental variations in trabecular and integral bone density of the vertebral bodies and their capacity for load bearing. Failure strength increased craniocaudally, whereas failure stress (load/cross-sectional area) decreased. Vertebral compressive strength was moderately correlated with bone mineral density as assessed with dual energy X-ray absorptiometry. In contrast, trabecular bone density determined from quantitative computed tomography was a poor predictor of compressive strength, as was bone mineral content. Use of an integral measure of bone density may provide a more practical guide to bone fragility.