PREDICTION OF THORACIC AND LUMBAR VERTEBRAL BODY COMPRESSIVE STRENGTH- CORRELATIONS WITH BONE-MINERAL DENSITY AND VERTEBRAL REGION

The bone density of thoracolumbar vertebral columns (T-1 to L(5)) from 18 individuals was measured using quantitative computed tomography an d dual energy x-ray absorptiometry. Three hundred six isolated vertebr al bodies were tested in a materials test device to determine their co mpressive strength. Between T-1 and L(5) the mean segmental increase i n bone mineral content was 0.3 g, while the corresponding mean decreas e in trabecular density was 4.7 HU. Midvertebral body cross-sectional area increased by an average of 46 mm(2) per segment and the mean segm ental increase in compressive strength was 0.17 kN. Compressive streng th was significantly correlated with bone mineral density measured wit h dual energy x-ray absorptiometry (r = 0.86). Vertebral trabecular de nsity samples measured with quantitative computed tomography were poor ly correlated with compressive strength (r = 0.28); however, this was improved when the trabecular density was multiplied by the midvertebra l body cross-sectional area (r = 0.83). This study provides informatio n concerning the relationships between density and mechanical properti es of all thoracic and lumbar vertebral bodies across a wide age range . While the load-bearing capacity of the vertebral bodies is largely d ependent on their geometry and bone density, this relationship has bee n only extensively tested for the lumbar spine. This study extends the se observations over the lumbar and thoracic regions to provide a comp rehensive analysis of the strength characteristics of each vertebral b ody. This is particularly important given the paucity of data on the t horacic spine where age-related vertebral fractures predominate. These data provide a basis for the development of models to predict the pot ential for thoracolumbar fractures in the elderly vertebral column.