STATIC AND FATIGUE FAILURE PROPERTIES OF THORACIC AND LUMBAR VERTEBRAL BODIES AND THEIR RELATION TO REGIONAL DENSITY

This study investigated (1) whether a characterization of the macrosco pic architecture within the vertebral centrum would improve prediction s of vertebral strength, (2) if regions in the centrum where least bon e loss with age occurs are more predictive of vertebral strength, and (3) whether different patterns of the macroscopic architecture are pre dictive of static as compared to fatigue strength. To characterize the vertebral macroscopic architecture, a regional bone mineral density ( rBMD) technique was used that estimated the cancellous density distrib ution (in 18 specific regions of the vertebral centrum) for vertebrae T7-L4, from spines of 20 female cadavers. Static and fatigue failure p roperties of whole vertebrae were obtained, and predictive models of s tatic and fatigue failure properties of whole vertebrae were examined. We found that (1) vertebral failure properties were better predicted by combinations of vertebral regional cancellous density (multiple lin ear regressions) rather than by any individual region of cancellous de nsity alone (simple linear regressions); (2) models using regions of d ensity that demonstrated minimum decline with age [from the data of Fl ynn and Cody (Calcif. Tissue Int. 53, S170-S175 (1993))] resulted in b etter correlations with ex vivo vertebral static failure properties th an models using density regions that showed maximum decline with age, and (3) static and fatigue characteristics required different density regions to reach significance. (A comparison of models predictive of s tatic and fatigue failure properties revealed that anterior density re gions were most often included in predictive models of the static prop erties while posterior regions were more predictive of the fatigue pro perties). The role of the distribution of cancellous density in contri buting to vertebral strength has been demonstrated, and these results may be useful in future studies focused on disease processes such as o steoporosis.