INTERVERTEBRAL VARIATION IN TRABECULAR MICROARCHITECTURE THROUGHOUT THE NORMAL SPINE IN RELATION TO AGE

The vertebral bodies of the complete spine (C-3-L-5) were removed in 26 autopsy cases without evidence for primary or secondary bone disease (13 males aged 19-79 years and 13 females aged 17-90 years). A sagittal segment through the center of all vertebral bodies was embedded undecalcified in hydroxyethylmethacrylate and processed to so-called surface stained block grindings. Histomorphometric analysis of the complete segment was performed using a computer-assisted image analysis system (IBAS 2000). The structural parameters investigated were bone volume (BV/TV) and trabecular interconnection quantificated by trabecular bone pattern factor (TBPf). A close correlation of BV/TV and TBPf was found in all vertebral bodies irrespective of vertebral region (r = 0.8, p < 0.001). This indicates that the age-related decrease of trabecular bone mass is primarily the consequence of the transformation from plates to rods and the loss of whole trabecular structures. This basic principle is valid throughout the complete spine. However, the systematic analysis of vertebral trabecular bone from C-3 to L-5 revealed a significant intervertebral variation of trabecular microarchitecture. The density of trabecular structure of cervical vertebrae is much higher than that of thoracic and lumbar vertebrae (p < 0.001). The extent of age related loss of trabecular bone mass and structure showed a decrease within the spine from the caudal to the cranial region (p < 0.05). The loss of bone volume in individuals between the ages of 30 and 80 years in the lumbar spine was 53%, whereas in the thoracic spine the decrease was 41%, and in the cervical spine only 24%. In C-3 and C-4 no significant age-related loss of trabecular structure density was observed. The bone volume of a single vertebra was noted to differ from the mean of its respective vertebral region by as much as 30%. The present study showed that trabecular structure of lumbar vertebrae and its age-related changes only partially represented thoracic and cervical vertebrae. It was of limited value, especially for the prediction of structure of a single unmeasured vertebral body, The consequences for the prediction of fracture risk were discussed.