Architecture and distribution of cancellous bone yield vertebral fracture clues. A histomorphometric analysis of the complete spinal column from 40 autopsy specimens.

The objective of this study was to analyze the structure of cancellous bone and its significance for vertebral fractures. Therefore, the complete spinal column from 40 autopsy cases (18 without diseases affecting the skeleton and 12 osteoporotic) was removed and sectioned in the sagittal plane to a thickness of 1 mm. A surface-stained block grinding technique allowed combined two- and three-dimensional histomorphometric analysis, which included an evaluation of the trabecular bone volume (BV/TV, in %) and the trabecular interconnection (TBPf, in mm). In addition, qualitative investigation of the structure of trabecular bone was done. The distribution of trabecular bone volume within the spinal column of a normal skeleton shows a curve, with the highest values in the cervical spine and a decline in the thoracic and lumbar spine. Osteoporosis presents itself with a pathologically diminished trabecular bone volume, whereas the distribution within the spine is comparable to that of the controls. Osteoporotic patients show an apparently reduced trabecular interconnection. It is important that the measured values for TBPf are not only in general higher, but also more widely dispersed. The age-related decrease of trabecular bone mass is due to the transformation from plates to rods. This is quantitatively indicated by the close correlation of BV/TV and TBPf (P < 0.001, r = 0.85). The bone loss in osteoporosis is a loss of structure and a loss of whole trabeculae, which is caused by perforations. It involves a gradual change from normal bone. However, the polyostic heterogeneity in osteoporosis is immense. These structural differences demonstrate the development of regions of least resistance within the spine, serving as an explanation of osteoporotic fractures. Due to the polyostotic heterogeneity it is impossible to define a threshold mineral content for crash fractures by diagnostic measurements at any reference site.