Consequences of the remodelling process for vertebral trabecular bone structure: a scanning electron microscopy study (uncoupling of unloaded structures).

Cylindrical trabecular bone specimens were obtained from the central part of the third lumbar vertebral body from 29 normal individuals aged 26-90 years (18 men, 11 women). The marrow was cleaned from the bone samples, but no removal of organic material was performed. The cylinders were freeze-dried and coated with gold. A Jeol JSM-840 scanning electron microscope was used for the investigation. The scanning electron microscopy (SEM) showed the loss of connectivity in the trabecular network with age--and the remodelling process causing this. Thin horizontal trabeculae with osteoclastic perforations could be demonstrated. These trabeculae, once disconnected and therefore no longer strained, seemed removed by an 'aggressive' osteoclastic resorption. On vertical trabeculae, microcallus formation was frequently seen in elderly individuals. Furthermore, the three-dimensional morphology of trabecular remodelling sites was also readily apparent. The remodelling sites covered areas of varying sizes (50 x 20-1000 x 1000 micron 2). SEM is an easy and refined tool for analysis of the mechanisms behind age-related changes in vertebral trabecular bone. It enables the whole remodelling process to be studied in the three-dimensional trabecular lattice and confirms and highlights the pathophysiological mechanisms suggested by normal histological studies.