Histologic and morphometric observations on vertebral bone of aging sand rats.

The trabecular bone of the vertebrae of 30 male and 30 female sand rats (Psammomys obesus) aged 13 to 33 months was examined histologically and morphometrically. The usual age-linked decline of bone mass failed to occur in females and was statistically not significant in males. A few changes with age were noted at the cellular level. Sex differences were statistically significant only in animals living into the third year of life, males having a smaller bone mass than females. This abnormality of the vertebral spongiosa is attributed to pathologic local stresses caused by the numerous instances of disc degeneration and herniation. Differences in size, location, and age of the herniations are thought to account for the wide fluctuations in the individual bone parameters examined. Whereas the spine of the sand rat provides an excellent model for the study of spondylosis, it is unsuited as a model for age-linked osteoporosis.