Contrasting microanatomy of idiopathic and corticosteroid-induced osteoporosis.

Previous studies of microanatomic changes in normal bone with age have suggested that underlying differences in bone remodeling between male subjects and female subjects give rise to different patterns of bone loss. The relationship between microanatomic and histologic levels of organization are herein examined in two groups of osteoporotic subjects, one with idiopathic and the other with corticosteroid-induced osteoporosis. Using tissue from the iliac crest, total trabecular surface and trabecular width and number were measured, together with bone volume and static and dynamic indices of formation (osteoid surface, seam width, mean wall thickness, lamellar thickness, calcification fronts, and mineralization rate) and resorption (total resorption cavities and osteoclast incidence). The results suggest that while a similar loss of trabecular bone volume is common to both groups, there is a marked distinction in the distribution of the remaining bony tissue and indices of remodeling. A decline in trabecular number accompanied by a relative increase in resorption characterized both sexes with primary osteoporosis, whereas a decline in trabecular width associated with depressed formation was the predominant feature in the secondary disease. Thus trabecular attenuation is principally the manifestation of depressed formation, while trabecular discontinuity is primarily the manifestation of bone resorption.