The Effect of Cortisone on Normal and Fractured Bone in the Rat

Summary Cortisone treated rats develop dense metaphyseal bone and, during the healing of frac‐tures, dense callus. At endochondral growth sites there is delay in maturation of chondrocytes and decreased extracellular Alcian blue‐staining mucopolysaccharide. Resorption ofcartilage is decreased so that more remains encased by bone in the metaphysis where trabeculae in their turn are not remodelled to form the diaphysis. In contrast to epiphyseal cartilage early callus growth is not greatly inhibited, but similar changes occur during remodelling. The result is a dense callus consisting of bone in various stages of maturation, prolonged retention of cartilage and failure of bony union. Thus in contrast to rabbits, where increased resorption is associated with osteoporosis, rats develop dense bone due partly to decreased resorption.