Physeal fractures, part II: fate of interposed periosteum in a physeal fracture.

This study describes the histologic features of periosteum interposed into a physeal fracture of the rat proximal tibia. Periosteum was introduced into a physeal fracture in two groups of animals: those with an intact physis after fracture, and those with the medial half of the physis surgically ablated. Specimens of the proximal tibia underwent histologic analysis at 2, 4, 6, 10, and 21 days after fracture to determine the histologic features of interposed periosteum in a physeal fracture. In animals with an intact physis, interposed periosteum underwent one of two fates: it was degraded by giant cells in the fracture plane, which allowed cellular infiltration, or if the periosteum was closely surrounded by physeal cartilage, the physis grew around it and appeared to force it toward the metaphysis. In animals whose physis received surgical ablation, physeal bar formation was always present, with poor organization of the remaining lateral growth plate. Histologic evidence from this study also underscores the fact that physeal bar formation occurs from the migration of osteoblasts and osteoclasts along vertical septa.