Microvascular and histologic effect of circumferential wire on appositional bone growth in immature dogs.

Circumferential wires were placed around both midshaft femora of six immature dogs. On one side the wires were placed under the periosteum and on the other side the wires were placed over the periosteum. All wires were tightened to an equivalent tension. A diffuse growth of periosteal new bone occurred in those femora in which wires were placed under the periosteum but not in those over the periosteum. Corresponding microangiographs at 3 weeks in those femora in which wires were placed under the periosteum revealed dramatically increased medullary and periosteal vascularity coupled with histologic active trabecular bone formation. In those femora in which the wires were placed over the periosteum, even though the placement of the wires should supposedly have been the most detrimental, vascularity was not restricted. There were perfused vessels within the cortex directly under the wires. At 8 weeks the wires in both preparations were becoming encased in the growing cortical bone. Cerclage did not devitalize immature bone nor did it restrict adjacent appositional bone growth.