Morphologic aspects of bone healing after third-degree open fractures. An experimental study.

The morphologic aspects of undisturbed and disturbed bone healing following third-degree open fractures is demonstrated by means of experimental investigations using animals. As an experimental model we used a canine thigh fractured by a shot. The data was obtained as part of bioballistic investigations of the effect of highvelocity bullets in living tubular bones. The shot fracture was immobilized by external fixation. Progressive radiological controls, as well as microangiographic, microradiographic and histological findings are used to show bone healing. Bone healing following shot fractures follows the basic pattern of secondary bone healing, which is manifested in an X-ray by the formation of periosteal callus. The periosteal callus tissue has its own vascular system and receives blood from the extraosseous vessels of the adjacent soft tissue surrounding it. It not only fulfills the function of the biological stabilizer of the fragments, but also contributes decisively to their revascularization through transcortical anastomosis. The morphologic appearance and the causes for the disruption of bone healing are demonstrated using individual examples. Predominant are insufficient stability and above all circulatory disturbances. In the case of fractures with considerable soft-tissue damage, not only is the intramedullary vascular system destroyed, but the blood supply to the periosteal vessels is also disrupted. The resulting delay to or absence of callus formation leads on the one hand to insufficient biological stabilization, and on the other hand to an impairment of fragment revascularization. The morphologic appearance is dominated by the fragment necroses and related complications, such as pseudarthrosis induced by bone necrosis and infected pseudarthrosis.