Fracture healing in compression osteosynthesis in the dog.

The healing of fractures varies in pattern within wide limits, depending on several factors. Taking the degree of stabilisation as a parameter, it is usually found that the more rigid the fixation the less the periosteal reaction. This can be observed clinically in the healing of fractures fixed by stable osteosynthesis, in so far as radiologically visible callus seldom appears. If callus does appear it is often an indication ofinadequate stability (Weiser and Allgower 1962). With adequate stability, direct bone bridging of the fracture gap-the “ soudure autog#{233}ne” -takes place (Danis 1949). Willenegger, Schenk, Straumann, MUller, Allgower and KrUger (1962) verified this hypothesis experimentally in sheep and dogs, which Danis had based on clinical experience. Schenk and Willenegger (1963, 1964) studied the healing of fractures histologically after fixation with compression and observed what they called “ intracanalicular osteogenesis “-that is, direct formation of secondary osteones across the fracture gap. After the first phase of bone healing, with exudation, a vascular reaction follows. New vessels branch out from undamaged blood vessels adjacent to the fracture site and invade the fracture site. These vessels have two functions: firstly to break down and remove the inevitable necrotic tissues in the damaged region and, secondly, to create the network of blood vessels and capillaries which is a prerequisite for the construction of new tissue. The aim of the present investigation was to study by microangiography the vascular reaction and new vessel formation within the fracture ends and in the fracture gap after compression osteosynthesis. By using terramycin* to label the newly formed bone, and by means of current histological methods, it was possible to correlate the bone healing with the vascular reaction.