The influence of muscle flap coverage on the repair of devascularized tibial cortex: an experimental investigation in the dog.

Segments (2 cm) of canine tibial diaphyseal bone were devascularized and internally fixed with a plate. The medial cortex of the devascularized tibia was covered with skin in one experimental group (n = 7) and a local muscle flap in the other (n = 6). The animals were given intravenous fluorochrome dye and killed 42 days postoperatively. Enveloping callus formed around the cortex which was repaired by the formation of resorptive cavities on its external surface. New bone formation occurred within the resorptive cavities. Muscle flap coverage was associated with a sixfold increase in cortical porosity (p less than 0.005) and a fourfold increase in the area of enveloping callus (p less than 0.05). The area of intracortical new bone formation was greater in the cortex with muscle flap coverage (p less than 0.05). The maximum depth of intracortical new bone formation increased from 0.46 +/- 0.14 mm with skin coverage to 0.95 +/- 0.14 mm with muscle flap coverage (p less than 0.001). This study demonstrates that muscle flaps are superior to skin coverage in initiating the repair of devascularized cortical bone.