THE RELATIVE IMPORTANCE OF INTRAMEDULLARY, INTRACORTICAL, AND EXTRAOSSEOUS SOFT-TISSUE BLOOD-FLOW TO THE REPAIR OF DEVASCULARIZED CANINE TIBIAL CORTEX

Previous studies have not quantified the relative contributions of int racortical and extracortical perfusion to cortical porosity and new bo ne formation. The current study was performed to determine the relativ e importance of intramedullary, intracortical, and extraosseous soft-t issue blood flow and type of tissue to the repair of devascularized ca nine tibial cortex. A 2.5-cm segment of tibia between two standardized osteotomies was devascularized. The segment was replaced anatomically and stabilized with a plate. The animals were divided randomly into t wo groups: skin coverage (N = 8) and muscle coverage (N = 8). Thirty-o ne days postoperatively, cerium(141) microspheres were injected, prior to sacrifice, to measure blood flow. Extraosseous soft-tissue perfusi on was the same in the skin coverage and muscle flap coverage groups. There was no relationship between intramedullary or extraosseous soft- tissue flow and depth of new bone formation and cortical porosity. Int racortical blood flow was directly related to depth of new bone format ion (p = 0.0006) and cortical porosity (outer cortex, p = 0.001; inner cortex, p = 0.0001). These findings indicate that the cortical repair process is linked to the restoration of perfusion and that muscle cov erage, rather than the quantity of blood flow, determines the extent o f cortical repair.