A study was performed to compare the effects of reamed versus unreamed locked intramedullary nailing on soft-tissue blood flow in a fractured sheep tibia model. After creation of a standardized short spiral fracture, each tibia was stabilized by insertion of a locked intramedullary nail. Ten animals were randomized into two groups: one that had reaming prior to nail insertion and one that did not. Blood flow was measured in real time, using laser Doppler flowmetry. Skin and muscle perfusion measurements were made at three locations (proximal diaphysis, fracture site, and distal diaphysis) and at five time intervals (postfracture; postnail insertion; and at 2-week, 6- week, and 12-week follow-ups). All animals were sacrificed at 12 weeks postoperatively. Muscle blood flow remained elevated longer in the reamed group than in the unreamed group, following completion of the procedure. Muscle perfusion was significantly greater in the reamed group than in the unreamed group (p < 0.033) and was significantly greater than skin perfusion at 2 weeks (p < 0.024). There was no difference in shin perfusion between the reamed and unreamed groups at any time interval. The study demonstrates that muscle perfusion is altered following reamed and unreamed intramedullary nailing. The findings demonstrate the change in blood flow in the surrounding soft-tissue envelope during the process of revascularization, following devascularization of a segment of tibial cortex by intramedullary nailing.