Introduction and Aims: We have developed a novel murine open tibial fracture model to compare the vascularity of muscle and fasciocutaneous flaps during fracture healing and investigate their role in angiogenesis.

Method: Flaps were emulated by insertion of a piece of sterile, inert material (Polytetrafluoroethylene, PTFE), at the fracture site to exclude either muscle posteriorly (fasciocutaneous flap) or skin and fascia anteriorly (muscle flap). Animals were harvested at days three, five, seven, nine and 14 post-fracture. Immunohistochemistry was performed on specimens, to estimate vascularity using an antibody to factor VIII, which selectively demonstrates vascular endothelium. Vascular densities were determined within the muscle and fasciocutaneous tissues adjacent to the fracture sites. Vascular Endothelial Growth Factor (VEGF) was measured by ELISA in tissue specimens. Immunohistochemistry was performed to qualitatively assess distribution of VEGF.

Results: Significantly greater vascular densities per unit area were observed in fasciocutaneous flaps at all time points compared to muscle flaps (p< 0.0001). VEGF levels peaked at day seven post-fracture, fell at day nine, and increased again at day 14. This time-dependent variation was statistically significant (p< 0.02). However, there was no significant difference between muscle and fasciocutaneous flaps. Maximal staining for VEGF occurred on the deep surface of the flaps adjacent to the fracture site. We found that fasciocutaneous flaps have significantly higher vascular densities compared to muscle flaps during early fracture healing.

Conclusion: Our results contradict the widely held view that muscle flaps are superior. However, there was no significant difference between levels of the pro-angiogenic factor VEGF within the flaps. This would suggest that both flaps are equally effective in supplying the factors necessary for new vessel formation. Our data supports the continuing use of muscle and fasciocutaneous flaps in the clinical setting.