Reinnervation and neovascularisation in prefabricated free muscle flaps

In this study, immediate muscle reinnervation in flap prefabrication was investigated and compared with those flaps which were reinnervated after prefabrication. Using the flow-through wrap-around technique for neovascularisation, denervated external abdominal oblique random muscle flaps in Lewis rats were either immediately reinnervated by implantation of the epigastric nerve or reinnervated late after free transfer, following the prefabrication period of 15 days. Half of the flaps from each group were microsurgically transferred to isogeneic rats. Thirty days later, the flaps were harvested, and neovascularisation and reinnervation were studied with microangiography and immunohistochemistry using antibodies to protein gene peptide (PGP) 9.5, calcitonin gene-related peptide (CGRP), and von Willebrand factor (vWF). Microangiography and quantification of the vWF-stained vessels in the flaps confirmed increased neovascularisation over a longer time course. Reinnervation was found to have no influence over neovascularisation. Nerve sprouting was present 15 days after nerve implantation to the muscle and became widespread by 30 days. CGRP immunoreactivity, which is thought to have some role in trophic and regulatory processes, was observed only after 30 days of reinnervation. Regardless of the timing and extent of reinnervation, a considerable amount of muscle atrophy was observed in the flaps.