Comparison of Perivascular and Intramuscular Applied Botulinum Toxin A Pretreatment on Muscle Flap Ischemia-Reperfusion Injury and Chemical Delay

Background and Purpose Muscle flaps are known to be prone to local ischemia more than other flaps. The local and systemic injury that ensues after reperfusion of ischemic skeletal muscle is an important clinical problem in flap surgery. Flap delay may be applied chemically or sympathetically. Early use of botulinum toxin A (Btx-A) in muscle flap surgery relied on chemical denervation; however, in our study, we tried to emphasize a possible chemical delay mechanism of Btx-A, through the release of substance P and calcitonin gene-related peptide (CGRP) and vascular endothelial growth factor (VEGF). Methods Pretreatment with perivascular or intramuscular Btx-A was applied 1 week before the flap elevation, 3.5 units in 2 experimental groups each containing 8 Sprague-Dawley rats. The control groups (2 groups, each containing 8 rats) received 0.07 mL saline perivascularly and intramuscularly. The right gastrocnemius muscle flap was used as the experimental model. Ischemia-reperfusion cycle was applied to all groups. On the seventh day, the gastrocnemius flap was elevated, and perivascular tissues were observed macroscopically. Comparisons between perivascular Btx-A and intramuscular Btx-A groups were made, and the animals were killed. Muscle biopsies were taken. Damaged myocytes were counted using McCormack technique, and chemical delay was shown as angiogenesis, lymphocyte counts, and edema formation with VEGF3-R, CGRP, and substance P markers as immunohistochemical staining. Results The amount of muscle necrosis was the highest in intramuscular Btx-A admitted groups. The intramuscular and perivascular Btx-A groups showed significant angiogenesis scored blindly by the senior pathologist. Conclusions Potential role of Btx-A in ischemic preconditioning of muscle flaps achieved through the release of substance P, CGRP, and VEGF was investigated. Chemical delay was shown objectively by Btx-applied groups.