Background: Although the use of the expanded myocutaneous flap has many advantages, the time course is prolonged. The net gain in surface area during acute expansion is insufficient. In this study, botulinum toxin type A was applied to shorten the flap expansion period while obtaining an adequate surface area that would meet surgical requirements.
Methods: Seven minipigs were used for the authors’ experiments. Two sides of the dorsolumbar section in each pig were divided randomly into the botulinum toxin type A–treated and the saline-treated groups. Two 200-ml expanders were implanted in the submuscular pocket. Inflation began 2 weeks later, and the period of expansion was observed in a double-blind manner. Two weeks after the final inflation, the expansion area was measured, and a 10 × 6-cm myocutaneous flap was elevated and sutured in situ, and the contraction of the myocutaneous flap was observed.
Results: Botulinum toxin type A shortened the expansion time by 17 days (p < 0.001). The average increment of effective expansion area (p = 0.009) and the average recruitment area (p = 0.001) in the botulinum toxin type A–treated group were significantly higher than in the saline-treated group. Moreover, contraction in axial length and width of the botulinum toxin type A–treated group was lower than that of the saline-treated group at each time point following transposition (p < 0.001).
Conclusions: Botulinum toxin type A could decrease the resistance to myocutaneous flap expansion, speed up the inflation, increase the expansion area, and reduce the contraction of the myocutaneous flap. It is a safe and convenient method with which to assist myocutaneous flap expansion.