Evaluation of the Appropriate Time of Botulinum Toxin Type A Injection To Increase the Survival of Random Flaps in Rat.

[BACKGROUND] Although many previous studies verified the role of BTX-A in the augmentation of flap survival and decreasing the rate of necrosis in random pattern cutaneous flaps, drug injection at different times has not been investigated in this regard. This study compares the effect of BTX- A injection time at 0, 3, and 7 days before surgery to determine the best and most effective injection time.

[METHODS] In 20 male rats, divided into four equal groups, on different days of pre-operation (0, 3, or 7 days) BTX-A or saline was administered to the whole length of the flap. Random pattern dorsal skin flaps with 4:1 length-to-width ratios were elevated and returned to the original position. Flap survival was evaluated on day 10 and 20 after surgery and a histopathological examination were performed 20 days after flap elevation.

[RESULTS] The BTX-A group had a greater survival mean compared with the saline group (87.92±16.30 vs 65.60±30.71 or 1.34 fold increase in survival rate) in flaps with a length-to-width ratio of 4:1 ( = 0.05), and If botulinum toxin is injected 7 days before flap elevation, this increase in survival will be 1.5 times (97.5±4.06 vs 65.60±30.71) compared to the saline group ( = 0.02).

[CONCLUSION] Preoperative injection of botulinum toxin type A in random pattern skin flaps increases skin flap survival in rats, and the best time for injections is 7 days before flap elevation. We found a reduction in the proliferation of cutaneous myofibroblasts in flaps by injecting BTX-A. It could play a role in increasing blood flow and survival by reducing wound contraction, however, more studies should be conducted to determine the possible mechanism.