Objective: To investigate the effects of botulinum toxin type A (BTXA) on the excessive expansion speed and blood supply of myocutaneous flap.
Methods: Seven adult Guizhou minipigs of clean grade were included, female or male and weighing 16-20 kg. The 2.4 mL BTXA solution (96 U) was injected in cutaneous muscle (24 points) of one side as experimental group (n = 7), the 2.4 mL saline in the other side as control group (n = 7). Two expanders (200 mL) were implanted beneath the cutaneous muscle on the bilateral flank of each pig symmetrically at 3 days after injection. One week later, the expanders were filled with saline every 4 days with an intracapsular pressure of 11.97 kPa, and accumulative total amounted to 400 mL for 3 weeks in control group and 5 weeks in experimental group. Then the expanders were taken out; the myocutaneous flaps formed and were sutured in situ. The myocutaneous flaps were cut for histological examination and capillary count. The expansion speed of the myocutaneous flap were recorded. The blood supply of the myocutaneous flap were observed by infrared thermography at 1 week after implantation expanders, before removing the expanders, and at 5 days after myocutaneous flap suture in situ.
Results: All the animals survived to the end of the experiment. The total expansion time was (54.0 +/- 3.1) days in experimental group and (67.0 +/- 3.9) days in control group, showing significant difference (t = -8.107, P = 0.000). All myocutaneous flaps survived after being sutured in situ. Infrared thermograph revealed that the temperature of the distal myocutaneous flap in experimental group was significantly higher than that in control group at 1 week after implantation of expanders (P < 0.05); at 5 days after myocutaneous flap suture in situ, the temperature of the central flap in experimental group was significantly higher than that in control group (P < 0.05); and there was no significant difference between 2 groups at the other time points (P > 0.05). The histological observation showed that the blood vessel density of the dermal layer and tissue between the capsule and the muscle layer in experimental group was significantly higher than those in control group (P < 0.05).
Conclusion: When excessive expansion is performed, BTXA can accelerate the expansion rate and improve the blood supply of expanded myocutaneous flaps.