Botulinum Toxin A In Forehead Soft Tissue Expansion

Background and Objective: The forehead expanded flap has been extensively used in therapy of facial trauma, scar, tumor and congenital deformity, because it have obvious advantages such as resembled color, abundant blood supply, and easy to be transferred. The forehead soft tissue expansion has become the best method for nasal reconstruction. However, the forehead anatomy demand the expander is implanted beneath the forehead muscle. So, the forehead soft tissue expansion is different from other region, as following: both skin and forehead muscle limit the expansion, prolong the therapy time; the patient feel headache and nausea while inflating, which slow the velocity of inflation; the forehead expanded flap, including the forehead muscle, is thick for the face; the forehead expanded flap tend to retraction. Therefore, we used the botulinum toxin A to make the forehead muscle paralysis and atrophy. The goal of our animal studies and clinical research is to investigate if the botulinum toxin A may reduce the expansion period, eliminate the pain and thin the expanded flap.PartⅠAnimal ExperimentsExperimentⅠAnimal experiment of using botulinum toxin A inforehead soft tissue expansionMethods: The six guinea pigs were the model of animal studies. Mark the bilateral chest and abdomen of every pig symmertrically in grid by tattoo. The botulinum toxin A was injected in cutaneous muscle of one side as experimental group, the saline in other side as the control group. Implant a 200ml expander beneath the cutaneous muscle on the bilateral chest and abdomen. The expander was inflated to the same pressure 90mmHg each time. It was inflated twice a week. Compare the basic expanded pressure, the inflated volume of each time, the expansion period, the expanded areas, the retraction rate of flap, as well as the histologic change of experimental group with the control group.Results: (1) the average expansion period in experimental group was 28±4.5 days, the control group was 42±3.5 days, there was significant difference between two groups(P<0. 01); (2) the inflated volume of each time in experimental group was 26.1±3.5ml, total 8±0.5 times, the control group was 16.7±0.9ml, total 12±0.8 times, there were significant differences(P<0. 01) ; (3) the basic expanded pressure in experimental group was 3.4±0.6mmHg, the control group was 10.1±0.8mmHg, there was significant difference between two groups(P<0. 01); (4) the increased ratio of centre part in experimental group was 69%, the increased ratio of whole area in experimental group was 58%, the increased ratio of centre part in control group was 57%, the increased ratio of whole area was 42%, there were significant differences between two groups(P<0. 01); (5)the instant retraction rate of flap in experimental group was smaller than the control group, not only in width and length, but in area(P<0.01); (6) the retraction of earlier period in experimental group was smaller than the control group(P<0. 05), but there was no difference in midanaphase between two groups(P>0.05); (7) the histologic examination suggested there was no differences in epidermis and derma between two groups, the cutaneous muscle in experimental group showed atrophy, electroscope examination showed A-H bands were dim and Z lines were irregular and curvate, the cutaneous muscle in experimental group showed necrosis 6 weeks later.ExperimentⅡStudy on biomechanical characteristics of using botulinum toxin A inforehead expanded flapMethods: The four guinea pigs were the model of animal studies. Mark the bilateral chest and abdomen of every pig symmertrically in grid by tattoo. The botulinum toxin A was injected in cutaneous muscle of one side as experimental group, the saline in other side as the control group. Implant a 200ml expander beneath the cutaneous muscle on the bilateral chest and abdomen. It was inflated 20ml each time, twice a week. After finished expansion, the speciments were cutted from the expanded flap, resect the capsule. The stress-strain relationship, stress relaxation and creep of these specimens were tested by using the material testing machine Instron4302.Results: the biomechanics properties in experimental group, such as stress-strain relationship, stress relaxation and creep, were better than the control group.PartⅡClinic research of using botulinum toxin A inforehead soft tissue expansionMethods: In clinic research, the 6 patients were in own control. The forehead was divided into two sides. Botulinum toxin A was injected in one side of forehead muscle and the saline in another side. After implanted the expander, the expansion period, pain and the thickness of flap were observed.Results: The average expansion period was 52 days; the pain index in experimental side was smaller than the control side; the expanded flap in experimental side was thinner than the control side; there was no side effect of botulinum toxin A and the patients were satisfied with the results.ConclusionsUsing the botulinum toxin A in forehead soft tissue expansion,1. it can reduce the inflational resistance, accelerate the expansion and shorten the expansion period;2. it can release the pain of expansion and accelerate the expansion;3. it can supply the more effective area of expansion;4. it can decrease the instant and early retraction of expanded flap, which is benefit for the scar of incision;5. it can improve the the biomechanics properties of forehead expanded flap;6. it make the forehead expanded flap thinner, which is suitable for facial repair.