Application Of Botulinum Toxin A In Myocutaneous Flap Expansion

Part one The Experiment Research of Application of Botulinum Toxin A in myocutaneous flap expansion in minipigsBackground:Myocutaneous flap has been widely used in nowadays,problems such as area deficient and donor defect still restrict its application.Expansion of myocutaneous flap can meet the large defect at the same time close the donor site,however,the long time of expansion and contraction causing deformity need to be improved.Application of botulinum toxin A in myocutaneous flap expansion can speed up the expansion,increase the effective area,induce muscle atrophy and make thinner of myocutaneous flap.This research went further to quantify the effect of botulinum toxin A,identify the feasibility and efficacy of clinical application.Objective:To investigate the following aspects:1.what will be the influence on the origin(eg:net increase area and recruitment area) of the expansion area when botulinum toxin A was applied on myocutaneous flap expansion.2.What the contraction condition of the expanded myocutaneous flap will be in and after the period of validity of botulinum toxin A.3.The biomectmanic character changes of myocutaneous flap which were the mechanism that affect the expansion rate and the origin of expansion area.4. Whether the botulinum toxin A will affect the blood supply of myocutaneous flap when it speeding up the expansion rate.Methods:Fifteen minipigs were included in this experiment.The botulinum toxin A was injected in cutaneous muscle of one side of flank as experimental group(E group),the saline in other side as the control group(C group).Two 200ml expanders were inserted beneath the cutaneous muscle on the bilateral flank of each pig symmertrically.The expanders were filled with saline four-days-intervals and they were inflated to the same intracapsular pressure 90mmHg each time.(1) Seven minipigs were performed full amount(200ml) of expansion and then two weeks of maintain expansion.The basic intracapsular pressure,the inflated volume of each time,the expansion period,origin of expanded areas,the contraction rate and histologic changes of myocutaneous flap were compared.Thickness of each layer in myocutaneous flap was measured in histological section.(2) Four minipigs were performed full amount expansion(200ml) and then following two weeks maintain expansion,then test pieces were taken to detect the biomechanics properties of myocutaneous flap.(3) Four minipigs were performed 100% excessive expansion(300ml) and following three to five weeks of maintain expansion. Infrared thermography was taken at different stage and the temperature of the flap were drawn to reflect the blood supply of the expanded myocutaneous flap.Results:(1) Speed of expansion:under the same time interval and reach the same intracapsular pressure,inflated volume at each time in both groups were different: 26.1±3.2ml in E group and 15.7±2.8ml in C group(p<0.01);The basic intracapsular pressure in both groups were different and pressures in E group were lower than that of C group(p<0.01);Times of inflation to achieve the full expansion(200ml) were different: 7.7±1.1 times in E group and 13.1±0.8 times in C group(p<0.01);The total expansion time was different:28±3.3 days in experimental group and 45±4.5 days in control group(p<0.01).(2) The expansion areas and their origin:The increased ratio of the total expansion area in E group was 51.67%higher than C group when the actual injection volume were the same(p<0.01),the natural growth area has no significant difference between the two groups(p>0.05);Net increase area of expansion district in E group has a 32%increment than C group(p<0.01).The recruitment area in E group has a 20.17% increment than C group,there was significant difference between the two groups(p<0.01);(3)The contraction:instant contraction rate in E group was lower than C group,not only in width but in length(p<0.01);The long-term contraction in E group was smaller than C group at one week,one month,three months and five months post flap reconstruction(p<0.01);(4)The histologic examination indicated that the cutaneous muscle,capsule,dermis and the whole myocutaneous flap became thinner in E group(p<0.01),meanwhile the content of collagen fibers in E group was lower than in C group(p<0.01);(5)The biomechanics properties in E group,such as Young's modulus of elasticity,creep and stress relaxation were improved better for expansion when compared with C group,however the tensile strength of experimental group was lower than that of control group;The deformability in direction parallel to the spine was better than that in vertical direction in both groups and the tensile strength in both groups were decreased in parallel direction(p<0.01).(6) Infrared thermograhy revealed that temperature of distal part of myocutaneous flap in E group was higher than that of C group during the expansion period(p<0.05),five days post the reconstruction of flap,temperature of central part of flap in E group was higher(p<0.05) and the temperature of distal part has no significant difference in both groups(p>0.05).Conclusions: 1.Application of botulinum toxin A in myocutaneous flap expansion can speed up the rate of expansion.The total expansion area in E group was 51.67%higher than in C group,the net increase area was 32%higher and the recruitment area was 20.17% higher when compared with C group.No report has been published with regard to effect of botulinum toxin A on the origin of expansion area.2.Botulinum toxin A can decrease the collagen content of capsule,make thinner of dermis,cutaneous muscle and capsule,thus thining the whole myocutaneous flap in E group.It can reduce the immediate stretch-back ratio and the long-term contraction which made myocutaneous flap suitable for facial repair.No quantification report was seen up to now.3.It was the first time that infrared thermography was used to monitor blood supply of expanded myocutaneous flap.Results indicated that it was safe to perform 100% excess expansion when using botulinum toxin A in expansion of myocutaneous flap. Botulinum toxin A can improve the blood supply of expanded myocutaneous flap while it accelaterate the expansion rate.4.Botulinum toxin A can improve the Young's modulus of elasticity,creep and stress relaxation of expanded myocutaneous flap,however the tensile strength of E group was lower when compared with C group; Part two Application of Botulinum Toxin A in Clinical researchObjective:Botulinum toxin A was applied to patients in clinical treatment.To investigate the expansion speed,the histological changes of capsule and muscle and the long-term clinical efficacy.Methords:In clinic research,6 patients were in experimental group and another 6 patients in control group.Botulinum toxin A was injected in frontal muscle before expander insertion in experimental group.Then the expansion period,the thickness of capsule,histological changes of frontal muscle and therapeutic effect were observed.Results:1.The average inflated volume was 259ml in experimental group and 250ml in control group,there was not significant difference between the two groups(p＞0.05);The average expansion period was 53±6.6 days in experimental group and was 67±5.66 days in control group,there was significant difference between two groups(p＜0.01);2.The thickness of capsule in experimental group was significant thinner than that of control group(p<0.01);3.In experimental group the frontal muscle was apparently atrophy and the distance between muscle fiber was greater than that in control group.Arrangement of fiber was not regularity and the shape of muscle fiber was normal.4.The long-term therapeutic effects were satisfied.Conclusion:1.Applicating botulinum toxin A in myocutaneous flap expansion can reduce the resistance of expansion and speed up the expansion;2.The thickness of the capsule can be decreased;3.It can make the myocutaneous flap thinner which is suitable for defects repair in face and neck.