| Summary of Background DataIt's rapid improved since Neuman created the conventional intermittent expansion in 1957.Now it's the most import method in plastic surgery But the survival of the skin flap after expanded was still exist controvert Starj G.B believed that expansion could cause neo-vascular proliferation because of dispnea and ischemia. Kaihuang Lu found not only areas of capillary was increased but also thicken after expanded. Thus caused blood flux raised and the survival of flap improved Xiaotiao Zhou also considered that it could lengthen the random flap 23% to 110%.But Chaojing Liu hold that it couldn't improve the survival of skin flap any more after long time clinical study.In our clinical we found that the distal area of flap always necrosis after broke the normal length. Especially on neck and head. Complete survival is aim in our work. In order to further research ,we designed this study. Becausethe skin structure on neck and head like it in loose-skin animal, So we toke rabbits as animal modelMaterials and methods1 animal model and experimental models20 female rabbits. Weighing 2500g-3200g were used. There were divide into 2 groups at random.Sham groups. lOrabbits. There were no expanded process. Four random skin flaps were designed at every rabbit Rates of length to wide were 2:1,2.5:1,3:1,3.5:1. observed the survive of skin flap on the first day, third day and seventh dayControl group chronic expanded(A)and acute expanded(B) 5 rabbits each. Group A. First 50cc expander was implant in each back deep to subdartrous layer. 8cc saline was injected in the meantime Intermittent saline injection after five days was performed. 3-4 each time. To 50cc in six weeks. After complete expanded Then implant was removed Two random skin flaps about 3:1 in wide to length were designed on each back. Observed the survival of skin flaps on the first day, third day and seventh day. Group B: First 50cc expander was implant in each back deep to subdartrous layer 8cc saline was injected in the meantime, saline injection after five days were performed. 6-8 each time, to 50cc in two weeks. After complete expanded. Then implant was removed. Two random skin flaps about 3:1 in length to wide were designed on each back. Observed the survival of skin flaps on the first day, third day and seventh day.1. Determination of rate of flap necrosisRatio of skin flap survival was determined at 7 days postoperatively the range of necrosis and survival of flap was estimated.2. histological examination.A full thick biopsy was toke from distal of skin flap (not necrosis) after 7 days in two groups. Samples were placed in 40% formalin and processed by paraffin embedding. And sectioned. Then stained with hematoxylin and eosin. Sections were evaluated at 400 flod magnification under light microscope. Pathogenic changes of capillary and tissue were also observedResult1 .Ratio of skin flap survivalRatio of skin flap surviveIn sham group. Skin flap survival of 2:1 was 100% And also 100% in 2.5:lcases, 85.1% in 3:1 cases. So we used 3: 1 in control group. Skin survival in chronic-expanded flaps was 79.8%,and 864% in acute-expanded flap.there was statistically significant between chronic-expanded skin flap and no-expanded skin flap. There was no statistically significant between acute-expanded skin flap and no expanded-skin flap It seem at expansion couldn't improve the skin flap survival.1. Histologically examinationThere were capillaries and thrombosis formation on chronic and acute expanded flap under light-scope. Especially on chronic expanded skin flaps. Capillary bleeding, articlethrombosis. Elastic and rctocular fiber proliferation, broken, and collagenolysis were observed after expansion .especially in chronic expanded sample.ConclusionAt present ways of maintaining skin flaps viability have:1 .colling. A process know to decrease metabalism and prolong tolerance to ischemia2.drugs Such as allopurinal or vasodilator Allopurinol has been show...
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