| Skin and soft tissue expansion has been an important therapy method and a basic technique in plastic and reconstructive surgery commonly used by plastic surgeons. It means implanting the skin tissue expander under the normal skin tissue and adding the capability of the expander in order to produce the pressure on the tissue of the skin surface to obtain the "additional " skin, which can be grafted for covering the wound. Its main drawback is that it has a long expansion period, which can be divided as injection expansion period and maintenance period. Although the expanded technique has been extensively recognized in clinic, the basic research about the method and mechanism of the skin expansion still exist some problems unsolved, the effect of maintenance period and its mechanism also needs to be further discussed. Biomechanics property is the base of getting "additional" skin of the expansion.Using biomechanics methods, through the study of the influence of different injection and maintain period on the expansion efficacy and shrinkage rate of skin, a rapid expansion method with relatively big expansion area is proposed; biomechanics analysis in vivo is been made on the expanded skin; comparing the biomechanics property in vitro of the rapid expansion and conventional expansion with different maintaining times, the parameters such as strength, stress-strain relationship, stress relaxation and creep which reflect the characteristic of the expanded skin have been obtained; making the research of the expanded skin's biomechanics changes at different stage after grafting, the long-term and short term diversified regular has been obtained; making experimental study and discussing the changes in the microcirculation and vessel structure of exceedingly expanded shin, the relationship between survival length of flap and the changes has been gotten.Dogs are set up as animal models. Six areas, 5 X 8cm each, are symmetrically designed on both sides of the dog back, marked by a machine for painting eyebrow. Expanders of 240/w/ are implanted in every area. Four groups is divided:1. Injection of 2 weeks, 2. Injection of 6 weeks, 3. sham-operation group, 4.Black control group. The first two groups are subdivided into three groups respectively according to maintaining time: one week, two week and fore week. Group 1 is injected every other day. Group 2 is injected once every week. The following items and data analysis are measured on the second stage surgery: (1) the area of the expanded skin. (2) Comparison with the rapid and the conventional expansion. (3) Tension of skin in vivo. (4) Immediate retraction rate of skin. (5) Histology examination. (6) The collagen content of skin. (7) Biomechanics properties of the skin, including: tensile strength and stiffness, stress-strain relationship, stress relaxation and creep.Experimental results are as following:1. Through the research of the tension in vivo, the immediate retraction rate and histology examination about the different ways and different maintaining, we get: the increase area of the rapid and conventional expansion has little difference with the expanded time; however it has significant difference with the maintaining time. It shows that shortening the expanded time is feasible in clinic, but shortening the maintaining time is out of the question; after the capsule is removed, immediate retraction rate of the expanded skin notably decreased, significantly different from those with intact capsule; the collagen content of the rapid expansion is just the same as the conventional expansion, but the changes of the histology dependences on the maintaining time. Comparison with conventional expansion, rapid expansion has no significant drawback; maintaining a period after expansion can greatly increase the area of expanded skin and reduce immediate retraction. Therefore maintaining a long period is necessary important for the expanded skin. Maintaining four weeks, the property of the skin is just the same as the normal skin.2. Comparison with the biom...
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