The Study Of The Biomechanical Characteristics Of Expanded Free Skin Graft

Utilizing the local slided or revolved flap which has been expanded to cover the adjacent skin defect has become a basic method in plastic and reconstructive surgery commonly used by plastic surgeons. But sometimes this method is limited because there is too little normal skin in the adjacent area to be used. At this time ,only skin graft can be made use of. The expanded free skin graft from distant area can provide a large amount of skin.This study is aimed at testing and analyzing the changes of the various biomechanical characteristics of the expanded free skin graft, in order to discover some changing rules of the biomechanical characteristics of the expanded skin graft. This study can provide some theoretical basis for the transplantation of expanded free skin graft in clinical practice.Pigs are set up as animal models. Two areas are designed alongside on single side of the pig back. Expanders of 180ml are implanted in every area. Four groups are divided: A. Normal skin. B. Expanded skin flap. C. (Normal) Free skin graft (3 months after transplantation).D. Expanded free skin graft (3 months after transplantation).The following items and data analysis are measured. (1).The parameters of biomechanical characteristics, such as: stress-strain relationship, stress relaxation, creep and tensile strength have been measured on the test machine—Instron. (2).The content of collagen of skin. (3).Histology examination. (4)The content of bFGF and EGF of skin. Experimental results are as following:1. The stress-strain relationship of skin reflect the possibility of transformation of skin under various stress. Under the same stress, the numerical value of the strain of the normal skin ,expanded skin flap, expanded free skin graft, free skin graft increase gradually. This indicates the tendency of decrease of these skin's elasticity. Analyzed with statistic method, the numerical value of the strain and linear relative of the expanded skin graft has no significant difference from that of the normal skin( P>0.05) and the numerical value of strain and linear relative of free skin graft show significant difference from normal skin (P<0.05). This indicates that the ability of stress-strain relation of expanded free skin graft is more close to normal skin than free skin graft.2.The stress relaxation curve of free skin graft is obviously fall off from the curves of the other three groups. Compare with normal skin, the numerical value of stress relaxation and linear relative of the free skin graft is significantly different (P<0.05).On the other hand, the expanded free skin graft shows no significant difference from normal skin graft (P>0.05).This result indicate that at the same relaxant time, the relaxant ability of the expanded free skin graft is more close to normal skin than free skin graft.3.Under the same stress and within the same drawing time, the amount of creep(Je) of the free skin graft is the largest, and the linear relative is the lowest in the four test groups. Analyzed with statistic method, it has extreme significant difference from the normal skin (P<0.01). For the expanded free skin graft, there is significant difference (P<0.05). This result indicates: The creep speed and the amount of creep of the expanded free skin graft is more close to normal skin than free skin graft.