title: Biomechanical characteristics investigation on long-term free graft with expanded porcine skin.
abstract: BACKGROUND
  Free skin graft has to be used when the large area skin are burned. The objective of this study is to quantify the influence of free graft and expansion on the skin biomechanical remodeling.
  
  
  METHODS
  Four white pigs (weighing from 17 kg to 23 kg) were used. Two 180 ml rectangle expanders were aseptically placed beneath the skin on the back of each pig. Four normal skin flaps and four expanded skin flaps were incised from the foreside back of each pig. Two normal skin flaps and two expanded skin flaps were then grafted to rearward back of the pig. Stress-strain relationship, stress relaxation and creep characters in normal skin: N(n=8), expanded skin without graft: E(n=8), normal skin with free graft after three months: NG(n=8) and expanded skin with free graft after three months: EG(n=8) were measured by using Instron material testing machine.
  
  
  RESULTS
  The strains at 3.5 MPa stress (mean (SD)) are 0.4436(0.1760), 0.4851(0.1401), 0.7750(0.1984) and 0.5854(0.0655) respectively in N, E, NG and EG groups. The maximum relaxations (mean (SD)) are 0.6324(0.0169), 0.6279(0.0401), 0.5630(0.0170) and 0.6057(0.0883) in N, E, NG and EG groups, respectively. The maximum creeps (mean (SD)) are 1.0876(0.0086), 1.1037(0.0116), 1.1948(0.0394) and 1.1328(0.0223) in N, E, NG and EG groups.
  
  
  CONCLUSIONS
  The biomechanical characteristics of free graft with expanded skin after three months have no significant difference with the normal skin, expansion skin and free graft with normal skin after three months (P>0.05). The free graft and expansion have no significant influence on the skin biomechanical remodeling.
authors.affiliation: Beijing Tongren Hospital, Affiliate of Capital University of Medical Science, Beijing 100730, PR China. zhang.en.p@163.com
authors.forename: En-ping
authors.initials: EP
authors.lastname: Zhang
authors.forename: Dong-hua
authors.initials: DH
authors.lastname: Liao
authors.forename: Ai-zhen
authors.initials: AZ
authors.lastname: Liu
authors.forename: Xiao-bing
authors.initials: XB
authors.lastname: Wang
authors.forename: Xiao-yang
authors.initials: XY
authors.lastname: Li
authors.forename: Yan-jun
authors.initials: YJ
authors.lastname: Zeng
authors.forename: Su-jie
authors.initials: SJ
authors.lastname: Wang
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D002056:Burns / Q000601:surgery / Q000628:therapy; D004548:Elasticity; D006801:Humans; D019651:Plastic Surgery Procedures / Q000379:methods; D012867:Skin / Q000033:anatomy & histology* / Q000473:pathology; D012879:Skin Physiological Phenomena; D016038:Skin Transplantation / Q000379:methods*; D013314:Stress, Mechanical; D013552:Swine; D013718:Tensile Strength; D015626:Tissue Expansion / Q000379:methods*