title: Skin response to repetitive mechanical stress: a new experimental model in pig.
abstract: OBJECTIVE
  To develop a new animal model for investigating the relations between interface stresses at the skin, adaptation, and breakdown. There were two hypotheses. (1) In skin subjected to varying types of repetitive mechanical stress, the tissue response depends on the direction and magnitude of the load. As the shear stress increases, tissue breakdown occurs earlier. (2) In skin subjected to repetitive mechanical stress of longer duration, there will be evidence of tissue adaptation.
  
  
  METHODS
  Multiple case control, single-blind.
  
  
  METHODS
  Varying combinations of normal and shear mechanical loads are applied to pig's skin for short durations (breakdown studies) or longer durations (adaptation studies).
  
  
  METHODS
  Gross evidence of breakdown (visual inspection of skin) and microscopic changes (eg, histologic features of breakdown; thickness of epidermis and dermis; the length and shape of the basement membrane; concentration of inflammatory cells, mast cells, and fibroblasts; and quantity of elastin fibers).
  
  
  RESULTS
  The instrumentation was reliable and a significant improvement over past models in that shear forces were delivered and measured in a controlled manner. The animal model and tissue methodology provided consistent results, and it was found that skin breakdown occurred earlier as shear forces were increased. Evidence of tissue adaptation occurred in the long-term experiments, although corresponding morphologic changes have been difficult to elucidate.
  
  
  CONCLUSIONS
  To address the problem of skin breakdown, new animal models are strongly needed to better understand basic biologic processes related to pressure ulcer development.
authors.affiliation: Department of Rehabilitation Medicine and the Center for Bioengineering, University of Washington, Seattle, USA.
authors.forename: B
authors.initials: B
authors.lastname: Goldstein
authors.forename: J
authors.initials: J
authors.lastname: Sanders
mesh_terms: D000222:Adaptation, Physiological; D000818:Animals; D004195:Disease Models, Animal; D008297:Male; D003668:Pressure Ulcer / Q000503:physiopathology*; D012867:Skin / Q000503:physiopathology*; D013314:Stress, Mechanical; D013552:Swine