title: Optimization of the use of skin expanders.
abstract: BACKGROUND
  Skin expansion is a physiological process that is defined as the ability of the human skin to increase its superficial area in response to stress or to a given deformation. Skin expanders are silicon bags that are implanted underneath the skin. Because the skin presents creep or relaxation, the resulting stress decreases after a time due to the imposed deformation. Skin expansions are used to reconstruct burned areas and breasts after a mastectomy or to hide scars.
  
  
  OBJECTIVE
  The question that constantly arises during skin expansion is whether it creates a sufficient amount of skin or, in other words, whether the achieved expansion is sufficient to resurface the defect. These questions are answered with information about how much new tissue is required to achieve the reconstruction in a given context and calculating the required tissue (surface area) in relationship with the volume infiltrated.
  
  
  METHODS
  Surface formulas for round and rectangular, and finite elements method for crescent skin expanders are used to calculate the relation between infiltrated volume and surface area. Those results were corrected or validated by an experimental work using 3D scanners to calculate the relation between surface area and internal volumes for the three types of expanders in question.
  
  
  RESULTS
  The research provides information to determine the type, number, and volume of skin expanders necessary to obtain an extra amount of skin to repair a specific medical condition and to determine the amount of skin obtained even in cases when the expansion does not come to term.
  fci, Correcting factor, which corrects the mathematical formulas using the experimental results, for i skin expander; i, geometry of the expander, round (c), rectangular (r), or crescent (cresc/cr); Sd , surface of the defect; Sds , surface area of the donor site; Sfi, surface area obtained using a mathematical calculation for the i skin expander; S¯fi, surface area obtained experimentally for the i skin expander; Sfi∗, corrected surface area obtained using a mathematical calculation for the i skin expander corrected by the correcting factor; S¯fi∗∗ extra flap of skin obtained by expansion for the i skin expander; Vii, internal volume infiltrated in the i skin expander; Vni, nominal internal volume of the i skin expander.
authors: Laboratory of Membranes and Biomembranes, Pontifical University of Rio (PUC-Rio), Rio de Janeiro, Brazil; Mechanical Engineering Department, Fluminense Federal University (UFF), Rio de Janeiro, Brazil.
authors: D C
authors: DC
authors: Pamplona
authors: H I
authors: HI
authors: Weber
authors: F R
authors: FR
authors: Leta
mesh_terms: D019245:Compressive Strength; D003198:Computer Simulation; D017076:Computer-Aided Design; D062109:Dermatologic Surgical Procedures / Q000295:instrumentation* / Q000379:methods*; D055119:Elastic Modulus / Q000502:physiology; D019544:Equipment Failure Analysis; D006801:Humans; D008962:Models, Theoretical; D011474:Prosthesis Design; D019919:Prosthesis Implantation / Q000379:methods; D012879:Skin Physiological Phenomena; D013314:Stress, Mechanical; D013718:Tensile Strength / Q000502:physiology; D015626:Tissue Expansion / Q000295:instrumentation* / Q000379:methods*; D015625:Tissue Expansion Devices
keywords: biomembranes; finite elements; plastic reconstructive surgery; skin expansion