title: Diffusion and perfusion: the keys to fat grafting.
abstract: BACKGROUND
  Fat grafting is now widely used in plastic surgery. Long-term graft retention can be unpredictable. Fat grafts must obtain oxygen via diffusion until neovascularization occurs, so oxygen delivery may be the overarching variable in graft retention.
  
  
  METHODS
  We studied the peer-reviewed literature to determine which aspects of a fat graft and the microenvironment surrounding a fat graft affect oxygen delivery and created 3 models relating distinct variables to oxygen delivery and graft retention.
  
  
  RESULTS
  Our models confirm that thin microribbons of fat maximize oxygen transport when injected into a large, compliant, well-vascularized recipient site. The "Microribbon Model" predicts that, in a typical human, fat injections larger than 0.16 cm in radius will have a region of central necrosis. Our "Fluid Accommodation Model" predicts that once grafted tissues approach a critical interstitial fluid pressure of 9 mm Hg, any additional fluid will drastically increase interstitial fluid pressure and reduce capillary perfusion and oxygen delivery. Our "External Volume Expansion Effect Model" predicts the effect of vascular changes induced by preoperative external volume expansion that allow for greater volumes of fat to be successfully grafted.
  
  
  CONCLUSIONS
  These models confirm that initial fat grafting survival is limited by oxygen diffusion. Preoperative expansion increases oxygen diffusion capacity allowing for additional graft retention. These models provide a scientific framework for testing the current fat grafting theories.
authors.affiliation: Division of Plastic Surgery, Brigham and Women's Hospital, Boston, Mass.; University of Michigan Medical School, Ann Arbor, Mich.; Gulliver Preparatory School, Pinecrest, Fla.; College of Engineering, Boston University, Boston, Mass.; Institute of Plastic Reconstructive and Aesthetic Surgery, University of Padova, Padova, Italy; and Harvard Medical School, Boston, Mass.
authors.forename: Roger K
authors.initials: RK
authors.lastname: Khouri
authors.affiliation: Division of Plastic Surgery, Brigham and Women's Hospital, Boston, Mass.; University of Michigan Medical School, Ann Arbor, Mich.; Gulliver Preparatory School, Pinecrest, Fla.; College of Engineering, Boston University, Boston, Mass.; Institute of Plastic Reconstructive and Aesthetic Surgery, University of Padova, Padova, Italy; and Harvard Medical School, Boston, Mass.
authors.forename: Raoul-Emil R
authors.initials: RE
authors.lastname: Khouri
authors.affiliation: Division of Plastic Surgery, Brigham and Women's Hospital, Boston, Mass.; University of Michigan Medical School, Ann Arbor, Mich.; Gulliver Preparatory School, Pinecrest, Fla.; College of Engineering, Boston University, Boston, Mass.; Institute of Plastic Reconstructive and Aesthetic Surgery, University of Padova, Padova, Italy; and Harvard Medical School, Boston, Mass.
authors.forename: Jorge R
authors.initials: JR
authors.lastname: Lujan-Hernandez
authors.affiliation: Division of Plastic Surgery, Brigham and Women's Hospital, Boston, Mass.; University of Michigan Medical School, Ann Arbor, Mich.; Gulliver Preparatory School, Pinecrest, Fla.; College of Engineering, Boston University, Boston, Mass.; Institute of Plastic Reconstructive and Aesthetic Surgery, University of Padova, Padova, Italy; and Harvard Medical School, Boston, Mass.
authors.forename: Khalil R
authors.initials: KR
authors.lastname: Khouri
authors.affiliation: Division of Plastic Surgery, Brigham and Women's Hospital, Boston, Mass.; University of Michigan Medical School, Ann Arbor, Mich.; Gulliver Preparatory School, Pinecrest, Fla.; College of Engineering, Boston University, Boston, Mass.; Institute of Plastic Reconstructive and Aesthetic Surgery, University of Padova, Padova, Italy; and Harvard Medical School, Boston, Mass.
authors.forename: Luca
authors.initials: L
authors.lastname: Lancerotto
authors.affiliation: Division of Plastic Surgery, Brigham and Women's Hospital, Boston, Mass.; University of Michigan Medical School, Ann Arbor, Mich.; Gulliver Preparatory School, Pinecrest, Fla.; College of Engineering, Boston University, Boston, Mass.; Institute of Plastic Reconstructive and Aesthetic Surgery, University of Padova, Padova, Italy; and Harvard Medical School, Boston, Mass.
authors.forename: Dennis P
authors.initials: DP
authors.lastname: Orgill