title: The effect of AlloDerm envelopes on periprosthetic capsule formation with and without radiation.
abstract: BACKGROUND
  The pathobiology of radiation-induced periprosthetic capsular formation and factors that may ameliorate its development have not been fully elucidated. The authors hypothesized that AlloDerm would diminish radiation-induced capsular formation.
  
  
  METHODS
  Two 5-ml implants were placed submuscularly in the backs of 41 rats. The right implant was wrapped with AlloDerm and the left remained bare. After 48 hours, 20 animals underwent irradiation to each implant, and 21 animals underwent no further treatment and served as controls. After 3 and 12 weeks, the capsules were harvested and submitted for tensile strength and histologic examination. Intraprosthetic pressures were measured in each implant at the time of surgery and when the animals were killed.
  
  
  RESULTS
  The intraprosthetic pressure decrease was uniform among all groups at 3 and 12 weeks. Between 3 and 12 weeks, capsular tensile strength increased in nonirradiated bare implants. There was considerable invasion of nonirradiated AlloDerm by inflammatory infiltrates at 3 weeks, and AlloDerm thickness decreased over time. Cellular invasion of AlloDerm was decreased with irradiation at both time points. Capsular tensile strength and thickness of the irradiated bare and AlloDerm capsules did not change between 3 and 12 weeks. Radiation increased inflammation of bare capsules at 12 weeks, but it was significantly reduced in irradiated AlloDerm capsules. The majority of irradiated bare capsules developed pseudoepithelium, whereas AlloDerm protected capsules from this transformation.
  
  
  CONCLUSIONS
  AlloDerm decreases radiation-related inflammation and delays or diminishes pseudoepithelium formation and thus may slow progression of capsular formation, fibrosis, and contraction.
authors.affiliation: Loma Linda, Calif. From the Division of Plastic and Reconstructive Surgery and Divisions of Human Anatomy and Pediatric Pathology, the Department of Pathology and Human Anatomy, Loma Linda University and Loma Linda University Medical Center; and Department of Surgery and Department of Radiation Medicine, Molecular Radiation Biology Laboratories, Loma Linda University.
authors.forename: Ewa
authors.initials: E
authors.lastname: Komorowska-Timek
authors.forename: Kerby C
authors.initials: KC
authors.lastname: Oberg
authors.forename: Tomasz A
authors.initials: TA
authors.lastname: Timek
authors.forename: Daila S
authors.initials: DS
authors.lastname: Gridley
authors.forename: Duncan A G
authors.initials: DAG
authors.lastname: Miles