title: Tracheal replacement with a bioabsorbable scaffold in sheep.
abstract: BACKGROUND
  A significant native tracheal approximation phenomenon was observed in our previous study [Tsukada H, Ernst A, Gangadharan S, et al. Tracheal replacement with a silicone-stented fresh aortic allograft in sheep. Ann Thorac Surg 2010;89:253-8], in which sheep trachea was replaced with an allogenic aortic graft in order to attempt transplantation. Because an appropriate tracheal replacement graft has yet to be determined, other means to repair or replace tracheal tissue have to be evaluated. The aim of this study was to test a bioabsorbable scaffold for temporary tracheal grafting.
  
  
  METHODS
  Eight male sheep underwent cervical tracheal replacement (5 cm) using a copolymer of L-lactide and ε-caprolactone sponge tube reinforced by polyglycolic acid. A silicone stent (7 cm) was placed perioperatively to prevent graft collapse. Routine bronchoscopy and computed tomographic scans were scheduled for up to 9 months and necropsies with histologic examinations were scheduled at 9 months (n = 3), 6 months (n = 2), 4 months (n = 1), 3 months (n = 1), and 2 months (n = 1) after surgery.
  
  
  RESULTS
  No procedural deaths and postoperative complications occurred. Planned follow-up points were reached in all animals. Computed tomographic imaging of the grafted area showed tracheal approximation up to 75% at 9 months after surgery. Silicone stents were removed at 9 months in three animals. Symptomatic airway collapse was observed at 6 hours, 1 week, and 2 weeks after stent removal. Epithelialization of the entire grafted area was confirmed in all sheep that were followed beyond 4 months.
  
  
  CONCLUSIONS
  Tracheal axial approximation occurs consistently after tracheal resection and replacement. Our data suggest that bioabsorbable materials can be used as a reliable, temporary, tracheal replacement conduit.
authors.affiliation: Chest Disease Center, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts 02215, USA.
authors.forename: Hisashi
authors.initials: H
authors.lastname: Tsukada
authors.forename: Sidhu
authors.initials: S
authors.lastname: Gangadharan
authors.forename: Robert
authors.initials: R
authors.lastname: Garland
authors.forename: Felix
authors.initials: F
authors.lastname: Herth
authors.forename: Malcolm
authors.initials: M
authors.lastname: DeCamp
authors.forename: Armin
authors.initials: A
authors.lastname: Ernst
mesh_terms: D020341:Absorbable Implants; D000818:Animals; D001013:Aorta, Thoracic / Q000637:transplantation*; D001999:Bronchoscopy; D004195:Disease Models, Animal; D005500:Follow-Up Studies; D006085:Graft Survival; D008297:Male; D011474:Prosthesis Design; D012756:Sheep; D015607:Stents; D013536:Suture Techniques; D014132:Trachea / Q000601:surgery*; D014133:Tracheal Diseases / Q000601:surgery*; D014184:Transplantation, Homologous; D016896:Treatment Outcome