title: Resorption rate and biocompatibility characteristics of two polyester ventilation tubes in a guinea pig model.
abstract: OBJECTIVE
  Determine the resorption rate and biocompatibility characteristics of 2 polyester ventilation tubes, and to determine whether soap and water exposure accelerates polyester tube degradation.
  
  
  METHODS
  50/50 poly (D, L-lactide-co-glycolide; PLGA-50) and poly (L-lactide; PLA) polymers were placed into the tympanic membranes of Hartley pigmented guinea pigs. Integrity of the tubes was determined by weekly otoscopic examination. Biocompatibility was assessed by comparing auditory brainstem response (ABR) thresholds and by examining tympanic membrane changes following tube resorption. Shah minigrommet ventilation tubes were used as controls. In the second portion of this study, implanted PLGA-50 and PLA tubes were exposed weekly to a mixture of soap and water (1:5) until complete resorption was observed. Biocompatibility was assessed by periodic ABR testing and tympanic membrane examination.
  
  
  RESULTS
  The PLA tubes remained in the tympanic membrane for a longer period (63.2 +/- 19.3 days) than the PLGA-50 (18.8 +/- 8.1 days). The tympanic membrane and resorbable tube interface demonstrated equivalent findings for auditory thresholds and tissue histopathology at the implant site compared to nonresorbable controls. The resorption behavior was not altered by exposure to soap and water. Tympanic membranes of all animals following tube degradation and soap water exposure were intact with minimal scarring and no signs of persistent foreign body response. The histological analysis showed that implantation of resorbable tubes was not accompanied by secondary infection with otorrhea through the tube, did not result in a permanent perforation or dislocation of the tube into the middle ear cavity, and was not followed by excess tympanosclerosis or localized or diffuse membrane atrophy.
  
  
  CONCLUSIONS
  Resorbable polyester pressure equalization tubes demonstrate predictable resorption behavior and similar biocompatibility characteristics when compared with nonresorbable Shah minigrommet ventilation tubes. Exposure to soap water does not accelerate polyester tube degradation nor change the host tissue response during the indwelling period or after complete resorption. The data suggests that resorbable ventilation tubes are substantially equivalent to other FDA-approved tympanostomy devices with regard to safety and biocompatibility in the guinea pig model examined and may provide improved clinical performance by combining this approach with sustained release technology.
  
  
  METHODS
  B-2.
authors.affiliation: Division of Otolaryngology--Head and Neck Surgery, University of Utah, Salt Lake City 84132, USA.
authors.forename: Becky L
authors.initials: BL
authors.lastname: Massey
authors.forename: Xuejun
authors.initials: X
authors.lastname: Wen
authors.forename: L Ralph
authors.initials: LR
authors.lastname: Rohr
authors.forename: Patrick A
authors.initials: PA
authors.lastname: Tresco
authors.forename: Lisa
authors.initials: L
authors.lastname: Dahlstrom
authors.forename: Albert H
authors.initials: AH
authors.lastname: Park
mesh_terms: D000818:Animals; D001672:Biocompatible Materials / Q000494:pharmacology*; D006168:Guinea Pigs; D008422:Materials Testing / Q000379:methods; D008876:Middle Ear Ventilation / Q000295:instrumentation*; D023421:Models, Animal; D011091:Polyesters / Q000494:pharmacology*; D011475:Prosthesis Failure; D012915:Soaps / Q000009:adverse effects*; D013997:Time Factors
chemical_list: D001672:Biocompatible Materials; D011091:Polyesters; D012915:Soaps