Hydrogel and Polyester Ventilation Tubes in an Animal Model

Abstract

Problem Determine the resorption rate and biocompatibility characteristics of novel cross-linked hydrogel ventilations tubes and varied formulations of polyester ventilation tubes. Methods Three cross-linked hydrogel ventilation tubes (chondroitin sulfate, Carbylan-S and Carbylan-Sx) and 5 different polyester ventilation tubes (PLA, PLGA, and silver impregnated versions of PLA and PLGA tubes) were placed into the tympanic membranes of chinchillas. Integrity of the tubes was assessed by weekly otoscopic examination. Collar or Armstrong ventilation tubes were used as controls on the opposite ear in each animal. Biocompatibility was assessed by comparing auditory brainstem response and by examining tympanic membrane changes following tube resorption. Results The PLA tubes remained in the tympanic membrane the longest (36.4 ± 5.2 days), while silver-impregnated PLA tubes lasted for a shorter period of time than non-impregnated tubes. The hydrogel tubes had very short resorption times (7–9.4 days) and were found on exam to significantly swell and expand the tympanic membrane perforation. Initial tissue histopathology confirmed these changes to the tympanic membrane. In contrast, the tympanic membrane and resorbable tube interface demonstrated equivalent findings for auditory thresholds and tissue histopathology at the implant site compared to nonresorbable controls for all polyester ventilation tubes with the exception of PLGA. Silver seemed to confer some stability for the PLGA tubes as tissue histopathology revealed significantly increased neutrophils and fibrosis in the PLGA tubes but not the silver-impregnated PLGA tubes. Conclusion Resorbable polyester pressure equalization tubes demonstrate predictable resorption behavior and similar biocompatibility characteristics when compared with nonresorbable tubes. Silver impregnation may confer some stability to PLGA tubes. Hydrogel tubes have very short resorption times and lack tissue biocompatibility due to increased injury and inflammation of the tympanic membrane. Significance The data suggests that resorbable polyester tubes are equivalent to other FDA-approved tympanostomy devices with regard to biocompatibility in the chinchilla model examined. Support American Society of Pediatric Otolaryngology Research Grant provided the majority of the funding for this research. Also, the USU Center for Integrated Biosystems provided additional funding. Drs. Park and Prestwich are co-founders of Sentrx Surgical, Inc.