Chronic tympanic membrane perforation: an animal model.

Acute perforations in the tympanic membranes (TM) of animals are not good models for assessment of materials used as graft membranes or of substances with the potential to activate tympanic membrane healing mechanisms for closing perforations. Most acute TM perforations heal spontaneously, in both animals and humans. Acute TM perforation models are not analogous to the pathologic human problem of long-standing TM perforation. Bilateral subtotal symmetric perforations, with each animal serving as its own control provide a suitable model. Fourteen dogs were operated. Subtotal perforation of TM in right ears were soaked with 2% glutaraldehyde to develop an animal model for persistent tympanic membrane perforation. Subtotal myringectomy was performed on left ears, without chemical treatment of the rim. Perforations were standardized in size. The healing pattern was evaluated weekly for a 15-week period. Six of the right ears and 14 of the left ears completely healed within 15 weeks. Statistically, the mean delay of closure was higher in the treated group than in the non-treated group, and the two groups were different according the closure rate criterion. Histologic analyses of persistent TM perforations and of healed cases were performed.