Tympanic Membrane Adhesion Model by Transcanal Endoscopic Ear Surgery in Rat

Tympanic membrane adhesion is a clinically significant and challenging complication of otologic surgery. However, a simple and reproducible animal model suitable for studying the pathogenesis of this disease and evaluating treatment strategies has not yet been established. This study aimed to develop a reproducible rat model of tympanic membrane adhesion using transcanal endoscopic ear surgery (TEES).

Twenty-eight Sprague-Dawley rats underwent TEES. In each rat, 1 ear underwent a complete adhesion-inducing procedure involving tympanic membrane perforation and removal of the middle ear mucosa (model group), whereas the contralateral ear underwent tympanic membrane perforation only (sham group). Adhesion formation and bone hyperplasia were evaluated using micro-computed tomography, macroscopic observation, and histological analysis up to 56 days postoperatively.

Tympanic membrane adhesion occurred in 81.8% of ears 14 days after the procedure. No adhesions were observed in the sham group. All adhesion-positive ears showed middle ear bone hyperplasia at the mucosa-ablated sites, and histological analysis confirmed fusion between the tympanic membrane epithelium and the newly formed bone. In cases where adhesion was not achieved after the initial procedure, reoperation led to successful adhesion in all ears. No tympanic membrane retraction or middle ear effusion was observed during the postoperative period.

A simple and highly reproducible rat tympanic membrane adhesion model was established using TEES. This model consistently reproduces postoperative tympanic membrane adhesion accompanied by middle ear bone hyperplasia and provides a useful platform for elucidating the mechanisms of adhesion and evaluating regenerative or antiadhesion therapies in the middle ear.