Tympanic Membrane Changes After Installation of Polyethylene Grommets: An Experimental Study in the Rat

Abstract

The morphological changes occurring when a polyethylene grommet is implanted in the normal tympanic membrane of animals was studied. A serous effusion around the grommet and in the attic during the 1st wk after installation was found. All the grommets were displaced away from the tympanic membrane in a medial direction into the middle ear cavity. The displacement was probably from a squamous cell epithelial and connective tissue hyperplasia, which reached its maximum after 2-3 wk. Atrophy, atelectasis and retraction were not observed in the pars flaccida or the pars tensa. A greyish, horseshoe-shaped configuration was seen in all specimens in the undisturbed front quadrants. No firm histopathological correlation was found to explain these changes. The perforation appeared to heal, although delayed, in the same way as after a central perforation, once the polyethylene grommet was ejected.