[Spontaneous healing of various types of rat tympanic membrane perforation]

To investigate the spontaneous healing process of various types of rat tympanic membrane perforation, study the perforation healing mechanism.

Fifty rats were divided into five groups in randomization, and performed perforations phi = 2.5 mm, 1 mm, respectively in the center of tympanic membrane pars tensa, posterior marginal perforation (phi = 1.5 mm) in pars tensa, the handle of malleus cauterized with chromic acid after tympanic membrane 3/4 excision, and perforation (phi = 1.5 mm) in the center of pars flaccid, The histology of the perforations healing process was observed with light microscope.

The epithelia retracted in the early stage after perforation. The epithelia near the annulus and manubrium showed hyperplasia. The epithelia hyperplasia also appeared the intact annulus region remote to the perforation. The middle connective tissue layer reacted later than the epithelial layer. The defects were closed first by the accumulation of the epithelial cells. The difference of healing time had no statistics significance between the big and small perforations. One ear perforated, but the other side intact ear appears no change. The epithelia didn't migrate into the tympanic cavity in the posterior marginal perforations. All the perforations healed after the manubriums of the malleus were damaged. Perforations in pars flaccid healed more quickly.

The normal migration of the epithelia of the tympanic membrane played an important role in the healing of perforation. The generation center was located near tympanic annulus and manubrium of the malleus, so the protection of these two regions was very important in the middle-ear surgery.