[Clinical study on perforation of the tympanic membrane and discussion based on experimentally induced tympanic...

Traumatic perforation of the tympanic membrane (TM) was clinically studied by analyzing photographs of 231 ears treated in the Department of Otolaryngology of Tokyo Women's Medical College from May 1983 to December 1991. The dynamic features of TM and the mechanism of perforation are discussed.

1) Direct and indirect injuries of the TM through the external auditory canals were observed in 101 and 130 ears, respectively. One hundred and twenty-seven injured ears were seen in males and 104 in females. Subjects ages ranged from 1 to 64 years. One hundred and thirty ears were on the left side and 101 on the right. 2) Approximately 80% of the perforated regions were observed in the antero-inferior or postero-inferior quadrant. "Triangular-type" perforation was predominant among direct injuries and "slit type" among indirect injuries. 3) Approximately 80% of the cases had a TM defect area smaller than 20%. 4) One hundred and twenty of 127 ears which were treated within 7 days after injury were healed by conservative treatment. One hundred and four ears among these 120 ears healed spontaneously. The average healing period for these 104 ears was 25 days. 5) It was suggested that the age of patients and the defect area of TM were factors that delayed healing. 6) The minimum breakage stress of human normal TM (the right angle to the radial fibers of TM) was 13.7 gf/mm2. 7) It was presumed that the strain stress and shear stress of TM contributed to traumatic TM perforation in indirect injuries.