鼓膜に生ずるRetraction Pocket発生機序の解明 : 理論的考察

抄録

When a pressure difference between the external auditory meatus and the tympanic cavity occurs due to a defect in the gas exchange function of the cavity, the tympamic membrane retracts toward the cavity and deforms. When this pressure difference is prolonged, plastic strain sometimes arises in the tympanic membrane, and the hearing threshold rises. This phenomenon is called the retraction pocket (RP). However, the generation mechanism of RP is unclear. Therefore, in this study, a finite-element method (FEM) is applied, and an attempt is made to clarify this mechanism by analyzing the relationship between the Tympanic displacement and the middle ear pressure. The results are as follows: RP is formed in the pars flaccida rather than the pars tensa, because the value of the yielding stress of the pars flaccida is smaller than that of the pars tensa; the strain in the pars flaccida is probably increased rapidly without the increase of the stress, when the negative pressure in the middle ear cavity is prolonged.