Free oscillations of the middle ear after total tympanoplasty and ossiculoplasty with functional mobility of the foot plate of stapes

Pathological changes in the oscillating system of the middle ear can lead to a decrease of the susceptibility threshold of the auditory analyser to sound vibrations and, consequently, to partial or complete hearing loss. Cartilage implants are most often used for the reconstruction of the tympanic membrane, since they help to avoid complications after treatment. Evaluation of the dynamic characteristics (eigenmodes and eigenfrequencies) of the reconstructed middle ear is the most important problem for analysing the quality of operations that improve the auditory conductivity and develop further recommendations for optimal prosthetics. The aim of this study is to estimate the eigenfrequencies of the middle ear free oscillations after prosthetics on the basis of a mathematical model involving transverse vibrations of the cartilage graft and movement of the prosthesis connecting the reconstructed tympanic membrane and the base of the foot stapes plate. The values of natural frequencies are evaluated for different positions of the nodal lines, averaged geometrical parameters and elastic properties of the tympanic membrane, as well as the foot plate of stapes and prosthesis.