Assessment of the cartilage transplant thickness after removing of the tympanic membrane retraction pocket (finite-element modelling)

The retraction pocket emergence of the tympanic membrane (eardrum) leads to the sound conduction disorder of the middle ear. Surgical removal of fixed retraction pockets leads to perforations. A cartilage grafts in the region of these perforations are installed. The aim of the study is to assess the geometric parameters of the cartilage graft, providing sound conductivity of the middle ear oscillatory system corresponding the auditory functions of the normal middle ear. The evaluation of the geometric parameters of the cartilage graft is carried out on the basis of the middle ear finite-element model. The eigenfrequencies are utilised as quantities characterising the auditory conductivity of the middle ear oscillatory system. The thickness of the graft attached on the posterosuperior quadrant after removal of the fixed retraction pocket is $0.193\pm 0.031$ mm. It is evaluated on basis of comparative analysis of the middle ear eigenfrequency spectra in normal conditions, the middle ear with attached cartilaginous grafts of different thicknesses. The obtained results can be used for planning of surgical operations to restore the integrity of the tympanic membrane and improve auditory conductivity.