[Numerical analysis of the effect of typical middle ear disease on bone conduction]

Objective:To study the effects of typical middle ear lesions on bone conduction, and to provide a theoretical basis for the optimized design of bone conduction hearing aids. Method:A finite element model including the middle ear and cochlea was established by using micro-CT scanning date from a case of adult male human-cadaver temporal bone. The reliability of the model was verified by comparison with relevant experimental data. Based on this model, the effects of several typical middle ear lesions on bone conduction were analyzed. Result:With the increase of tympanic membrane mass, the basilar membrane response at the frequency range of 0.25 kHz to 1 kHz was reduced, and the maximum decrease was 6.9 dB at the frequency of 0.5 kHz. The incus fixation reduced basilar membrane response at the frequency range of 0.2 kHz to 1 kHz, with the maximum decrease of 12.0 dB at 0.75 kHz. The ossicular chain disruption reduced the response of basilar membrane at the frequency range of 1 kHz to 4 kHz, which the decrease was 5.0 dB at 1.5 kHz in the case of incudomallear joint disruption and 11.0 dB at 2 kHz in the case of incudostapedial joint disruption. Conclusion:The results showed that the increased mass of the tympanic membrane and incus fixation mainly reduced the response of bone conduction at the low frequencies. The ossicular chain disruption mainly reduced the response of bone conduction at the middle frequencies. Moreover, the deterioration of incudostapedial disruption was more obvious.