A study on the effect of ligament and tendon detachment on human middle ear sound transfer using mathematic model

The objective of this study is to investigate the effects of ligament and tendon detachment on human middle ear sound transfer. For this purpose, a geometric human middle ear model was reconstructed based on the computed tomography scanning data of the temporal bones from healthy adult volunteers. For the ear model, pars tensa was assumed to be fit for a 5-parameter Maxwell model and inverse method was used to obtain the necessary coefficients. Furthermore, frequency response method was implemented to investigate the vibration behaviors of tympanic membrane umbo and stapes footplate under an acoustic stimulus of 90 dB within 0.2–8 kHz. Meanwhile, nine patterns of fractured ligaments and tendons, whose effects on the middle ear sound transfer function were simulated by setting free the nodes of the ligaments and tendons of interest. The results indicate that the displacement of tympanic membrane umbo and stapes footplate as well as the velocity transfer function lies within the bounds of the published experimental data. The detachments of ligaments or tendons except for lateral mallear ligament may incur both gains as much as 15 dB and losses of –8 dB in the velocity of stapes footplate at low frequencies ( f≤ 1 kHz), while no significant changes were observed at high frequencies ( f > 1 kHz). However, detachment of the ligaments or tendons induces tiny changes in the displacement of stapes footplate at the frequencies of 0.2–8 kHz.