Many experimental data on the human middle ear (ME) mechanics and dynamics can be found in the literature. Nevertheless, discussions about the uncertainties of these data are scarce. The present study compiles experimental data on the mechanical properties of the human ME. The summary statistics of mean and standard deviation of the data were collected and the coefficients of variation were computed and pooled. Moreover, the linear correlation and distribution were assessed for the ossicles' mass. Results show that, generally, the uncertainties of the stiffness properties of the tympanic membrane, ligaments, and tendons are larger than the uncertainties of the ossicles' mass. In addition, the uncertainties of the ME response vary across frequency. The vibration measures, such as the stapes' velocity normalized by the sound pressure at the tympanic membrane, are more uncertain than ME input impedance and reflectance. It is expected that the results presented in this study will provide the basis for the development of probabilistic models of the human ME.
The dynamics of the human middle ear (ME) has been studied in the past using several computational and experimental approaches in order to observe the effect on hearing of different conditions, such as conductive disease, corrective surgery, or implantation of a middle ear prosthesis. Multibody (MB) models combine the analysis of flexible structures with rigid body dynamics, involving fewer degrees-of-freedom (DOF) than finite element (FE) models, but a more detailed description than traditional 1D lumped parameter (LP) models. This study describes the reduction of a reference FE model of the human middle ear to a MB model and compares the results obtained considering different levels of model simplification. All models are compared by means of the frequency response of the stapes velocity versus sound pressure at the tympanic membrane (TM), as well as the system natural frequencies and mode shapes. It can be seen that the flexibility of the ossicles has a limited impact on the system frequency response function (FRF) and modes, and the stiffness of the tendons and ligaments only plays a role when above certain levels. On the other hand, the restriction of the stapes footplate movement to a piston-like behavior can considerably affect the vibrational modes, while constraints to the incudomalleolar joint (IMJ) and incudostapedial joint (ISJ) can have a strong impact on the system FRF.
Numerical models of the human middle ear have been developed throughout the last 30 years, for different purposes. While several types of pathologies have been studied, stapedial disorders were seldomly explored. This papers aims to clarify how stapes fracture and some forms of stapes ankylosis, such as stapedial tendon (ST) ossification, augmented pyramidal eminence (PE) and bony bar presence, affect the sound transmission through the middle ear. In addition, the stapes dynamics is also analyzed by means of total displacement and first principal strain. For the purpose of the study, first, a three-dimensional finite element model of the human middle ear is detailed and validated under normal (healthy) conditions. The model is then modified to represent the stapedial disorders of interest. A measure is established for evaluating how the disorders reduce sound transmission through the middle ear. Results of the reduction of sound transmission showed that the different forms of stapes ankylosis affect primarily low frequencies, while the stapes fracture mostly affects high frequency sound transmission. According to the results, an augmented PE does not restrict stapes movement unless followed by some ossification of the ST. In addition, the question whether the fracture is in the anterior or posterior crus and the distance of the fractured part from the stapes footplate have a relevant role in the reduction of the sound transmission. Finally, the analysis of total displacement and first principal strain of the stapes helped to highlight some differences among the stapedial disorders.
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