Three-dimensional finite element method (FEM) analysis of the middle ear

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The middle ear function is important for sound transmission to the cochlea. However, the middle ear dynamic characteristics are not easily measured by the conventional impedance meters, and thus, the dynamic behavior of the middle ear has not been well analyzed.
In our laboratory, based on the measurement results of the computer assisted three-dimensional reconstruction of human temporal bone (Fig.1), the FEM model of the middle ear (Fig.2) has been established, and using this model, its dynamic behavior is analyzed.
Figures 3 and 4 show the numerically obtained vibration patterns of the middle ear at the frequencies of 0.5 kHz and 2.0 kHz, respectively. The diferences in the ampitude and phase of the tympanic membrane are demonstrated. Figures 5 and 6 show the vibration modes of the ossicles view from the inferior. At the low frequency of 0.5 kHz, the ossicles are rotating around the axis between the anterior malleal ligament and the posterior incudal ligament, and the umbo and stapes head have piston like movements. At the frequency of 2.0 kHz, the axis of rotation lean and whirl, and the umbo and stapes head have elliptical movements.
Currently, we intend to develop an optimal method of middl ear reconstruction using this model.



Fig.1. Three-dimensional reconstruction of human temporal bone.

Fig.2. FEM model of the middle ear.
1, Tympanic membrane (pars tensa); 2, tympanic membrane (pars flaccida); 3, malleus; 4, incus; 5, stapes; 6, anterior malleal ligament; 7, posterior incudal ligament; 8, tensor tympani tendon; 9, stapedial tendon; 10, annular ligament.


Fig.3. Numerically obtained vibration pattern of the middle ear at 0.5 kHz.
Sound pressure level at the tympanic membrane is 80 dB SPL. Displacement is magnified 7,000 times.
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Fig.4. Numerically obtained vibration pattern of the middle ear at 2.0 kHz.
Sound pressure level at the tympanic membrane is 80 dB SPL. Displacement is magnified 7,000 times.
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Fig.5. Numerically obtained vibration pattern of the ossicles at 0.5 kHz.
Displacement is magnified 30,000 times.
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Fig.6. Numerically obtained vibration pattern of the ossicles at 2.0 kHz.
Displacement is magnified 30,000 times.
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