A geometrically nonlinear finite-element model of the cat eardrum

Area of Science:

• Biomechanics
• Computational modeling
• Otolaryngology

Background:

• Current finite-element (FE) models of the eardrum are limited by linearity assumptions, restricting their accuracy at higher pressures.
• Understanding eardrum mechanics is crucial for diagnosing middle ear conditions via clinical tympanometry.

Purpose of the Study:

• To investigate the impact of geometric nonlinearity on finite-element models of the cat eardrum.
• To assess model accuracy for eardrum response to pressures up to +/-2.2 kPa, relevant to clinical tympanometry.

Main Methods:

• Development of nonlinear finite-element (FE) models of the cat eardrum, assuming an immobile malleus.
• Simulation of eardrum response to static pressures ranging from -2.2 kPa to +2.2 kPa.
• Comparison of computed displacements and strain patterns with experimental data.

Main Results:

• Nonlinear models showed displacements increasing less than proportionally with pressure, aligning with experimental findings.
• Both simulations and experiments revealed an inferior shift in maximum displacement location with increasing negative middle-ear pressures.
• Model adjustments, specifically increasing pars tensa thickness, improved the accuracy of maximum displacement location prediction.

Conclusions:

• Geometric nonlinearity is essential for accurate finite-element simulations of eardrum behavior at high pressures.
• Linear material models are adequate for the computed strains (mostly <2%), but geometric changes significantly alter displacement patterns.
• Nonlinear FE models provide a more realistic representation of eardrum mechanics under physiological pressure variations.