Three-dimensional modeling of middle ear biomechanics and its applications

Hypothesis: This study investigated whether combined technologies of finite clement (FE) analysis and three-dimensional reconstruction of human temporal bones could be used to construct a computational model, useful in describing normal and pathologic middle ear sound conduction. Background: FE models for biologic systems have been used in ear biomechanics. Three-dimensional reconstructions have also been made, but not in combination with FE modeling and laser interferometry measuring of human temporal bones, Furthermore, an FE model for the human middle ear with its ossicular attachments has not been reported on the basis of temporal bone histologic sections and morphometric reconstruction, to the authors' best knowledge. Because of the size, variability, and complexity of the middle ear, accurate morphologic data and boundary conditions are necessary for accurate FE modeling. Methods: A fresh temporal bone was decalcified, embedded in celloidin, sectioned and stained, scanned, and digitized, and the normal middle ear was reconstructed. The histologic sections were used to construct a computer-aided design model with ligaments, muscles, and tendons as boundary conditions. The data thus obtained were converted into an FE mechanical model that was validated by comparison with displacements obtained by laser Doppler interferometry on 17 fresh human temporal bones. Results: An FE model was generated, demonstrating dynamic behavior that moderately approximated the laser interferometric data from human temporal bones receiving 90-dB sound pressure level auditory frequencies at the tympanic membrane. Conclusion: Accurate FE modeling, incorporating both morphometric and interferometric performance data, predicted both normal and pathologic mechanical performance of the human ossicular chain.