Developing an Advanced Biophysical Model for Optimal Cartilage Myringoplasty

Objectives: The purpose of this study was to determine the acoustic transfer characteristics of cartilage for optimal cartilage myringoplasty. Material and Methods: We developed a cartilage plate-tympanic membrane-coupled model using finite element (FE) analysis. Cartilage specimens of the tragus were obtained from fresh human cadavers, and the parameters of the tragus were determined by curve fitting and cross-calibration. A cartilage plate was used to repair an eardrum perforation, and the new coupled tympanic membrane-cartilage complex was loaded into our 3-dimensional biomechanical model of the middle ear. Different sizes of tympanic membrane perforation (15%- and 55%-areas) were created for analysis. Results: Our results show that first, the β-damping value of the cartilage plate depends on frequency. The value of β damping was close to 3×10^(-4) s at lower frequencies and 5×10^(-6) at higher frequencies. Secondly, reducing cartilage thickness leads to an improvement of its acoustic transfer qualities. The predicted vibration amplitude of different thicknesses of cartilage plate (in 55%-area perforation of TM) of the coupled FE model shows the thickness of cartilage plate less than 0.2 mm showed a frequency response function similar to that of tympanic membrane in umbo-and stapes-footplate displacement. Likewise, the predicted vibration amplitude of different thicknesses of cartilage plate (in 15%-area perforation of TM) of the coupled FE model demonstrates that the thickness of cartilage plate less than 0.5 mm showed a frequency response function similar to that of tympanic membrane in umbo-and stapes-footplate displacement. Conclusions: We determined the basic mechanical and acoustic behaviors of reconstructed cartilage plate compared to the tympanic membrane. This model offers the advantages of reproducible test conditions and diminished additional confounding parameters, and it keeps the boundary conditions constant. From an acoustics point of view, the 0.2 to 0.5 mm cartilage plate depending on different areas of perforation seems to be most preferable with regard to tympanic membrane vibration.