Dynamics of middle ear prostheses - Simulations and measurements

The efficient and systematic development of a middle ear prosthesis necessi tates the use of computer models for the prosthesis itself and the reconstr ucted middre ear. The structure and parameters of the computer model have t o be verified by specific measurements of the implant and the reconstructed ear, To obtain a realistic model of a reconstructed ear, three steps of mo deling and measurements have been carried out. To get a first approach of t he coupling elements a mechanical test rig representing a simplified recons tructed middle ear was built. The velocity of the stapedial footplate was m easured with a laser Doppler vibrometer, The corresponding computer model w as formulated, and the respective parameters were determined using the meas ured dynamical transfer functions, In the second step, a prosthesis was imp lanted into a human temporal bone without inner ear. Exciting this system w ith noise, the velocity of the stapes footplate was measured with the laser Doppler vibrometer, Based on the multibody system approach, a mechanical c omputer model was generated to describe the spatial motions of the reconstr ucted ossicular chain, Varying some significant parameters, simulations hav e been carried out. To describe the dynamical behavior of the system consis ting of middle and inner ear, the computer model used in the second step ha s been enlarged by adding a simplified structure of the inner ear, The resu lts were compared with in situ measurements taken from living humans.