Finite-element Modeling of the Normal and Surgically Repaired Cat Middle Ear

In this work, three-dimensional finite-element models of the normal and surgically repaired cat middle ear were developed. The normal middle-ear model was formed by adding explicit representations for the footplate and cochlear load to an existing model of the cat eardrum. The footplate was modeled as a thin plate with a thickened rim. The cochlear load was represented by springs attached along the footplate's periphery. The model is valid for frequencies below 1 kHz and for physiological sound levels. Eardrum and manubrium displacement, and out-of-plane displacements of the footplate's center, were found to compare well with experimental results. The normal model was modified to simulate the effects of two types of middle-ear surgery, both of which are used to repair a discontinuous ossicular chain. Bulging of the footplate was found to occur when a prosthesis made direct contact with the footplate. The location of the prosthesis along the manubrium did not affect the motion of the footplate as long as the joints were all rigid. When the joints were flexible, the largest displacements occurred when the prosthesis was positioned near the upper end of the manubrium.