Two degree of freedom model for prosthetic devices for the middle ear

Current prosthetic devices for the human middle ear are essentially mechanical rods. This paper will first point out that such devices essentially conform to the old piston and lever model. Neither these devices nor any variation of the piston and lever model take into account the articulation of the joint between the malleus and the incus. The substantial evidence for the articulation of the malleoincudal joint is reviewed. In addition, in a normal ear the acoustic middle ear reflex seems to provide protection against harmful high-amplitude signals. The current models provide no such protection. A new model for a prosthetic device based on a two degree of freedom model will be proposed and compared with current models. Methods of limiting response at high amplitudes will also be proposed.