[Experimental studies of static stress on the footplate in the reconstruction of the sound conduction system].

If a destroyed ossicular chain is substituted by a drum-to-footplate prosthesis (TORP), not only sound pressures but also static pressures are conducted via this new connection. To measure these effects in the area of the oval window, in isolated temporal bones the stapes was removed and substituted by a piece of plastipore, attached to the incus. This piece was connected by a very fine needle to a foil strain gauge, in order to registrate the effects of experimentally changed pressures in the external ear canal towards the inner ear. The incus was then also removed too and a TORP was introduced. Under the same measuring condition we found the conducted pressures ten times higher than in the previous situation. This can only be explained by movements in the incudo-malleal joint, if this is intact. Consequently patients with TORPs should avoid all situations of rapid changes of surrounding pressure, such as diving etc., especially if the tube function is impaired. These situations may be dangerous for the footplate and the inner ear. In fortunately rare cases perforations of the footplate were reported by some ear surgeons.