AN OSSEOINTEGRATED MANIPULATOR DEVICE FOR THE POSITIONING AND FIXATION OF IMPLANTABLE HEARING-AID TRANSDUCERS - PART 1 - ADAPTATION TO THE SURGICAL ANATOMY OF THE TEMPORAL BONE AND SURGICAL ASPECTS

The first electronic implantable hearing aids for patients with hearin g loss are coupled to the ossicular chain or perilymph during implanta tion and are now available. Our new Tubingen implant designed for sens orineural hearing loss (SNHL) is the combination of an implantable mic rophone and piezotransducer. To avoid hearing losses during implantati on,the Tubingen piezotransducer will be (1) fixed to the mastoid cavit y and (2) positioned to one of the ossicular target points. This can b e done with a micromanipulator which will be implanted together with t ransducer and microphone in the mastoid cavity. The manipulator weight s 0.7 g. With four degrees of freedom, it allows highly secure and saf e positioning of the transducer's probe tip to the ossicular chain und er close to stereotactic conditions. The main advantages of the presen t micromanipulator are (1) easy handling during surgery,(2) the transd ucer's precise positioning to the ossicular target point with sufficie nt degrees of freedom,and (3) the transducer's stable fixation in the mastoid cavity in the final position. Following integrated safety as t he leading principle, ossicular or inner ear injuries caused, e.g., by the patient's head movement or unintentional manual contact by the su rgeon,are minimized. The micromanipulator is, as it were, the surgeon' s vibration-free''artificial hand.''The manipulator's development and its optimization to the mastoid cavity by test implantation in 50 huma n temporal bones are shown in detail. While coupling the transducer to the body of the incus, transducer, micro phone, and micromanipulator can be implanted into 76% of all mastoid cavities without protrusion.I n the case of transducers coupling to the long process of the incus,th e protrusion-free implantation rate of the above-mentioned three impla nt modules is 78%.