[A micromanipulator for intraoperative vibratory hearing assessment with an implantable hearing aid transducer]

First concepts of implantable hearing aids to be coupled to the ossicular chain are available for patients with combined or sensorineural hearing loss (SNHL). To ensure that hearing can be improved intraoperative coupling of a test transducer to the ossicular chain is mandatory for allowing surgical anatomy to be checked and vibratory hearing tests to be performed. To achieve this, the test transducer has to be held and positioned securely in situ for some minutes, avoiding risks for middle or inner ear structures. This is not possible using conventional surgical instruments. Thus, a micromanipulator to hold the test transducer during intraoperative hearing tests was developed. This surgical device allows the surgeon safe, risk-free, and controlled coupling of the test transducer to the ossicular chain with one axial and three rotational degrees of freedom. With the aid of a conventional ear retractor (2x2 prongs), the manipulator is fixed at the patient's ear. In conjunction with a piezoelectric test transducer, the manipulator was used in nine patients during local anesthesia. The test transducer is part of an electronic hearing implant (Tübingen implant) specifically designed for SNHL that may be coupled to a middle ear ossicle or the perilymph of the cochlea. The micromanipulator was easy to handle. It allowed accurate positioning of the test transducer in the ear and the desired coupling of the transducer's probe tip to the ossicular chain during auditory tests. According to the principles of integrated safety, the intraoperative risk of ossicular or inner ear injuries caused, for instance, by the patient's head movement is minimized. The design of the manipulator system is universal, also allowing its use for other electronic hearing implants or minimal invasive surgery after minor modifications.