Partially implantable bone conduction hearing aids without a percutaneous abutment (Otomag): technique and preliminary clinical results.

INTRODUCTION Patients with air-bone gaps who cannot be corrected successfully by tympanoplasty or with mixed hearing loss may be treated with bone conduction hearing aids. Their disadvantages are the obvious external fixation components or the biological and psychosocial problems of open implants. We have developed new partially implantable bone conduction hearing aid without a percutaneous abutment and have been using them clinically for 4 years. The principle of these bone conduction hearing aids is a magnetic coupling and acoustic transmission between implanted and external magnets. The goal of this study was to evaluate clinical and audiological results. METHODS Magnets are implanted into shallow bone beds in a one step procedure. The skin above the magnets is also reduced to a thickness of 4-5 mm, which reduces the attenuation to less than 10 dB compared to direct bone stimulation. Over 100 patients have been implanted in the last 5 years. RESULTS Except for temporary pressure marks in 4%, which healed after careful shimming of the external base plate, there were no other complications. DISCUSSION The holding strength of the external components is equivalent to partially implantable hearing aids and cochlea implants and the hearing improvement is similar to other bone conduction hearing aids. We have found the comfort and safety of this system is significantly improved compared to conventional or percutaneous bone conduction hearing aids.