Patients with air-bone-gaps that cannot be corrected successfully by tympanoplasty or with mixed hearing loss may be treated with bone conducting hearing aids. Their disadvantages are the obvious external fixation components or the biological and psychosocial problems of open implants. We have developed a new partially implantable Bone Conduction Hearing Device (BCHD) without a percutaneous abutment and have been using them clinically for over 6 years. The principle of these BCHD is a magnetic coupling and acoustic transmission between implanted and external magnets. The goal of this study was to evaluate its clinical and audiologic results in patients with unilateral or bilateral congenital aural atresia.
Magnets are implanted into shallow bone beds in a 1-step procedure. The skin above the magnets is slightly thinned. The external device fixed with counter magnets in a base plate.
Twenty-one patients who have been implanted due to congenital atresia showed up for this follow-up study. The follow-up period was 19.3 ± 12.2 months, with a range of 0.2 to 46.6 months. The average age of the patients at the time of implantation was 12.4 years with a wide range from 6.0 to 50.0 years.
The average hearing gain was 31 ± 8 dB, and the suprathreshold word recognition tests increased by 57% ± 23%. Strength of the magnetic force that the patients had chosen themselves measured 0.9 ± 0.4 N with a range from 0.3 to 1.8 N. Skin thickness over the implants measured sonographically was 3.9 ± 0.8 mm (range, 2.5–5.6 mm).
This new bone conducting hearing device only needs one operation, has a very low risk for complication, and a hearing gain similar to other bone conducting hearing aids. We have found high comfort and safety of this system and conclude that it could be a valuable alternative to other conventional or percutaneous bone conducting hearing solutions.