The old type of hearing aids, using bone for transduction of the sound, depend oninterposed soft tissue between the bone and vibrator. Sound quality depends on complete vibratorand skin surface contact above the mastoid.
There are many problems concerning the fixation bya spring or spectacles. By using bone anchored hearing aids we can eliminate painful, annoyingpressure of the spring.
From the cosmetic point of view - the snail device behind the ear is almostinvisible.