1. Introduction
For about four decades, a bone conduction (BC) hearing device may lead to hearing improvement in patients with single-sided deafness (SSD) and conductive or mixed hearing loss (CHL or MHL)(1). By vibration of the skull or structures of the middle ear, these devices transmit a signal directly into the cochlea.
BC hearing devices (BCHDs) can be divided into implantable and non-implantable devices. While implantable devices consist of an implant and an audio processor, with surgery necessary, non-implantable devices consist of an adapter and an audio processor, with surgery nor necessary(2, 3). For implantable BCHDs well known the percutaneous and transcutaneous bone-anchored hearing aids (BAHAs) like Ponto™ System and the BAHA® Attract or Connect Systems(4), the transcutaneous osseointegrated steady-state system (Osia™)(5) or the transcutaneous BC implant Bonebridge®(6), as well as the transcutaneous middle ear implant system Vibrant Soundbridge®(7). As non-implantable BCHDs, in 2001 a softband adapter for a BCHD audio processor was introduced, especially for children. Many studies showed that the softband BAHA is a successfully treatment for CHL(8-10). However, due to the static pressure on the head, some children and adults don’t tolerate a softband as a long-term solution(11). As a new non-implantable BCHD was introduced, the ADHEAR(12, 13). System, especially for small children(14-16). This system works without putting any pressure on the skin. The key concept of the ADHEAR system is a disposable adapter sticking to the hairless skin behind the ear, with an audio processor clicking onto this adapter. Previous studies showed that the audiometric results using the ADHEAR system are similar to those using a softband BAHA system(16), while the wearing time and acceptance in children and adults is preferred over a softband BAHA system(12, 16).