Bone-Anchored Hearing Aids
Bone-anchored hearing aids are implantable devices used to improve hearing by transmitting sound directly to the inner ear through the skull. They work by stimulating the inner ear through vibrations of the bone, and have been successfully used to improve patients' hearing for more than 30 years.
There are three types of hearing loss: conductive, sensorineural and mixed. Bone-anchored hearing aids are designed for patients with less severe cases of conductive hearing loss, or for those with mixed hearing loss, which is a combination of conductive and sensorineural. They are also used for patients with single-ear impairment. These hearing aids can assist patients for whom typical hearing aids are not appropriate, either because the patients have anatomical anomalies, such as small or misshapen ear canals, or are prone to frequent ear infections.
Each bone-anchored hearing aid consists of a permanently implanted titanium fixture, and a detachable sound processor that clips onto that fixture. Using a minimally invasive procedure, a bone-anchored hearing aid is surgically implanted in the skull behind the ear. It works by sending environmental vibrations through the implant into the bone, causing it to vibrate. Bypassing the outer and middle ear, this bone vibration stimulates the inner ear directly, enabling the patient to hear.
Implanting a bone-anchored hearing aid involves two outpatient procedures. During the first, the titanium screw is placed. During the second, which takes place several months later, the hearing aid is implanted. The wait of several months is necessary to ensure that the titanium and bone fuse. Children usually receive general anesthesia when obtaining a bone-anchored hearing aid, but adults may only receive a local anesthetic.