A bone-anchored hearing aid (BAHA), also called a bone-anchored hearing system or bone-anchored auditory implant, is a type of surgically implanted hearing aid. Instead of amplifying sound outside the ear, a bone-anchored hearing aid will conduct sound via vibrations to the inner ear. Not all patients are good candidates for bone-anchored hearing aids since they are considered specialty hearing devices for particular types of hearing impairment. Typically, a bone-anchored hearing device is the best fit for individuals who have at least one normally-functioning inner ear. Good candidates for this type of hearing loss treatment are patients with single-sided deafness or significant middle or outer ear malformations that impact hearing. During the implantation of a BAHA, a surgeon will place a tiny titanium implant into the mastoid bone, which sits behind the ear. The implant is roughly 3-4 mm in size and is attached to an external sound processing device.
Bone to implant contact, sometimes called bone implant contact, is a term that refers to how much of the implant surface is touching bone on a microscopic level and is graded as a percentage. The type of bone plays a significant role in the percentage of bone to implant contact. In soft or medium bone, stability is typically not as good. When osseointegration occurs, stability increases and therefore the percentage of bone to implant contact increases. In dense bone, stability is typically much better and when osseointegration occurs, stability typically remains the same, or it may increase slightly but not significantly. In cases of failed implants, stability is generally low and the bone to implant contact may go down as well. After a dental implant is placed, measurements are taken to determine the level of bone to implant contact and may use this information to modify the patient treatment plan.