A bonebridge implant is an option where hearing loss is caused by a physical problem with the outer or middle ear in turn causing so-called 'conductive hearing loss'.
A bone bridge implant transmits sound captured on a small external device (generally located on the head just behind the affected ear) to the inner ear (cochlea) via a process known as 'bone conduction'.
Bone conduction describes how sound can be transmitted through bone to the inner ear and was even used by the composer Beethoven when he became deaf later in life - he would bite on his conductor's baton when holding it against his piano so he could hear the notes more clearly.
Bone conduction devices have also been used in the military and in scuba diving for many years, with the first bonebridge implants specifically for hearing loss being developed in the 1970s.
Many devices for people with hearing loss use bone conduction via the jaw bone or the cheek bones, although the bonebridge implant conducts sound through the mastoid bone behind the ear.
A bonebridge device has two components - the outer listening device ('external sound processor') described above, and an internal component (the implant) just below the skin, underneath the external component. The outer listening device is held in place over the implant by magnetism and the two components communicate via a wireless link.
The implant is made of titanium, which over time bonds with the underlying bone in a process known as 'osseointegration'.
The internal component must be surgically implanted behind the ear and this procedure usually takes around an hour and a half under a general anaesthetic.
Post Operative Care
Patients will need to take a week off school or work after the operation. Any sports or heavy physical activity should be avoided until a month after the operation.
Bone bridge implants are designed to last for many years. Very rarely an infection may develop of the internal component which will then require replacement. People with a bonebridge implant can conduct life normally, although an implant may also need to be removed where the wearer needs to undergo an MRI scan (although some of the less powerful MRI scanning machines can still be used without removing the implant).
The main advantage of bonebridge implants over conventional bone conduction hearing aids is superior sound quality, since the sound does not have to be transmitted through the skin. Also the implant is more comfortable as it does not need to be pressed against the skin, as conventional bone conduction hearing aids have to.