Bone Conduction Hearing Device

How it Works

Bone anchored device or bone anchored hearing aid (Baha) is a surgically implantable system for treatment of hearing impairment that works through direct bone conduction. Baha sends sound directly to inner ear, bypassing problems in outer or middle ear.

How Bone Conduction Device Works
Fig 1: How Bone Conduction Device Works

The process (of sending sound through bones) is known as direct bone conduction where the system is surgically implanted and allows sound to be relayed through the bone instead via the middle ear.

The bone anchored device consists of three components:

Bone Conduction Device Fitting
Fig 2: Bone Conduction Device Fitting

  1. Implant: Using bone conduction, the titanium implant transfers sound vibrations directly to the hearing nerve via cochlea. The implant is a very small titanium screw which is implanted into the skull.

  2. Abutment: This is secured to the implant into which the sound processor will connect.

  3. Sound Processor: This mimics middle ear, transforming the sound waves into vibrations, passed through the implant to the bone and from there to the working inner ears (cochlea).

Who will benefit from Baha?

Baha devices are helpful for the people with conductive and mixed hearing loss, for whom conventional hearing aids provide little or no benefit. This includes people with:

  • Chronic infection in the ear canal (external otitis)
  • Absence or malformation of the outer ear, ear canal, or middle ear
  • Congenital external auditory canal atresia
  • And people with a single sided hearing impairment which are caused due to surgery for a tumour of the balance and hearing nerves (vestibular schwannoma)

Surgery Procedure

The process involved in getting a Baha comparatively is simple. Surgery generally takes place in an outpatient setting, and the patient can resume normal activities within a few days. There are 4 steps involved in the process:

Baha Implant
Fig 3: Baha Implant

1. Implantation

The procedure of implantation is relatively small and can be carried in an outpatient facility. Only local/general anaesthesia is needed for the procedure. Before the surgery, a surgeon shaves of a small area behind the ear where the implant will be implanted. The area closest to the abutment will remain hair free. A Baha titanium implant with an abutment is implanted in the center of this area.

Baha Dressing
Fig 4: Baha Dressing

2. Healing

After surgery, a dressing which should be changed regularly is required. The stitches are removed after approximately 10 –14 days, provided the area has healed. There may be a feeling of numbness around the abutment, this feeling is most likely to be temporary and will go away. The area around the abutment should be kept clean as there will be an open wound which will have risk of contamination if not clean.

Baha Osseointegration
Fig 5: Baha Osseointegration

3. Osseointegration

Once the titanium implant is implanted, the bone will bond with the titanium implant. This process of bonding of external material with bone is know as osseointegration and takes some time. Once healed, the sound processor is ready to be attached. A surgeon will be able to give an indication of how long to wait before being able to fit the sound processor. The invention of new material and design of implants make it quicker to bond then it used to be before.

Baha Fitting
Fig 6: Baha Fitting

4. Fitting

The Baha sound processor will be fitted at a hearing clinic. A audiologist adjusts the settings of Baha device to suit the sound output based on patient's personal requirements and type/degree of hearing loss.