Bone-anchored hearing prosthesis

Deafness (or hypoacusis) is a generic term for reduced hearing acuity. Although there are rare cases of deafness of central origin, i.e. involving the brain or the auditory nerve (following a stroke or tumour, for example), the vast majority of deafness is linked to a problem in one or both ears. These are known as peripheral deafnesses. Peripheral deafness is subdivided into two broad categories, depending on the location of the lesion: conductive deafness, when the problem is in the outer or middle ear, and sensorineural deafness, when the problem is in the inner ear. The degree of deafness is assessed by audiometry (tonal by listening to pure tones, and vocal by listening to dissyllabic words), and classified as mild, moderate, profound or total deafness, also known as cophosis. Deafness can be unilateral, bilateral, symmetrical or not, or mixed when it is both conductive and perceptive.
Unilateral deafness is called SSD (single-sided deafness) when it affects one ear with moderate deafness up to cophosis, and a contralateral ear with normal hearing. There are many causes of SSD: sudden deafness, trauma, surgery for acoustic neuroma, meningioma, etc.
Sound can be transmitted to the inner ear in two different ways: by air and by bone. The first, called air conduction, uses the outer ear, the eardrum and the middle ear.

A bone-anchored prosthesis consists of three parts:

• A titanium bone conduction implant osseointegrated into the temporal bone and fitted by the ENT surgeon during surgery.
• A titanium abutment attached to the bone conduction implant, onto which the sound processor will be clipped (only 6-8 weeks after surgery).
• An external sound processor that clips onto the abutment. This housing includes a microreceiver for external sounds and a transducer that creates vibrations for the bone. It may also have a sound amplifier.

There are currently 2 bone-anchored hearing aids supplied by 2 companies:

• BAHA© for Bone Anchored Hearing Aid from ENTIFIC MEDICAL SYSTEMS ®.
• PONTO© from OTICON MEDICAL ®.

It is performed under general or local anesthesia in the operating room, on an outpatient basis unless medically contraindicated. Dr. Delagranda reserves the use of local anesthesia for this procedure for very special cases.

The surgery consists of several stages:

• Locating the ideal area for insertion (at the top and back of the external auditory canal, at a distance from the outer ear so that the case cannot touch it, which would interfere with proper functioning, on a smooth area, putting the top of the outer ear and the top of the case on the same horizontal line). A CT scan can be useful, but is not compulsory.
• Measure skin and sub-skin thickness.
• Infiltrate with a product that limits bleeding.
• Remove a core of skin and subcutaneous tissue.
• Remove the periosteum from the area to be milled.
• Mill the temporal bone of the skull to form a well.
• Screw the titanium abutment-fixture assembly into the shaft bone using a very slow but high-torque motor.
• Place greasy tulle around the abutment and a protective silicone cap on the abutment.

The patient is discharged home the same day, unless living alone in the event of general anaesthesia.
A 7-day leave from work is possible.
Pain is minimal and brief. It is controlled by Class I analgesics.
Post-operative care at home: nothing for 5 days, no nursing care, the protective cap and fatty tulle must be left in place for 5 days. These will be removed by the surgeon himself. Then clean daily with soap and water, for the rest of your life.
Scarring : No visible scarring, but the abutment remains visible.
Precautions: Shock should be avoided for the first 8 weeks to prevent osseointegration of the titanium fixture.