BONE ANCHORED HEARING AID (BAHA)

What is a BAHA?

A Bone-Anchored Hearing Aid - is a type of

implantable hearing aid primarily suited to

people who have

conductive hearing loss,

unilateral hearing loss

mixed hearing loss who cannot otherwise

wear 'in the ear' or 'behind the ear' hearing

aids.

It has been in use

from 1977 in Europe

It got approved by

FDA in 1996

Principle

Directly stimulates the

inner ear via bone

conduction bypassing

middle and outer ear

Indications for BAHA

1. When air conduction hearing aid

cannot be used

Canal atresia, congenital or acquired

not amneble to treatment

Chronic ear discharge not amneble to

treatment

Excessive discomfort from air

conduction hearing aid

2. Conductive or mixed hearing

loss Ex: otosclerosis and

tympanosclerosis where surgery

is contraindicated

3. Single-sided hearing loss

Three components of the BAHA system

The sound processor

The abutment

The fixture (or implant)

Titanium screw

4mm long implanted

into skull bone behind

the ear

Permanent, not

adjusted or removed

Becomes firmly

anchored to the bone

by process called

osseointegration

Titanium abutment

is a socket fitted to the

titanium screw

is shaped to hold coupling

of the sound processor

can be unscrewed from

the fixture for maintenance

or replacement by the

specialist audiologist.

Sound processor

Is attached to the

abutment once

osseointegration is

complete

Takes 2 weeks to 6

months after

implantation

Detachable, can be taken

off during hair washing or

swimming

Criteria required for BAHA

There should be at least one working

cochlea

Minimum bone conduction threshold

level required is 45db for effective

function of BAHA

speech discrimination should be more

than 60 percent for BAHA implantation

to be successful.

Implantation procedure

The site for the implant is

identified behind the ear

and is marked.

Usually post-superior to

the EAC.

A split thickness graft is

raised using a

dermatome.

The subcutaneous

tissue is removed

leaving the

periosteum intact.

The site to receive

the implant is

drilled.

The titanium implant

is slowly inserted

under constant

irrigation.

The split skin graft is

returned and

abutment is fitted .

Surgical technique

Single stage : The transcutaneous

abutment is placed at the same setting.

Double stage : Usually done in children

and babies. In the first stage the implant is

placed. After 3 months when

osseointegration is complete the second

stage i.e placing of the abutment is done.

Follow up

First at 2 weeks after the surgery for

inspection of the site. Then at 2

months,when the hearing of the

patient is assessed again.

The patient is asked to maintain the

abutment site clean to prevent

infection and skin reaction.

Complications

Soft tissue overgrowth

Skin infection

Abutment and fixture dislodgement

Trauma

Persistent pain at abutment site

Failure to osseointegrate

Granulation tissue at abutment site

Persistent bleeding at the abutment site

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