Bone-anchored hearing implants: when sound needs another route

When sound cannot find its way

Normal hearing depends on a sequence: sound enters the ear canal, sets the eardrum vibrating, the ossicles pass that vibration on, and the cochlea turns it into a signal for the brain. When that chain is interrupted somewhere before the cochlea, the loss is called conductive. The inner ear is still able to hear; it is the sound that does not reach it.

The bone-anchored hearing implant follows from that observation. Instead of amplifying sound in the ear canal, it turns sound into vibration and delivers it directly to the skull bone. The bone carries that vibration to the cochlea, bypassing the blocked stretch entirely.

Who this is for

Three scenarios account for most cases:

1. Conductive or mixed hearing loss. Malformations of the ear, the aftermath of chronic otitis, previous ear surgery, selected cases of otosclerosis, and problems of the ossicles with no satisfactory surgical correction.
2. An ear that cannot tolerate a conventional aid. The canal that discharges often, the open cavity left by old surgery, the dermatitis that an earmould makes worse. In those cases the problem is not amplification, it is what amplification requires: a closed, healthy ear canal.
3. Single-sided deafness. Here the logic is different. The device sits on the side that does not hear, picks up sound from that side and carries it through the bone to the cochlea on the good side. It does not restore hearing in the deaf ear: it reduces the head shadow effect, the sound that is lost when it comes from the side the person cannot hear.

In children with microtia or an atretic ear canal, this is often the first route of auditory stimulation, frequently on a softband before they are old enough to be implanted.

How the assessment works

Audiometry is the starting point, and what it shows about bone conduction is decisive: that cochlear reserve is what the implant will use. To it are added speech testing, examination of the ear and, where indicated, a CT scan of the temporal bones, which shows the thickness of the bone and the anatomy available.

Before any surgical decision comes the softband trial. The processor is attached to a band that presses against the bone and transmits sound by that route, with no incision at all. The result is not identical to the implant, because skin and tissue between the processor and the bone damp the vibration, but it allows a concrete experience of hearing by bone conduction and an honest conversation about what to expect.

The models

Bonebridge, Osia and Sentio are active bone conduction implants from different manufacturers, available in Brazil. All three share the same principle: the implanted part sits under intact skin, with no abutment passing through it, and the external processor is held in place by a magnet. They differ in transducer technology, in the dimensions of the implant, in MRI compatibility criteria and in the range of hearing loss they were designed for.

There is also the older percutaneous model, in which a titanium abutment passes through the skin and receives the processor. It still has its place in specific situations, and choosing between the options is part of the assessment.

No model is better than another in the abstract. What settles the choice is the type and degree of the loss, the anatomy of the bone in that patient, the likely need for imaging in future and the daily life of the person who will wear the device.

After surgery

The implant needs time to integrate with the bone before it can receive the processor. Once that time has passed comes activation and fitting, which is not a single event: the processor is adjusted over the first weeks, as the person reports what they hear. Adapting to a new route of hearing takes time, and follow-up with a speech-language pathologist is part of the treatment.

The path at Clínica Rhinus

Diagnostic investigation, audiometry and the candidacy assessment are carried out at the clinic. The surgery is performed by Prof. Aline Bittencourt in hospital, and follow-up before and after happens here.

The consultation and the surgery follow different rules. Consultations with Prof. Aline Bittencourt are self-pay: she does not see patients under health plans. Bone conduction implant surgery, however, may be funded by any Brazilian health plan, as it appears in the ANS list of mandatory procedures (Rol de Procedimentos), including plans that Clínica Rhinus does not accept.

Sources: Brazilian Society of Otology (SBO) · Brazilian Association of Otorhinolaryngology and Cervico-Facial Surgery (ABORL-CCF) · Flint PW, Francis HW, Haughey BH, et al. Cummings Otolaryngology: Head and Neck Surgery. 7th ed. Elsevier; 2020. · Tratado de Implante Coclear e Próteses Auditivas Implantáveis. 2nd ed. Thieme Revinter. · Bento RF, Bittencourt AG, Voegels RL. Seminários em Otorrinolaringologia. Fundação Otorrinolaringologia.