Indian Journal of Otology

ORIGINAL ARTICLE
Year
: 2018  |  Volume : 24  |  Issue : 4  |  Page : 252--256

New transcutaneous bone conduction hearing implant system: Surgical and audiological outcomes


Himanshu Swami1, Viswanathan Anand2, Sweekritha N Bhat1,  
1 Department of ENT-HNS, Command Hospital Airforce, Bengaluru, Karnataka, India
2 Department of ENT-HNS, Armed Forces Medical College, Pune, Maharashtra, India

Correspondence Address:
Dr. Viswanathan Anand
Department of ENT-HNS, Armed Forces Medical College, Wanowarie, Pune - 411 040, Maharashtra
India

Abstract

Aim: A new generation of bone-anchored hearing aid, Baha® 4 Attract System has been introduced as a single-stage procedure with the magnet and abutment implanted on the skull with complete skin cover. Aim is to discuss the surgical and audiological outcome of this new device. Materials and Methods: This was a prospective study. There were 34 patients who fulfilled criteria for bone conduction hearing aid. Out of these patients, 27 were unwilling for the surgical procedure. Prior to the surgery, a trial with a soft band was carried out and seven patients were satisfied with the trial. The outcomes were measured in the form of free-field pure-tone audiometry (PTA) after 3 months of surgery and quality of life gain using Speech, Spatial and Quality of hearing scale (SSQ-12B) questionnaire. Results: Outcomes in terms of gain in free-field PTA were good in all the seven patients. An average gain of 37.85 dB was observed. There was an improvement in quality of life as assessed by SSQ 12B questionnaire. An average score of 40.25 was achieved. Conclusion: Transcutaneous bone conduction aids are fast emerging as a viable alternate to traditional devices. These devices provide almost similar functional gain in hearing along with better cosmetic results, less complications, and minimal wound care.



How to cite this article:
Swami H, Anand V, Bhat SN. New transcutaneous bone conduction hearing implant system: Surgical and audiological outcomes.Indian J Otol 2018;24:252-256


How to cite this URL:
Swami H, Anand V, Bhat SN. New transcutaneous bone conduction hearing implant system: Surgical and audiological outcomes. Indian J Otol [serial online] 2018 [cited 2019 Aug 24 ];24:252-256
Available from: http://www.indianjotol.org/text.asp?2018/24/4/252/254229


Full Text



 Introduction



Bone conduction devices are used for assisting impaired hearing due to conductive hearing loss (HL) (CHL), mixed HL, or single-sided sensorineural HL (SNHL).[1] There are numerous bone conduction devices available for use as illustrated in [Figure 1].[2]{Figure 1}

Direct-drive bone conduction aids transmit the vibration directly to the bone. The most common example is a conventional Baha® percutaneous system in which the abutment projects through the skin and the transducer is external [Figure 2]. The more recent Bonebridge™ system has transducer placed under the skin.{Figure 2}

The more recent passive transcutaneous systems such as Baha Attract® and Sophono® have intact skin, and transducer is externally attached by magnet. There are obvious advantages of lack of soft-tissue complications, better esthetics, and less risk of failure of abutment.[3] In this study, the selection criteria, surgical technique, audiological outcomes, and quality of life outcomes are discussed.

We have performed transcutaneous bone-anchored hearing aid (BAHA) in seven patients of which four patients had single-sided deafness and three patients suffered from bilateral CHL.

Objective

The objective of this study was to assess outcome of transcutaneous bone conduction system in patients with bilateral CHL and single-sided deafness.

 Materials and Methods



Inclusion criteria

CHL or mixed HL in ears to be implanted with bone conduction (BC) thresholds <30 dB HL (average of 500, 100, 2000, and 3000 Hz)Unilateral SNHL with BC thresholds <30 dB HL (average of 500, 100, 2000, and 3000 Hz) in contralateral ear.

Exclusion criteria

Inadequate skull thickness (<4 mm)Previous radiotherapy at the site to be implantedChronic conditions such as uncontrolled diabetes which could impair osseointegration.

There were 34 patients who fulfilled criteria for bone conduction hearing aid. Out of these patients, 27 were unwilling for the surgical procedure. Prior to the surgery, a trial with a soft band was carried out and seven patients were satisfied with the trial.

This study was a prospective case review of seven patients, details of which are summarized in [Table 1].{Table 1}

The pure-tone average for air conduction and BC was calculated for frequencies of 500, 1000, 2000, 3000, and 4000 Hz in the right and left ears separately and measured in dB preoperatively.

The following parameters were recorded after 3 months postsurgery:

Pure tone audiometry (PTA) was conducted using a loudspeaker placed in front for frequencies of 500, 1000, 2000, 3000, and 4000 Hz in a sound-proof audiometry room. The nontest ear was blocked using foam ear plugsQuality of life gain using Speech, Spatial and Qualities of hearing scale (SSQ 12-B) questionnaire.[4]

The device

Baha® attract system is a newly developed transcutaneous bone conduction device by Cochlear Bone Anchored Solutions AB, Konstruktionsvägen 14, Mölnlycke, Sweden. The main components are (a) titanium implant, (b) implant magnet, (c) soft pad, and (d) sound processor [Figure 3].{Figure 3}

The magnet and implant are internal components remaining under the skin which can be attached through invisible connection by magnet on the sound processor. The intervening soft pad distributes pressure evenly for wearing comfort.

Surgery

The surgical steps are illustrated in [Figure 4]:{Figure 4}

Marking the incision and elevation of flap

The implant site is selected; hairs are shaved and care to be taken not to damage the skinPrior to skin incision, the marking is done using a template provided in reference to the ear canal and care taken that the upper limit of the marking should not cross the level of pinna (where the sound processor will attach itself to the magnet)After marking the C-shaped incision about 15 mm away from the implant size, measuring the depth of the tissue is done using a hypodermic needle. Tissue thickness of 6 mm or less is acceptable more thickness needs tissue reductionOnce the marking are done, Gentian Violet dye is injected at the center of the markingSkin incision is given and deepened till it reaches the periosteum and flap is elevatedHemostasis is achieved. Flap stitch is takenFlat periosteal surface is identified and the periosteum is elevated.

Drilling the bone surface

Using the 3-mm spacer, drill the bone such that it should be perpendicular to the bony surface. Use the 2000 rpm setting and constantly irrigate using normal saline, if thick bone is encountered, the 4-mm spacer is used.

Using bone bed indicator

Place the bone bed indicator on the implant and gently hand-tighten it to the implant threads by turning the top knob. Rotate it to ensure it does not touch the bone. This will allow sufficient clearance for the correct mounting of the implant magnetUse the bone bed indicator to drill out (using diamond burr) excessive bone intervening the flat surface.

Widening drill and countersink

Once the drilling is done widening is done using 3 mm or 4 mm spacer and a 0.5 mm countersink is madeCare should be taken not to bend or press the drill while drillingUse 200 rpm setting and drill is designed in such a manner that when the counter sink is complete the drilling stops automatically.

Placing the implant

Once the well is made, change the drill setting to torque mode and pick the implant by using implant inserter placing it in a horizontal placeDo not irrigate during this process.

Attach the implant magnet

Once the implant is inserted and adequately tightened the magnet is inserted by holding with the fingers and tightening using a unidirectional screw driver. The magnet has the marking of “UP” which should orient in superior direction with respect to patients head.

Measure soft-tissue thickness

More than 6 mm thickness may require thinning for proper attachment of magnet.

Closure of incision

Incision is closed in single layer with interrupted sutures.

 Results



Surgical outcomes

The surgical parameters and outcomes are depicted in [Table 2]. In patient 1, a modified anteriorly based flap was raised to avoid scar of previous pinna reconstruction surgery. In patient 2, soft-tissue reduction, due to thick flap, was carried out. This patient also required bone polishing using high-speed drill till bone bed indicator clearance was seen. No intraoperative or postoperative complications were observed.{Table 2}

Audiological outcomes

Audiological parameters were measured 12 weeks postsurgery. The results are tabulated in [Table 3] and [Figure 5]. Patients 1, 3, and 6 had bilateral CHL, whereas patient 7 had unilateral conductive deafness and three patients had single-sided sensorineural deafness. Aided free-field PTA was done for the test ear (implanted side), and the contralateral ear was blocked using foam ear plug.{Table 3}{Figure 5}

Quality of life gain

SSQ-12 B questionnaire was utilized to ascertain benefit in ability to hear and listen in different situations. All patients benefitted from this procedure. Maximum improvement was observed in patient numbers 1, 3, and 6 who suffered from bilateral CHL. The scores are summarized in [Figure 6].{Figure 6}

 Discussion



The aim of this study was to share the experience of newly introduced transcutaneous bone BAHA in terms of surgical outcomes, audiological outcomes, and patient satisfaction. This surgery was performed for the first time in Indian Armed Forces Hospital.

Percutaneous bone-anchored devices are available since few decades.[5] The indications for its use are bilateral, mixed, or CHL and single-sided deafness.[1],[2],[6] These devices have abutment jutting through the skin to which the external transducer is attached. There are numerous studies which confirmed the benefit of using such devices.[7],[8] However, the acceptance and patient satisfaction remained low due to associated skin infections and complications, poor cosmesis, and difficulty in osseointegration. The complication rates in percutaneous technique have ranged from 8% to 59% and revision rates from 5% to 42%.[8],[9],[10],[11],[12],[13] The transcutaneous devices like the BAHA® Attract system overcome these problems. This device is abutment free allowing the bone vibrations through intact skin by magnetic coupling between internal and external components. This in turn results in the elimination of skin complications and better cosmesis. This is evident from [Figure 2] which depicts a child using old BAHA percutaneous system as compared with [Figure 7] showing a child using newer transcutaneous system. The osseointegration is easier allowing implantation in skull as thin as 3 mm as opposed to conventional percutaneous devices where at least 4 mm skull thickness is required. In our series of cases, we did not encounter any complications. All the patients were using the device for more than 8 h a day.{Figure 7}

There are a few studies which establish that satisfactory functional gains are achieved using transcutaneous devices.[14],[15] At present, two transcutaneous devices are commercially available namely Sophono® (Boulder, CO, USA) and Baha® (Cochlear Bone Anchored Solutions AB). We used the latter in seven patients. The audiological outcomes in terms of gain in free-field PTA were good in all the seven patients. An average gain of 37.85 dB was observed on the implanted side, which is comparable to gain achieved in other studies using traditional BAHA devices.[7],[16],[17] In the future, we will consider conducting speech in noise test and localization studies, especially for single-sided deafness.

There was an improvement in quality of life as assessed by SSQ 12B questionnaire developed by MRC Institute of hearing research, UK.[4] An average score of 40.25 was achieved. Predictably, the maximum benefit was seen in patients with bilateral CHL. Patients with single-sided deafness were implanted with aim to improve localization. As they had normal hearing on the other side, the expected functional benefit of hearing was less.

 Conclusion



Transcutaneous bone conduction aids are fast emerging as a viable alternate to traditional devices. These devices provide almost similar functional gain in hearing along with better cosmetic results, less complications, and minimal wound care. Patient selection is of utmost importance to achieve good results.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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