Active bone conduction system: outcomes with the Bonebridge transcutaneous device.

ORL 2015;77:17–26 DOI: 10.1159/000371425 Received: November 3, 2014 Accepted: December 5, 2014 Published online: January 30, 2015

© 2015 S. Karger AG, Basel 0301–1569/15/0771–0017$39.50/0 www.karger.com/orl

Original Paper

Active Bone Conduction System: Outcomes with the Bonebridge Transcutaneous Device Giovanni Bianchin a

Marco Bonali b

Melania Russo a

Lorenzo Tribi c

a Department

of Otolaryngology and Audiology, S. Maria Nuova Hospital of Reggio Emilia, Reggio Emilia, b Department of Otolaryngology – Head and Neck Surgery, University Hospital of Modena, Modena, and c Department of Otorhinolaryngology – Head and Neck Surgery, University Hospital of Parma, Parma, Italy

Key Words Active bone conduction implant · Bonebridge device · Partially implantable bone conduction system · Conductive and mixed hearing loss · Single-sided deafness

Giovanni Bianchin, MD Department of Otolaryngology and Audiology S. Maria Nuova Hospital of Reggio Emilia Viale Risorgimento 80, IT–42123 Reggio Emilia (Italy) E-Mail bianchin.giovanni @ asmn.re.it

Downloaded by: UCSF Library & CKM 169.230.243.252 - 3/25/2015 1:26:17 PM

Abstract Objective: To describe our experience with positioning the Bonebridge (BB) device, a semiimplantable transcutaneous bone conduction implant for patients with conductive and mixed hearing loss as well as for those suffering from single-sided deafness. Methods: The following is a retrospective case review of 4 adults suffering from conductive or mixed hearing loss and single-sided deafness. The BB device was implanted unilaterally via 2 different approaches selected case by case: the presigmoid transmastoid and the retrosigmoid approach. An audiological evaluation in the free field was conducted to observe the functional benefit with this device. The Glasgow Health Status Inventory (GHSI) and the Glasgow Benefit Inventory (GBI) questionnaires were filled out to evaluate patients’ quality of life in relationship to the intervention. Results: No intra- or postoperative complications were observed. The performance in the speech test in all 4 cases reached 100% in the aided condition at 65 dB, while in the unaided condition at 65 dB, it was less than 10%. The GHSI and GBI questionnaires showed an improvement in quality of life after implantation. Conclusions: The BB device is a safe and effective solution for individuals with pathologies such as chronic otitis media, atresia auris and otosclerosis with inadequate benefit from conventional surgery or bone conduction hear© 2015 S. Karger AG, Basel ing aids.

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ORL 2015;77:17–26 DOI: 10.1159/000371425

© 2015 S. Karger AG, Basel www.karger.com/orl

Bianchin et al.: Active Bone Conduction System: Outcomes with the Bonebridge Transcutaneous Device

Introduction

The Bonebridge (BB) device is an implant system for individuals suffering from conductive and mixed hearing loss as well as for patients affected by single-sided sensorineural deafness (SSD) who are not able to obtain adequate benefit from conventional surgery or bone conduction (BC) hearing aids [1, 2]. This transcutaneous device consists of an external part, the audio processor (AP), and an implantable part, the BC implant (BCI), which lies completely under the skin and the AP. The AP contains microphones, a digital signal processor and a battery. The BCI is composed of an active electromagnetic BC floating mass transducer (BC-FMT), an electrical demodulator and a receiver coil (fig. 1) [3]. The BC-FMT is a cylinder with a diameter of 15.8 mm and a thickness of 8.7 mm inserted in the mastoid or temporal bone in order that the AP may be worn easily [3]. It is anchored to the bone by screws. All parts of the BCI are made of silicon and titanium, which are biocompatible with the human body. In BC hearing systems, the vibrations through the skull are transmitted directly to the inner ear [4, 5]. With the BB device, the AP records the sound and converts it into radio signals, which are then transferred through the skin to the coil of the BCI. Thus, the BC-FMT vibrates in a controlled manner through the screws that fix the implant on the bone surface. The bone then conducts these vibrations to the inner ear, where they are converted into nerve signals and transmitted as impulses to the auditory nerve, similar to the natural hearing process. The surgical procedure may be performed under local or total anesthesia. With dedicated software, the positioning of the BC-FMT can be planned in order to avoid any compression of the sinus and dura, and to locate the screws on the same plane [6, 7]. In case of atresia auris, where a pinna reconstruction is planned at a later stage, the incision should be done further posteriorly [8]. In the classic location, the BC-FMT is placed near the sinodural angle anterior to the sigmoid sinus (presigmoid). By drilling with a cutting burr into the sinodural angle of the mastoid, you can create a bone recess for the implant [9]. In some cases, the bone recess is located behind the sigmoid sinus (retrosigmoid). A periosteal pocket should be prepared to accommodate the coil and the demodulator of the BCI. With screws, the implant is fixed on the bone surface. The scalp wound can be closed in layers, after which the skin flap should be sutured. Osseointegration of the screws is not needed [10]. Materials and Methods

Audiometric Assessment Tone and speech audiometry were performed pre- and postoperatively. Measurements of BC and air conduction (AC) were individually tested at frequencies of 0.25, 0.5, 1, 2, 4 and 8 kHz. The pure tone average threshold (PTA4) was measured at 0.5, 1, 2 and 4 kHz for AC and BC. The type of hearing loss and the audiometric threshold were evaluated [11]. There were no retrocochlear problems. A CT scan was performed in all patients to study the anatomical features of the bony structures of the


We report a case series of 4 patients submitted to BB implantation between April 2013 and January 2014 at the Department of Otolaryngology and Audiology, S. Maria Nuova Hospital of Reggio Emilia, Reggio Emilia, Italy. The subjects’ demographics and clinical factors are displayed in table 1. All subjects had a BB semi-implantable BC system unilaterally. Two patients had mixed hearing loss, 1 patient had conductive hearing loss and 1 patient was treated as having SSD. The etiology of the hearing loss was as follows: atresia auris (n = 1), chronic otitis media with cholesteatoma (n = 2) and otosclerosis (n = 1). Two patients were treated via the retrosigmoid approach and 2 patients via the presigmoid-transmastoid approach. This way, we considered all possible kinds of hearing loss and surgical approaches for the implantation of the BB device. In addition, in 1 case, only one screw was enough to fix the implant. The mean age of the subjects was 50 years (range 31–66). Three subjects are Italians and 1 is Tunisian.

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Color version available online


Fig. 1. The BB system.

Table 1. Demographics and clinical factors of the operated patients Case Sex No.

Age, Etiology years

Hearing loss

Preoperative audiometric threshold (BB side)

Preoperative speech perception

Previous surgery

Side of BB implantation

Approach

1

F

31

stapedioplasty

right side

3

M

52

F

49

COC

mixed bilateral

PTA4AC 75 dB PTA4BC 30 dB

CWU tympanoplasty via transmeatal approach CWD tympanoplasty

left side

4

speech test at 65 dB: 0% SRT: 60 dB speech test at 65 dB: 0% SRT: 70 dB speech test at 65 dB: 0% SRT: 90 dB speech test at 65 dB: 10% SRT: 60 dB

retrosigmoid

66

PTA4AC 66 dB PTA4BC 23 dB PTA4AC 60 dB PTA4BC 23 dB PTA4AC 100 dB

left side

F

conductive bilateral mixed bilateral SSD

none

2

atresia auris bilateral otosclerosis COC

presigmoid transmastoid presigmoid transmastoid retrosigmoid

right side

COC = Chronic otitis with cholesteatoma; CWU = canal wall up; CWD = canal wall down.

petrosal bone. Possible positioning of the BC-FMT was conducted in order to plan the surgical technique [5]. A brain MRI was also performed preoperatively, even though the BB device allows undergoing an MRI up to 1.5 T. Surgery We used the presigmoid transmastoid or the retrosigmoid approach for the positioning of the BCI on the basis of the underlying pathology and the anatomical and radiological features of each patient. The authors considered the surgery successful if the following 4 criteria were met: no complications after the surgery, hearing gain in the free-field aided and unaided conditions as well as patient satisfaction according to a quality of life questionnaire and the evaluation of speech in noise.

Postoperative Care A postoperative CT scan of the skull was performed 2 days after surgery to check the positioning of the hearing device. A BC audiometric evaluation of the implanted ear was also conducted after the surgical procedure and before discharge. Antibiotic drugs were also administered in the postoperative period to avoid infections.


Questionnaire The Glasgow Health Status Inventory (GHSI) and the Glasgow Benefit Inventory (GBI) were used to measure the preoperative effect of hearing loss on the quality of life and the change in health status produced by the surgical intervention, respectively [8]. Both the GBI and the GHSI are composed of 18 questions. There are 5 possible answers to each question, with scores ranging from 1 to 5. The total score was divided by the number of questions, then multiplied by 50 after subtracting 3, thus yielding a final score between 0 and +100. Subscale scores were also assessed (general overview as well as social and physical scores) [8].

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Results

Case 2 A 66-year-old female suffered from bilateral mixed hearing loss due to bilateral otosclerosis. At the age of 14 years, she had undergone stapedioplasty on the right side without any significant improvement in conductive gap. The patient refused revision surgery and stapedioplasty on the contralateral ear. In recent years, she had complained of a fast deterioration of conductive hearing, and thus she had the BB device implanted in order to improve her hearing. The preoperative PTA4BC was 23 dB and the PTA4AC was 60 dB for the implanted side, with an air-bone gap of 37 dB. The performance in the speech test was 0% in the unaided condition at 65 dB, and the SRT was 70 dB. In the middle ear, there were fibrotic tissues, and the passive prosthesis was dislocated. The presigmoid transmastoid surgical approach was applied (fig. 3). As the previous surgical treatment had left enough bone in order to safely place the BC-FMT, the BB device was put in a presigmoid transmastoid position. The positioning of the BC-FMT was planned before studying the CT scan. There were no complications after surgery, and the hearing threshold was the same as preoperatively. The AP was activated after 4 weeks; from the beginning, the perception of more clear sounds was accepted. Eight months after the implantation, the gain in the free-field condition for the patient was 41.75 dB. The performance in the speech test with disyllabic words was 100% in the aided condition at 65 dB, and the SRT was 35 dB.


Case 1 A 31-year-old female was affected by bilateral atresia auris with a pure conductive hearing loss on both sides. For more than 25 years, she had worn a BC headset. She was quite satisfied with its performance but had considerable difficulties to obtain a new one; thus, she decided to use a different device. The PTA4AC was 66.25 dB and the PTA4BC was 23 dB; thus, the air-bone gap was 43.25 dB for the implanted side. The performance on the speech test was 0% in the unaided condition at 65 dB, and the speech reception threshold (SRT) was 60 dB. The benefit in the free field with the BC headset was 7.5 dB for PTA4 only. The subject had not had any surgery before BB implantation. The device was put in the left side, where a CT scan had shown malformation of the ossicular chain (the malleus and incus were fused together) and the facial nerve was prolapsing. The approach was retrosigmoid (fig. 2) in order to preserve the portion of the tissue behind the pinna. Positioning of the BC-FMT was planned using dedicated CT software. A bony island between the BC-FMT and the dura was made because there was insufficient bone thickness. There were no complications after surgery, and CT scanning was performed 2 days later. The AP was activated after 4 weeks; at the beginning, the perception of more clear sounds was not accepted quickly because the patient was used to the BC headset. However, within 2 months, she was completely satisfied. Fourteen months after implantation, the gain in the free-field condition for this patient was 30 dB for all frequencies tested. The performance in the speech test with disyllabic words was 100% in the aided condition at 65 dB, and the SRT was 30 dB. The GHSI score before surgery was 19.44, while the GBI score was 44.4 after surgery. The questionnaire showed a better quality of life after BB implantation (table 2a). In the speech-in-noise test at a word intensity of 70 dB SPL, performance was very good with the BB device. Table 2b shows the improvement compared to the unaided condition and with the BC headset.

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DOI: 10.1159/000371425



Fig. 2. Retrosigmoid approach for case 1. CT scan after operation. Axial and coronal views of the implant (see atresia auris).

Table 2. Evaluation of the questionnaire and the speech-innoise test 14 months after the implantation (case 1)

a

Questionnaire

Total score General score Social score Physical score b

GHSI

GBI

19.44 68.75 58 83.33

44.44 66.66 50 50

Speech-in-noise test at 70 dB SPL

SNR

Words recognized in unaided condition

Words recognized in BCHA condition

Words recognized in aided condition

+10 +5 0 –5

1/20 0/20 0/20 0/20

15/20 14/20 2/20 0/20

20/20 20/20 19/20 5/20

SNR = Signal-to-noise ratio; BCHA = BC hearing aid.

Case 3 A 52-year-old male suffered from chronic otitis cholesteatomatosa on the right side with ipsilateral severe hearing loss. The patient had a tympanoplasty via the transmeatal approach without mastoidectomy. The pathology was eradicated without any improvement of hearing. The patient was treated as a case of SSD. The presigmoid transmastoid (fig. 4) approach was used due to the anatomical condition. The PTA4AC was 100 dB for the implanted side. The performance in the speech test was 0% in the unaided condition at 65 dB, and the SRT was 90 dB. The positioning of the BC-FMT was planned before studying the CT scan. The mastoid cells were aerated, and the bone was thick enough to permit the insertion of the implant and the fixation of both screws. There were no complications after surgery, and CT scanning was performed 2 days later.


The GHSI score before surgery was 0, while the GBI score was 44.4 after surgery. The questionnaire showed a better quality of life after BB implantation (table 3a). In the speechin-noise test at a word intensity of 70 dB SPL, performance was very good with the BB device. Table 3b shows the improvement compared to the unaided condition.

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Fig. 3. Presigmoid transmastoid approach for case 2.


a

Questionnaire GHSI


–5.5 25 33.33 50

GBI 44.44 58.33 0 33.33


SNR



+10 +5 0

18/20 6/20 0/20

20/20 10/20 6/20

SNR = Signal-to-noise ratio.

Case 4 A 49-year-old female suffered from chronic otitis cholesteatomatosa on the left side and chronic otitis on the right side. She had had 7 surgical interventions on the left side in the previous 20 years, and the cholesteatoma was eradicated. During the surgical procedure, the facial nerve was sacrificed. The evaluation of the CT scan showed that, on the left side, there was no bone to put the BC-FMT on, and thus it was allocated to the right side.


The AP was activated after 4 weeks; from the beginning, the perception of more clear sounds was accepted, even though the skin was too thick and the patient had to wear a No. 5 magnet to hold the implant on the head. After 6 months, the PTA4 in the aided condition in the free field was 30 dB. The performance in the speech test with disyllabic words was 100% in the aided condition at 65 dB, and the SRT was 30 dB. The GHSI score before surgery was 2.7, while the GBI score was 33.33 after surgery. The questionnaire showed a better quality of life after BB implantation (table 4a). In the speechin-noise test at a word intensity of 70 dB SPL, performance was very good with the BB device. Table 4b shows the improvement compared to the unaided condition.

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Fig. 4. Presigmoid transmastoid approach for case 3. CT 3D view.


a

Questionnaire GHSI


2.7 –22.91 58.33 66.66

GBI 33.33 50 33.33 0


SNR



+10 +5 0 –5

20/20 19/20 8/20 1/20

20/20 20/20 15/20 10/20

The PTA4BC was 30 dB and the PTA4AC was 75 dB for the implanted side. The performance in the speech test was 10% in the unaided condition at 65 dB, and the SRT was 60 dB. The retrosigmoid approach (fig. 5) was used due to the anatomical condition of the sigmoid sinus. The positioning of the BC-FMT was planned before studying the CT scan. The sigmoid sinus was dehiscent and did not permit any other approach. The bone on the temporal line was prominent, so it did not allow putting two screws on the same plane. Only one screw was fixed because washers were not available. There were no complications after surgery, and CT scanning was performed again 2 days later. The AP was activated after 4 weeks. After 3 months, the gain in the free-field condition for the patient was 27.5 dB. The performance in the speech test with disyllabic words was 100% in the aided condition at 65 dB, and the SRT was 35 dB. The GHSI score before surgery was 55.55, while the GBI score was 69 after surgery. The questionnaire showed a better quality of life after BB implantation (table 5a). In the speechin-noise test at a word intensity of 70 dB SPL, performance was very good with the BB device. Table 5b shows the improvement compared to the unaided condition.



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Fig. 5. Retrosigmoid approach for case 4. CT postoperative axial and coronal views showing the shape of the BCI. The sinus on the left side is prolapsing.


a

Questionnaire


GHSI

GBI

55.55 62.5 41.66 58.33

41.66 58.33 0 0


SNR



+10 +5 0 –5

15/20 12/20 1/20 0/20

20/20 20/20 15/20 2/20


The BB device is a new transcutaneous semi-implantable hearing implant which has been available since March 2012 and is used in patients with conductive and mixed hearing loss who do not benefit from conventional AC hearing aids [1, 3]. In general, these bone-anchored hearing devices are used in cases of conductive and mixed hearing loss not treatable by surgery and by traditional AC hearing aids or in patients with bilateral middle ear agenesis [3]. The device offers acoustic and aesthetic benefits that make it a new alternative to other types of BC devices [2]. The main limitation of the BB device is due to the artifact that can occur when a patient undergoes an MRI test. It does not preclude MRI, but there is a limitation to 1.5 T [12, 13]. According to our experience, the position of the BB device was determined via exact evaluation of preoperative CT images in relation to the anatomical structures and their possible anomalies. There are two possible locations of the BC-FMT: the retrosigmoid or the presigmoid area (sinodural angle). The presigmoid transmastoid approach for BB implantation is the preferred choice in case of normal anatomy; the BC-FMT is positioned in the sinodural angle to reduce interference with


Discussion

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the sigmoid sinus and the dura. The well-known reference points are easy to drill if the mastoid is well aerated and the bone is thick enough. In 2 patients, we could do this because the ear was intact. The retrosigmoid approach (used in 2 patients) was performed in cases of an abnormality of the sigmoid sinus or the dura and in patients who had already undergone surgery where it was not possible to place the BC-FMT in the sinodural angle, as well as in patients who were candidates for reconstructive surgery. Outcome and Complications The mean follow-up was 7.25 months (range 3–14). No intraoperative complications were observed. None of the patients in our case series presented complications in the postoperative period. No skin reactions, wound infections or implant extrusions were observed locally in all 4 patients. Audiological Results and Impact on Quality of Life The implant was activated 4 weeks after the surgery for fitting the BB device, and the GHSI and the GBI questionnaires were completed when the free-field and speech-in-noise tests had been conducted. We evaluated satisfaction and the health benefit achieved. The audiological measurements were performed according to the standards of the Committee on Hearing and Equilibrium guidelines for the evaluation of results of treatment of conductive hearing loss (1995). Our study showed a substantial improvement in both tonal and speech audiometry in all 4 patients, better than with conventional BC hearing aids, especially in the speech-in-noise condition. This is due to the fact that direct conduction is more effective than the BC hearing device, where the attenuation of the signal is up to 10–15 dB [11]. The BB device avoids the most common problems presented with traditional hearing aids, such as local irritation, itching and headaches caused by the pressure that must necessarily be applied by the transducer behind the ear [14]. The position of the implant was determined by evaluating the preoperative CT scans, considering different factors such as skull thickness as well as dura and sigmoid sinus exposure. The GBI and GHSI questionnaires before and after the operation demonstrated an improvement in quality of life regarding social support and physical health for all patients. Conclusion

In our opinion, the BB semi-implantable BC system represents a safe and effective solution for individuals with mixed or conductive hearing loss, or with single-sided deafness that cannot be aided with conventional hearing prostheses. Its transcutaneous technology results in a reduction in local infections and skin reactions. Our experience with the BB device has shown good results, in particular with regard to the quality of life of the implanted patients. Disclosure Statement None of the authors have any financial relationship to disclose.

1 2

Huber AM, Sim JH, Xie YZ, Chatzimichalis M, Ullrich O, Röösli C: The Bonebridge: preclinical evaluation of a new transcutaneously-activated bone anchored hearing device. Hear Res 2013;301:93–99. Sprinzl G, Lenarz T, Ernst A, Hagen R, Wolf-Magele A, Mojallal H, Todt I, Mlynski R, Wolframm MD: First European multicenter results with a new transcutaneous bone conduction hearing implant system: shortterm safety and efficacy. Otol Neurotol 2013;34:1076–1083.


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