- Email: [email protected]
Hearing Outcomes of the Active Bone Conduction System Bonebridge® in Conductive or Mixed Hearing Loss
Acta Otorrinolaringol Esp. 2019;70(2):80---88
www.elsevier.es/otorrino
ORIGINAL ARTICLE
Hearing Outcomes of the Active Bone Conduction ® System Bonebridge in Conductive or Mixed Hearing Loss夽 Claudio Carnevale,∗ Guillermo Til-Pérez, Diego J. Arancibia-Tagle, Manuel D. Tomás-Barberán, Pedro L. Sarría-Echegaray Servicio de Otorrinolaringología y Cirugía de Cabeza y Cuello, Hospital Universitario Son Espases, Palma de Mallorca, Spain Received 12 December 2017; accepted 22 February 2018
KEYWORDS Conductive hearing loss; Bone conduction; Audiometry
Abstract ® Objective: The active transcutaneous bone conduction implant Bonebridge , is indicated for patients affected by bilateral conductive/mixed hearing loss or unilateral sensorineural hearing loss, showing hearing outcomes similar to other percutaneous bone conduction implants, but with a lower rate of complications. The aim of this study was to analyse the hearing outcomes in a series of 26 patients affected by conductive or mixed hearing loss and treated with ® Bonebridge . ® Methods: 26 of 30 patients implanted with Bonebridge between October 2012 and May 2017, were included in the study. We compared the air conduction thresholds at the frequencies 500, 1000, 2000, 3000, 4000 Hz, the SRT 50% and the percentage of correct answers at an intensity of 50 dB with and without the implant. Results: ‘‘Pure tone average’’ with the implant was 34.91 dB showing an average gain of 33.46 dB. Average SRT 50% with the implant was 34.33 dB, whereas before the surgery no patient achieved 50% of correct answers at a sound intensity of 50 dB. The percentage of correct answers at 50 dB changed from 11% without the implant to 85% with it. We only observed one complication consisting of an extrusion of the implant in a patient with a history of 2 previous rhytidectomies. Conclusions: The hearing outcomes obtained in our study are similar to those published in the ® literature. Bonebridge represents an excellent alternative in the treatment of conductive or mixed hearing loss, and with a lower rate of complications. © 2018 Sociedad Espa˜ nola de Otorrinolaringolog´ıa y Cirug´ıa de Cabeza y Cuello. Published by Elsevier Espa˜ na, S.L.U. All rights reserved.
夽
Please cite this article as: Carnevale C, Til-Pérez G, Arancibia-Tagle DJ, Tomás-Barberán MD, Sarría-Echegaray PL. Resultados auditivos ® del sistema activo de conducción ósea BonebridgeB en hipoacusias conductivas o mixtas. Acta Otorrinolaringol Esp. 2019;70:80---88. ∗ Corresponding author. E-mail address: [email protected] (C. Carnevale). 2173-5735/© 2018 Sociedad Espa˜ nola de Otorrinolaringolog´ıa y Cirug´ıa de Cabeza y Cuello. Published by Elsevier Espa˜ na, S.L.U. All rights reserved.
®
Bonebridge and Conductive or Mixed Hearing Loss: Hearing Outcomes
81
®
Resultados auditivos del sistema activo de conducción ósea Bonebridge en hipoacusias conductivas o mixtas
PALABRAS CLAVE Hipoacusia conductiva; Transmisión ósea; Audiometría
Resumen ® Objetivo: El implante activo de conducción ósea transcutáneo Bonebridge está indicado en pacientes con hipoacusia conductiva/mixta bilateral o en casos de hipoacusia neurosensorial unilateral, mostrando resultados auditivos similares a otros dispositivos percutáneos de conducción ósea pero con menor tasa de complicaciones. El objetivo del siguiente trabajo ha sido analizar los resultados auditivos en una serie de 26 pacientes con hipoacusia conductiva/mixta ® tratados con Bonebridge . ® Métodos: Veintiséis de un total de 30 pacientes implantados con Bonebridge entre octubre 2012 y mayo 2017 fueron incluidos en el estudio. Se compararon los umbrales de vía aérea a las frecuencias 500, 1.000, 2.000, 3.000 y 4.000 Hz, umbral de reconocimiento verbal 50% y el porcentaje de aciertos a 50 dB sin y con el implante. Resultados: El umbral tonal medio en campo libre con el dispositivo en funcionamiento fue de 34,91 dB, obteniendo unas ganancias medias de 33,46 dB. La SRT 50% media con el implante fue de 34,33 dB mientras que sin él nadie alcanzaba el 50% de aciertos a una intensidad de hasta 50 dB. Con respecto al porcentaje de aciertos a 50 dB, mejoró desde un 11% sin implante a un 85% con el mismo. Entre las complicaciones solo se observó un caso de extrusión del dispositivo en una paciente con antecedentes de 2 ritidoplastias previas. Conclusiones: Los resultados audiológicos obtenidos en nuestro estudio son similares a los pub® licados en la literatura. Bonebridge representa una excelente alternativa en el tratamiento de la hipoacusia conductiva/mixta, pero con una tasa menor de complicaciones. © 2018 Sociedad Espa˜ nola de Otorrinolaringolog´ıa y Cirug´ıa de Cabeza y Cuello. Publicado por Elsevier Espa˜ na, S.L.U. Todos los derechos reservados.
Introduction Bone conduction implants are indicated for patients affected by conductive or mixed hearing loss who are unable to benefit from standard hearing devices or those who cannot use them due to anatomical anomalies or medical conditions. These implants are also indicated in patients with sensorineural severe-profound single-sided deafness and contralateral normal hearing.1 There are different types of bone conduction devices which may be classified according to the mode of conduction into: - Cutaneous: the vibration is transmitted through the skin ® (passive transcutaneous, for example Sophono, BAHA [Bone Anchored Hearing Aid, Cochlear Co., Australia] attract); - Direct: the vibration is transmitted directly to the bone without passing through the skin. These are divided into ® percutaneous (BAHA , Ponto) and active transcutaneous ® (Bonebridge [Vibrant MED-EL, Innsbruck, Austria]). ®
The percutaneous BAHA system is one of the most commonly used and well known system, with contrasted validity and has become a good prosthetic alternative both because of its gains in the range of high frequencies and for presenting less signal distortion when compared with standard prostheses.2 Since its establishment in 1977 surgical techniques used for its implantation have progressively improved and become increasingly less invasive, with a lower rate
of intra and postoperative complications. It was Tjellström who described the surgical technique for the first time for this device, who foresaw the creation of a skin flap through a dermatome and the reduction of subcutaneous tissues. However, this technique was associated with a high rate of complications, including skin infections (30%---37%) or an overgrowth of soft tissue around the implant. Both required correct daily hygiene with regular medical check-ups and also revision surgery in 26%---42% of cases.3 In successive years other types of techniques were introduced which aimed at lowering the previously described complications. These included the U flap described by Woolford et al. and the lineal incision technique described by Tjellstrom, which were subsequently perfected and were both associated with the reduction of subcutaneous tissue. Following this, the introduction of longer anchors (from 8.5---9 mm to 12 mm versus 6 mm) led to the development of increasingly less invasive surgical techniques (lineal incision without subcutaneous tissue reduction, punch technique), with respect of the subcutaneous cellular tissue (its reduction is associated with skin vascularisation problems), and reducing the risk of infections, poor wound healing, overgrowth of skin around the implant, without affecting its stability and with no sign of a higher rate of extrusion. Currently published data regarding the complications relating to percutaneous devices are promising, with skin complication rates of 10%---30% and surgical revision rates of between 0% and 10%.4 Simultaneously, and with the intention of avoiding these disadvantages observed with the percutaneous devices, which generated increased treatment costs and upsets for the
82
C. Carnevale et al.
patients who temporarily or definitively unable to use the implant use at some time during follow-up, passive transcutaneous bone conduction implants were developed. These devices avoided the cutaneous trauma of the percutaneous devices, and were known to reduce complications but had somewhat lower audiological outcomes because the signal was attenuated by the skin. ® Bonebridge was the first active transcutaneous bone conduction system. It is a partially implantable device which consists of 2 components. One component is external and includes an audio processor with 2 microphones for receiving sounds in the environment, a digital compression processor and a battery. The other internal component or Bone Conduction Implant (BCI) system includes a magnet surrounded by a receptor wheel, an electronic device (demodulator), a transition and an electromagnetic BCI601 (BC-FMT)5---7 floating mass transducer. The implant is inserted completely below the skin, connected to a processor through magnetic attraction and transforms the signal received in mechanical vibrations which are transmitted through the temporal bone to the inner ear. ® The first implant of the Bonebridge device was in June 2011 and formed part of a clinical trial. It was launched onto the market in September 2012. Initially the implantation was approved in adults over 18 years of age and in 2014 in children over 5 years of age.8 The bone conduction implant (BCI) may be implanted at mastoid level, retrosigmoid level or in the middle fossa.
Audiological criteria8 (Fig. 1) The audiological criteria for implantation with the ® Bonebridge device are as follows: 1. Conductive or mixed hearing loss, with bone thresholds over 45 dB in frequencies of .5; 1, 2, 3 kHz. This is contraindicated if the disorder is retrocochlear or central. 2. Severe-profound sensorineural single-sided hearing loss, with normal hearing in the contralateral ear, with
The following factors must also be taken into consideration: • Tympanoplasty surgery, stenosis of the external auditory canal or chronic infections which do not permit the use of standard hearing aids. • Otosclerosis or tympanosclerosis which are unable to be treated with surgery or with standard devices. • Congenital malformations with external auditory canal atresia which would not benefit from reconstructive surgery. • Sudden deafness, schwannomas of the viii cranial nerve or other conditions which cause severe-profound singlesided sensorineural deafness. • Anatomy which enables the correct positioning of the implant, assessed by computerised tomography. • Absence of retrocochlear or central auditive disorder. • Psychological stability with realistic expectations ® regarding the benefits and limitations of the Bonebridge system. The aim of this article was to conduct a retrospective study of the audiological outcomes in a series of 26 patients affected by conductive or mixed hearing loss who had received implants at a tertiary level hospital between 2012 and 2017. The different surgical techniques were also described and the criteria used to choose each one of them, according to the anatomy and background history of the patients.
Materials and Methods A retrospective study was made of a series of 30 patients ® who had been given implants with the Bonebridge system between October 2012 and April 2017 in the Otorrhinolaringology and Head and Neck Surgery Department of the University Hospital Son Espases, aimed at assessing
Frequency (Hz)
A 125 -10 0
250
500
1000
2000
8000
125 -10 0
BC
10
10
20
20
30 40 50 60 70 80
Frequency (Hz)
B 4000
Hearing level (dB HL)
Hearing level (dB HL)
thresholds in air conduction equal to or above 20 dB in frequencies of .5; 1, 2, 3 kHz.
250
500
1000
2000
4000
8000
Contralat. Ear
30 40 50 60 70 80
90
90
100
100
110
110
120
120 ®
Figure 1 Audiological criteria for implantation of the Bonebridge device. (A) Conductive or mixed hearing loss. (B) Unilateral sensorineural hearing loss.
®
Bonebridge and Conductive or Mixed Hearing Loss: Hearing Outcomes Table 1
83
Patient Characteristics Included in the Study.
No.
Background history
Side
Age
Gender
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26
Bilateral cholesteatoma Bilateral cholesteatoma Bilateral cholesteatoma Bilateral cholesteatoma Bilateral COM Bilateral COM Bilateral COM Bilateral COM Bilateral COM Bilateral COM Bilateral COM Bilateral COM Bilateral COM Bilateral COM Bilateral COM Bilateral COM Bilateral COM Bilateral COM Bilateral COM Recurrent external otitis Recurrent external otitis Recurrent external otitis Otosclerosis Otosclerosis Otosclerosis Otosclerosis
L D D D D L L D D L D L L R R R L L L R L R R R R L
45 44 59 61 51 53 28 41 19 32 25 73 66 68 63 45 57 37 43 35 40 57 65 51 52 52
F M M M F M F F F M M M FM F F M M F F F F M F M F F
Complications
Extrusion
COM: chronic otitis media; F: female; M: male.
the audiological outcomes obtained. A pre and postoperative audiological analysis was carried out which included free-field total laminar audiometry and speech audiometry with contralateral masking. Minimum follow-up was 6 months. Out of the 30 patients we selected those who presented with a conductive or mixed bilateral hearing loss with thresholds in bone conduction equal to or better than 45 dB in frequencies of .5; 1, 2, 3 kHz, excluding 4 cases of severe profound single-sided sensorineural hearing loss. Finally, 26 patients met with the inclusion criteria and were included in the study. In order to choose which side to implant, all patients underwent a bandwidth test, observing improvement in tonal and speech audiometry and basing this on the subjective sensation of wellbeing reported by the patient. An audiological pre and postoperative study was undertaken, analysing the thresholds of the air conduction (free field in the postoperative analysis) and bone conduction in the liminar tonal audiometry and the determination of the discrimination thresholds in the speech audiometry. The pure tone average (PTA) was calculated for the air and bone conduction prior to surgery, with frequencies of 500, 1000, 2000 and 4000 Hz and this was compared with the free-field air conduction PTA with the use of the device. With regards to the speech audiometry, pre and postoperative calculation was made of the 50% speech recognition threshold (SRT), the intensity in dB to which the patient gets 50% right and percentage of correct answers at an intensity of 50 dB. All patients
were preoperatively subjected to a CT scan with contrast to assess the necessary approach for the correct positioning of the device.
Results A total of 26 patients were included in the study (Table 1), 15 women and 11 men with a ratio of 1.36---1 and aged between 19 and 73 years (mean age: 48.53 years). Fifteen devices were implanted in the right ear and 11 in the left ear, all unilateral. With regard to medical history, 4 patients had previously had surgery for bilateral cholesteatomatous otitis media, 15 for chronic bilateral otitis media, 3 for recurrent external otitis which prevented the use of standard hearing aids, 4 for ososclerosis, from which 3 had not improved with stapedotomy surgery and one for whom the surgery could not be completed due to the existence of stapedial artery which obliterated the oval window. There were no complications except in one case, which presented with a wound healing problem whereby further surgery was required to perform a rotating cutaneous flap. Mean time in surgery was 65 minutes, with activation of the devices after 3 weeks. In all cases patients were visited 10 days after intervention to remove the sutures. In 16 patients the implant was inserted at presigmoid mastoid level, in 4 at retrosigmoid level and in 6 at temporal squama mid fossa level.
84
C. Carnevale et al. ®
Table 2 Air Conduction Threshold Mean in dB Prior to Surgery at 500, 1000, 2000, 3000 and 4000 Hz. ®
Free field in dB without Bonebridge (without contralateral hearing aid, if they use it) 500 Hz 70.36 dB
1000 Hz 64.41 dB
2000 Hz 64.52 dB
3000 Hz 69.66 dB
4000 Hz 74.22 dB
Table 3 Air Conduction Threshold Mean in dB at 6 Months of Using the Device at 500, 1000, 2000, 3000 and 4000 Hz. Free field in dB in the last review with ® Bonebridge (without contralateral hearing aid, if they use it)
With Bonebridge mean SRT was 34.33 dB, whilst without ® Bonebridge practically none of the patients obtained 50% of correct answers to the assessed intensities (up to 50 dB), save one which attained it at 50 dB. This indicates that when they used the processor they were able to understand half of the words at a mean of 34.33 dB, masking the contralateral ear. However, practically all of them were not able to obtain 50% of correct answers without the processor. When we value the percentage of correct answers at 50 dB, the patients with the processor obtained 85% of correct answers, whilst without it only 11% obtained this.
Discussion ®
500 Hz 40.36 dB
1000 Hz 29.64 dB
2000 Hz 31.79 dB
3000 Hz 33.75 dB
4000 Hz 37.86 dB
Table 4 Mean Gain in dB of Air Conduction Thresholds at 500, 1000, 2000, 3000 and 4000? Hz. Range Between 30 and 37 dB. Mean gain in dB (free field post implant at last check-up compared with preoperative air conduction) 500 Hz 30 dB
1000 Hz 34.77 dB
2000 Hz 32.73 dB
3000 Hz 35.91 dB
4000 Hz 36.36 dB
Tonal Audiometry Comparison All the patients met the audiological criteria for ® Bonebridge indication for the bone conduction thresholds (equal to or lower than 45 dBHL); the mean preoperative bone conduction thresholds being at 23, 25, 39, 39 and 37 dB, respectively for frequencies of 500, 1000, 2000, 3000 and 4000 Hz. The preoperative free-field air conduction thresholds were 70.8 dB at 500 Hz; 64.42 dB at 1000 Hz; 64.52 dB at 2000 Hz; 69.66 dB at 3000 Hz; and 74.22 dB at 4000 Hz (Table 2) The audiological outcome with the device functioning in free field was 40 dB at 500 Hz; 29.61 dB at 1000 Hz; 3179 dB at 2000 Hz; 33.75 dB at 3000 Hz; and 37.86 dB at 4.000 Hz (Table 3) with a gain in dB of 30.38, 34.81, 32.73, 35.91 and 36.36 dB in the respective frequencies (Table 4). In Fig. 2 we may observe the average thresholds of the air conduction before and after surgery. Average hearing outcomes or PTA of the bone conduction were 31 dB. PTA of free-field liminar tonal audiometry for air conduction was 68.37 dB. After 6 months PTA for freefield liminar tonal audiometry with a functioning device was 34.91 dB obtaining mean gain of 33.46 dB (Table 5).
Speech Audiometry Comparison With regard to the result of the speech audiometries we studied 2 parameters: - SRT 50% up to an intensity of 50 dB. - Percentage of correct answers at an intensity of 50 dB.
The active transcutaneous Bonebridge implant is indicated in cases of conductive or mixed bilateral hearing loss, in patients with atresia with or without microtia, in patients who have been previously subjected to surgery for malformation for middle ear pathology and in those who are affected by persistent or recurrent otorrhoea, who are not candidates for a surgical intervention or a standard hearing aid. Another indication is severe-profound sensorineural hearing loss in the presence of one contralateral ear with normal hearing, with air conduction thresholds equal to or better than 20 dB in frequencies of .5; 1, 2, 3 kHz. Compared with other bone conduction implantable hear® ing aids, Bonebridge has several advantages: First, being implanted under the skin avoids the sound attenuation effect which is characteristic of transcutaneous devices, and may be greater in the presence of scar tissue from previous surgery. At the same time, the skin remains intact and the risk of infections is practically nonexistent. Another major advantage is that the users do not usually suffer from pressure pain. This problem may occur with other implantable bone conduction hearing devices that have to be compressed onto the scalp with a specific pressure so that the vibration is transmitted through the skin to the bone and this may cause skin problems and headache. Compared with other pas® sive transcutaneous devices, Bonebridge has a lighter (8 versus 15---23 g) and thinner (9 versus 16 mm, or more) audio processor, which reduces the possibilities of skin injuries and increases usage hours. Finally, the audio processor may be worn discreetly and comfortably under the hair, which is aesthetically also an advantage in its favour. All of the above reduce the need for daily care, the rate of complications and to a great extent improve the patient’s quality of life. In the Zernotti et al.9 series, where the passive transcutaneous Sophono device was com® pared with the active transcutaneous Bonebridge device, no major complications were observed in either of the 2 groups, but of the 4 patients implanted with Sophono, 2 (50%) were affected by problems of pressure and one (25%) had erythema around the implant. These problems were resolved with the reduction of the magnet strength. Despite the fact that in both groups an improvement in air conduction thresholds was observed, the patient implanted ® with the Bonebridge device presented with a greater gain in all frequencies, and especially in middle and high ones (4000 Hz), which we know are important for speech
®
Bonebridge and Conductive or Mixed Hearing Loss: Hearing Outcomes
85
Figure 2 Average graphic audiometrical outcomes obtained using free-field tonal audiometry. AC: air conduction prior to adapta® tion; Bonebridge AC : free-field air conduction with the device. The gain is calculated as the difference in dB between the average values of the thresholds of free-field air conduction prior to adaptation and then with the device.
Table 5
Mean Gain of PTA at 6 Months of Using the Device at 500, 1000, 2000 and 4000 Hz. Mean gain of PTA values for free-field liniar tonal audiometry
Frequency PTA
AC
BC
31 dB
68.37 dB
®
Bonebridge BC in free field 34.91 dB
®
discrimination. Lastly, patients implanted with Bonebridge also demonstrated a higher daily use of the device (8---12 versus 7---10 h/day). Our outcomes confirm the efficacy of the ® Bonebridge device, with aetiological outcomes comparable to those described with other percutaneous implantable devices10 and with a lower rate of complications. Our study demonstrates a major improvement both in air conduction thresholds in tonal audiometry and in the percentages of discrimination in speech audiometry. Of the 26 cases analysed there was one complication in a patient aged 69 who had a history of 2 ritidoplasty operations. This patient presented with poor wound healing and extrusion of the implant which led to further surgery and a local rotation flap. Revision surgery percentages were therefore 4.34%.11 We also had a patient who after initial improvement, 4 years after surgery, presented with a progressive reduction in hearing ability with impairment of the bilateral bone conduction. They are currently not a user of the device and are waiting for cochlear implant surgery. With the exception of the previously described complication, no other skin complications were observed (versus 10%---30% of skin complications with percutaneous devices)4 and therefore the problems of osseointegration with percutanous devices previously ® described was avoided (Bonebridge does not require osseointegration).
Gain 33.46 dB
The lower rate of complications reported with the ® Bonebridge system usage comparied with percutaneous ® devices like the BAHA 4 may be due to 2 factors: the penetrating skin trauma which occurs in the percutaneous implants and not in the transcutaneous ones, which leads to further and greater complications in the skin and the fact ® that the transcutaneous devices such as the Bonebridge system are attached to the bone with screws and covered by healthy skin and their function does not depend on osseointegration. Finally, the lack of need for osseointegration allows for faster activation of the device which in our case always occurred at 3 weeks. With regard to audiological outcomes, considering tonal audiometry, the mean gain of thresholds by air conduction 6 months following surgery was of 30, 34.77, 32.73, 35.91 and 36.36 dB in the 5 analysed frequencies (500, 1000, 2000, 3000, 4000 Hz). The average PTA values for air conduction improved from 68.37 dB preoperatively to 34.91 dB after surgery and with use of the device. These outcomes are similar to those reported in other studies, where functional gain ranged between 24 and 43 dB, and in 50% of cases it is higher than 30 dB.6,7 In the study by Rivas et al.6 average gain of air conduction thresholds ® with the Bonebridge device was 33 dB, totally in keeping with our outcomes (average gain of air conduction thresholds was 33.46). Regarding speech audiometry we observed how 6 months after surgery the patients had a mean of
86
C. Carnevale et al.
Figure 3
Intraoperative image. Middle fossa approach.
85% correct responses at 50 dB (only 11% preoperatively) with a mean SRT 50% of 34,33 dB. Sprinzl et al.,5 in the first multicentre European study with safety and efficacy ® outcomes of the Bonebridge system in 12 patients with conductive/mixed hearing loss, identified a change in language recognition thresholds (SRT 50%) from 61.9 to 42 dB during the first month and of 36.6 dB in the third month, and these results were very similar to those found in our series. The authors argued that this improvement over time took place because language comprehension is influenced by the device accommodation period. Due to this we decided to use the values obtained 6 months after implantation for our comparison. In an interesting article published by Gerdes et al. in 2016, where audiological outcomes obtained with the ® percutaneous device BAHA and the transcutaneous device ® Bonebridge were compared in the treatment of conductive deafness with a minimal sensorineural component, it was proven that they were equivalent alternatives, with comparable outcomes both in average gain of air conduction thresholds and in speech discrimination.12 We have been ® using the Bonebridge device in our hospital since 2012 and consider it a valid option in the treatment of patients with conductive/mixed bilateral hearing loss with bone conduction thresholds over 45 dB. The 26 patients of the series only required one visit from the doctor during the postoperative
period prior to the programming and this was to remove the suture points. With the exception of one patient who needed revision surgery, no skin complications were observed and in all cases the activation of the external processor was 3 weeks, without the need for further visits due to problems relating to the implant in follow-up. All of this may be interpreted as a reduction of overall time in care, which in our case was of particular importance because some of the patients live on different islands to where the hospital is located, and this incurs expenses for the health system. Among the limitations to the use of this device is that required when a patient needs a nuclear magnetic reso® nance. Bonebridge allows for the performing of nuclear magnetic resonance of 1.5 T.13,14 During surgical drilling, special attention should be paid so as not to damage the sigmoid sinus and/or the dura mater, which increases the risk of complications. Prior mastoid conditions (open or obliterated radical cavities, subtotal petrosectomy, and normal external auditory canal) do not affect the efficaciousness of the device nor do they increase the risk of complications. It is recommended in all cases that a preoperative imaging study with computerised tomography be performed15 to determine the correct positioning of the implant in relation to the anatomical structures and the possible anatomical variables (bone thickness, height of the dura mater
®
Bonebridge and Conductive or Mixed Hearing Loss: Hearing Outcomes and of the sigmoid sinus).6 The presigmoid transmastoid approach is preferred in cases of a normal anatomy, where the implant is inserted in the sinodural angle. This reduces interference with the sigmoid sinus and the dura mater. This is also the most commonly used approach in patients with atresia. When anatomical variations will not admit presigmoid insertion and particularly in the presence of radical cavities, it is preferable to position the implant far away from the cavity, and a better option is retrosigmoid. In this position the implant lies far removed from the cavity, and the use of second look surgery is possible, if required.9 A possible alternative to the standard, presigmoid transmastoid or retrosigmoid approaches, should the anatomy not be admissible, the tegmen tympani low or the sigmoid sinus protruding or radical cavities exist which it is preferable not to explore surgically, is the possibility of middle fossa approach which may be directly assessed.1 A retroauricular incision is made above the pinna which is usually small (around 3 cm) after which 2 flaps are made: one of skin and subcutaneous layers and the other fasciomuscular, exposing the parietal temporal cortical bone. At this level below the temporal muscle the floor bed is made (the bone conduction floating mass transducer --- BC-FMT is 9 mm thick) in the temporal squama, above the supramastoid crest or the temporal line, between the lower temporal line and the middle temporal artery groove. This approach may be fast because a 14 mm drill head (neurosurgical drill) may be used, and this considerably reduces time in surgery. We extend the diameter up to 16 mm with a cutter or kerrison punch, with subsequent closure with flaps covered with a compressive bandage (Fig. 3). In our series we were able to insert 16 implants in presigmoid position, 4 in retrosigmoid and 6 in temporal squama at middle fossa level.
Conclusions ®
The Bonebridge system is an effective, safe alternative in patients with bilateral conductive/mixed hearing loss. It obtains significant audiological outcomes and a notable improvement in speech discrimination. Surgical complications that may arise in these interventions are similar to those of other implantable prostheses, including cochlear implant.16 Nevertheless, we should not forget that this is a refined technique requiring preoperative planning with computerised tomography to prevent the majority of complications. The rate of necrosis or infection of the flap is similar to cochlear implant surgery.17 To avoid this we recommend making a double flap, one of skin and subcutaneous layers and the other fasciomuscular, exposing the cortical of the parietal temporal bone, with good vascularisation and minimum incisions which result in minimising the risk of flap complications. In our series of 26 patents we obtained audiological outcomes comparable to those described in the literature. The rate of complications was low, with a single case of implant extrusion, due to a problem of vascularisation related to a history of 2 previous ritidoplasty ® operations. We therefore believe that the Bonebridge system is an excellent alternative for the treatment of patients
87
with conductive or mixed hearing loss and offers lower complication rates.
Conflict of Interests The authors have no conflict of interests to declare.
Acknowledgements We would like to give our thanks to Mr. Vicente Ferro Llanos for his great professionalism.
References 1. Zernotti M, Bravo Sarasty A. Active bone conduction prosthesis: Bonebridge (TM). Int Arch Otorhinolaryngol. 2015;19: 343---8. 2. García Gómez JM, Pe˜ naranda Sanjuán AM, Aparicio ML, Barón C, Zamora L, Puerta M, et al. Resultados auditivos y de beneficios comunicativos en pacientes tratados con el implante activo de ® transmisión ósea Bonebridge . Acta Otorrinolaringol Cir Cabeza Cuello. 2014;42:158---62. 3. Van Rompaey V, Claes G, Verstraeten N, van Dinther J, Zarowski A, Offeciers E, et al. Skin reactions following BAHA surgery using the skin flap dermatome technique. Eur Arch Otorhinolaryngol. 2011;268:373---6. 4. Altuna X, Navarro JJ, Palicio I, Alvarez L. Cirugía del implante osteointegrado con incisión lineal y sin reducción de tejido subcutáneo. Acta Otorrinolaringol Esp. 2015;66: 258---63. 5. Sprinzl G, Lenarz T, Ernst A, Hagen R. First European multicenter results with a new transcutaneous bone conduction hearing implant system: short term safety and efficacy. Otol Neurotol. 2013;34:1076---83. 6. Rivas JA, Rincón LA, Garcia L, Rivas A, Tamayo C, Forero VH. Implantes auditivos de conducción ósea percutáneo, transcutáneo: comparación. Acta Otorrinolaringol Cir Cabeza Cuello. 2013;41:17---24. 7. Manrique M, Sanhueza I, Manrique R, de Abajo J. A new bone conduction implant: surgical technique and results. Otol Neurotol. 2014;35:216---20. 8. Sprinzl GM, Wolf-Magele A. The bonebridge bone conduction hearing implant: indication criteria, surgery and a systematic review of the literature. Clin Otolaryngol. 2016;41: 131---43. 9. Zernotti ME, di Gregorio MF, Galeazzi P, Tabernero P. Comparative outcomes of active and passive hearing devices by transcutaneous bone conduction. Acta Oto-Laryngol. 2016;136:556---8. 10. Pfiffner F, Caversaccio M, Kompis M. Audiological results with Baha in conductive and mixed hearing loss. Adv Otorhinolaryngol. 2011;71:73. 11. Sarría Echegaray PL, Til Pérez G, Arancibia Tagle D, Carnevale C, Tomás Barberán MD. Implantable audiologic devices and facial plastic surgery in elderly patients. MOJ Gerontol Ger. 2017;2:00054. 12. Gerdes T, Salcher RB, Schwab B, Lenarz T, Maier H. Comparison of audiological results between a transcutaneous and a percutaneous bone conduction instrument in conductive hearing loss. Otol Neurotol. 2016;37:685---91. 13. Steinmetz C, Mader I, Arndt S, Aschendorff A, Laszig R, Hassepass F. MRI artefacts after Bonebridge implantation. Eur Arch Otorhinolaryngol. 2014;271:2079---82.
88 14. Nospes S, Mann W, Keilmann A. Magnetic resonance imaging in patients with magnetic hearing implants: overview and procedural management. Radiologe. 2013;53:1026---32. 15. Canis M, Ihler F, Blum J, Matthias C. CT-assisted navigation for retrosigmoidal implantation of the Bonebridge. HNO. 2013;61:1038---44.
C. Carnevale et al. 16. Geraghty M, Fagan P, Moisidis E. Management of cochlear implant device extrusion: case series and literature review. J Laryngol Otol. 2014;128:55---8. 17. Kim YH, Cho SI. Skin flap necrosis by bone marking with methylene blue in cochlear implantation. J Audiol Otol. 2015;19:108---10.
www.elsevier.es/otorrino
ORIGINAL ARTICLE
Hearing Outcomes of the Active Bone Conduction ® System Bonebridge in Conductive or Mixed Hearing Loss夽 Claudio Carnevale,∗ Guillermo Til-Pérez, Diego J. Arancibia-Tagle, Manuel D. Tomás-Barberán, Pedro L. Sarría-Echegaray Servicio de Otorrinolaringología y Cirugía de Cabeza y Cuello, Hospital Universitario Son Espases, Palma de Mallorca, Spain Received 12 December 2017; accepted 22 February 2018
KEYWORDS Conductive hearing loss; Bone conduction; Audiometry
Abstract ® Objective: The active transcutaneous bone conduction implant Bonebridge , is indicated for patients affected by bilateral conductive/mixed hearing loss or unilateral sensorineural hearing loss, showing hearing outcomes similar to other percutaneous bone conduction implants, but with a lower rate of complications. The aim of this study was to analyse the hearing outcomes in a series of 26 patients affected by conductive or mixed hearing loss and treated with ® Bonebridge . ® Methods: 26 of 30 patients implanted with Bonebridge between October 2012 and May 2017, were included in the study. We compared the air conduction thresholds at the frequencies 500, 1000, 2000, 3000, 4000 Hz, the SRT 50% and the percentage of correct answers at an intensity of 50 dB with and without the implant. Results: ‘‘Pure tone average’’ with the implant was 34.91 dB showing an average gain of 33.46 dB. Average SRT 50% with the implant was 34.33 dB, whereas before the surgery no patient achieved 50% of correct answers at a sound intensity of 50 dB. The percentage of correct answers at 50 dB changed from 11% without the implant to 85% with it. We only observed one complication consisting of an extrusion of the implant in a patient with a history of 2 previous rhytidectomies. Conclusions: The hearing outcomes obtained in our study are similar to those published in the ® literature. Bonebridge represents an excellent alternative in the treatment of conductive or mixed hearing loss, and with a lower rate of complications. © 2018 Sociedad Espa˜ nola de Otorrinolaringolog´ıa y Cirug´ıa de Cabeza y Cuello. Published by Elsevier Espa˜ na, S.L.U. All rights reserved.
夽
Please cite this article as: Carnevale C, Til-Pérez G, Arancibia-Tagle DJ, Tomás-Barberán MD, Sarría-Echegaray PL. Resultados auditivos ® del sistema activo de conducción ósea BonebridgeB en hipoacusias conductivas o mixtas. Acta Otorrinolaringol Esp. 2019;70:80---88. ∗ Corresponding author. E-mail address: [email protected] (C. Carnevale). 2173-5735/© 2018 Sociedad Espa˜ nola de Otorrinolaringolog´ıa y Cirug´ıa de Cabeza y Cuello. Published by Elsevier Espa˜ na, S.L.U. All rights reserved.
®
Bonebridge and Conductive or Mixed Hearing Loss: Hearing Outcomes
81
®
Resultados auditivos del sistema activo de conducción ósea Bonebridge en hipoacusias conductivas o mixtas
PALABRAS CLAVE Hipoacusia conductiva; Transmisión ósea; Audiometría
Resumen ® Objetivo: El implante activo de conducción ósea transcutáneo Bonebridge está indicado en pacientes con hipoacusia conductiva/mixta bilateral o en casos de hipoacusia neurosensorial unilateral, mostrando resultados auditivos similares a otros dispositivos percutáneos de conducción ósea pero con menor tasa de complicaciones. El objetivo del siguiente trabajo ha sido analizar los resultados auditivos en una serie de 26 pacientes con hipoacusia conductiva/mixta ® tratados con Bonebridge . ® Métodos: Veintiséis de un total de 30 pacientes implantados con Bonebridge entre octubre 2012 y mayo 2017 fueron incluidos en el estudio. Se compararon los umbrales de vía aérea a las frecuencias 500, 1.000, 2.000, 3.000 y 4.000 Hz, umbral de reconocimiento verbal 50% y el porcentaje de aciertos a 50 dB sin y con el implante. Resultados: El umbral tonal medio en campo libre con el dispositivo en funcionamiento fue de 34,91 dB, obteniendo unas ganancias medias de 33,46 dB. La SRT 50% media con el implante fue de 34,33 dB mientras que sin él nadie alcanzaba el 50% de aciertos a una intensidad de hasta 50 dB. Con respecto al porcentaje de aciertos a 50 dB, mejoró desde un 11% sin implante a un 85% con el mismo. Entre las complicaciones solo se observó un caso de extrusión del dispositivo en una paciente con antecedentes de 2 ritidoplastias previas. Conclusiones: Los resultados audiológicos obtenidos en nuestro estudio son similares a los pub® licados en la literatura. Bonebridge representa una excelente alternativa en el tratamiento de la hipoacusia conductiva/mixta, pero con una tasa menor de complicaciones. © 2018 Sociedad Espa˜ nola de Otorrinolaringolog´ıa y Cirug´ıa de Cabeza y Cuello. Publicado por Elsevier Espa˜ na, S.L.U. Todos los derechos reservados.
Introduction Bone conduction implants are indicated for patients affected by conductive or mixed hearing loss who are unable to benefit from standard hearing devices or those who cannot use them due to anatomical anomalies or medical conditions. These implants are also indicated in patients with sensorineural severe-profound single-sided deafness and contralateral normal hearing.1 There are different types of bone conduction devices which may be classified according to the mode of conduction into: - Cutaneous: the vibration is transmitted through the skin ® (passive transcutaneous, for example Sophono, BAHA [Bone Anchored Hearing Aid, Cochlear Co., Australia] attract); - Direct: the vibration is transmitted directly to the bone without passing through the skin. These are divided into ® percutaneous (BAHA , Ponto) and active transcutaneous ® (Bonebridge [Vibrant MED-EL, Innsbruck, Austria]). ®
The percutaneous BAHA system is one of the most commonly used and well known system, with contrasted validity and has become a good prosthetic alternative both because of its gains in the range of high frequencies and for presenting less signal distortion when compared with standard prostheses.2 Since its establishment in 1977 surgical techniques used for its implantation have progressively improved and become increasingly less invasive, with a lower rate
of intra and postoperative complications. It was Tjellström who described the surgical technique for the first time for this device, who foresaw the creation of a skin flap through a dermatome and the reduction of subcutaneous tissues. However, this technique was associated with a high rate of complications, including skin infections (30%---37%) or an overgrowth of soft tissue around the implant. Both required correct daily hygiene with regular medical check-ups and also revision surgery in 26%---42% of cases.3 In successive years other types of techniques were introduced which aimed at lowering the previously described complications. These included the U flap described by Woolford et al. and the lineal incision technique described by Tjellstrom, which were subsequently perfected and were both associated with the reduction of subcutaneous tissue. Following this, the introduction of longer anchors (from 8.5---9 mm to 12 mm versus 6 mm) led to the development of increasingly less invasive surgical techniques (lineal incision without subcutaneous tissue reduction, punch technique), with respect of the subcutaneous cellular tissue (its reduction is associated with skin vascularisation problems), and reducing the risk of infections, poor wound healing, overgrowth of skin around the implant, without affecting its stability and with no sign of a higher rate of extrusion. Currently published data regarding the complications relating to percutaneous devices are promising, with skin complication rates of 10%---30% and surgical revision rates of between 0% and 10%.4 Simultaneously, and with the intention of avoiding these disadvantages observed with the percutaneous devices, which generated increased treatment costs and upsets for the
82
C. Carnevale et al.
patients who temporarily or definitively unable to use the implant use at some time during follow-up, passive transcutaneous bone conduction implants were developed. These devices avoided the cutaneous trauma of the percutaneous devices, and were known to reduce complications but had somewhat lower audiological outcomes because the signal was attenuated by the skin. ® Bonebridge was the first active transcutaneous bone conduction system. It is a partially implantable device which consists of 2 components. One component is external and includes an audio processor with 2 microphones for receiving sounds in the environment, a digital compression processor and a battery. The other internal component or Bone Conduction Implant (BCI) system includes a magnet surrounded by a receptor wheel, an electronic device (demodulator), a transition and an electromagnetic BCI601 (BC-FMT)5---7 floating mass transducer. The implant is inserted completely below the skin, connected to a processor through magnetic attraction and transforms the signal received in mechanical vibrations which are transmitted through the temporal bone to the inner ear. ® The first implant of the Bonebridge device was in June 2011 and formed part of a clinical trial. It was launched onto the market in September 2012. Initially the implantation was approved in adults over 18 years of age and in 2014 in children over 5 years of age.8 The bone conduction implant (BCI) may be implanted at mastoid level, retrosigmoid level or in the middle fossa.
Audiological criteria8 (Fig. 1) The audiological criteria for implantation with the ® Bonebridge device are as follows: 1. Conductive or mixed hearing loss, with bone thresholds over 45 dB in frequencies of .5; 1, 2, 3 kHz. This is contraindicated if the disorder is retrocochlear or central. 2. Severe-profound sensorineural single-sided hearing loss, with normal hearing in the contralateral ear, with
The following factors must also be taken into consideration: • Tympanoplasty surgery, stenosis of the external auditory canal or chronic infections which do not permit the use of standard hearing aids. • Otosclerosis or tympanosclerosis which are unable to be treated with surgery or with standard devices. • Congenital malformations with external auditory canal atresia which would not benefit from reconstructive surgery. • Sudden deafness, schwannomas of the viii cranial nerve or other conditions which cause severe-profound singlesided sensorineural deafness. • Anatomy which enables the correct positioning of the implant, assessed by computerised tomography. • Absence of retrocochlear or central auditive disorder. • Psychological stability with realistic expectations ® regarding the benefits and limitations of the Bonebridge system. The aim of this article was to conduct a retrospective study of the audiological outcomes in a series of 26 patients affected by conductive or mixed hearing loss who had received implants at a tertiary level hospital between 2012 and 2017. The different surgical techniques were also described and the criteria used to choose each one of them, according to the anatomy and background history of the patients.
Materials and Methods A retrospective study was made of a series of 30 patients ® who had been given implants with the Bonebridge system between October 2012 and April 2017 in the Otorrhinolaringology and Head and Neck Surgery Department of the University Hospital Son Espases, aimed at assessing
Frequency (Hz)
A 125 -10 0
250
500
1000
2000
8000
125 -10 0
BC
10
10
20
20
30 40 50 60 70 80
Frequency (Hz)
B 4000
Hearing level (dB HL)
Hearing level (dB HL)
thresholds in air conduction equal to or above 20 dB in frequencies of .5; 1, 2, 3 kHz.
250
500
1000
2000
4000
8000
Contralat. Ear
30 40 50 60 70 80
90
90
100
100
110
110
120
120 ®
Figure 1 Audiological criteria for implantation of the Bonebridge device. (A) Conductive or mixed hearing loss. (B) Unilateral sensorineural hearing loss.
®
Bonebridge and Conductive or Mixed Hearing Loss: Hearing Outcomes Table 1
83
Patient Characteristics Included in the Study.
No.
Background history
Side
Age
Gender
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26
Bilateral cholesteatoma Bilateral cholesteatoma Bilateral cholesteatoma Bilateral cholesteatoma Bilateral COM Bilateral COM Bilateral COM Bilateral COM Bilateral COM Bilateral COM Bilateral COM Bilateral COM Bilateral COM Bilateral COM Bilateral COM Bilateral COM Bilateral COM Bilateral COM Bilateral COM Recurrent external otitis Recurrent external otitis Recurrent external otitis Otosclerosis Otosclerosis Otosclerosis Otosclerosis
L D D D D L L D D L D L L R R R L L L R L R R R R L
45 44 59 61 51 53 28 41 19 32 25 73 66 68 63 45 57 37 43 35 40 57 65 51 52 52
F M M M F M F F F M M M FM F F M M F F F F M F M F F
Complications
Extrusion
COM: chronic otitis media; F: female; M: male.
the audiological outcomes obtained. A pre and postoperative audiological analysis was carried out which included free-field total laminar audiometry and speech audiometry with contralateral masking. Minimum follow-up was 6 months. Out of the 30 patients we selected those who presented with a conductive or mixed bilateral hearing loss with thresholds in bone conduction equal to or better than 45 dB in frequencies of .5; 1, 2, 3 kHz, excluding 4 cases of severe profound single-sided sensorineural hearing loss. Finally, 26 patients met with the inclusion criteria and were included in the study. In order to choose which side to implant, all patients underwent a bandwidth test, observing improvement in tonal and speech audiometry and basing this on the subjective sensation of wellbeing reported by the patient. An audiological pre and postoperative study was undertaken, analysing the thresholds of the air conduction (free field in the postoperative analysis) and bone conduction in the liminar tonal audiometry and the determination of the discrimination thresholds in the speech audiometry. The pure tone average (PTA) was calculated for the air and bone conduction prior to surgery, with frequencies of 500, 1000, 2000 and 4000 Hz and this was compared with the free-field air conduction PTA with the use of the device. With regards to the speech audiometry, pre and postoperative calculation was made of the 50% speech recognition threshold (SRT), the intensity in dB to which the patient gets 50% right and percentage of correct answers at an intensity of 50 dB. All patients
were preoperatively subjected to a CT scan with contrast to assess the necessary approach for the correct positioning of the device.
Results A total of 26 patients were included in the study (Table 1), 15 women and 11 men with a ratio of 1.36---1 and aged between 19 and 73 years (mean age: 48.53 years). Fifteen devices were implanted in the right ear and 11 in the left ear, all unilateral. With regard to medical history, 4 patients had previously had surgery for bilateral cholesteatomatous otitis media, 15 for chronic bilateral otitis media, 3 for recurrent external otitis which prevented the use of standard hearing aids, 4 for ososclerosis, from which 3 had not improved with stapedotomy surgery and one for whom the surgery could not be completed due to the existence of stapedial artery which obliterated the oval window. There were no complications except in one case, which presented with a wound healing problem whereby further surgery was required to perform a rotating cutaneous flap. Mean time in surgery was 65 minutes, with activation of the devices after 3 weeks. In all cases patients were visited 10 days after intervention to remove the sutures. In 16 patients the implant was inserted at presigmoid mastoid level, in 4 at retrosigmoid level and in 6 at temporal squama mid fossa level.
84
C. Carnevale et al. ®
Table 2 Air Conduction Threshold Mean in dB Prior to Surgery at 500, 1000, 2000, 3000 and 4000 Hz. ®
Free field in dB without Bonebridge (without contralateral hearing aid, if they use it) 500 Hz 70.36 dB
1000 Hz 64.41 dB
2000 Hz 64.52 dB
3000 Hz 69.66 dB
4000 Hz 74.22 dB
Table 3 Air Conduction Threshold Mean in dB at 6 Months of Using the Device at 500, 1000, 2000, 3000 and 4000 Hz. Free field in dB in the last review with ® Bonebridge (without contralateral hearing aid, if they use it)
With Bonebridge mean SRT was 34.33 dB, whilst without ® Bonebridge practically none of the patients obtained 50% of correct answers to the assessed intensities (up to 50 dB), save one which attained it at 50 dB. This indicates that when they used the processor they were able to understand half of the words at a mean of 34.33 dB, masking the contralateral ear. However, practically all of them were not able to obtain 50% of correct answers without the processor. When we value the percentage of correct answers at 50 dB, the patients with the processor obtained 85% of correct answers, whilst without it only 11% obtained this.
Discussion ®
500 Hz 40.36 dB
1000 Hz 29.64 dB
2000 Hz 31.79 dB
3000 Hz 33.75 dB
4000 Hz 37.86 dB
Table 4 Mean Gain in dB of Air Conduction Thresholds at 500, 1000, 2000, 3000 and 4000? Hz. Range Between 30 and 37 dB. Mean gain in dB (free field post implant at last check-up compared with preoperative air conduction) 500 Hz 30 dB
1000 Hz 34.77 dB
2000 Hz 32.73 dB
3000 Hz 35.91 dB
4000 Hz 36.36 dB
Tonal Audiometry Comparison All the patients met the audiological criteria for ® Bonebridge indication for the bone conduction thresholds (equal to or lower than 45 dBHL); the mean preoperative bone conduction thresholds being at 23, 25, 39, 39 and 37 dB, respectively for frequencies of 500, 1000, 2000, 3000 and 4000 Hz. The preoperative free-field air conduction thresholds were 70.8 dB at 500 Hz; 64.42 dB at 1000 Hz; 64.52 dB at 2000 Hz; 69.66 dB at 3000 Hz; and 74.22 dB at 4000 Hz (Table 2) The audiological outcome with the device functioning in free field was 40 dB at 500 Hz; 29.61 dB at 1000 Hz; 3179 dB at 2000 Hz; 33.75 dB at 3000 Hz; and 37.86 dB at 4.000 Hz (Table 3) with a gain in dB of 30.38, 34.81, 32.73, 35.91 and 36.36 dB in the respective frequencies (Table 4). In Fig. 2 we may observe the average thresholds of the air conduction before and after surgery. Average hearing outcomes or PTA of the bone conduction were 31 dB. PTA of free-field liminar tonal audiometry for air conduction was 68.37 dB. After 6 months PTA for freefield liminar tonal audiometry with a functioning device was 34.91 dB obtaining mean gain of 33.46 dB (Table 5).
Speech Audiometry Comparison With regard to the result of the speech audiometries we studied 2 parameters: - SRT 50% up to an intensity of 50 dB. - Percentage of correct answers at an intensity of 50 dB.
The active transcutaneous Bonebridge implant is indicated in cases of conductive or mixed bilateral hearing loss, in patients with atresia with or without microtia, in patients who have been previously subjected to surgery for malformation for middle ear pathology and in those who are affected by persistent or recurrent otorrhoea, who are not candidates for a surgical intervention or a standard hearing aid. Another indication is severe-profound sensorineural hearing loss in the presence of one contralateral ear with normal hearing, with air conduction thresholds equal to or better than 20 dB in frequencies of .5; 1, 2, 3 kHz. Compared with other bone conduction implantable hear® ing aids, Bonebridge has several advantages: First, being implanted under the skin avoids the sound attenuation effect which is characteristic of transcutaneous devices, and may be greater in the presence of scar tissue from previous surgery. At the same time, the skin remains intact and the risk of infections is practically nonexistent. Another major advantage is that the users do not usually suffer from pressure pain. This problem may occur with other implantable bone conduction hearing devices that have to be compressed onto the scalp with a specific pressure so that the vibration is transmitted through the skin to the bone and this may cause skin problems and headache. Compared with other pas® sive transcutaneous devices, Bonebridge has a lighter (8 versus 15---23 g) and thinner (9 versus 16 mm, or more) audio processor, which reduces the possibilities of skin injuries and increases usage hours. Finally, the audio processor may be worn discreetly and comfortably under the hair, which is aesthetically also an advantage in its favour. All of the above reduce the need for daily care, the rate of complications and to a great extent improve the patient’s quality of life. In the Zernotti et al.9 series, where the passive transcutaneous Sophono device was com® pared with the active transcutaneous Bonebridge device, no major complications were observed in either of the 2 groups, but of the 4 patients implanted with Sophono, 2 (50%) were affected by problems of pressure and one (25%) had erythema around the implant. These problems were resolved with the reduction of the magnet strength. Despite the fact that in both groups an improvement in air conduction thresholds was observed, the patient implanted ® with the Bonebridge device presented with a greater gain in all frequencies, and especially in middle and high ones (4000 Hz), which we know are important for speech
®
Bonebridge and Conductive or Mixed Hearing Loss: Hearing Outcomes
85
Figure 2 Average graphic audiometrical outcomes obtained using free-field tonal audiometry. AC: air conduction prior to adapta® tion; Bonebridge AC : free-field air conduction with the device. The gain is calculated as the difference in dB between the average values of the thresholds of free-field air conduction prior to adaptation and then with the device.
Table 5
Mean Gain of PTA at 6 Months of Using the Device at 500, 1000, 2000 and 4000 Hz. Mean gain of PTA values for free-field liniar tonal audiometry
Frequency PTA
AC
BC
31 dB
68.37 dB
®
Bonebridge BC in free field 34.91 dB
®
discrimination. Lastly, patients implanted with Bonebridge also demonstrated a higher daily use of the device (8---12 versus 7---10 h/day). Our outcomes confirm the efficacy of the ® Bonebridge device, with aetiological outcomes comparable to those described with other percutaneous implantable devices10 and with a lower rate of complications. Our study demonstrates a major improvement both in air conduction thresholds in tonal audiometry and in the percentages of discrimination in speech audiometry. Of the 26 cases analysed there was one complication in a patient aged 69 who had a history of 2 ritidoplasty operations. This patient presented with poor wound healing and extrusion of the implant which led to further surgery and a local rotation flap. Revision surgery percentages were therefore 4.34%.11 We also had a patient who after initial improvement, 4 years after surgery, presented with a progressive reduction in hearing ability with impairment of the bilateral bone conduction. They are currently not a user of the device and are waiting for cochlear implant surgery. With the exception of the previously described complication, no other skin complications were observed (versus 10%---30% of skin complications with percutaneous devices)4 and therefore the problems of osseointegration with percutanous devices previously ® described was avoided (Bonebridge does not require osseointegration).
Gain 33.46 dB
The lower rate of complications reported with the ® Bonebridge system usage comparied with percutaneous ® devices like the BAHA 4 may be due to 2 factors: the penetrating skin trauma which occurs in the percutaneous implants and not in the transcutaneous ones, which leads to further and greater complications in the skin and the fact ® that the transcutaneous devices such as the Bonebridge system are attached to the bone with screws and covered by healthy skin and their function does not depend on osseointegration. Finally, the lack of need for osseointegration allows for faster activation of the device which in our case always occurred at 3 weeks. With regard to audiological outcomes, considering tonal audiometry, the mean gain of thresholds by air conduction 6 months following surgery was of 30, 34.77, 32.73, 35.91 and 36.36 dB in the 5 analysed frequencies (500, 1000, 2000, 3000, 4000 Hz). The average PTA values for air conduction improved from 68.37 dB preoperatively to 34.91 dB after surgery and with use of the device. These outcomes are similar to those reported in other studies, where functional gain ranged between 24 and 43 dB, and in 50% of cases it is higher than 30 dB.6,7 In the study by Rivas et al.6 average gain of air conduction thresholds ® with the Bonebridge device was 33 dB, totally in keeping with our outcomes (average gain of air conduction thresholds was 33.46). Regarding speech audiometry we observed how 6 months after surgery the patients had a mean of
86
C. Carnevale et al.
Figure 3
Intraoperative image. Middle fossa approach.
85% correct responses at 50 dB (only 11% preoperatively) with a mean SRT 50% of 34,33 dB. Sprinzl et al.,5 in the first multicentre European study with safety and efficacy ® outcomes of the Bonebridge system in 12 patients with conductive/mixed hearing loss, identified a change in language recognition thresholds (SRT 50%) from 61.9 to 42 dB during the first month and of 36.6 dB in the third month, and these results were very similar to those found in our series. The authors argued that this improvement over time took place because language comprehension is influenced by the device accommodation period. Due to this we decided to use the values obtained 6 months after implantation for our comparison. In an interesting article published by Gerdes et al. in 2016, where audiological outcomes obtained with the ® percutaneous device BAHA and the transcutaneous device ® Bonebridge were compared in the treatment of conductive deafness with a minimal sensorineural component, it was proven that they were equivalent alternatives, with comparable outcomes both in average gain of air conduction thresholds and in speech discrimination.12 We have been ® using the Bonebridge device in our hospital since 2012 and consider it a valid option in the treatment of patients with conductive/mixed bilateral hearing loss with bone conduction thresholds over 45 dB. The 26 patients of the series only required one visit from the doctor during the postoperative
period prior to the programming and this was to remove the suture points. With the exception of one patient who needed revision surgery, no skin complications were observed and in all cases the activation of the external processor was 3 weeks, without the need for further visits due to problems relating to the implant in follow-up. All of this may be interpreted as a reduction of overall time in care, which in our case was of particular importance because some of the patients live on different islands to where the hospital is located, and this incurs expenses for the health system. Among the limitations to the use of this device is that required when a patient needs a nuclear magnetic reso® nance. Bonebridge allows for the performing of nuclear magnetic resonance of 1.5 T.13,14 During surgical drilling, special attention should be paid so as not to damage the sigmoid sinus and/or the dura mater, which increases the risk of complications. Prior mastoid conditions (open or obliterated radical cavities, subtotal petrosectomy, and normal external auditory canal) do not affect the efficaciousness of the device nor do they increase the risk of complications. It is recommended in all cases that a preoperative imaging study with computerised tomography be performed15 to determine the correct positioning of the implant in relation to the anatomical structures and the possible anatomical variables (bone thickness, height of the dura mater
®
Bonebridge and Conductive or Mixed Hearing Loss: Hearing Outcomes and of the sigmoid sinus).6 The presigmoid transmastoid approach is preferred in cases of a normal anatomy, where the implant is inserted in the sinodural angle. This reduces interference with the sigmoid sinus and the dura mater. This is also the most commonly used approach in patients with atresia. When anatomical variations will not admit presigmoid insertion and particularly in the presence of radical cavities, it is preferable to position the implant far away from the cavity, and a better option is retrosigmoid. In this position the implant lies far removed from the cavity, and the use of second look surgery is possible, if required.9 A possible alternative to the standard, presigmoid transmastoid or retrosigmoid approaches, should the anatomy not be admissible, the tegmen tympani low or the sigmoid sinus protruding or radical cavities exist which it is preferable not to explore surgically, is the possibility of middle fossa approach which may be directly assessed.1 A retroauricular incision is made above the pinna which is usually small (around 3 cm) after which 2 flaps are made: one of skin and subcutaneous layers and the other fasciomuscular, exposing the parietal temporal cortical bone. At this level below the temporal muscle the floor bed is made (the bone conduction floating mass transducer --- BC-FMT is 9 mm thick) in the temporal squama, above the supramastoid crest or the temporal line, between the lower temporal line and the middle temporal artery groove. This approach may be fast because a 14 mm drill head (neurosurgical drill) may be used, and this considerably reduces time in surgery. We extend the diameter up to 16 mm with a cutter or kerrison punch, with subsequent closure with flaps covered with a compressive bandage (Fig. 3). In our series we were able to insert 16 implants in presigmoid position, 4 in retrosigmoid and 6 in temporal squama at middle fossa level.
Conclusions ®
The Bonebridge system is an effective, safe alternative in patients with bilateral conductive/mixed hearing loss. It obtains significant audiological outcomes and a notable improvement in speech discrimination. Surgical complications that may arise in these interventions are similar to those of other implantable prostheses, including cochlear implant.16 Nevertheless, we should not forget that this is a refined technique requiring preoperative planning with computerised tomography to prevent the majority of complications. The rate of necrosis or infection of the flap is similar to cochlear implant surgery.17 To avoid this we recommend making a double flap, one of skin and subcutaneous layers and the other fasciomuscular, exposing the cortical of the parietal temporal bone, with good vascularisation and minimum incisions which result in minimising the risk of flap complications. In our series of 26 patents we obtained audiological outcomes comparable to those described in the literature. The rate of complications was low, with a single case of implant extrusion, due to a problem of vascularisation related to a history of 2 previous ritidoplasty ® operations. We therefore believe that the Bonebridge system is an excellent alternative for the treatment of patients
87
with conductive or mixed hearing loss and offers lower complication rates.
Conflict of Interests The authors have no conflict of interests to declare.
Acknowledgements We would like to give our thanks to Mr. Vicente Ferro Llanos for his great professionalism.
References 1. Zernotti M, Bravo Sarasty A. Active bone conduction prosthesis: Bonebridge (TM). Int Arch Otorhinolaryngol. 2015;19: 343---8. 2. García Gómez JM, Pe˜ naranda Sanjuán AM, Aparicio ML, Barón C, Zamora L, Puerta M, et al. Resultados auditivos y de beneficios comunicativos en pacientes tratados con el implante activo de ® transmisión ósea Bonebridge . Acta Otorrinolaringol Cir Cabeza Cuello. 2014;42:158---62. 3. Van Rompaey V, Claes G, Verstraeten N, van Dinther J, Zarowski A, Offeciers E, et al. Skin reactions following BAHA surgery using the skin flap dermatome technique. Eur Arch Otorhinolaryngol. 2011;268:373---6. 4. Altuna X, Navarro JJ, Palicio I, Alvarez L. Cirugía del implante osteointegrado con incisión lineal y sin reducción de tejido subcutáneo. Acta Otorrinolaringol Esp. 2015;66: 258---63. 5. Sprinzl G, Lenarz T, Ernst A, Hagen R. First European multicenter results with a new transcutaneous bone conduction hearing implant system: short term safety and efficacy. Otol Neurotol. 2013;34:1076---83. 6. Rivas JA, Rincón LA, Garcia L, Rivas A, Tamayo C, Forero VH. Implantes auditivos de conducción ósea percutáneo, transcutáneo: comparación. Acta Otorrinolaringol Cir Cabeza Cuello. 2013;41:17---24. 7. Manrique M, Sanhueza I, Manrique R, de Abajo J. A new bone conduction implant: surgical technique and results. Otol Neurotol. 2014;35:216---20. 8. Sprinzl GM, Wolf-Magele A. The bonebridge bone conduction hearing implant: indication criteria, surgery and a systematic review of the literature. Clin Otolaryngol. 2016;41: 131---43. 9. Zernotti ME, di Gregorio MF, Galeazzi P, Tabernero P. Comparative outcomes of active and passive hearing devices by transcutaneous bone conduction. Acta Oto-Laryngol. 2016;136:556---8. 10. Pfiffner F, Caversaccio M, Kompis M. Audiological results with Baha in conductive and mixed hearing loss. Adv Otorhinolaryngol. 2011;71:73. 11. Sarría Echegaray PL, Til Pérez G, Arancibia Tagle D, Carnevale C, Tomás Barberán MD. Implantable audiologic devices and facial plastic surgery in elderly patients. MOJ Gerontol Ger. 2017;2:00054. 12. Gerdes T, Salcher RB, Schwab B, Lenarz T, Maier H. Comparison of audiological results between a transcutaneous and a percutaneous bone conduction instrument in conductive hearing loss. Otol Neurotol. 2016;37:685---91. 13. Steinmetz C, Mader I, Arndt S, Aschendorff A, Laszig R, Hassepass F. MRI artefacts after Bonebridge implantation. Eur Arch Otorhinolaryngol. 2014;271:2079---82.
88 14. Nospes S, Mann W, Keilmann A. Magnetic resonance imaging in patients with magnetic hearing implants: overview and procedural management. Radiologe. 2013;53:1026---32. 15. Canis M, Ihler F, Blum J, Matthias C. CT-assisted navigation for retrosigmoidal implantation of the Bonebridge. HNO. 2013;61:1038---44.
C. Carnevale et al. 16. Geraghty M, Fagan P, Moisidis E. Management of cochlear implant device extrusion: case series and literature review. J Laryngol Otol. 2014;128:55---8. 17. Kim YH, Cho SI. Skin flap necrosis by bone marking with methylene blue in cochlear implantation. J Audiol Otol. 2015;19:108---10.