Active transcutaneous bone conduction implant: audiological results in paediatric patients with bilateral microtia associated with external auditory canal atresia

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(1)See discussions, stats, and author profiles for this publication at: https://www.researchgate.net/publication/319412853. Active transcutaneous bone conduction implant: audiological results in paediatric patients with bilateral microtia associated with external auditory canal atresia Article in International Journal of Audiology · August 2017 DOI: 10.1080/14992027.2017.1370137. CITATIONS. READS. 3. 84. 3 authors, including: Eduardo Fuentes López Pontificia Universidad Católica de Chile 27 PUBLICATIONS 29 CITATIONS SEE PROFILE. Some of the authors of this publication are also working on these related projects:. Validation of a dysphagia screening in elderly population in Chile View project. All content following this page was uploaded by Eduardo Fuentes López on 25 May 2018.. The user has requested enhancement of the downloaded file..

(2) International Journal of Audiology. ISSN: 1499-2027 (Print) 1708-8186 (Online) Journal homepage: http://www.tandfonline.com/loi/iija20. Active transcutaneous bone conduction implant: audiological results in paediatric patients with bilateral microtia associated with external auditory canal atresia Sofía Bravo-Torres, Carolina Der-Mussa & Eduardo Fuentes-López To cite this article: Sofía Bravo-Torres, Carolina Der-Mussa & Eduardo Fuentes-López (2017): Active transcutaneous bone conduction implant: audiological results in paediatric patients with bilateral microtia associated with external auditory canal atresia, International Journal of Audiology, DOI: 10.1080/14992027.2017.1370137 To link to this article: http://dx.doi.org/10.1080/14992027.2017.1370137. Published online: 31 Aug 2017.. Submit your article to this journal. View related articles. View Crossmark data. Full Terms & Conditions of access and use can be found at http://www.tandfonline.com/action/journalInformation?journalCode=iija20 Download by: [191.113.74.241]. Date: 31 August 2017, At: 17:57.

(3) International Journal of Audiology 2017; Early Online: 1–8. Original Article. Active transcutaneous bone conduction implant: audiological results in paediatric patients with bilateral microtia associated with external auditory canal atresia. Downloaded by [191.113.74.241] at 17:57 31 August 2017. Sofı́a Bravo-Torres1,2, Carolina Der-Mussa1,3, and Eduardo Fuentes-López4,5 1. Unidad de Otorrinolaringologia, Servicio de Cirugia, Hospital Dr. Luis Calvo Mackenna, Santiago, Chile, 2Carrera de Fonoaudiologia, Facultad de Ciencias de la Rehabilitacion, Universidad Andres Bello, Santiago, Chile, 3Clinica Alemana de Santiago, Facultad de Medicina Universidad del Desarrollo, Santiago, Chile, 4Programa de Doctorado en Salud Pública, Escuela de Salud Pública, Universidad de Chile, Santiago, Chile, and 5Carrera de Fonoaudiologı́a, Departamento de Ciencias de la Salud, Facultad de Medicina, Pontificia Universidad Católica de Chile, Santiago, Chile. Abstract Objective: To describe, in terms of functional gain and word recognition, the audiological results of patients under 18 years of age implanted with the active bone conduction implant, BonebridgeÔ. Design: Retrospective case studies conducted by reviewing the medical records of patients receiving implants between 2014 and 2016 in the public health sector in Chile. Study sample: All patients implanted with the Bonebridge were included (N ¼ 15). Individuals who had bilateral conductive hearing loss, secondary to external ear malformations, were considered as candidates. Results: The average hearing threshold one month after switch on was 25.2 dB (95%CI 23.5–26.9). Hearing thresholds between 0.5 and 4 kHz were better when compared with bone conduction hearing aids. Best performance was observed at 4 kHz, where improvements to hearing were observed throughout the adaptation process. There was evidence of a significant increase in the recognition of monosyllables. Conclusions: The Bonebridge implant showed improvements to hearing thresholds and word recognition in paediatric patients with congenital conductive hearing loss.. Key Words: Implantable hearing aids, paediatrics, speech perception, behavioural measures, hearing aids, pathology. Introduction Atresia of the external auditory canal affects one in every 10,000– 20,000 live births. It is mostly present unilaterally (only 30% is bilateral), in men and in the right ear (Jafek et al. 1975; Kelley and Scholes 2007; El-Begermy et al. 2009); and can be associated with microtia (Lo et al. 2014). A large percentage occurs in isolation, while associated forms often have genetic causes as part of craniofacial disorders (Nazer, Lay-Son, and Cifuentes 2006). Varying degrees of conductive hearing loss are present in 80–90% of patients (Siegert, Matthies, and Kasis 2007). An aesthetic and functional approach can be adopted in treating patients with atresia and microtia. Reconstructive surgery with autologous cartilage has shown to be successful (Long et al. 2013). In the functional correction of hearing loss, bone conduction hearing aids pose as first-line treatment. These systems have several. disadvantages – they are visible, cosmetically unappealing and sometimes cause pain due to pressure being exerted on the skin (Jafek et al. 1975; Lo et al. 2014). An alternative to bone conduction hearing aids are hearing implants (Colletti et al. 2006). These can be divided into middle ear implants, including the VIBRANT SOUNDBRIDGEÔ (MED-EL GmbH, Innsbruck, Austria) and CarinaÔ (Cochlear Ltd, New South Wales, Australia), and bone conduction implants. The latter can be either percutaneous, including the BahaÕ Connect (Cochlear Ltd., New South Wales, Australia) and PontoÔ (Oticon Medical AB, Gothenburg, Sweden); passive transcutaneous like the BahaÔ Attract (Cochlear Ltd., New South Wales, Australia) and SophonoÔ Alpha (Sophono Inc., Boulder, CO) or active transcutaneous like the BonebridgeÔ (MED-EL GmbH, Innsbruck, Austria). Percutaneous systems have an implanted skin-penetrating. Correspondence: Sofı́a Bravo-Torres, Unidad de Otorrinolaringologia, Servicio de Cirugia, Hospital Dr. Luis Calvo Mackenna, Santiago, Chile. E-mail: so.bravo@gmail.com. (Received 5 December 2016; revised 31 July 2017; accepted 7 August 2017) ISSN 1499-2027 print/ISSN 1708-8186 online ß 2017 British Society of Audiology, International Society of Audiology, and Nordic Audiological Society DOI: 10.1080/14992027.2017.1370137.

(4) 2. S. Bravo-Torres et al. Abbreviations. Downloaded by [191.113.74.241] at 17:57 31 August 2017. dBHL dB kHz PTA BAHA JUNAEB SPL. Decibel hearing level Decibel Kilohertz Pure tone average Bone-anchored hearing aid National School and Scholarship Assistance Council Sound Pressure Level. titanium screw with an external processor attached to it in order to transmit vibrations to the inner ear (Park et al. 2016). While such systems may have certain advantages over bone conduction hearing aids, they also have their limitations: (1) permanent pillar percutaneous treatment is required to prevent skin problems; (2) skin infections are recurrent; (3) feedback can limit the amplification provided and (4) screw extrusions due to a failure to osseointegrate may require re-implantation (Huber et al. 2013). The Bonebridge is the only active transcutaneous system available in the market (MEDEL 2016). It consists of an implantable coil and transducer that convert the delivered signals into vibrations that are subsequently transmitted to the inner ear via the skull (Sprinzl et al. 2013). Transcutaneous direct stimulation of the bone minimises the risk of skin irritation and lends towards good sound transmission (Sprinzl et al. 2013). As the implant lies completely under the skin, it is not visible and complications rarely occur (Reinfeldt et al. 2015; Sprinzl and Wolf-Magele, 2016). There are several studies on adults showing improvements in hearing thresholds and speech recognition with the Bonebridge (Barbara et al. 2013; Rivas et al. 2013; Sprinzl et al. 2013; Lassaletta et al. 2014). In 2014, the first paediatric cases were documented, with clear improvements in hearing thresholds (functional gain 430 dB), word recognition (Riss et al. 2014; Hassepass et al. 2015; Rahne et al. 2015), sound localisation and speech recognition in background noise (Plontke et al. 2014; Rahne et al. 2015). In addition, an improvement in quality of life has also been documented in adults (Ihler et al. 2014; Bianchin et al. 2015). A recent systematic review identified 29 studies that showed a positive effect on hearing thresholds, speech recognition and patient satisfaction in children and adults with various types of hearing loss (Sprinzl and Wolf-Magele 2016). The Bonebridge was approved for the European market in 2012 for use in adults and in 2014 for children above five years of age (Reinfeldt et al. 2015). Despite being available for more than three years, Baumgartner et al. (2016) are the only ones to have published a repeated-measures study of paediatric patients (between 5 and 17 years) using the Bonebridge, in which the majority of the subjects (10 out of 12) suffered from ear malformations. This research is of particular interest for a country like Chile, where outer ear malformations are four times more likely to occur than the reported worldwide average (Nazer, Lay-Son, and Cifuentes 2006). Moreover, the relatively high cost of this implant means the most disadvantaged people in the country cannot afford it. Funds provided by public institutions aim to provide equal access for all from an early age. One purpose of this study was to provide input for public policy in Chile, and also serve as a clinical reference for other centres in the region. Taking all these into consideration, the present study aimed to assess the audiological outcomes of patients implanted with the BonebridgeÔ. This involved a comparative description of performance at the different stages of the adaptation process: before surgery. unaided and with bone conducted hearing aids (BCHA), at switchon, and after a month of using the device.. Methods Study design and participants A retrospective case study was conducted using patients implanted with the Bonebridge between 2014 and 2016. The medical records of all implanted patients were reviewed at the Luis Calvo Mackenna Hospital (N ¼ 15) after obtaining approval from the Ethics Committee and gaining parental consent (including approval from the children themselves). Since 2014, both the hospital and the National School and Scholarship Assistance Council have incorporated the Bonebridge implant into their coverage plan. All implant users were covered by the public health insurance system, which does not require copayments for these benefits. Individuals were considered candidates if they had bilateral conductive hearing loss secondary to external ear malformations.. Surgery, activation and follow-up Three surgical approaches are described in the literature: via the mastoid, retro-sigmoid or middle fossa (Barbara et al. 2013; Zernotti and Bravo 2015). The choice of surgical technique depended on the patient’s anatomy and whether the ear was to be reconstructed. The surgical approaches used in this group were via the mastoid or middle fossa. The operation generally lasted about 1.5–2 hours under general anaesthesia and requires a day of hospitalisation. After four weeks, the implant was activated by fitting and placing the audio processor on the head. A vibrogram was performed using the Connexx 6.4.3 and Symfit 6.0 (St Suite 115, Denver, CO) software. These tools allow for hearing thresholds to be tested directly using the implant. A month after implant activation, patients attended the hospital for reassessment and follow-up. Audiometric thresholds in free field, word recognition scores and hearing requirements were confirmed. Gain was increased or decreased at specific frequencies according to individual needs. After this procedure, performance was reassessed.. Audiological evaluation protocol Hearing thresholds and word recognition scores were measured in four different circumstances: before surgery unaided, with bone conduction hearing aids, at switch on and a month after. Hearing was evaluated by warble tones in the sound-field using an Interacoustics AC-33 clinical audiometer (ANSI S3.6/1996). The frequencies measured were 0.25, 0.5, 1, 2 and 4 kHz. Speech perception was evaluated using phonetically-balanced monosyllables, disyllables or spondees, and known terms in Spanish (Rosemblut and De Cruz 1962). Known terms included common words used in the spoken language. The word lists represented the variety of phonemes that were phonetically balanced and belonged to everyday vocabulary (Rosemblüt and De Cruz 1962). The tests were performed in a sound-proof booth at 65 dB SPL using a loudspeaker. Different word lists were presented at different test intervals to avoid learning effect.. Statistical analysis The patients’ average performance was described in terms of the pure tone average, calculated over 0.5, 1.0, 2.0 and 4 kHz, and the.

(5) Downloaded by [191.113.74.241] at 17:57 31 August 2017. Bravo S. active transcutaneous bone conduction implant mean speech recognition score. This was carried out for each stage of the adaptation process: before surgery unaided, with BCHA, at switch on and after a month of device use. For each value, 95% confidence intervals were determined. In order to compare performance, simple and multiple linear regression models were constructed. The dependent variables used were hearing thresholds and the percentage of correct word recognition. The different stages of the adaptation process were used as the predictive variable. Pairwise comparisons were made, with multiple comparisons being adjusted by Tukey’s test. The influence of specific frequencies or verbal material (monosyllabic, disyllabic and known terms) was explored using interaction models. Multilevel models for all the above calculations were used to consider the correlation between measurements taken from the same subject (Rabe-Hesketh and Skrondal 2012a). A random intercept, corresponding to each subject, was specified. Multilevel methods are more efficient than the analysis of the variance of repeated measures, obtaining greater statistical power, which is important in small samples such as in the present study (Ma, Mazumdar, and Memtsoudis 2012). With the aim of obtaining reliable confidence intervals, the asymptotic standard errors of the fixed and random parameters were corrected, using the so-called Huber/White or sandwich estimator (Huber and Ronchetti 2009; White 1980). Inferences based on robust standard errors (‘‘sandwich estimator’’) are less dependent on normal distribution assumptions than the maximum likelihood (Maas and Hox 2004). Moreover, it performs better when estimating the standard errors of the variance of random effects than the maximum likelihood when residuals are non-normal. The latter is likely to occur in small samples such as in the present study (Maas and Hox 2004). Finally, for all models, the assumption of symmetrically distributed residuals was checked. Trajectory performance in terms of hearing thresholds was estimated using growth curve modelling (Rabe-Hesketh and Skrondal 2012b), specifying an intercept and a random coefficient. First, a linear model and then a non-linear piecewise model were adjusted. In the latter, ‘‘knots’’ were created for each condition in order to identify differences in the trajectories of different frequencies.. Results Demographic characteristics of the sample The patients’ age ranged from 5 to 17 with an average of 11. Eight were female and seven male. All were diagnosed with bilateral microtia and congenital aural atresia and presented with moderate bilateral conductive hearing loss. The most frequently implanted ear was the right one. Four had congenital disorders (Treacher Collins or Goldenhar syndrome). All were registered in the Chilean public health system (National Health Fund) (Table 1). Eight patients underwent a complete aesthetic reconstruction of the ear at the time of implantation. Ear reconstruction is carried out sequentially at 6 and 12 years of age and is independent from the implantation of the Bonebridge.. Hearing thresholds Before surgery, the average hearing threshold was 66.5 dBHL (95%CI 64.2–68.9). When aided with a BCHA, an average threshold of 35.8 dBHL was obtained (95%CI 32.5–39.1). With the Bonebridge switched on, the average threshold was 31.0 dBHL. 3. Table 1. Demographic and surgery-related characteristics of paediatric patients implanted with the Bonebridge system (N ¼ 15). Age at time No. of surgery 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15. 11 17 17 7 16 8 8 6 9 12 15 6 5 12 13. Associated pathology. Selected ear. Complications. Surgery. None None None Goldenhar Goldenhar None Treacher collins None Treacher collins None None None Piere robin None None. R L L R L R R R R R R R R R L. Broken processor None Broken processor Broken processor None Feedback Feedback Skin redness Feedback None None Broken processors Skin redness Feedback None. Mastoid Mastoid Mastoid Middle fossa Middle fossa Middle fossa Middle fossa Middle fossa Middle fossa Middle fossa Middle fossa Middle fossa Middle fossa Middle fossa Middle fossa. R: Right ear; L: Left ear.. (95%CI 28.2–33.8), decreasing to 25.2 dBHL (95%CI 23.5–26.9) (Figure 1) after a month of use. The greatest difference was observed when comparing the average thresholds recorded before surgery and after the one month follow-up (mean 41.3 dBHL; 95%CI 37.7–44.9; p50.001). This was followed by the comparison between before surgery and switch on (mean 35.5 dBHL; 95%CI 31.9–39.1; p50.001). There were also significant differences in hearing thresholds when comparing the one month follow-up to switch on (mean 5.8 dBHL; 95%CI 2.2– 9.4; p50.001) and the BCHA (mean 10.6 dBHL; 95%CI 7.0–14.2; p50.001). The difference between preoperative hearing and BCHA use was 30.7 dBHL on average (95% CI 27.1–34.3; p50.001); and between BCHA use and switch on was 4.8 dBHL on average (95% CI 1.2–8.4; p50.001). Frequency-specific hearing thresholds at the different time intervals are depicted in Figure 2. There was an interaction between evaluation and sound frequency (2(12) ¼ 33.5; p50.001) – in other words, the effect of the device was different depending on frequency. At 0.25 kHz, the difference between the one month follow-up and switch on was 4.0 dBHL (95%CI 0.4–7.6; p50.05). At 0.5 kHz, the difference between the one month follow-up and switch on was 4.3 dBHL, although this was not significant (95%CI –0.3–9.0; p ¼ 0.069). There were significant differences in hearing thresholds when comparing the one month follow-up with the BCHA (mean 10 dBHL; 95%CI 5.6–14.4; p50.001). At 1 kHz, there was a significant difference when comparing thresholds between the one month follow-up and switch on (mean 8.7 dBHL; 95%CI 4.7–12.7; p50.01). The comparison between the BCHA and switch on was not significant (mean 2 dBHL; 95%CI –3.1–7.1; p ¼ 0.445). At 2 kHz, there were significant differences between the one month follow-up and switch on (mean 5.6 dBHL; 95%CI 2.0–9.4; p50.01). At 4 kHz, all comparisons were found to be significant. The difference between switch on and the BCHA was on average 14.3 dBHL (95%CI 8.0–20.7; p50.001), and between the one month follow-up and switch on was 6.3 dBHL (95%CI 1.5–11.2; p50.05). Finally, there were no significant differences between the audiometric thresholds measured at the different time intervals.

(6) Downloaded by [191.113.74.241] at 17:57 31 August 2017. 4. S. Bravo-Torres et al.. Figure 1. Audiometric thresholds in evaluation conditions. Mean values with 95% confidence intervals are shown.. Figure 2. Audiometric thresholds in the evaluation process for the 0.25–4 kHz frequency range. Mean values with 95% confidence intervals are shown.. according to the surgical approach performed (medial fossa versus mastoid) (p ¼ 0.562). Although the sample size was small, the difference observed was not clinically relevant (51 dBHL).. Speech recognition The overall average percentage of correct speech recognition before surgery was 29.4% (95%CI 25.2–34.6); with the BCHA, this. reached 78.9% (95%CI 73.5–84.4). When the Bonebridge was switched on, performance increased to 90.7% (95%CI 87.4–93.9) and, a month afterwards, reached 96.4% (95%CI 92.7–100.2). The greatest difference was observed when comparing the mean recognition scores before surgery and after one month follow-up (mean 67.0%; 95%CI 60.4–73.7; p50.001). This was followed by the comparison between before surgery and switch on (mean 61.2%; 95%CI 54.6–67.9; p50.001). There was also a significant.

(7) Downloaded by [191.113.74.241] at 17:57 31 August 2017. Bravo S. active transcutaneous bone conduction implant. 5. Figure 3. Results of the model showing the interaction between word recognition as verbal, material and evaluation condition variables. Mean values with 95% confidence intervals are shown.. difference in speech scores when comparing the one month followup to the BCHA (mean 17.5%; 95%CI 10.9–24.2; p50.001). There was no significant difference between the scores from the one month follow-up and switch on (mean 5.8; 95%CI 0.87–12.43; p ¼ 0.113). Speech recognition varied according to the type of material used. On average, performance was significantly better when using known terms rather than monosyllables (mean difference 9.1%; 95%CI 6.6–11.5; p50.001). Speech scores obtained with the different verbal materials at the different time intervals are presented in Figure 3. The interaction between evaluation conditions and the verbal material used was significant (2(6) ¼ 223.04; p50.001). There were statistically significant differences in speech scores between evaluation conditions when using monosyllables, with scores ranging from 19.6% (95%CI 17.7–21.5; p50.001) to 2.1% (95%CI 1.3–2.9; p50.001). For disyllabic words, the results were similar; however, the differences between conditions were significant. For known terms, statistically significant differences were observed for all the comparisons except between switch on and one month follow-up (mean 0.7% IC95% –0.04–1.4; p ¼ 0.065) (Figure 3).. Trajectory performance While variations occur when estimating ‘‘linear growth curves,’’ several differences in the trajectories of hearing thresholds according to sound frequency were observed (Figure 4). These differences are evident when estimating non-linear trajectories through piecewise models. For example, at 4 kHz, the difference between before surgery and BCHA corresponded to 25.3 dBHL (95%CI 20.0–30.7; p50.001) and 14.3 dBHL between BCHA and switch on (95%CI 8.0–20.7; p50.001). Fitting after one month of follow-up led to a further improvement of 6.3 dBHL (95% CI 1.5–11.2; p50.05). At 0.25 kHz, there was an increase of 32.3 dBHL (95% CI. 24.5–40.2; p50.001) from before surgery to BCHA use; fitting after one month of follow-up led to a further significant improvement of 4 dBHL (95% CI 0.4–7.6; p50.05). No statistically significant improvements were recorded between the remaining conditions (Figure 5).. Adverse events Patients included in this study had no serious complications. The most frequent complications were minor feedback (N ¼ 4), broken processors (due to faults) before six months of use (N ¼ 4) and mild skin redness (N ¼ 2). Feedback problems were resolved by activating the audio processor’s feedback-cancelling algorithm. In the cases of skin redness, as a precaution for possible complications with the skin flap, the audio processor was removed for two to three weeks and, if necessary, the magnet was swapped for one of a lower strength.. Discussion The outcomes of this study demonstrate the effectiveness of the Bonebridge system. The average hearing threshold after one month of device use was 25.2 dBHL (95%CI 23.5–26.9), with a narrowing of the air-bone gap in every case. Hearing thresholds were better than those with BCHAs at the frequencies important for speech perception (0.5–4 kHz). The best performance was at 4 kHz, with improvements in hearing throughout the adaptation process (Figure 2). The Bonebridge had a better performance than the BCHA, which can be explained by direct, transcutaneous stimulation of the skull. BCHAs produce and exert exterior sound energy on to the skin; the skin then conveys these vibrations to the inner ear. With the direct stimulation of the skull in transcutaneous bone conduction implants, 5–15 dBHL improvement in sensitivity at 1 kHz and above can be.

(8) Downloaded by [191.113.74.241] at 17:57 31 August 2017. 6. S. Bravo-Torres et al.. Figure 4. Predicted and observed linear growth curves for the pure tone thresholds of frequencies evaluated in the four conditions (1st ¼ before surgery unaided, 2nd ¼ and with bone conducted hearing aids, 3rd ¼ switch on and 4th ¼ after a month of device use).. Figure 5. Non-linear growth curves (piecewise) predicted for 0.250 and 4 kHz in the four conditions (1st ¼ before surgery unaided, 2nd ¼ and with bone conducted hearing aids, 3rd ¼ switch on and 4th ¼ after a month of device use). Mean values with 95% confidence intervals are shown.. expected (Stenfelt 2011). Another factor that contributes to improved performance could be the shorter distance between the point of vibration and the inner ear. Studies have shown that positioning a bone conduction transducer closer to the ear canal and inner ear improves sound transmission (Eeg-Olofsson et al. 2008,. 2011; Häkansson et al. 2008; Rivas et al. 2013), leading to better hearing (Reinfeldt et al. 2014). Comparisons between BCHA implementation and the switched on Bonebridge showed no significant differences in hearing thresholds between 0.5 kHz and 2 kHz. This is essentially in line.

(9) Downloaded by [191.113.74.241] at 17:57 31 August 2017. Bravo S. active transcutaneous bone conduction implant with therapeutic expectations. Changes at these frequencies will probably be seen after one month of use, when the device is calibrated and checked. Significant improvements in hearing at 4 kHz at all stages of the adaptation process could be an important consideration in further adjustment and fitting of the device. In terms of word recognition, there was a significant improvement with the Bonebridge compared to the BCHA. An average score of 96.4% was obtained after one month of use. The most effective verbal material was monosyllabic word lists, which were more sensitive to differences in performance. This could be explained by their characteristics in Spanish: Monosyllabic words are rare in spontaneous speech and, since they do not involve contextual or semantic cues, recognition is mainly auditory. As mentioned before, there is only one clinical trial (Baumgartner et al. 2016) that has included paediatric patients with similar characteristics to those in this study. Those authors reported significant improvements in speech perception and functional gain with the Bonebridge. The individuals with better hearing performance included in this study were those with a pure conductive hearing loss who exhibited a maximum air-bone gap (60 dBHL). Riss et al. (2014) evaluated 11 patients with atresia, of whom six were under 18 years of age and exhibited a functional gain of 32.5 ± 14.3 dBHL. The lower gain and greater variability compared to our study could be explained by some of the subjects having mixed hearing loss (Riss et al. 2014). Ihler et al. (2014) assessed six adult patients with conductive and mixed hearing losses, whose functional gain was lower than that obtained in the present series, with an average of 34.5 ± 6.9 dBHL. Preoperative air conduction thresholds were slightly lower than in our series, averaging 58.8 ± 8.2 dBHL, and half of the patients had bone conduction thresholds between 26–34.5 dBHL. This could be due to the fact that patients with radical operations were included in the study. In this study, only minor complications were observed and all of these were resolved during the adaptation process. The most common complication was feedback. With a transcutaneous system feedback is less likely to occur, due to the higher impedance of the mechanical signal transmitted from the processor microphone (Taghavi et al. 2012). Another frequent minor complication was technical faults and failure of the audio processors before six months of use (N ¼ 4). This complication is not surprising, given that the processor is a small, lightweight device that uses magnets to hold it against the skin; and that children and adolescents have an active lifestyle. Various solutions have been developed; the most effective one in this sample was the use of a hair clip. It is important to mention that monitoring and check-ups are essential for preventing further complications. Major complications have been identified regarding the surgical requirements inherent to any implantable device, with the most common being related to the skin flap (Zernotti and Bravo 2015). There is the possibility that an implant presses on the meninges; however, no up-to-date report has indicated a higher prevalence of headaches and/or cranial pressure in the implanted population (Zernotti and Bravo 2015). The longterm side effects of vibrations on the dura matter and on the sigmoid sinus are unknown; therefore, more follow-up studies are required.. Limitations and projections In this study, outcomes were collected within a month after implantation; there is a need to follow-up patients to assess if performance varies over time. The data collected here comes from. 7. patients presenting with rare, severe ear malformations. There is a limited amount of literature related to this new device and therefore it is difficult to compare results. Since some of the patients have not yet completed their aesthetic treatment, it is not known how this could affect their audiological performance. Patients who have undergone the full course of treatment (plastic and ear surgery) have reported no significant changes. We are in the process of assessing patient satisfaction, as well as speech recognition in noise; both involve validating instruments in Spanish for the paediatric population. It is also necessary to evaluate the impact this device could have on children’s performance at school. Finally, as the Bonebridge has only recently become available on the national market, it was not possible to compare it to a preoperatively worn headband in the majority of patients. It would be interesting to compare performance with the preoperative headband to that observed in the post-operative period. Future research should address this issue.. Conclusion In the present study, the Bonebridge implant system provided an overall improvement in hearing thresholds and word recognition. In addition, improved hearing was demonstrated in the low (0.5 and 1 kHz) and high frequencies (mainly 4 kHz) when compared to the BCHA. This indicates that the Bonebridge is a viable alternative for the treatment of paediatric patients with congenital conductive hearing loss. Early hearing rehabilitation provides access to speech sounds and is important for auditory development and improving the quality of life (Fan et al. 2013). Patients should continue to be monitored to determine how hearing improvements affect school performance and everyday life.. Acknowledgements The authors thank the Otorhinolaryngology Unit at the Dr. Luis Calvo Mackenna Hospital and the Student Health Program of the National School and Scholarship Assistance Council (JUNAEB), both of whom are sponsors of the hearing implant programme. They are also thankful to Melodi Kosaner Kliess from MEDEL (Austria) for her help in language editing of the manuscript. Declaration of interest: This study did not receive any funding. Eduardo Fuentes-López received support from the National Commission for Scientific and Technological Research (CONICYT) for pursuing doctoral studies in Chile. The authors declare they had no conflicts of interest in conducting this study.. References Barbara, M., M. Perotti, B. Gioia, L. Volpini, and S. Monini. 2013. ‘‘Transcutaneous Bone-Conduction Hearing Device: Audiological and Surgical Aspects in a First Series of Patients with Mixed Hearing Loss.’’ Acta Otolaryngol 133: 1058–1064. Baumgartner, W., J. Hamzavi, K. Böheim, A. 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