Journal of Otology & RhinologyISSN: 2324-8785

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Research Article, J Otol Rhinol Vol: 2 Issue: 3

A Systematic Review of the Safety and Effectiveness of the Vibrant Soundbridge

Kristin Klein1*, Alexa Nardelli2 and Tania Stafinski2
1Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada
2Health Technology & Policy Unit, School of Public Health, University of Alberta, Edmonton, Alberta, Canada
Corresponding author : Kristin Klein
3021, 8308 – 114 Street, Edmonton, Alberta, T6G2V2, Canada
Tel: 780-248-1526; Fax: 780-248-1546
E-mail: [email protected]
Received: November 25, 2012 Accepted: May 25, 2013 Published: June 11, 2013
Citation: Klein K, Nardelli A, Stafinski T (2013) A Systematic Review of the Safety and Effectiveness of the Vibrant Soundbridge. J Otol Rhinol 2:3. doi:10.4172/2324-8785.1000124

Abstract

A Systematic Review of the Safety and Effectiveness of the Vibrant Soundbridge

Objective: To examine the current state of the science related to the safety and effectiveness of the Vibrant Soundbridge middle ear implant in the treatment of hearing loss.

Data Sources: MEDLINE, EMBASE, The Cochrane Library, Web of Science, CINAHL, PsycINFO and the Centre for Reviews and Dissemination were searched without date or language limits.

Study Selection: Titles and abstracts of 7700 citations were screened and 69 articles selected for full review, of which 44 studies involving a total 832 patients met the study’s eligibility criteria.

Data Extraction: Information was extracted using a pre-tested data abstraction form and study quality was assessed using the Oxford Centre for Evidence-Based Medicine Levels of Evidence.

Data Synthesis: Due to heterogeneity across studies, metaanalysis was not performed and comparisons were made by structured review.

Conclusion: Of the studies that compared the VSB to conventional hearing aids, the majority reported statistically significant improvements in functional gain, speech reception, and quality of life with the VSB. Regarding speech recognition, the findings were mixed. Among studies that compared the VSB to the unaided condition, there was clinical benefit observed in all categories with the device. Adverse event rates were reasonably low, although VSB implantation poses a significant risk compared to non-invasive treatment with conventional hearing aids. The Vibrant Soundbridge middle ear implant appears to offer a safe and effective alternative for patients able and unable to wear conventional hearing aids.

Keywords: Vibrant soundbridge; Patients; Vibrating ossicular prosthesis

Keywords

Vibrant soundbridge; Patients; Vibrating ossicular prosthesis

Introduction

Most patients with mild to severe hearing loss are able to benefit from conventional hearing aids. However, hearing aids are associated with problems that can lead to non-use, including acoustic feedback, discomfort, inadequate amplification, maintenance requirements, or perceived social stigma. Also, certain medical conditions may preclude their use, such as chronic otitis externa or media (both of which are exacerbated by ear occlusion) or the absence or malformation of the external ear. Middle ear implants (MEI) have been developed to address some of these challenges.
Various models of MEIs have been available for over 10 years [1]. For some patients, MEI’s represent an attractive option because they can be left in place while swimming or showering and do not block the ear canal. They may also be preferable for individuals in certain professions (e.g., musicians) or who fall in the “gray zone” between conventional hearing aids and cochlear implants (i.e., those who do not have profound hearing loss but whose hearing loss is severe enough that they do not experience benefit from hearing aids) [2]. However, there are potential surgical risks associated with MEI devices. Moreover, should patients experience feedback problems or device failure, surgical removal/explantation or revision is needed. This review focuses on the Vibrant Soundbridge (VSB) middle ear implant, which has been the most widely used and studied of currently available devices.
The VSB is a partially implantable middle ear implant with both external and implanted components. The external component is held on the scalp over the implant by magnetic attraction and consists of a battery, a signal processor and a microphone [3]. Sound is collected through the microphone and converted to an electrical signal that is sent to the implanted component - the vibrating ossicular prosthesis (VORP). The VORP contains three components: a receiver which picks up the signal, a conductor which links the receiver to the floating mass transducer (FMT), and the floating mass transducer which causes the ossicular chain in the middle ear to vibrate. The FMT was originally designed to be attached to the long process of the incus, but in some patients with abnormal middle ear anatomy, devices have been placed on other ear structures such as the round window membrane [3]. The round window approach is becoming more frequently used because of its effectiveness and ability to be applied to difficult cases [4]. In patients with malformed ossicular chains, coupling to the incus may be difficult or impossible. In contrast, round window placement allows one to bypass the middle ear beyond the site of pathologic findings [5].
Initially, the VSB was recommended for use in adults with moderate to severe sensorineural hearing loss. The indications have recently been expanded to include conductive and mixed hearing loss. The purpose of this review is to determine the safety and effectiveness of the VSB middle ear implant in the treatment of sensorineural, conductive, and mixed hearing loss. In 2010, Tysome et al. [6] published a review of studies that compared middle ear implants to conventional hearing aids, but it was limited to sensorineural hearing loss in adults. To our knowledge, a systematic review of studies that include patient populations with all three types of hearing loss has yet to be published.

Methods

A systematic review of evidence from existing research on the safety and efficacy of the Vibrant Soundbridge MEI (Med El, Austria) was performed following Cochrane guidelines and the QUORUM statement.
Search for relevant studies
To identify studies published as of September 2011, a structured search strategy, which combined relevant controlled vocabulary terms (such as MEDLINE’s Medical Subject Headings) with additional nonindex terms, was developed. Terms included middle ear implants, hearing loss, and Vibrant Soundbridge. The search strategy was applied to the following major biomedical bibliographic databases: MEDLINE, EMBASE, The Cochrane Library, Web of Science, CINAHL, PsycINFO and the Centre for Reviews and Dissemination, without date or language limits. Unpublished and non-peer-reviewed literature was located through internet searches using Google® and scans of web sites of manufacturers and professional associations. For completeness, the electronic search was supplemented by a manual search of the reference lists from included articles.
Selection of relevant studies
Two researchers independently screened the titles and abstracts of citations identified through the literature search using predetermined inclusion criteria (Table 1). Corresponding papers of those deemed potentially relevant were then retrieved for full review by the same two researchers. Any discrepancy between reviewers was resolved through discussion, with no need for third party adjudication. The level of consensus between reviewers was assessed using kappa statistics, giving a Kappa value of 0.90.
Table 1: Criteria for review protocol for the Vibrant Soundbrige middle ear implant.
Data extraction and critical appraisal of selected studies
Information from each study was systematically extracted by one of two reviewers using a standard, pre-tested data abstraction form. The form contained elements for describing the patient population, study design, methods and findings of each study. Additionally, the quality of each study was assessed using the Oxford Centre for Evidence-Based Medicine Levels of Evidence. When required, missing data was sought from the study’s author. For 10% of the studies, data were extracted twice by two different researchers and then compared. Agreement was, once again, assessed using the Kappa statistic (K=1.0).
Data analysis
Information collected from studies was summarized in tabular form to more easily identify trends and patterns in results across studies. To minimize bias caused by duplicate patient populations, careful analysis was performed to identify articles reporting on the same study participants. Records of cases of partial overlap in populations were also kept and noted in the results summary tables.
While a meta-analysis of extracted data was planned, one was not performed because of heterogeneity in patient populations and outcome measures used across studies.

Results

Of seventy-seven hundred discrete citations initially identified through the literature search, 69 potentially relevant articles were selected for full review (Figure 1). Forty-seven papers met the study’s eligibility criteria and were included in the review. Excluded studies along with reasons for exclusion can be found as Supplementary Digital Content in Appendix Table A.
Figure 1: Literature search results and study selection for clinical review.
Overall description of included studies
The VSB was investigated in 44 unique studies, which spanned 832 patients in 10 countries and typically involved single European centers. In the vast majority, aided and unaided conditions were compared, with patients serving as their own controls. While across studies, patients ranged from 3 months to 86 years old, the majority involved adults only. The number of males and females was approximately equal. All had mild to severe sensorineural, mixed, or conductive hearing loss. Some studies selected patients unable to wear or intolerant of conventional hearing aids. However, the majority recruited consecutive patients receiving VSB implantation without strict inclusion/exclusion criteria. Across studies, some heterogeneity in the implantation method was found. The most common alternative to the traditional ossicular chain placement was placement on the round window membrane. Eight studies focussed on round window placement, while several others used a combination of surgical modifications. A complete description of the studies, including patient demographics, surgical modifications, and study design, can be found as Supplementary Digital Content in Appendix Table B.
Overall quality of included studies
Based on the Oxford Center for Evidence-based Medicine levels of evidence, studies were predominantly level IV, with 5 studies being considered a level IIb. One study reported a potential conflict of interest related to receipt of partial funding from the Institute for Implantable Electronic Hearing Systems [7].
Safety
Twenty-two studies described adverse events related to the Vibrant Soundbridge, the most common of which was taste disturbance or damage to the chorda tympani nerve. The latter occurred in 6.3% of cases and was permanent in 19/33 cases. It should be noted that these numbers likely represent an overestimate because they originated from two studies in which there were overlapping patient populations and higher rates [8,9]. Device malfunction or failure occurred in 4.8% of patients and required explantation of 19 devices and 6 revision surgeries. Of the nine patients who experienced device extrusion or migration (1.7%), 8 required revision surgery. Transient pain or headache (5.7%), skin reactions (4.4%), and vertigo or dizziness (2.7%) were the most common minor complications. The sensation of aural fullness was only reported in two studies, but experienced by over 20% of those patients in those studies. Two cases of surgical errors were reported. In one case, the implant was placed upsidedown, and in the other, the receiver was improperly placed. Both cases required revision surgery. A full description of adverse events can be found as supplemental digital content in Appendix Table C.
Efficacy
Clinical efficacy or effectiveness was assessed based on the following outcomes: functional gain, speech reception, speech recognition, and quality of life. Findings, discussed by comparator and outcome measure, are presented below. Individual study results are available in supplemental digital content in Appendix Tables D1- 4.
Compared to hearing aids: Nine studies involving a total of 153 patients compared the Vibrant Soundbridge to hearing aids.
Functional gain: The average functional gain for the VSB was 25.9dB while the average gain for hearing aids was 18.6dB. Six of nine studies (N= 129) found a clinically significantly greater benefit (defined as a 5dB difference in gain [10]) with the VSB, while the remaining three studies (N=24) reported a statistically significantly higher gain with hearing aids. All of the studies reporting higher gain with the VSB used the patient’s own hearing aid as a comparator. In contrast, all studies showing greater benefit with the hearing aid used specific devices (ex. Siemens Signia Hearing Aid).
Speech reception: The average SRT50% with the VSB was 47.7dB, compared to 50.6dB with hearing aids. The VSB demonstrated a statistically significant improvement (p<0.05) over hearing aids in 4/5 studies (N=34), but no statistically significant difference in one study (n=25).
Speech recognition: There was a statistically significant improvement (p<0.05) in percentage of words recognized with the VSB compared to hearing aids in two studies (N=64), a non-significant difference in two studies (N=12), and variable results in one study (n=6). An additional case study [11] reported a trend towards greater word recognition with the VSB over hearing aids but no information on statistical significance of the findings was presented.
Quality of life: The Abbreviated Profile of Hearing Aid benefit was used to compare quality of life using the VSB to hearing aids in three studies. In all studies, a statistically significant benefit with the VSB over hearing aids in some subcategories was found. Luetje et al. [12] (n=51) reported Profile of Hearing Aid Performance and demonstrated statistically significant improvement with the VSB over hearing aids for all subcategories (p<0.001). Additionally, two studies (N=58) reported a higher degree of patient satisfaction with the VSB over hearing aids using the Hearing Device Satisfaction Scale.
Compared to unaided: The VSB was compared to the unaided condition in 39 studies that included a total of 796 patients.
Functional gain: There was clinically significant benefit observed with the VSB device compared to the unaided condition in all studies. The average functional gain for the VSB ranged from 12.9 dB to 47.2 dB across studies, resulting in a pooled average of 27.1 dB. There was a significant difference in functional gain among studies of patients with sensorineural hearing loss compared to those with mixed or conductive hearing loss (pooled averages were 25.9 dB and 34.0 dB, respectively). Significantly higher gains were also seen for the digital version of the device (Vibrant D) compared to analog version (Vibrant P), although the vast majority of studies did not specify the device model used. There was also a trend towards greater gains in the mid-range frequencies (1-3 kHz) compared to the extremes.
Speech reception: The speech reception threshold for recognition of 50% of words in quiet ranged from 58 dB to 94.28 dB in the unaided condition and from 40 dB to 61 dB in the aided condition, representing a wide variation in gain (4 dB to 40.95 dB across studies). The VSB was found to be significantly superior to the unaided condition in the four studies reporting statistical evidence (p<0.05).
Speech recognition: There was significant heterogeneity in the method of assessment for speech recognition across studies, with the most commonly reported outcome comprising recognition of syllables or words presented at 65 dB (10 studies; N=195). Across studies, unaided speech recognition ranged from 0% to 72% and aided ranged from 55% to 95%. There were nine studies comparing unaided to aided word recognition, eight of which demonstrated a statistically significant improvement with the VSB (P<0.05). The exception was Rajan et al. [13], who reported nonsignificance when testing in noise, but a statistically significant benefit with the VSB when testing in quiet.
Quality of life: The Glasgow Benefit Inventory (GBI) was reported in four studies. GBI is a quality of life questionnaire designed to measure outcomes of an otolaryngological procedure based on questions in three domains: general improvement of quality of life, social improvement, and physical improvement. All studies reporting this outcome demonstrated benefit with the VSB in the “general” subcategory. However, in the “physical” category, one study reported improvement, two reported no benefit, and one reported worsening with the VSB. Rajan et al. [13] used the Abbreviated Profile of Hearing Aid Benefit to measure quality of life and reported a statistically significant improvement with the VSB compared to the unaided condition in all categories except for aversiveness (P<0.05).

Discussion

This review aimed to assess the safety and clinical effectiveness of the Vibrant Soundbridge MEI for the management of hearing loss. As mentioned previously, MEI’s offer a potential treatment for patients who are medically unable to wear or have not achieved success with conventional hearing aids (i.e., patients lacking other treatment options). Given the absence of an active treatment comparator, the range of study designs for assessing the effectiveness of MEI’s is limited. Many of the papers included in this review were pre-post studies in which patients served as their own controls. While this design is not considered “level I” evidence, it becomes a legitimate and appropriate one for this context. Further, although several of the studies reviewed compared the VSB to conventional hearing aids, patients eligible for both treatments may not represent those who could achieve the greatest clinical benefit from MEI’s.
Thus, despite heterogeneity in patient populations and outcome measures across studies (which precluded performance of a metaanalysis), trends across studies indicate that the VSB is relatively safe. Regarding effectiveness, in patients medically able to wear hearing aids, the VSB was found to be at least comparable to that of the patient’s own hearing aid in terms of functional gain, speech reception and recognition. However, when compared to specific devices such as the Siemens Signia digital hearing aid, which may be a more appropriate comparator, conventional hearing aids resulted in greater functional gain than the VSB. Nonetheless, the VSB is likely superior to conventional hearing aids in terms of improvement in quality of life. In patients unable to wear hearing aids; the VSB was shown to offer improvements in functional gain, speech perception, speech recognition, and quality of life.
The findings of the review support recommendations from Verhaegen et al. [14], who conducted a comparative analysis of speech recognition in patients with sensorineural hearing loss using the VSB, hearing aids, or cochlear implants. They proposed that up to a threshold level of 95 dB, non-invasive approaches (i.e., conventional hearing aids) be used as first line therapy in patients who are medically able to wear the device. Middle ear implants may be indicated in patients who are medically unable to wear a conventional hearing aid (for reasons such as otitis media).
The available, albeit limited, evidence indicates that the Vibrant Soundbridge MEI provides similar improvement in functional gain to that achieved with a patient’s own hearing aid but may offer less benefit than an optimized “state of the art” hearing aid. However, the VSB appears to offer a greater improvement in quality of life. Thus, it represents an important treatment option, particularly for patients who are medically unable to use a conventional hearing aid.

Acknowledgment

The authors would like to thank those who contributed to this paper: Dr. Allan Ho for his clinical expertise, Dr. Devidas Menon for his comments and leadership and Leigh-Ann Topfer for her invaluable work in the literature search process.

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