Bone Conduction Hearing Research Articles

Characterization and Clinical Use of Bone Conduction Transducers at Extended High Frequencies

Measurement of bone conduction (BC) hearing thresholds at extended high frequencies (EHF; above 8 kHz) is of clinical interest but is technically complicated by limitations in standard BC transducer output, a lack of calibration standards and sparse clinical data from human subjects. A recently described calibration scheme using an artificial mastoid and interposed accelerometer is applied in this study to characterize and compare acceleration and computed force outputs over the 4–20 kHz range of two standard BC transducers: the RadioEar® B71 and B81, as well as two non-standard, commercially available BC transducers: the Tascam® HP-F200 and the Aftershokz® AS400. Measures of linear output growth, harmonic distortion and acoustic radiation are assessed and compared across devices. A maximum linear input voltage is established for each BC transducer using measurements of linear output growth and total harmonic distortion. At maximum linear input level, the Tascam shows superior force output by 25 to 40 dB above 8 kHz and the widest dynamic EHF range. Acoustic radiation per output force was lowest for the Tascam, whereas the AS400 behaved more like an air conduction earphone than a force generator. In a cohort of 15 normal hearing volunteers, BC thresholds, measured with the Tascam and reported in dB re 1 rms μN, were consistent with historical measures of EHF BC thresholds in similar subjects using an alternative BC transducer.

Improved Prediction of Hearing Loss after Temporal Bone Fracture by Applying a Detailed Classification for Otic Capsule-Violating Fracture: A Wide Scope Analysis with Large Case Series.

This study aimed to analyze the predictability of temporal bone (TB) fracture-associated hearing loss by applying a detailed classification separating individual injury of the cochlea, vestibule, and semicircular canals (SCC). In this retrospective study, patients with otic capsule-violating (OCV) fractures were further classified as OCV-C(VS) when the cochlea was involved regardless of vestibule or SCC involvement, OCV-V(S) when the vestibule was involved regardless of SCC involvement, and OCV-S when the fracture only involved SCC. Hearing changes were compared by applying the above-mentioned classification, and TB fracture-induced facial palsy was also analyzed. A total of 119 patients were included. Patients with OCV fractures had significantly worse bone conduction (BC) and air conduction (AC) thresholds (59.1 ± 25.3 and 87.0 ± 29.5 dB) than those with otic capsule-sparing (OCS) fractures (20.1 ± 17.9 and 36.5 ± 21.9 dB; p < 0.001 for each comparison). The BC and the AC thresholds of OCV-C(VS) (77.5 ± 11.0 and 114.2 ± 14.3 dB) and OCV-V(S) (69.3 ± 27.7 and 98.0 ± 22.2 dB) were significantly higher than OCV-S (40.1 ± 22.9 and 62.1 ± 25.6 dB; p < 0.001 for each comparison). The BC hearing thresholds were not significantly improved in the last pure tone audiometry when compared for total, OCV, or OCS cases. The AC threshold significantly improved in OCS cases. In a considerable number of cases with facial palsy, causative fracture lines involved the geniculate ganglion or tympanic segment without the involvement of the otic capsule. Most cases showed significant improvement; however, recovery was limited in cases with obvious fallopian canal disruption. The cases with sole involvement of SCC had significantly better hearing thresholds than those with cochlear or vestibule involvement, even in OCV fracture cases.

Learning curve comparable study of microscopic and endoscopic type 1 tympanoplasty.

The comparative efficacy of microscopic tympanoplasty (MT) and endoscopic tympanoplasty (ET) has been widely studied to some extent through meta-analyses. However, most studies on learning curve comparisons between the two surgeries were performed by experienced ET surgeons. We compared the surgical outcomes of MT and ET and evaluated the difference of learning curve between ET and MT performed by a single unskilled, in both MT and ET, surgeon. A total of 91 patients underwent ET and MT at a tertiary hospital. We reviewed the patients' medical records and analyzed all findings, including otoscopic pictures, pure tone audiometry (PTA) before and after surgery, and operation records. All operations were performed by a single otologist who had an experience of a year of otology fellowship at a tertiary university hospital. We compared the demographic and clinical characteristics, including age, sex, admission duration, and audiological outcomes before and after surgery. We also assessed the difference in the decrease in operation time. Among 91 patients, 44 were in the ET group and 47 were in the MT group. The mean age was 51.15years, and 37 (40.7%) were men. Eighty-two (90.1%) patients were administered local anesthesia. Graft failure was observed in 19 (20.9%) patients, and the mean postoperative follow-up duration was 66.42days. There were no statistically significant differences in age, sex, affected side, graft failure rate, and operation time between the ET and MT groups. There was a significant improvement in air conduction hearing and air-bone gap after surgery in both groups. Bone conduction hearing did not change before and after the surgery in either group. However, the improvement in air condition and reduction in the air-bone gap did not differ between the two groups. Multivariate linear regression analysis showed that there were no significant variables that affected operation time among age, sex, operation method (ET or MT), anesthesia, graft material, and technique. The spline regression analysis showed the decrease in operative time in ET was significantly faster than MT in the period from 8th to 19th cases. The surgical outcomes of ET are comparable to those of MT in terms of operation time, graft uptake, and postoperative hearing results, even in surgeons who are not experienced with both MT and ET. The operation time of ET was longer than that of MT in the early phase, and the decrease in the operating time was significantly faster in ET than in MT. Both MT and ET reached a plateau in the operation time, and this plateau appeared to be similar in both surgeries.

An objective bone conduction verification tool using a piezoelectric thin-film force transducer.

All hearing aid fittings should be validated with appropriate outcome measurements, whereas there is a lack of well-designed objective verification methods for bone conduction (BC) hearing aids, compared to the real-ear measurement for air conduction hearing aids. This study aims to develop a new objective verification method for BC hearing aids by placing a piezoelectric thin-film force transducer between the BC transducer and the stimulation position. The newly proposed method was compared with the ear canal method and the artificial mastoid method through audibility estimation. The audibility estimation adopted the responses from the transducers that correspond to the individual BC hearing thresholds and three different input levels of pink noise. Twenty hearing-impaired (HI) subjects without prior experience with hearing aids were recruited for this study. The measurement and analysis results showed that the force transducer and ear canal methods almost yielded consistent results, while the artificial mastoid method exhibited significant differences from these two methods. The proposed force transducer method showed a lower noise level and was less affected by the sound field signal when compared with other methods. This indicates that it is promising to utilize a piezoelectric thin-film force transducer as an in-situ objective measurement method of BC stimulation.

Modern Advances in Bone Conduction–Hearing Devices

Modern Advances in Bone Conduction–Hearing Devices

Efficient Bone Conduction Hearing Device With a Novel Piezoelectric Transducer Using Skin as an Electrode.

Bone conduction hearing aids are the only non-surgical devices used for conductive hearing loss. However, they are impractical for lifelong use since they require close contact of the transducer with the head skin, causing skin erosion and discomfort. Bone conduction hearing implants and active middle ear implants do not present these issues; however, they require surgery and can sometimes cause issues in the skin surrounding the devices. This study aimed to develop a new bone conduction hearing device that does not exert pressure on the skin or require surgery. Our device modified a piezoelectric element by using the skin of a pinna as one of the two electrodes of a conventional piezoelectric device. We compared the sound transmission of a speaker, a conventional piezoelectric device, or the new device to the Guinea pig cochlea, a physiological sound transducer to the auditory nerve, in normal and air-conductive hearing loss conditions. The novel device transmitted sound to the cochlea even after causing air-conductive hearing loss. Its bone conduction was more efficient than the speaker and the conventional piezoelectric device. We developed a novel type of bone conduction device that efficiently transmits sound to the cochlea by skipping the external auditory canal, tympanic membrane, and middle ear ossicles. This device does not exert pressure on the skin that can result in skin damage, an adverse effect of a conventional bone conduction hearing aid. Our novel hearing device can be used as a substitute for current bone-conduction hearing devices.

A comparative study of audiological outcomes and compliance between the Osia system and other bone conduction hearing implants.

To examine the subjective and objective audiological benefits of the Osia system compared to devices commonly implanted prior to the introduction of this system. Osia recipients with either conductive hearing loss (CHL/MHL) (n = 9) or single-sided deafness (SSD) (n = 8) who underwent surgery from February 2021 to March 2022 were prospectively recruited. The audiological outcomes and usage rate of Osia implantees were compared with those of retrospectively recruited patients implanted with other devices (n = 50). The subjective satisfaction of the Osia implantees was also evaluated through questionnaires. All users of the Osia system were classified as regular users. In the CHL/MHL group, the effective gain of the Osia system (11.1 ± 14.9dB) surpassed that of the Baha and Bonebridge (- 2.7 ± 12.6dB) at 2kHz (p = 0.01, Mann-Whitney U test). Among the devices, the Osia system tended to tolerate the worst bone conduction thresholds, up to the level of 61dB. In the SSD group, the functional gain of Osia at 4kHz (37.5 ± 3.1dB) was higher than that of the Baha and Bonebridge group (26.9 ± 3.0dB) (p = 0.05, Mann-Whitney U test). The Osia system yielded larger audiological gain than the Baha Attract and Bonebridge devices, especially at high frequencies, leading to substantially higher compliance. The Osia system tended to have the strongest tolerance to aggravated bone conduction thresholds among the available transcutaneous bone conduction hearing implants. Therefore, the Osia system could potentially be a good option for CHL/MHL patients with bone conduction thresholds of 50dB HL or more, as well as patients with SSD.

Optimal Choice for Improving the Hearing in Children with Unilateral Microtia and Atresia: Softband or Adhesive Adapter?

Introduction: A nonsurgical bone conduction hearing aid (BCHA) is a well-established treatment for children with congenital unilateral microtia and atresia (UMA). To date, limited studies have evaluated the audiological characteristics of the different wearing modes in the same nonsurgical BCHA. Methods: Eighteen patients with UMA aged 5–24 years were included. Warble tones at frequencies of 0.5, 1, 2, and 4 kHz were presented to determine functional hearing gain (FHG) of hearing thresholds (in dB HL) in the sound field. The speech perception abilities were assessed by the speech discrimination score (SDS, in %) of monosyllables, disyllables, and sentences in quiet and noise using the Chinese Mandarin speech test materials. Hearing outcomes were evaluated with the ADHEAR™ worn on a softband and with an adhesive adapter. A correlational analysis was conducted to analyze the correlations between variables (e.g., age, height, weight, body mass index [BMI], bone conduction pure-tone threshold, and air conduction pure-tone threshold) and the differences in the two wearing modes. Results: The mean FHG (standard deviation, SD) at 0.5–4 kHz was 20.63 (3.94) dB HL with the adhesive adapter and 26.39 (3.15) dB HL with the softband. When aided with the BCHA, significant improvements in SDS were revealed in all Mandarin speech test material lists either in quiet or noise for both wearing modes. Compared with the adapter mode, the softband provided higher aided SDS values. Correctional analyses revealed that higher BMI values were positively associated with larger delta outcomes between the two coupling methods of the softband and adhesive adapter in patients with UMA. Furthermore, a larger delta average FHG of 0.5–4 kHz was consistently associated with larger delta monosyllabic SDS in quiet, disyllabic SDS in quiet, and disyllabic SDS in noise. Discussion: To the best of our knowledge, this is the first study to compare the hearing benefits of coupling methods using novel adhesive adapters and conventional softbands with the same audio processor (ADHEAR™). Under uniform internal settings, softband integration provided more hearing benefits than adhesive adapter integration, and the differences were more obvious in patients with higher BMI values. Besides, a brief measurement of FHG can be utilized to predict individualized speech perception levels.

Improved Bone Conduction Hearing After Middle Ear Surgery: Investigation of the Improvement Mechanism.

When performing middle ear operations, such as ossiculoplasty or stapes surgery, patients and surgeons expect an improvement in air conduction (AC) hearing, but generally not in bone conduction (BC). However, BC improvement has often been observed after surgery, and the present study investigated this phenomenon. We reviewed the preoperative and postoperative surgical outcomes of 583 patients who underwent middle ear surgery. BC improvement was defined as a BC threshold decrease of >15 dB at two or more frequencies. Subjects in group A underwent staged ossiculoplasty after canal wall up mastoidectomy (CWUM), group B underwent staged ossiculoplasty after canal wall down mastoidectomy (CWDM), group C underwent ossiculoplasty only (thus, they had no prior history of CWUM or CWDM), and group D received stapes surgery. We created a hypothetical circuit model to explain this phenomenon. BC improvement was detected in 12.8% of group A, 9.1% of group B, and 8.5% of group C. The improvement was more pronounced in group D (27.0%). A larger gain in AC hearing was weakly correlated with greater BC improvement (Pearson's r=0.395 in group A, P<0.001; r=0.375 in group B, P<0.001; r=0.296 in group C, P<0.001; r=0.422 in group D, P=0.009). Notably, patients with otosclerosis even experienced postoperative BC improvements as large as 10.0 dB, from a mean value of 30.3 dB (standard error [SE], 3.2) preoperatively to 20.3 dB (SE, 3.2) postoperatively, at 1,000 Hz, as well as an improvement of 9.2 dB at 2,000 Hz, from 37.8 dB (SE, 2.6) to 28.6 dB (SE, 3.1). BC improvement may be explained by a hypothetical circuit model applying the third window theory. Surgeons should keep in mind the possibility of BC improvement when making a management plan.

Influence of Bone Conduction Hearing Implantation on Health-Related Quality of Life for Patients with Chronic Otitis Media.

Background: Chronic otitis media is a major public health burden that can result in a disabling hearing loss. Bone conduction hearing implants are an accepted form of hearing rehabilitation in these patients, but evidence supporting their usage typically comes from studies investigating mixed indications. The objective of our study was to examine how these devices impact health-related quality of life and hearing-disability in adult patients suffering from chronic otitis media. Methods: Health Utilities Index-mark III (n = 10) and Speech Spatial and Qualities of Hearing-49 data (n = 6) were extracted for adult patients with chronic otitis media from an international hearing implant registry. Data were compared at baseline and at 12-month post-implantation with a bone conduction hearing implant. Results: Patients demonstrated a clinically relevant mean utility gain of 0.145 following implantation and clinically relevant mean improvement in global speech spatial and qualities of hearing score following implantation. Conclusions: Bone conduction implantation was found to improve hearing and health-related quality of life and reduce hearing disability in a small cohort of patients with chronic otitis media. These data highlight the importance of providing appropriate hearing rehabilitation for individuals with chronic otitis media.

Individual computer-assisted 3D planning for placement of auricular prosthesis anchors in combination with an implantable transcutaneous bone conduction hearing device in patients with aural atresia.

The simultaneous implantation of the Bonebridge (MED-EL, Innsbruck, Austria), asemi-implantable active transcutaneous bone conduction hearing device and anchors for auricular prostheses can be challenging as both implants contain magnets and compete for the narrow space in the designated implantation area. Apreoperative planning tool (virtual surgery) was used with individual 3D computer models of the skull and implants for finding optimal implant positions for both the floating mass transducer (FMT) and the anchors for the auricular prosthesis. The interaction between the magnetic prosthesis anchors and the FMT was measured by means of static magnetic forces. A retrospective data analysis was conducted to evaluate the surgical and audiological outcome. Between 2014 and 2021, a3D planning of a simultaneous implantation of the Bonebridge with auricular prosthesis anchors was conducted on 6 ears of 5 patients (3males, 2females; age range 17-56years). The individual preoperative planning was considered very useful for the optimal placement of bone anchors in combination with the Bonebridge. Audiological data showed aclear benefit for hearing 3months and > 11months after implantation. No adverse interactions between the magnetic prosthesis anchors and the FMT were observed. In two patients, revision surgery was carried out due to skin inflammation or wound healing problems. No long-term complications were observed 3-5 years after surgery. Preoperative 3D planning represents a clear benefit for the simultaneous audiological and esthetic rehabilitation using the Bonebridge and anchors for auricular prostheses.

Hearing Outcomes of a New Cartilage Conduction Device vs Bone Conduction Devices.

To compare audiometric outcomes of a new cartilage conduction hearing device (CCD) with traditional bone conduction hearing devices (BCDs). Clinical trial and crossover study design. Tertiary academic center. Sixteen adults (19 ears) with congenital aural atresia or overclosed ear canals who previously underwent BCD implantation were fitted with a CCD. Audiometric data were collected with use of the BCD and the CCD. The mean pretreatment 4-frequency pure tone average was 81 dB. The mean aided pure tone averages with the BCD and CCD were 27 and 32 dB (P = .002), and the mean functional gains were 54 and 49 dB (P = .002), respectively. The mean consonant-nucleus-consonant scores with the BCD were 90% (best aided) and 80% (aided ear isolated), and those with the CCD were 86% and 76%. Mean AzBio scores were 90% (quiet), 77% (+10 dB SNR [signal to noise ratio]), and 52% (+5 dB SNR) when isolating the BCD ear and 90%, 73%, and 41% when isolating the CCD ear. No difference in speech scores achieved statistical significance except the AzBio isolated to the aided ear in the +5-dB SNR condition, which favored the BCD (P = .01). Pure tone audiometric outcomes with the BCD show a small advantage over the CCD, with the difference driven mainly by high-frequency responses. Speech outcomes were equivalent apart from the +5-db SNR condition, which favored the BCD.

유한요소 모델을 이용한 머리뼈의 영률에 따른 골전도 반응 차이 분석

The bone compression and the inertia from cochlear fluid or middle ear (ME) ossicles, are generally considered to be important components inducing bone-conducted (BC) hearing. To clarify the bone compression effect on the BC hearing caused by variation of Young’s modulus of skull, two different types of three-dimensional finite-element models were used in this study. The FE models were (1) Isolated cochlea model comprising ME and cochlea containing basilar membrane (BM) and (2) Head model comprising the isolated cochlea structure. The model was validated by comparison of cochlear responses such as BM velocities with those of otosclerosis patients’ clinical data. Additionally, results showed that the bone compression effects on a BC hearing is highly depended on the Young’s modulus of a skull. Also, the bone compression effects could be underestimated at low frequencies in temporal bone experiments, whereas the effects could be overestimated at high frequencies in cadaver experiments.

The sensitivity of bone conduction for dental implants.

Dental implants are connected to the alveolar bone by osseointegration. Dental implants could be used as a potential bone conduction (BC) hearing assistive device in the mouth. However, the BC threshold of dental implants has not been reported. The present study aimed to examine the pure tone auditory thresholds of normal human subjects to BC stimulation of the implants. Dental implants showed a significantly lower BC threshold than natural teeth and mastoids. Mandibular dental implants had BC sensitivity similar to that of maxillary dental implants. The BC threshold of anterior dental implants was significantly lower than that of posterior dental implants. Dental implants exhibited excellent BC properties.

Audiometric and Surgical Outcomes of a Novel Bone-Conduction Hearing Aid.

To report the audiometric and surgical outcomes of a series of patients having undergone implantation of a novel transcutaneous bone conduction implant (t-BCI). Retrospective case series. Single academic tertiary referral center. Adults (≥18 yr) implanted between December 1, 2019, and August 1, 2021, with audiometric data available before and after device implantation and a minimum of 4 weeks follow-up. Surgical t-BCI. Change in aided pure tone average (PTA) after implantation. Secondary outcomes include average operative time, and adverse events. Twenty-three patients underwent implantation of the t-BCI via either a conventional or minimally invasive surgical approach. The most common indication for implantation was unilateral conductive hearing loss with a history of chronic otitis media. The mean operative time was 59 minutes. The mean preimplantation unaided air conduction PTA was 65 dB, and mean postimplantation was 27.2 dB. The mean change in PTA was 37.8 dB, which was significant ( p < 0.0001). There were 30.4% of the patients that suffered from adverse events, the most common of which were pain (8.7%) and device-related complications (13%). One major adverse event occurred, involving magnet displacement that impaired device activation and required reoperation for replacement. Forming the largest series of patients implanted with this t-BCI in the published literature, our data demonstrate that implantation of the device is feasible via either a traditional or minimally invasive surgical approach, with good audiometric benefit and a favorable safety profile.

Individual computer-assisted 3D planning for placement of auricular prosthesis anchors in combination with an implantable transcutaneous bone conduction hearing device in patients with aural atresia. German version

The simultaneous implantation of the Bonebridge (MED-EL, Innsbruck, Austria), asemi-implantable active transcutaneous bone conduction hearing device and anchors for auricular prostheses can be challenging as both implants contain magnets and compete for the narrow space in the designated implantation area. Apreoperative planning tool (virtual surgery) was used with individual 3D computer models of the skull and implants for finding optimal implant positions for both the floating mass transducer (FMT) and the anchors for the auricular prosthesis. The interaction between the magnetic prosthesis anchors and the FMT was measured by means of static magnetic forces. A retrospective data analysis was conducted to evaluate the surgical and audiological outcome. Between 2014 and 2021 a3D planning of a simultaneous implantation of the Bonebridge with auricular prosthesis anchors was conducted on 6 ears of 5 patients (3males, 2females; age range 17-56years). The individual preoperative planning was considered very useful for the optimal placement of bone anchors in combination with the Bonebridge. Audiological data showed aclear benefit for hearing 3months and > 11months after implantation. No adverse interactions between the magnetic prosthesis anchors and the FMT were observed. In two patients, revision surgery was carried out due to skin inflammation or wound healing problems. No long-term complications were observed 3-5 years after surgery. Preoperative 3D planning represents a clear benefit for the simultaneous audiological and esthetic rehabilitation using the Bonebridge and anchors for auricular prostheses.

Sound Localization of Listeners With Normal Hearing, Impaired Hearing, Hearing Aids, Bone-Anchored Hearing Instruments, and Cochlear Implants: A Review.

This review article reviews the contemporary studies of localization ability for different populations in different listening environments and provides possible future research directions. The ability to accurately localize a sound source relying on three cues (interaural time difference, interaural level difference, and spectral cues) is important for communication, learning, and safety. Confounding effects including noise and reverberation, which exist in common listening environments, mask or alter localization cues and negatively affect localization performance. Hearing loss, a common public health issue, also affects localization accuracy. Although hearing devices have been developed to provide excellent audibility of speech signals, less attention has been paid to preserving and replicating crucial localization cues. Unique challenges are faced by users of various hearing devices, including hearing aids, bone-anchored hearing instruments, and cochlear implants. Hearing aids have failed to consistently improve localization performance and, in some cases, significantly impair sound localization. Bone-conduction hearing instruments show little to no benefit for sound localization performance in most cases, although some improvement is seen in binaural users. Although cochlear implants provide great hearing benefit to individuals with severe-to-profound sensorineural hearing loss, cochlear implant users have significant difficulty localizing sound, even with two implants. However, technologies in each of these areas are advancing to reduce interference with desired sound signals and preserve localization cues to help users achieve better hearing and sound localization in real-life environments.

The Relationship between Bone Conduction Hearing Threshold Shifts after Surgery for Chronic Otitis Media with Cholesteatoma According to STAM, EAONO/JOS, and SAMEO-ATO Classifications.

Background: This study focuses on the hearing threshold for bone conduction (BC) after middle-ear surgery. Methods: A total of 92 patients (120 ears) were treated for newly diagnosed chronic otitis media with cholesteatoma (2013–2018). BC was examined at frequencies of 0.5, 1, 2, and 4 kHz prior to and 1 year after surgery. STAM classification for cholesteatoma location, EAONO/JOS for stage, and surgery according to SAMEO-ATO classification were applied. The bone conduction threshold was compared for individual frequencies in patients with occurrence/absence of cholesteatoma in different locations. Results: For the occurrence of cholesteatoma in the attic (A), a statistically significant difference was found at 4 kHz (p < 0.001), in the supratubal recess (S1) at 4 kHz (p = 0.003), and for the mastoid (M) at 0.5 kHz (p = 0.024), at 1 kHz (p = 0.032), and at 2 kHz (p = 0.039). Conclusions: Cholesteatoma location can influence the post-operative hearing threshold for bone conduction.

Otitis media with antineutrophil cytoplasmic antibody-associated vasculitis

Objective:To analyze clinical features, diagnosis and treatment of otitis media with antineutrophil cytoplasmic antibody（ANCA） -associated vasculitis（OMAAV）. Methods:This study reported three OMAAV patients and discussed the diagnosis and treatment of OMAAV combined with the recent literature. Results:Two males and one female were included. The age of these three patients ranged from 56 to 72 years. Their characteristics were as follows: ①tympanic membrane with granulation and bloody secretions in two patients; ②progressive bone-conducted hearing loss within a short period of time; ③facial palsy in two patients; ④the laboratory test of ANCA is positive; ⑤conventional treatment of otitis media is ineffective, while glucocorticoid combined with immunosuppressive therapy is effective. Conclusion:OMAAV is a rare disease and prone to misdiagnosis. Early diagnosis and treatment with corticosteroids and immunosuppressants are critical. Invasive tests and surgery during the active phase of OMAAV may aggravate symptoms and should be avoided.

Influence of the Coupling on the Hearing Outcome After Implantation of an Active Middle Ear Implant: Comparison of the Transmission Behavior in Temporal Bone Experiments With Clinical Data.

The active middle ear implant, Vibrant Soundbridge (VSB), can be implanted with a variety of couplers. Hearing outcome after implantation has been investigated in both temporal bone (TB) experiments and patient studies, but the relationship between experimental and clinical data is still weak in the literature. Therefore, experimental data from TB experiments should be compared with patient data in a retrospective study, in which the floating mass transducer is used with couplers of the third generation. Actuator coupling structures included the long (LP coupler) and short (SP coupler) incus process, the stapes head (Clip coupler), and the round window membrane (RW soft coupler). In the TB experiments, the sound transmission after vibroplasty on the above-mentioned actuator coupling structures was determined in 32 specimens by means of laser Doppler vibrometry on the stapes footplate. Data of 69 patients were analyzed. The main target audiometric parameters were the postoperative aided word recognition score (WRS) in the free field at 65 dB SPL (WRS 65 dB in %), the preoperative and postoperative pure-tone average (PTA4, including the frequencies 0.5, 1, 2, and 4 kHz) of the bone conduction hearing threshold (PTA4BC), the aided postoperative air conduction hearing threshold in the free field (PTA4FF) and the direct threshold (Vibrogram) at least 6 months postoperatively. The coupling efficiency of the actuator (Vibrogram-PTA4BC) as well as the effective hearing gain (PTA4FF-PTA4BC) was compared between the couplers. The analysis in the main speech range (0.5-4 kHz) indicated that in the TB experiments, the LP coupler tends to have the best coupling quality at low frequencies (500-1000 Hz). This was up to 15 dB above the worst actuator (RW soft coupler). However, the results missed the significance level ( p > 0.05). In the high frequencies (2000-4000 Hz), the Clip coupler showed the best coupling quality. This was 15 dB above the worst actuator (SP coupler). However, the results missed the significance level ( p > 0.05), too. The postoperative WRS at 65 dB SPL and the postoperative PTA4FF were independent of the actuator coupling structure. The PTA4BC was stable at 6 months postoperatively. For the PTA4 of the coupling efficiency, there were no significant differences between the actuator coupling structures (LP 8.9 dB ± 12.9; SP 9.5 ± 6.5 dB; Clip 5.2 ± 10.5 dB; RW 12.7 ± 11.0 dB). However, the tendential inferiority of the RW soft coupler with regard to transmission in the low-frequency range and the tendential superiority of the Clip coupler in the high-frequency range that have already been displayed experimentally could be confirmed in the clinical results. However, the clinical results missed the significance level, too ( p > 0.05). In vivo, there are no significant differences in the postoperative outcome stratified according to coupling the target structure. The differences known from the experimental setting were repressed by individual biasing factors. However, to ensure sufficient postoperative speech intelligibility, the frequency-specific transmission behavior of the couplers should be taken into account when setting the indication for VSB implantation.