Floating Mass Transducer Research Articles

Outcomes of Active Middle Ear Implants: Speech Perception and Quality of Life.

To evaluate audiological outcomes, quality of life, and complications in patients implanted with Active middle ear implants (AMEI). The secondary objective is to investigate the required duration after implantation to reach satisfactory outcomes. This retrospective study included 31 patients implanted with Active middle ear implants (AMEI) with different methods of floating mass transducer attachment. Patients with incomplete medical records and those who did not respond to postoperative follow-up were excluded. Patients were assessed preoperatively, and at one, three, and six months postoperatively. The assessment included Pure Tone Average (PTA4), speech reception threshold (SRT), and speech discrimination score (SDS). The Speech Spatial and Qualities of Hearing scale (SSQ12) was also used to evaluate levels of satisfaction. There are no significant differences found in PTA and SRT between the 3-, 6-, and 12-month visits. The speech reception threshold (SRT) showed a statistically significant improvement at 3, 6, and 12 months post-operative measures compared to pre-operative. Additionally, the SDS exhibited a significant increase only after 12 months, compared to the 3-month time point. However, satisfaction levels did not significantly differ between the 6-month and 12-month measurements following surgery. The Vibrant Soundbridge improves subjective satisfaction scores and audiological test scores in patients with different types of hearing loss. AMEI has a low risk of medical or surgical complications, the ease of using a hearing implant, and the social benefits of good hearing and communication.

Effectiveness of active middle ear implant placement methods in pathological conditions: basilar membrane vibration simulation.

Active middle ear implants (AMEI) amplify mechanical vibrations in the middle ear and transmit them to the cochlea. The AMEI includes a floating mass transducer (FMT) that can be placed using two different surgical approaches: "oval window (OW) vibroplasty" and "round window (RW) vibroplasty." The OW and RW are windows located on the cochlea. Normally, sound stimulus is transmitted from the middle ear to cochlea via the OW. RW vibroplasty has been suggested as an alternative method due to the difficulty of applying OW vibroplasty in patients with ossicle dysfunction. Several reports compare the advantages of each approach through pre and postoperative hearing tests. However, quantitatively assessing the treatment effect is challenging due to individual differences in pathologies. This study investigates the vibration transmission efficiency of each surgical approach using a finite-element model of the human cochlea. Vibration of the basilar membrane (BM) of the cochlea is simulated by applying the stimulus through the OW or RW. Pathological conditions, such as impaired stapes mobility, are simulated by increasing the stiffness of the stapedial annular ligament. RW closure due to chronic middle ear diseases is a common clinical occurrence and is simulated by increasing the stiffness of the RW membrane in the model. The results show that the vibration amplitude of the BM is larger when the stimulus is applied to the RW compared to the OW, except for cases of RW membrane ossification. The difference in these amplitudes is particularly significant when stapedial mobility is limited. These results suggest that RW vibroplasty would be advantageous, especially in cases of accompanying stapedial mobility impairment. Additionally, it is suggested that transitioning to OW vibroplasty could still ensure a sufficient level of vibratory transmission efficiency when placing the FMT on the RW membrane is difficult due to anatomical problems in the tympanic cavity or confirmed severe pathological conditions around the RW.

A novel coupling qualityindex to estimate the coupling efficiency in Vibrant Soundbridge.

The objective-based methods for intraoperative monitoring have been suggested to assess the coupling and the outcomes of Vibrant Soundbridge (VSB). Although several techniques were proposed, they have not been widely adopted due to their complexity and invasiveness. This study aimed to investigate the accuracy of a new coupling quality index using an intraoperative ABRthreshold via AcoustiAP and its correlation with the perioperative measures. This is a prospective study conducted at a tertiary center. The medical records were retrieved for all patients who underwent VSB implantation and had an intraoperative objective assessment for the coupling efficiency. AcoustiAP was used to evaluate the intraoperative ABR thresholds, which were assessed directly after the floating mass transducer (FMT) placement using acoustic CE-Chirp signals. The Vibrogram was used for the postoperative audiological evaluation. A new coupling quality index was calculated based on the intraoperative ABR thresholds. Ten patients were eligible for the present study. The ABR thresholds for good coupling ranged from 35 to 60 dBnHL. The loose coupling thresholds ranged considerably from 40 to 100 dBnHL. Overall, the median intraoperative ABR threshold at good coupling was 42.5 (40-60) dBnHL and 60 (40-100) dBnHL at loose coupling. The analysis showed that there was a significant change in the coupling quality index at the good and loose coupling points (24.3 ± 14 vs 38.8 ± 18.2, respectively, p < 0.001). At a cut-off value of 22.6dB, the coupling quality index had a sensitivity of 70% and specificity of 90% for discriminating good and loose coupling. This study provides evidence for the utility of intraoperative ABR measurements in predicting the coupling efficiency in patients with VSB. Our results showed that the coupling quality index had an acceptable accuracy in discriminating betweengood and poor coupling, which can help clinicians optimize the fitting process for individuals and may ultimately lead to improved patient outcomes.

Comparison of auditory brainstem response and electrocochleography to assess the coupling efficiency of active middle ear implants.

This study aimed to compare the effectiveness of auditory brainstem response (ABR) and extracochlear electrocochleography (ECochG) in objectively evaluating the coupling efficiency of floating mass transducer (FMT) placement during active middle ear implant (AMEI) surgery. We enrolled 15 patients (mean age 58.5 ± 19.4 years) with mixed hearing loss who underwent AMEI implantation (seven ossicular chain and eight round window couplings). Before the surgical procedure, an audiogram was performed. We utilized a clinical measurement system to stimulate and record intraoperative ABR and ECochG recordings. The coupling efficiency of the VSB was evaluated through ECochG and ABR threshold measurements. Postoperatively, we conducted an audiogram and a vibrogram. In all 15 patients, ABR threshold testing successfully determined intraoperative coupling efficiency, while ECochG was successful in only eight patients. In our cohort, ABR measurements were more practical, consistent, and robust than ECochG measurements. Coupling efficiency, calculated as the difference between vibrogram thresholds and postoperative bone conduction thresholds, was found to be more accurately predicted by ABR measurements (p = 0.016, R2 = 0.37) than ECochG measurements (p = 0.761, R2 = 0.02). We also found a non-significant trend toward better results with ossicular chain coupling compared to round window coupling. Our findings suggest that ABR measurements are more practical, robust, and consistent than ECochG measurements for determining coupling efficiency during FMT placement surgery. The use of ABR measurements can help to identify the optimal FMT placement, especially with round window coupling. Finally, we offer normative data for both techniques, which can aid other clinical centers in using intraoperative monitoring for AMEI placement.

The influence of intraoperative auditory brainstem responses on vibroplasty coupling-quality and analysis of the impact of different fixation steps on the coupling.

The Vibrant Soundbridge (VSB) is an established active-middle-ear-implant for patients with moderate-to-profound hearing-loss. This surgery is referred to as "Vibroplasty". Sufficient transfer of the VSB's floating-mass-transducers (FMT) energy to the inner ear is a crucial factor influencing the coupling-quality (CQ). However, assessing CQ is hamper by two issues: the method of CQ-assessment itself and the method of FMT-fixation during Vibroplasty. This prospective study explored the influence of intraoperative auditory-brainstem-response (+ ABR) measurements and various fixation methods on postoperative CQ after Vibroplasty as compared to matched-patients after Vibroplasty without intraoperative ABR (-ABR). Propensity-score-matching was performed based on preoperative bone-conduction-pure-tone-average-3 (BC-PTA3) at 1-, 2- and 4kHz. Primary outcome parameters were postoperative CQ-PTA3, intraoperative ABR threshold for various fixation methods and postoperative BC-PTA3. A total of 28 patients were included, of which 14 were + ABR. Preoperative BC-PTA3, sex, age, and number of previous surgeries did not differ significantly between groups (all p > 0.301). Mean postoperative CQ-PTA3 was significantly better for + ABR (1.8 vs. 12.3dB-HL; p = 0.006). Mean intraoperative ABR threshold was superior for cartilage-counter-bearing and cartilage-housing compared to additional fixation with injectable-platelet-rich- fibrin (53 vs. 56 & 57dB-HL, respectively; p = 0.04; η2 = 0.33). Mean postoperative BC-PTA3 did not significantly differ between patients (41.4 vs. 41.8dB-HL; p = 0.77). A total of 7% of the patients required intraoperative readjustment of the FMT based on unsatisfactory intraoperative ABR threshold. Intraoperative ABR measurement resulted in significantly better postoperative CQ. Cartilage-counter-bearing and cartilage-housing were observed to have superior CQ. A total of 7% of the patients could be spared revision-Vibroplasty due to intraoperative ABR measurement.

Effect of magnet position in an electromagnetic transducer for the middle ear implant

The paper is devoted to modelling and numerical analysis of the middle ear with an implantable middle ear hearing device. The main focus is put on electromechanical coupling between the biomechanical subsystem of the middle ear and the electrical subsystem of the implant. The electromechanical coupling describes the interaction between the electrical and mechanical systems, and it is defined as a nonlinear dependence between magnet position and coil transducer centre. This is a novel approach, one that generates new resonances, instabilities, subharmonic as well as chaotic stapes vibrations depending on the voltage excitation. Numerical results of the stapes motion stimulated by a floating mass transducer are compared with the results of experiments performed on the human temporal bones. Findings of this study can be used in practice to develop a better design of a floating mass transducer.

Stapes vibrations induced by piezoelectric floating mass transducer

The paper presents a problem of nonlinear vibrations in the human middle ear stimulated by a piezoelectric floating mass transducer. The transducer is connected to the malleus by means of a coupler that is nonlinear. This nonlinearity together with the transducer has a key meaning for the middle ear behaviour because the improved model of piezoelectric transducer is used compared to previous papers. Nonlinear coupler stiffness and the applied voltage to the transducer produce a change of middle ear natural frequency. Moreover, a bistability effect of periodic solution and irregular vibrations are observed as well. The chaotic motion can exist in the hearing range that is especially harmful for patients who use implants with piezoelectric floating mass transducer.

Long-term outcomes of retrospective case series of middle ear implantation with Vibrant Soundbridge in children with congenital aural atresia.

to assess audiological performance in quiet and noise, quality of life and side effects of Vibrant Soundbridge (VSB) in children with congenital aural atresia (CAA). A retrospective study including consecutive patients with unilateral or bilateral CAA implanted with VSB from 2009 to 2020 in a tertiary referral centre. 18 patients with CAA and a present stapes were included (3 simultaneous bilateral VSB implants) and 21 ears: 17 VSB were attached to the short incus process, and four to the stapes. Age at implantation ranged from 4.7 to 15.8years. Average follow-up was 6.5years (± 3.7years). In unilateral VSB, air conduction pure tone average (ACPTA) thresholds increased from 75.3 ± 15.2 to 32.6 ± 8.3dB post-operatively (VSB activated) (n = 15; p < 0.01). The speech reception threshold (SRT) and the word recognition score (WRS) were significantly improved from 81.5 ± 10.4 to 43.9 ± 7.6dB and 0% to 84.8 ± 8.5% postoperatively (n = 15; p < 0.01). The signal to noise ratio (SNR) was significantly improved from 2.1 ± 2.9dB VSB inactivated to 0.3 ± 2.7dB VSB activated (n = 15; p < 0.01). There was no significant difference in performance according to floating mass transducer (FMT) placement. 5/15 children were non-users at last follow-up in unilateral VSB and 0/3 in bilateral. CAA ears with VSB activated had a significant improvement of ACPTA, WRS, SRT and SNR. A third of patients with unilateral CAA became non-users at last follow-up. The main challenge is to target the indications for the implantation of the VSB to avoid its discontinuation.

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.

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.

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.

Clinical feasibility of a novel test setup for objective measurements using the VIBRANT SOUNDBRIDGE.

ObjectivesThe VIBRANT SOUNDBRIDGE is a widely used active middle ear implant to treat hearing loss. The floating mass transducer is surgically coupled to the ossicles, the round or oval window. A reliable method to monitor the coupling efficiency intraoperatively is highly desired. Research groups have developed several methods, but limitations remain. This study aims to evaluate the clinical feasibility of a new research setup for auditory brainstem response measurement to evaluate the coupling efficiency.MethodIn 14 subjects, the new tool was used to record VSB‐evoked ABR thresholds during surgery. The intra‐op ABR thresholds were compared to pre‐op bone conduction (BC) thresholds and post‐op vibrogram thresholds to evaluate the feasibility of the method as a tool to monitor coupling efficiency.ResultsThe mean pre‐op BC threshold average at 1, 2, and 4 kHz (PTA3) was 47 dB HL, the mean intra‐op ABR threshold was 54 dB nHL, and the mean post‐op vibrogram PTA3 was 60 dB HLeq. ABR was measurable in all subjects using the new tool. Correlation between pre‐op BC thresholds and intra‐op ABR thresholds was statistically significant; however, one outlier was present.ConclusionIntra‐op hearing threshold detection through ABR and direct stimulation of the VSB implant was reliable using this new tool. Despite some individual variability, first results correlate well with pre‐op BC and post‐op vibrogram thresholds.

The Hannover Coupler V2: Audiological outcomes of a round window coupler for the Vibrant Soundbridge.

IntroductionThe Hannover Coupler version 2 (HC2) was designed to (1) adapt the coupler geometry to the round window (RW) niche (2) to stabilize the floating mass transducer, and (3) to control static coupling forces to the RW. First audiological outcomes with a custom‐made HC2 are reported here.Material and MethodsTen patients were enrolled in our site‐initiated, prospective study. To assess audiological outcomes up to 6 months, preoperative and postoperative hearing thresholds, word recognition score (WRS) at 65 dB SPL and the speech recognition threshold in quiet and noise were performed. The effective gain (EG) and the coupling efficiency were calculated.ResultsOne revision surgery had to be performed during the study period and a significant, but clinically not relevant bone conduction thresholds change was observed at 4 and 6 kHz at 6‐month follow‐up. At 6 months, the median WRS (n = 10) improved significantly from 0% to 80%. The median speech reception threshold in noise improved significantly from 11.6 to −2.4 dB SNR, and in quiet significantly from 79.6 to 44.4 dB SPL. The average EG of −1.3 dB indicated a closure of the air bone gap. The determined average coupling efficiency of 23.3 dB was within the acceptance range suggested by the manufacturer.ConclusionFor patients with mixed hearing loss and multiple ear surgeries, the HC2 provided good and stable speech recognition results exceeding published results of RW coupling without a coupler or coupling with the RW soft coupler.

Round window stimulation with an interface coupler demonstrates proof of concept

HypothesisTo mechanically stimulate the round window (RW) membrane, an actuator with an interface coupler (IC) has the potential to improve sound transmission to the cochlea as compared to the most used RW stimulation device implanted today. If a proof-of-concept IC prototype shows promise as compared the most common method for RW stimulation, there is potential that future design development of an IC will be worthwhile. BackgroundA variety of hearing pathologies resulting in mixed and conductive hearing loss can be addressed by mechanically stimulating the RW to transmit sound to the cochlea. The most common method for RW stimulation is with the floating mass transducer (FMT, Med-El). However, the FMT suffers poor sound transmission and unreliable device positioning. The dynamic range and bandwidth of the FMT as a RW stimulator is limited because the entire FMT needs freedom to vibrate. Thus the FMT has difficulty overcoming its own inertia and it cannot be stabilized in a manner that may limit its motion. Here we test an idea of using a generic actuator that vibrates on one side while stationary and held stable on the other (unlike the FMT), and coupling the actuator vibration to the RW membrane with a proof-of-concept IC designed to safely transmit sound to the cochlea. We determine if this proof-of-concept IC can perform as well or better than the FMT in one specimen. If so, further developments of the IC would be worthwhile. MethodsRW sound transmission comparison was made between an ideally implanted FMT and a proof-of-concept IC prototype driven by a piezoelectric stack actuator with vibrating tip in a fresh human temporal bone. Velocities of stapes, FMT, and IC actuator were measured with laser Doppler vibrometry to determine bandwidth, linearity, and dynamic range of cochlear sound transmission. ResultsStimulation with proof-of-concept prototype of the IC provided increased sound transmission, more linear output for larger dynamic range, and wider frequency range as compared to the FMT. This experiment demonstrates the potential of the IC concept to improve performance, and that it merits further development. However, it was challenging to stabilize the coupling between an external actuator and the proof-of-concept IC prototype. Thus, although we were successful in showing that this IC concept has promise, major design improvements and developments are required in the future. ConclusionsWe demonstrated that the proof-of-concept IC prototype driven with a tip connected to a piezoelectric stack actuator can stimulate the RW membrane with improved acoustic performance as compared to the FMT in one specimen. This study demonstrated proof of concept: that the idea of an IC for sound transmission to the cochlea through the RW has potential, and that it would be worthwhile to pursue the IC idea with further developments. This idea has the potential to provide robust sound transmission to the cochlea via the RW while preventing possible trauma to the cochlea. We also learned that critical design improvements are necessary because coupling the generic external actuator to the IC was challenging. A possible future IC design is to integrate a piezoelectric actuator permanently to the IC, allowing only the soft balloon membrane of the IC to vibrate the RW while the rest of the exterior housing of the combined IC (with actuator) would not vibrate and would be stabilized in a fixed manner.

Speech performance and subjective satisfaction of middle ear implant in congenital aural atresia.

SUMMARYObjectivesTo evaluate the safety, speech performance in noise and subjective satisfaction of patients with congenital aural atresia (CAA) implanted with the active middle ear implant.MethodsThis retrospective study included 13 patients (15 ears) implanted with middle ear implants with different methods of floating mass transducer attachment. In 6 ears, the floating mass transducer (FMT) was coupled with the short process of incus; in 8 ears, a clip coupler was used; and in one ear, a round window coupler was used. Patients were assessed preoperatively, and at one, three, and six months postoperatively. The assessment included Pure Tone Average (PTA4), Speech Reception Threshold (SRT) and Speech Discrimination Score (SDS). The Speech Spatial and Qualities of Hearing scale (SSQ12) was also used to evaluate levels of satisfaction.ResultsThe mean aided PTA4 using Vibrant Sound Bridge (VSB) was 26.44 4.03 dB HL compared to 61.88 ±1.53 dB HL unaided. The SDS improved significantly (p = 0.002) from 51% (± 9.17%) to 94.60% (± 4.43%). Furthermore, there was a significant improvement in SDS in noise (p = 0.008) and SSQ12 responses (p < 0.0001).ConclusionsPatients with hearing loss due to CAA can substantially benefit from VSB, with highly satisfactory subjective results and a negligible rate of complications.

Effects of design and coupling parameters on the performance of electromagnetic transducers in round-window stimulation.

Many studies have investigated factors contributing to large variations in the outcomes of round-window (RW) stimulation but most have focused on the floating mass transducer (FMT). To determine whether results for the FMT hold for a fixed-type transducer (FTT), this study constructs two coupled finite element models of the transducer and the human ear that incorporate the cochlear third windows and inner structures of these two electromagnetic transducers. We use these FE models of the human ear and transducers to investigate the influence of four design parameters and coupling conditions for the transducers, i.e., the support's Young's modulus, the coupling layer's cross sectional area and Young's modulus, and the transducer's cross sectional area. The results show that an increase in the support's Young's modulus reduces the output of the FMT but increases that of the FTT. Reducing the cross sectional area and Young's modulus of the coupling layer significantly increases the low-frequency response of the FMT but slightly reduces that of the FTT. Reducing the cross sectional area of the transducer increases the output of the FMT but reduces that of the FTT. This shows that inner structures of electromagnetic transducers should be considered in the optimal design parameters and coupling conditions for RW stimulation.

Analysis of design parameters of round-window stimulating type electromagnetic transducer by a nonlinear lumped parameter model of implanted human ear.

Round-window stimulating transducer is a new solution to treat mixed hearing loss. To uncover the factors affecting the round-window stimulation's performance, we investigated the influence of four main design parameters of round-window stimulating type electromagnetic transducer. Firstly, we constructed a human ear nonlinear lumped parameter model and confirmed its validity by comparing the stapes responses predicted by the model with the experimental data. Following this, an electromagnetic transducer's mechanical model, which simulates the floating mass transducer, was built and coupled to the human ear model; thereby, we established a nonlinear lumped parameter model of implanted human ear under round-window stimulation and verified its reliability. Finally, based on this model, the influences of the four main design parameters, i.e., the excitation voltage, the electromechanical coupling coefficient, the support stiffness, and the preload force, were analyzed. The results show that the change of excitation voltage does not alter the system's natural frequency. Chaotic motion occurs when the electromechanical coupling coefficient is small. Meanwhile, the stapes displacement appears to increase firstly and then decrease with the increase of the electromechanical coupling coefficient. The increase of the support stiffness enlarges the resonance frequency of the stapes displacement and reduces the stapes displacement near the resonance frequency, deteriorating the transducer's hearing compensation at low frequency. The preload force can improve the transducer's hearing compensation performance in mid-high frequency region.

Comparative study of efficiency and characteristics of FMT and DRT installed in human cadavers for round-window stimulation

Acoustic hearing aids generate amplified sound in the ear canal, and they are the standard of care for patients with mild to moderate sensorineural hearing loss. However, because of their limited frequency bandwidth, gain, and feedback, there is substantial room for improvement. Active middle ear implants, which directly vibrate the middle ear and cochlea, are an alternative approach to conventional acoustic hearing aids. They provide an opportunity to improve sound quality and speech understanding with amplification rehabilitation. For floating-mass type and direct-rod type (DRT) middle ear transducers, a differential floating-mass transducer (DFMT) and a tri-coil bellows transducer (TCBT), respectively, were fabricated to measure the output characteristics in four human temporal bones. Both were fabricated to have similar output forces per unit input and were placed in four human temporal bones to measure their output performances. The TCBT resulted in higher output than did the DFMT throughout the audible frequency range, and the output was more prominent at lower frequency ranges. In this study, we showed that DRT was a more effective method for round window stimulation. Because of its frequency characteristics and vibration efficiency, this implantation method can be utilized as a driving solution for middle ear implants.

Combination of Direct Oval Window Vibroplasty With Customized Partial Ossicular Replacement Prosthesis (PORP): A Novel Reconstruction Technique to Rehabilitate Mixed Hearing Loss.

Hearing rehabilitation with an active middle ear implant (AMEI) in patients with mixed hearing loss (MHL) after multiple ear surgeries is surgically challenging and requires individual solutions in some cases. Our objective was to introduce a feasible novel technique for direct oval window vibroplasty (OW vibroplasty) using a partial ossicular replacement prosthesis (PORP) to ensure stability and enable active and passive sound transmission. Four patients with MHL following multiple middle ear surgeries and indication for an AMEI received direct OW vibroplasty in combination with a customized PORP between the enwrapped actuator and reconstructed tympanic membrane (TM). Postoperative bone conduction was stable in all patients. All patients benefitted from the AMEI in combination with PORP with a mean functional gain of 31.5 ± 17.0 dB. Mean aided postoperative pure tone average was 27.3 ± 2.6 dB. Speech discrimination in quiet at 65 dB with the German Language Freiburg Monosyllabic Test improved for all patients to 68.8 ± 6.3% and in noise with the German Language Oldenburger Sentence Test to -10.4 ± 3.3 dB SNR. No complications were observed. This novel technique of direct OW vibroplasty extends the portfolio of reconstructive middle ear procedures by combining an intraoperatively customized "off-the-shelf" PORP as a coupler between floating mass transducer (FMT) and a cartilage TM. We found satisfying functional hearing results. Benefits of the reported technique comprise 1) stabilization and optimized coupling of the reconstruction, 2) possibility of passive sound transmission, 3) general feasibility due to great availability of a regular PORP, and 4) flexibility in bridging of large gaps between TM and actuator.

Long-Term Safety and Quality of Life after Vibroplasty in Sensorineural Hearing Loss: Short/Long Incus Process Coupler

Objective: The study shows the long-term effectiveness, safety, and quality of life after Vibrant Soundbridge (VSB) implantation in sensorineural hearing loss (SNHL) using the short process coupler (SP) or the long process coupler (LP). Methods: This retrospective study evaluated 77 VSB cases. Follow-up (F/U) time-dependent objective measurements (audiological outcomes), subjective data collection (quality-of-life questionnaire), and safety measures are presented. Results: Sixty-two ears were included in the analysis with up to 116 months of postsurgical F/U data (mean 32.15 ± 37.97 months LP and SP coupler). Fifty-three ears (13 bilateral cases) received the LP coupler and 9 subjects the SP coupler. The post-operative bone conduction thresholds remained stable and, in both groups, <10 dB. The benefit in word recognition scores measured at 65 dB SPL and 80 dB SPL showed no significant difference between the couplers (p = 0.559 and p = 0.088, respectively). The functional gain was not significantly different (p > 0.05) with a mean of 20.91 ± 9.77 and 17.19 ± 5.75 for LP and SP coupler, respectively. The utility score deciphered from the Assessment of Quality-of-life Questionnaire-8 dimensions revealed a mean score of 0.75 ± 0.16 which is not significantly different to the age- and sex-matched healthy control group with 0.81 ± 0.02 (p = 0.3547). Conclusion: The Incus Vibroplasty utilizing both couplers is a safe and effective method to treat mild-to-severe SNHL. Both fixation methods of the floating mass transducer exhibit good clinical and audiological outcomes with high patient quality of life. The SP coupling method can be a good alternative when the long process is anatomically inaccessible, or the approach is limited due to anatomical reasons.