Floating Mass Transducer Research Articles

Does Coupling and Positioning in Vibroplasty Matter? A Prospective Cohort Study.

Vibroplasty has offered a new modality of hearing rehabilitation in patients with mixed, conductive, and sensorineural hearing loss who cannot wear hearing aids. Potentially, the positioning of the floating mass transducer (FMT) in vibroplasty surgery has a critical effect on hearing outputs. In this study, the impact on hearing outputs and coupling efficiency are evaluated by comparing various vibroplasty applications in the middle ear. No other study to date has examined the coupling efficiency of round window (RW) versus an ossicular vibroplasty application. Prospective cohort study of patients with underlying ear pathologies who were not able to wear hearing aids. This is an ongoing prospective study of 16 patients. All patients had a standard audiological test battery. Direct drive transfer function analysis results were correlated with bone conduction thresholds to assess the efficiency of the FMT coupling. Speech perception in quiet and quality of life measure questionnaires were used to assess outcomes. Nine patients had round window vibroplasty, six patients had stapes vibroplasty, and one patient had traditional incus vibroplasty. Patients with a soft tissue coupler between the FMT and the RW had significantly reduced coupling efficiency. Patients who had direct RW contact had significantly improved coupling efficiency. Patients who underwent stapes or incus vibroplasty had the greatest coupling efficiency. This study demonstrates that attachment to the stapes or incus provides the best coupling when compared to round window vibroplasty. When applicable, stapes or incus coupling should be the first choice when implementing vibroplasty.

Cone beam computed tomography after round window vibroplasty: do the radiological findings match the auditory outcome?

Conclusion: The cone beam computed tomography (CBCT) imaging technique has proved to be reliable for assessing the appropriate positioning of the floating mass transducer (FMT) in the round window (RW) niche, although some parameters do not seem to be essential for achieving a satisfactory functional outcome. Objectives: To evaluate the role that specific imaging parameters derived from CBCT of the temporal bone have for predicting the functional outcome after RW vibroplasty (RW-VP). Methods: CBCT imaging was carried out in a homogeneous group of patients who presented with a mixed type of hearing loss after open tympanoplasty. Three arbitrary radiological parameters were taken into account: the FMT/RW membrane contact, bony contacts of the FMT margins, and the inferior FMT tissue support. The audiological assessment took into consideration the PTA4 (500–4000 Hz), the PTA2 (125–250 Hz), and the word recognition score (WRS) in quiet and in noise. Results: One subject presented with all positive CBCT parameters and showed a good, but not the best auditory performance among the study group. In the majority of the subjects, with a satisfactory postoperative hearing improvement, at least two of the three radiological parameters were present. In comparison with the unaided condition, an improvement in both the PTA4 and PTA2 was found in all the subjects.

Impact of coupling techniques of an active middle ear device to the round window membrane for the backward stimulation of the cochlea.

Interposed cartilage and the round window coupler (RWC) increase the efficiency of cochlea stimulation with the floating mass transducer (FMT) of a single active middle ear implant (AMEI) placed against the round window membrane. Treatment of mixed and conductive hearing loss with an AMEI attached to the round window is effective, yet the best placement technique of its FMT for the most efficient stimulation of the cochlea remains to be determined. Experimental study on human temporal bones with the FMT placed against firstly the unaltered round window niche and then subsequently against the fully exposed round window membrane with and without interposed cartilage and the RWC. Cochlea stimulation is measured by the volume velocities of the stapes footplate using LASER vibrometry. At the undrilled round window niche, placement of the FMT by itself and with the RWC resulted in similar volume velocities. The response was significantly raised by interposing cartilage into the undrilled round window niche. Complete exposure of the round window membrane allowed for significantly increased volume velocities. Among these, coupling of the FMT with interposed cartilage yielded responses of similar magnitude compared with the RWC but significantly higher compared with the FMT by itself. Good contact to the round window membrane is essential for efficient stimulation of the cochlea. Therefore, interposing cartilage into the undrilled round window niche is a viable option. At the drilled round window membrane, the FMT with interposed cartilage and attached to the RWC are similarly effective.

Vibro-EAS: a proposal for electroacoustic stimulation.

In situ evaluation of the vibration performance of a hybrid system for intracochlear fluid stimulation, constructed from a floating mass transducer (FMT) coupled to an electric acoustic stimulation (EAS) cochlea implant (CI) electrode. EAS uses both CI technology to restore severe-to-profound hearing loss at high frequencies and acoustic amplification for mild-to-moderate hearing loss in the low-to-mid frequency range. More patients with residual hearing are becoming candidates for EAS surgery because of the improved techniques for hearing preservation. Most patients with partial deafness fulfill the audiological criteria at low and mid-frequencies for the active middle-ear implant with FMT (VSB). The FMT of the VSB is a potential device for acoustical stimulation in EAS. In seven fresh human temporal bones, stapes amplitude responses for fixation of a FMT to the long incus process (standard coupling) was compared with those for FMT fixation to a 20-mm inserted standard cochlea electrode array (31.5 mm) via the round window (Vibro-EAS). Vibration of the stapes footplate was measured by laser Doppler vibrometry. For 0.316 Vrms drive voltage, stimulation of the intracochlear fluid using a FMT-driven CI electrode (Vibro-EAS) yielded stapes amplitude responses comparable to those for acoustic stimulation with 84 dB SPL. These amplitude responses are 30 to 42 dB lower at frequencies up to 4 kHz than those for VSB standard coupling. Intracochlear combined electrical and mechanical stimulation may be a viable technique for electroacoustic stimulation. A reliable technique for attachment or integration of the FMT to the cochlea electrode array has yet to be developed.

Reinforced active middle ear implant fixation in incus vibroplasty.

The active middle ear implant Vibrant Soundbridge® was originally designed to treat mild-to-severe sensorineural hearing losses. The floating mass transducer (FMT) is crimped onto the long incus process. The procedure is termed incus vibroplasty to distinguish from other attachment sites or stimulus modi for treating conductive and mixed hearing losses. Rare but possible complications are difficult incus anatomy, necrosis of the long incus process, secondary detachment, and loosening of the FMT with concomitant amplification loss. The aim of this study was to functionally evaluate reinforcement of the standard attachment of the FMT to the long incus process. The head of a Soft CliP® stapes prosthesis was used for reinforcement. Functional evaluation was performed in temporal-bone preparations and in clinical practice. A subtotal mastoidectomy and a posterior tympanotomy were performed in ten fresh human temporal bones. As a control for normal middle-ear function, the tympanic membrane was stimulated acoustically and the vibration of the stapes footplate and the round-window (RW) membrane, respectively, were measured by laser Doppler vibrometer (LDV). FMT-induced vibration responses of the stapes and RW were then measured for standard attachment and attachment reinforced with the head of a Soft CliP® stapes prosthesis. Additionally, the outcome in two groups of patients with incus vibroplasty using standard and the reinforced FMT attachment were compared. Eleven patients were treated by standard coupling; nine patients obtained reinforcement with the head of the Soft CliP® stapes prosthesis. Three to six months postoperatively, auditory thresholds for frequency-modulated (warble) tones and vibroplasty thresholds for pure tones were measured. In temporal bone, laser Doppler vibrometer measurements showed significantly enhanced vibration amplitudes of the stapes footplate and the RW membrane for the reinforced attachment compared with those for the standard attachment (on average, 5-10 dB at frequencies below 1 kHz and above 4 kHz). Interindividual amplitude variations were also smaller for reinforced attachment (on average, the standard deviation was 4-7 dB smaller). The clinical data showed lower vibroplasty thresholds for reinforced attachment compared with standard attachment, which amounted to, on average, 16 dB at 500 Hz and 12 dB at 4 kHz. Auxiliary fixation of the FMT by reinforcing the attachment to the long incus process, in these experiments with the head of a Soft CliP stapes prosthesis, leads to enhanced mechanical and functional coupling, evidenced by lower vibroplasty thresholds and increased bandwidth together with reduced variability of the vibrational frequency responses of the stapes footplate and RW membrane.

人工聴覚機器の現状

Remarkable advances have been made in the field of cochlear implantation, especially the new trends of hearing and structure preservation. Electric acoustic stimulation (EAS) is becoming a standard procedure worldwide and has improved the quality of life of patients with a ski-slope type audiogram, while Vibrant Soundbridge (VSB) and Bone Conductive Implant are also becoming available as hearing implants for the hearing-impaired population. We present the current information about hearing implants in Japan. Advances in the development of new atraumatic concepts of electrode design as well as in surgical techniques have enabled structure preservation after cochlear implantation, and EAS is a new trend for patients with residual hearing at lower frequencies, that became eligible for coverage by the national health insurance in Japan in 2014. The VSB is an active middle ear implant that was developed for the treatment of sensorineural hearing loss. Stimulation of the cochlea by coupling the small electromagnetic element called the floating mass transducer (FMT) to the round window membrane was a promising second alternative for the treatment of conductive or mixed hearing loss. A multicenter clinical study for VSB with a round window approach was conducted in Japan in 2014. Bone conductive implants allow direct transmission to the bone of the skull, and Baha is a semi-implantable percutaneous BC hearing device. A multicenter clinical study with 9 participant institutions was conducted in Japan between 2006 and 2009 to compare the efficacy of Baha with that of conventional hearing aids. Baha became eligible for coverage by the national health insurance in 2013. Several types of bone conductive implants have been developed and may be used in Japan in the near future.

VIBRANT SOUNDBRIDGE<sup>®</sup> 国内臨床治験の有効性と安全性の評価

Middle ear implants (MEIs) such as the Vibrant Soundbridge (VSB) are attractive and alternative treatments for patients with conductive, sensorineural, and mixed hearing loss who do not benefit from, or who choose not to wear, conventional hearing aids (HAs). Recent studies suggest that MEIs can provide better improvements in functional gain, speech perception, and quality of life than HAs, although there are certain risks associated with the surgery which should be taken into consideration, including facial nerve or chorda tympanic nerve damage, dysfunctions of the middle and inner ears, and future device failure/explantation. In Japan, a multi-center clinical trial of VSB was conducted between 2011-2014. A round window vibroplasty via the transmastoid approach was adopted in the protocol. The bony lip overhanging the round window membrane (RWM) was extensively but very carefully drilled to introduce the Floating Mass Transducer (FMT). Perichondrium sheets were used to stabilize the FMT onto the RWM. According to the audiological criteria, the upper limit of bone conduction should be 45 dB, 50 dB, and 65 dB from 500 Hz to 4, 000 Hz. Twenty-five patients underwent the surgery so far at 13 different medical centers. The age at the surgery was between 26-79 years old, and there were 15 males and 10 females. The cause of conductive or mixed hearing loss was middle ear diseases in 23 cases and congenital aural atresia in two cases. The data concerning on the effectiveness and safety of VSB was collected before the surgery and 20 weeks after the surgery. Significant improvements of free-field Pure Tone Audiogram (PTA) from 250 Hz to 8, 000 Hz were confirmed (p < 0.001). Hearing gain up to 40 dB was achieved in the 1, 000 Hz to 4, 000 Hz range. No deterioration in either air conduction or bone conduction at PTA was noted at 20 weeks after the surgery. Monosyllable speech perception in both quiet and noisy conditions improved significantly (p < 0.001). The speech discrimination score in both quiet and noisy conditions improved significantly too (p < 0.001). In the future, it is likely that there will be an increasing population even in Japan that will meet the criteria for MEIs such as VSB. However, the long-term efficacy and safety of these devices should be established.

Morphological Characteristics of Round Window Niche in Congenital Aural Atresia and Stenosis Patients.

The aim of this study was to measure the round window niche (RWN) among congenital aural atresia (CAA), congenital aural stenosis (CAS) and control groups and to analyze whether differences exist between them. Computed tomography images of 10 normal subjects (20 ears), 27 CAS patients (30 ears) and 25 CAA patients (30 ears) were analyzed. We measured RWN on the basis of 3-dimensional reconstruction. The anterior wall length and the depth of RWN were smaller in control group than those in the CAS group; furthermore, the anterior wall length and the depth of RWN in CAS group were smaller than those in CAA group (P < 0.05). The posterior wall length of RWN was found smaller in the control group than that in both hCAS and CAA groups (P < 0.05). The superior and inferior wall lengths of RWN were found smaller in control group than those in the CAA group (P < 0.05). There were no statistically significant differences in the sizes of the round window membrane and niche opening or the angle between the plane of the RWN opening and the round window membrane plane among all groups. The RWN walls lengths and its depth tended to be longer with the aggravation of the aural malformations. Our calculation results may provide some information for a better design and a safer implantation of the floating mass transducer in the area of RWN.

Bonebridge Implantation with Image Guidance Localization

Objectives: The Bonebridge implant (BBI) is a bone-conduction hearing implant with a relatively large floating mass transducer (FMT), which is seated within a bony well. This well is drilled in the mastoid process and the FMT is anchored onto the bony cortex with screws on the side of the well. The location of the well has to avoid vital structures, such as the posterior canal wall, the dura mater of the middle cranial fossa, and the sigmoid sinus. The size of the well must be sufficient to accommodate the size of the FMT. This becomes more important in patients with contracted mastoids. Methods: This case series aims to review the use of image guidance localization (IGL) in planning the site of the well. Under general anaesthesia, the patient was positioned supine, with the head turned away from the site of the BBI. Local anaesthetic was administered and a postauricular incision was made and deepened down to bone. The subperiosteal flap was elevated and the surgeon determined the location of the FMT, with the help of the IGL. A conservative cortical mastoidectomy was performed to create a well for the FMT to sit in. A subperiosteal pocket for the receiver coil was created posterior-superior to the well. Results: Five patients underwent BBI surgery with IGL. Rapid and accurate localization of the site of the well for the FMT was possible in each case. Conclusions: The authors recommend IGL as a safe, rapid, and reproducible technique in localization of the site for the well of the BBI.

The Effect of Angulation of the Vibrating Floating Mass Transducer on Stapes Velocity

Changes to the angular position of the vibrating floating mass transducer (FMT) coupled to the long process of the incus will not affect stapes velocity. The MED-EL Vibrant Soundbridge is an active middle ear implantable device, which constitutes an effective alternative to acoustic hearing aids for the rehabilitation of patients with sensorineural and mixed hearing loss. Because of varied anatomy, it is not always possible to position the FMT in line with the vibrating axis of the stapes. Changes in stapes velocity after angulation of the FMT are measured using laser Doppler vibrometry (LDV). The study was performed on 7 human cadaveric temporal bones. The FMT was attached to the incus and angled at the recommended 0 degree or at 45 degrees relative to the vibrating axis of the stapes, and the stapes velocity measured using LDV. In comparison to the 0-degree position, angulating the FMT to 45 degrees reduced cochlea input as measured by stapes velocity, although there was no statistical significance to this difference. Placing the FMT at 45 degrees did not compromise the peak output of the device but resulted in a phase lag which was more marked compared with the 0-degree position. If it is not anatomically possible to position the FMT in line with the vibrating axis of the stapes, then placement at up to 45 degrees does not significantly alter the performance of the implant particularly in the midfrequencies that are crucial to the understanding of speech.

Individual computer-assisted 3D planning for surgical placement of a new bone conduction hearing device.

To evaluate the benefit of a preoperative three-dimensional (3D) planning tool for surgically placing the bone conduction floating mass transducer (BC-FMT) of the Bonebridge (BB) bone conduction implant. Adult patients (n = 5) and one pediatric patient (n = 1) with conductive or mixed hearing loss caused by chronic ear disease, malformation, or single-sided deafness. Development of a preoperative planning tool that allowed free adjustment of the implant in an individual 3D model of the skull to evaluate completely fitting the BC-FMT into a bony bed and to identify an optimal implant position. Implantation of the BB with mastoid or retrosigmoid placement after individual preoperative planning and "virtual surgery". Feasibility of the preoperative 3D planning process, transfer into the intraoperative situation, and audiologic results after BB implantation. Individual preoperative planning was considered beneficial especially in cases of small mastoid bone volume, for example, because of previous canal wall down mastoidectomies, and in the case with malformation. For optimal placement of the BC-FMT of the BB, preoperative 3D planning is recommended especially in primarily small poorly pneumatized mastoids, hypoplastic mastoids in malformations, reduced bone volume after canal wall down mastoidectomy, or the small mastoids in children. Effort should be made to reduce segmentation and surgical planning time by means of automation.

Intraoperative measurement for a new transcutaneous bone conduction hearing implant.

To investigate the possibility of using a modified reverse transfer function (RTF) measurement intraoperatively during surgery of a new transcutaneous bone conduction hearing implant to evaluate the status of the device. Tests were performed on a cadaver skull (preclinically) and two conductive hearing loss patients implanted with a new transcutaneous bone conduction implant. During intraoperative activation, the RTF was measured using a microphone attached perpendicularly and directly to the skin in the middle section of the forehead. The RTF could be measured for all frequencies from 500 to 6, 000 Hz. The usage of an intraoperative RTF measurement may be a good method to verify the mechanical coupling of the bone conduction floating mass transducer and to test the functional integrity of the implant in an objective way.

Consensus statement on round window vibroplasty.

This study aimed to review current knowledge regarding implantation of the Vibrant Soundbridge floating mass transducer (FMT) at the round window (round window vibroplasty) as well as to form a consensus on steps for a reliable, stable surgical procedure. Review of the literature and experimental observations by the authors. Round window (RW) vibroplasty has been established as a reliable procedure that produces good and stable results for patients with conductive or mixed hearing loss. The experience gained over the past few years of the authors' more than 200 implantations has led to consensus on several key points: (1) a wide and bloodless access to the middle ear with facial nerve monitoring, (2) the careful and correct identification and exposure of the round window membrane, (3) a good setup for efficient energy transition of the FMT, namely, perpendicular placement of the FMT with no contact to bone and the placement of cartilage behind the FMT to create a preloaded "spring" function, and (4) 4 points of FMT fixation: a rim of the round window bony overhang left intact both anterior and posterior to the FMT, conductor link stabilization, and cartilage behind the FMT. In addition, the FMT should be covered with soft tissue.

Comparison of auditory responses determined by acoustic stimulation and by mechanical round window stimulation at equivalent stapes velocities

Active middle ear implants (AMEIs) have been studied to overcome the limitations of conventional hearing aids such as howling, occlusion, and social discrimination. AMEIs usually drive the oval window (OW) by means of transmitting vibrational force through the ossicles and the vibrational force corresponding to sound is generated from a mechanical actuator. Recently, round window (RW) stimulation using an AMEI such as a floating mass transducer (FMT) to deliver sound to the cochlea has been introduced and hearing improvement in clinical use has been reported. Although previous studies demonstrated that the auditory response to RW stimulation was comparable to a sound-evoked auditory response, few studies have investigated the quantification of the physiologic performance of an AMEI through RW stimulation on the inner ear in vivo. There is no established relationship between the cochlear responses and mechanical stimulation to RW.The aim of this study is to assess the physiologic response in RW stimulation by an AMEI. The transferred energy through the RW to the inner ear could estimate the response corresponding to acoustic stimulation in order to quantify the AMEI output in the ossicular chain or OW stimulation. The parameters of the auditory brainstem responses (ABRs) were measured and compared based on stapes velocities similar enough to be regarded as the same for acoustic stimulation to the external auditory canal (EAC) and mechanical stimulation to the RW in an in vivo system. In conclusion, this study showed that the amplitudes and latencies of the ABRs of acoustic and RW stimulation showed significant differences at comparable stapes velocities in an in vivo system. These differences in the ABR amplitudes and latencies reflect different output functions of the cochlea in response to different stimulation pathways. Therefore, it is necessary to develop a new method for quantifying the output of the cochlea in the case of RW stimulation.

Round window stimulation with the floating mass transducer at constant pretension

ObjectiveMechanical stimulation of the round window (RW) of the cochlea is successfully done with the Vibrant Soundbridge (Med-El), but clinical outcomes show a substantial degree of variability. One source of variability is variation in the static force applied by the stimulator to the round window (Maier et al., 2013). In this study we investigated other sources of variability by maintaining a constant pre-load testing the effect of a coupler device and the interposition of soft tissue between the stimulator and the RW. Study designExperimental. MethodsThe stapes footplate displacement produced by stimulation of the round window was determined in fresh human temporal bones. The response to sound and actuator stimulation was measured with a Laser Doppler Velocimeter at the stapes footplate. The RW was stimulated by a Floating Mass Transducer (FMT) with/without (1) an additional RW coupler (supplied by the manufacturer), and (2) the interposition of TUTOPATCH® between the stimulator and the RW, while maintaining a pre-load of ∼1.96 mN. ResultsIn 8 temporal bones with normal stapes footplate response to sound, we found an average 11.9 dB increase (500 Hz–2 kHz) under controlled conditions by using the coupler together with the interposition. The increase was statistically significant at 500 Hz (p < 0.01). Additionally, the coupler/interposition combination reduced the variability between experiments (FMT alone SD = 10.9 dB; FMT with TUTOPATCH® & coupler: SD = 3.4 dB @ 500 Hz) and increased the repeatability. ConclusionAt controlled static force an improved output level, inter-subject variability and repeatability were found by using a coupler/TUTOPATCH combination in RW stimulation with the FMT. The high variability found in clinical experience is not solely due to inter-subject variability, but to coupling conditions and can be optimized further.

Active Middle Ear Implants in Patients Undergoing Subtotal Petrosectomy

In 2009, we had introduced the active middle ear implant (aMEI) round window coupling in patients undergoing a subtotal petrosectomy and reported our first results. In the current study, we evaluated the long-term firmness of the vibranting floating mass transducer (FMT) within the round window niche, the long-term audiologic results and the patient's perspective of wearing the speech processor over time. Of 10 patients, 6 female and 1 male patients (age range from 30 to 71 yr) had undergone subtotal petrosectomy with aMEI round window vibroplasty and were available for a long-term follow-up. Indications were recurrent or chronic ear infections with preserved inner ear function and inability for ossicular chain reconstruction. A thin piece of fascia was placed between the FMT and the round window membrane once the round window niche had been enlarged by drilling. The operative cavity was filled with fat and a muscle flap in all cases. Audiologic evaluations included pre- and postoperative pure-tone audiometry, Freiburger syllable and numeric tests. All patients underwent preoperative computed tomographic (CT) scans and magnetic resonance imaging (MRI) examination. Postoperative follow-up included CT scans at 1 and preferentially 3 to 5 years to confirm the correct positioning of the FMT and the complete removal of the underlaying pathology. Subjective benefit was rated by the Glasgow Hearing Aid Benefit Profile. There were no immediate postoperative complications. CT scans confirmed the correct and durable positioning of the FMT. Audiometric tests revealed a stable and adequate functional gain in all patients with limited adjustments over time. Subjective rating reached a high satisfaction score, and all patients remained long-term implant users. One patient developed a skin necrosis over the implant because of excessive pressure exerted by the retaining magnet of the headpiece. Revision was performed using local skin flaps with preservation of the functioning implant. Our radiologic, audiometric, and subjective data show stable long-term results of round window vibroplasty in patients undergoing subtotal petrosectomy, and we continue to recommend this treatment option instead of another mastoid revision procedure.

Transducer Type and Design Influence on the Hearing Loss Compensation Behaviour of the Electromagnetic Middle Ear Implant in a Finite Element Analysis

Several types of electromagnetic transducer for the middle ear implants (MEIs) have been developed as an alternative to conventional hearing aids for the rehabilitation of sensorineural hearing loss. Electromagnetic transducer type and design are thought to have a significant influence on their hearing compensation performance. To investigate these effects, a middle ear computational model was constructed based on a complete set of microcomputerized tomography section images of a human ear. Its validity was confirmed by comparing the model predicted motions with published experimental measurements. The result shows that the eardrum driving transducer (EDT) is superior to the floating mass transducer (FMT) in hearing compensation when the transducer mass is small but inferior to the FMT when the mass gets bigger. The incus body driving transducer (IBDT) is the most ineffective type of transducer for hearing compensation. Moreover, the masses of the EDT and the FMT decrease the transducer performance mainly at higher frequencies: the greater the transducer mass, the lower the displacement of the stapes excited by these transducers. On the other hand, the IBDT driving rod stiffness decreases transducer's performance severely at low frequencies and its adverse effect on transducer performance increases with the decrease of the stiffness of the IBDT driving rod.

The Round Window Diameter in Congenital Aural Atresia and Comparison With Sensorineural Hearing Loss and Control Group

The aim of this study was to measure round window (RW) diameters in patients with congenital aural atresia (CAA) or sensorineural hearing loss (SNHL) and a normal control group and to analyze whether differences exist between these groups. Temporal bone computed tomographic scans of 12 patients with CAA (5 males, 7 females) aged 1 to 50 years (median age, 6 years), 12 patients with SNHL (8 males, 4 females) aged 2 to 32 years (median age, 5 years), and 11 patients (3 males, 7 females) aged 2 months to 53 years (median age, 8 years) randomly selected from a pool of patients with unilateral chronic otitis media or cholesteatoma were reviewed. We measured RW diameter on oblique reconstruction planes. To prevent possible individual differences, skull width was measured. There were no statistically significant differences between all groups for skull width. Both RW diameter and RW membrane width were found smaller in the CAA group than both SNHL group and control group with statistical significance, whereas there were no statistically significant differences between the SNHL group and the control group. We found that both the RW diameter and RW membrane width in CAA were smaller than those in the control group. If this finding is supported in future studies, the production of floating mass transducer with different sizes may be useful. We suggest that RW diameter should be measured in each patient before operation and thus a floating mass transducer with the appropriate caliber should be chosen.

Vibroplasty in mixed and conductive hearing loss: Comparison of different coupling methods

To evaluate modified coupling techniques of the Vibrant Soundbridge system in patients with mixed and conductive hearing loss and to compare it with conventional vibroplasty. Retrospective study. Two different groups were evaluated: 1) nine cases of conventional incus vibroplasty in comparison with 2) nine patients with modified coupling of the floating mass transducer. In the modified coupling approach, the vibrant floating mass transducer was attached to 1) the stapes/oval window, 2) the round window, or 3) the drilled promontory bone (promontory fenestration window). In three patients, an additional ossiculoplasty was performed. Preoperative and postoperative aided and unaided pure-tone and free-field audiometry and Freiburg monosyllabic word test were used to assess hearing outcome. Functional hearing gain obtained in patients with mixed and conductive hearing loss who underwent modified coupling was 39 dB. Patients with pure sensorineural hearing loss who received conventional incus coupling showed a functional hearing gain of 25 dB. Average functional gain was 41 dB in the oval window group, 45 dB in the round window group, and 30 dB in the promontory fenestration window group. Word recognition test revealed an average improvement of 51% and 21% in the modified and in the conventional approach, respectively. Modified vibroplasty is a safe and effective treatment for patients with conductive and mixed hearing loss. Coupling the floating mass transducer to the promontory bone (promontory fenestration window) is a viable option in chronically disabled ears if oval and round window coupling is not possible. 4.

Magnetic field effect analysis of electromagnetic transducer for implantable hearing device

Electromagnetic transducers are widely used for implantable hearing devices because they can be miniaturized, and their vibration intensity is suitable for middle ear stimulation. There are two types of electromagnetic transducers: a floating mass transducer (FMT) and differential floating mass transducer (DFMT). Both transducers have a permanent magnet and a coil to generate electromagnetic force. However, FMTs have disadvantage in that unwanted vibration can be generated in a static magnetic field, such as in MRI. In this paper, a magnetic field effect analysis of two types of electromagnetic transducers was performed. The torque that is generated by the static magnetic field has been calculated through finite element analysis (FEA). Then, the effects of the static magnetic field in both transducers were compared through an experiment based on the simulated results. The results of FEA and the experiment show that the torque of the DFMT are smaller than that of the FMT in a static magnetic field. Therefore, it is expected that the DFMT is a suitable transducer for implantable hearing devices.