Visualisation of the Bonebridge by means of CT and CBCT

Long-Term, Multicenter Results With the First Transcutaneous Bone Conduction Implant

OBJECTIVE

Investigation of long-term safety and performance of an active, transcutaneous bone conduction implant in adults and children up to 36 months post-implantation.

STUDY DESIGN

Prospective, single-subject repeated-measures design.

SETTING

Otolaryngology departments of eight German and Austrian hospitals.∗†‡§||¶#∗∗†† Affiliations listed above that did not participate in the study.‡‡§§||||¶¶.

PATIENTS

Fifty seven German-speaking patients (49 adults and eight children) suffering from conductive or mixed hearing loss, with an upper bone conduction threshold limit of 45 dB HL at frequencies between 500 and 3000 Hz.

INTERVENTION

Implantation of the Bonebridge transcutaneous bone conduction hearing implant (tBCI).

MAIN OUTCOME MEASURES

Patients' audiometric pure tone averages (PTA4) (0.5, 1, 2, 4 kHz) thresholds (air conduction, bone conduction, and sound field) and speech perception (word recognition scores [WRS] and speech reception thresholds [SRT50%]) were tested preoperatively and up to 36 months postoperatively. Patients were also monitored for adverse events and administered quality-of-life questionnaires.

RESULTS

Speech perception (WRS: pre-op: 17.60%, initial activation [IA]: 74.23%, 3M: 83.65%, 12M: 83.46%, 24M: 84.23%, 36M: 84.42%; SRT50%: pre-op: 65.56 dB SPL, IA: 47.67 dB SPL, 3M: 42.61 dB SPL, 12M: 41.11 dB SPL, 24M: 41.74 dB SPL, 36M: 42.43 dB SPL) and sound field thresholds (pre-op: 57.66 dB HL, IA: 33.82 dB HL, 3M: 29.86 dB HL, 12M: 28.40 dB HL, 24M: 28.22 dB HL, 36M: 28.52 dB HL) improved significantly at all aided postoperative visits. Air and bone conduction thresholds showed no significant changes, confirming preservation of patients' residual unaided hearing. All adverse events were resolved by the end of the study.

CONCLUSIONS

Safety and performance of the tBCI was demonstrated in children and adults 36 months postoperatively.

Systematic review of outcome domains and instruments used in designs of clinical trials for interventions that seek to restore bilateral and binaural hearing in adults with unilateral severe to profound sensorineural hearing loss ('single-sided deafness')

BACKGROUND

This systematic review aimed to identify, compare and contrast outcome domains and outcome instruments reported in studies investigating interventions that seek to restore bilateral (two-sided) and/or binaural (both ears) hearing in adults with single-sided deafness (SSD). Findings can inform the development of evidence-based guidance to facilitate design decisions for confirmatory trials.

METHODS

Records were identified by searching MEDLINE, EMBASE, PubMed, CINAHL, ClinicalTrials.gov, ISRCTN, CENTRAL, WHO ICTRP and the NIHR UK clinical trials gateway. The search included records published from 1946 to March 2020. Included studies were those as follows: (a) recruiting adults aged 18 years or older diagnosed with SSD of average threshold severity worse than 70 dB HL in the worse-hearing ear and normal (or near-normal) hearing in the better-hearing ear, (b) evaluating interventions to restore bilateral and/or binaural hearing and (c) enrolling those adults in a controlled trial, before-and-after study or cross-over study. Studies that fell just short of the participant eligibility criteria were included in a separate sensitivity analysis.

RESULTS

Ninety-six studies were included (72 full inclusion, 24 sensitivity analysis). For fully included studies, 37 exclusively evaluated interventions to re-establish bilateral hearing and 29 exclusively evaluated interventions to restore binaural hearing. Overall, 520 outcome domains were identified (350 primary and 170 secondary). Speech-related outcome domains were the most common (74% of studies), followed by spatial-related domains (60% of studies). A total of 344 unique outcome instruments were reported. Speech-related outcome domains were measured by 73 different instruments and spatial-related domains by 43 different instruments. There was considerable variability in duration of follow-up, ranging from acute (baseline) testing to 10 years after the intervention. The sensitivity analysis identified no additional outcome domains.

CONCLUSIONS

This review identified large variability in the reporting of outcome domains and instruments in studies evaluating the therapeutic benefits and harms of SSD interventions. Reports frequently omitted information on what domains the study intended to assess, and on what instruments were used to measure which domains.

TRIAL REGISTRATION

The systematic review protocol is registered on PROSPERO (International Prospective Register of Systematic Reviews): Registration Number CRD42018084274 . Registered on 13 March 2018, last revised on 7th of May 2019.

Retrospective Analysis of Hearing-Impaired Adult Patients Treated With an Active Transcutaneous Bone Conduction Implant

OBJECTIVE

To determine the therapeutic success and safety of an active transcutaneous bone conduction implant (tBCI) in adult patients with conductive or mixed hearing loss.

STUDY DESIGN

Retrospective case review.

SETTING

Five university hospitals in Frankfurt, Hannover, Dresden, Würzburg, and Vienna.

PATIENTS

Data were analyzed from 61 patients (31 women, 30 men) with a mean age of 50 years (min. 26, max. 80). Forty patients had mixed, and 21 conductive hearing loss. Typical etiologies were history of otitis media (n = 20) and cholesteatoma (n = 17).

INTERVENTIONS

Implantation of the active tBCI.

MAIN OUTCOME MEASURES

Data were analyzed for the following time points: up to 6 months postoperatively ("short-term"), 6 to 37 months postoperatively ("long-term"), and the last available measurement per patient ("most recent"). Pure-tone audiometry (air and bone conduction, AC and BC) and sound field thresholds with warble tones (WT), word recognition scores with Freiburger monosyllables (WRS), as well as speech reception thresholds (SRT) using the Oldenburg sentence test (OLSA) in quiet (SRT) and in noise (signal-to-noise ratio, SNR) were collected.

RESULTS

No significant changes in air- and bone-conduction thresholds were observed after implantation. A mean WRS improvement of 54% using the active tBCI was shown at the short-term assessment, i.e., a mean score of 79% compared with 25% in the unaided condition. Results remained stable, with a mean score of 75% at the long-term assessment. SRT in noise improved by 3.6 dB SNR in the implanted ear at the short-term assessment. Overall six adverse events and four serious adverse events were reported, resulting in a rate of 9.84 and 6.56%, respectively.

CONCLUSION

The tBCI clearly improves speech intelligibility in patients with conductive or mixed hearing loss, showing stable results up to 1 year post-implantation.

MRI Metal Artifact Reduction Sequence for Auditory Implants: First Results with a Transcutaneous Bone Conduction Implant

Objective: Magnetic resonance imaging (MRI) is often limited in patients with auditory implants because of the presence of metallic components and magnets. The aim of this study was to evaluate the clinical usefulness of a customized MRI sequence for metal artifact suppression for patients with implants in the temporal bone region, specifically patients with a transcutaneous bone conduction implant. Methods: Two whole head specimens were unilaterally implanted with a transcutaneous bone conduction implant. MRI examinations with and without a primarily self-build sequence (SEMAC-VAT WARP) for metal artifact suppression were performed. The diagnostic usefulness of the acquired MRI scans was rated independently by two neuroradiologists. The sequence was also used to acquire postimplantation follow-up MRI in a patient with a transcutaneous bone conduction implant. Results: The customized SEMAC-VAT WARP sequence significantly improved the diagnostic usefulness of the postimplantation MRIs. The image acquisition time was 12 min and 20 s for the T1-weighted and 12 min and 12 s for the T2-weighted MRI. There was good agreement between the two blinded raters (Cohen’s κ = 0.61, p < 0.001). Conclusion: The sequence for metal artifact reduction optimized in Bern enables MRI at 1.5 T in patients with active transcutaneous bone conduction implants without sacrificing diagnostic imaging quality. Particularly on the implanted side, imaging of intracranial and supra- and infratentorial brain pathologies is clinically more valuable than standard diagnostic MRI without any artifact reduction sequences.

Design of a dual-coil type electromagnetic actuator for implantable bone conduction hearing devices

BACKGROUND

This paper describes the design and implementation of a dual-coil type electromagnetic actuator for implantable bone conduction hearing devices.

OBJECTIVE

The structure of the proposed actuator was designed to generate maximum Lorentz force via the dual-coil method with a closed magnetic circuit. To satisfy the indications required by implantable bone conduction hearing devices, high output was generated within a specific frequency range using a vibrational membrane with a cantilever.

METHODS

The structure of the membrane consists of a fixed ring, a circular plate, and two cantilevers connected symmetrically. Variable elements of the vibrational membrane affecting the actuator frequency characteristics were analyzed through mathematical modeling and finite element analysis, based on the analysis used to derive the optimum structure of the vibrational membrane. The components of the actuator were fabricated through chemical etching and computer numerical control process, and the bone conduction actuator was fabricated through the precision assembly process.

RESULTS

The output characteristics of the implemented actuator were measured using a laser Doppler vibrometer. As a result of measurement, the proposed actuator generated mechanical resonance at 1.2 kHz.

CONCLUSIONS

By comparing the measured results with the finite element analysis results, we confirmed the validity of the proposed actuator design.

A New Transcutaneous Bone Conduction Hearing Implant: Short-term Safety and Efficacy in Children

OBJECTIVE

To investigate the safety and efficacy of a new bone conduction hearing implant in children, during a 3-month follow-up period.

STUDY DESIGN

Prospective, single-subject repeated-measures design in which each subject serves as his/her own control.

SETTING

Otolaryngology departments of four Austrian hospitals.

PATIENTS

Twelve German-speaking children aged 5 to 17 suffering from conductive or mixed hearing loss, with an upper bone conduction threshold limit of 45 dB HL at frequencies between 500 and 4000 Hz.

INTERVENTION

Implantation of the Bonebridge transcutaneous bone conduction hearing implant (tBCI).

MAIN OUTCOME MEASURES

The subjects' audiometric thresholds (air conduction, bone conduction, and sound field at frequencies 500 Hz to 8 kHz) and speech perception (word recognition scores [WRS] and 50% word intelligibility in sentences [SRT50%]) were tested preoperatively and at 1 and 3 months postoperatively. The patients were also monitored for adverse events and they or their parents filled out questionnaires to analyze satisfaction levels.

RESULTS

Speech perception as measured by WRS and SRT50% improved on average approximately 67.6% and 27.5 dB, respectively, 3 months after implantation. Aided thresholds also improved postoperatively, showing statistical significance at all tested frequencies. Air conduction and bone conduction thresholds showed no significant changes, confirming that subjects' residual unaided hearing was not damaged by the treatment. Only minor adverse events were reported and resolved by the end of the study.

CONCLUSION

Safety and efficacy of the new bone conduction implant was demonstrated in children followed up to 3 months postoperatively.

Possibility of differentiation of cochlear electrodes in radiological measurements of the intracochlear and chorda-facial angle position

Due to an increasing number of cochlear implantations, quality control has become more important. In addition to intraoperative biophysical measurements, radiological imaging is another possibility. An upcoming technique regarding this is Cone Beam CT (CBCT). Sixty-five data sets (35 Nucleus Contour Advance–Cochlear; 30 Flex Soft–MedEl) of postoperative imaging by CBCT (Accu-I-tomo F17, Morita, Kyoto, Japan) underwent further evaluation. Insertion angle, height of the cochlea, distance of the electrode to the medial or lateral wall, angle between chorda tympani and facial nerve and the precise position of the electrode cable in the facial-chordal angle were determined. The typical difference between the perimodiolar and lateral course of the electrodes could also be shown in radiological measurements. This demonstrates the accuracy and advantage of CBCT in visualisation of small structures with fewer metal artifacts. Furthermore, in 75% of patients, the angle of the chorda and facial nerve could be visualised. Significant differences in dependence of the electrode type for the relation of them to the facial nerve could be seen. In conclusion, CBCT achieves reliable visualisation and detailed imaging-based measurements of the intracochlear position of different cochlea electrodes. Additionally, clinically known differences can be reproduced. Even visualisation of the position of the electrode in the chorda-facial angle is possible. Therefore, CBCT is a useful tool in intra- and postoperative control of cochlear implants.

Repeatability and agreement of ultrasonography with computed tomography for evaluating forefoot structure in the coronal plane

Background

Forefoot structure is important to understand some foot problems such as hallux valgus and metatarsalgia. Ultrasonography (US) is a highly portable, noninvasive, low cost, and fast imaging method, especially when compared to magnetic resonance imaging (MRI), computed tomography (CT), and radiography. As the use of US for evaluating forefoot bony structure has not been validated, except for the presence of synovitis, erosions and bursitis within the forefoot in people with inflammatory arthritis, the purpose of this study was to determine whether US is a reliable method for evaluating forefoot structure.

Methods

Sixty feet (30 women, age = 40.1 ± 11.8 years) were examined by US and CT to assess agreement with CT and repeatability of US evaluation of the 2nd metatarsal head height, length between the medial sesamoid bone and 5th metatarsal head, transverse arch height, transverse arch index, sesamoid rotation angle, and area under the transverse arch. The measurement data were evaluated for agreement with CT using the intra-class correlation coefficient (ICC)_{3, 1}, Pearson correlation coefficient, and Bland-Altman plot, and with ICC_{1, 1} for repeatability.

Results

The ICC_{3, 1} values of 0.78–0.89, Pearson correlation coefficient of 0.78–0.90, and Bland-Altman plots showed almost perfect agreements between the US and CT method for all parameters, except the area under the transverse arch (AUTA). The ICC_{1, 1} also showed perfect agreements (0.84–0.92) between two sets of US measurements in all parameters.

Conclusions

The US evaluation of forefoot structure in the coronal plane showed good agreement with CT and repeatability of two ultrasonograms in adult women. This reliable evaluation method of forefoot structure can contribute to a quick clinical assessment screening for risk factors of foot problems such as hallux valgus and metatarsalgia. However, because of some limitations such as a lack of inter-observer reliability, more research is needed to validate US evaluation of forefoot structure.

Trial registration

The current study (trial registration number: R0297) was approved by the Ethical Committee for Human Experiments of Kyoto University (http://www.ec.med.kyoto-u.ac.jp) on December 3, 2015. The first participant in this study was enrolled on November 17, 2015 and retrospectively registered.

Magnetic resonance imaging investigation of the bone conduction implant - a pilot study at 1.5 Tesla

PURPOSE

The objective of this pilot study was to investigate if an active bone conduction implant (BCI) used in an ongoing clinical study withstands magnetic resonance imaging (MRI) of 1.5 Tesla. In particular, the MRI effects on maximum power output (MPO), total harmonic distortion (THD), and demagnetization were investigated. Implant activation and image artifacts were also evaluated.

METHODS AND MATERIALS

One implant was placed on the head of a test person at the position corresponding to the normal position of an implanted BCI and applied with a static pressure using a bandage and scanned in a 1.5 Tesla MRI camera. Scanning was performed both with and without the implant, in three orthogonal planes, and for one spin-echo and one gradient-echo pulse sequence. Implant functionality was verified in-between the scans using an audio processor programmed to generate a sequence of tones when attached to the implant. Objective verification was also carried out by measuring MPO and THD on a skull simulator as well as retention force, before and after MRI.

RESULTS

It was found that the exposure of 1.5 Tesla MRI only had a minor effect on the MPO, ie, it decreased over all frequencies with an average of 1.1±2.1 dB. The THD remained unchanged above 300 Hz and was increased only at lower frequencies. The retention magnet was demagnetized by 5%. The maximum image artifacts reached a distance of 9 and 10 cm from the implant in the coronal plane for the spin-echo and the gradient-echo sequence, respectively. The test person reported no MRI induced sound from the implant.

CONCLUSION

This pilot study indicates that the present BCI may withstand 1.5 Tesla MRI with only minor effects on its performance. No MRI induced sound was reported, but the head image was highly distorted near the implant.

Active Bone Conduction Prosthesis: Bonebridge(TM)

Introduction Bone conduction implants are indicated for patients with conductive and mixed hearing loss, as well as for patients with single-sided deafness (SSD). The transcutaneous technology avoids several complications of the percutaneous bone conduction implants including skin reaction, skin growth over the abutment, and wound infection. The Bonebridge (MED-EL, Austria) prosthesis is a semi-implantable hearing system: the BCI (Bone Conduction Implant) is the implantable part that contains the Bone Conduction-Floating Mass Transducer (BC-FMT), which applies the vibrations directly to the bone; the external component is the audio processor Amadé BB (MED-EL, Austria), which digitally processes the sound and sends the information through the coil to the internal part. Bonebridge may be implanted through three different approaches: the transmastoid, the retrosigmoid, or the middle fossa approach. Objective This systematic review aims to describe the world́s first active bone conduction implant system, Bonebridge, as well as describe the surgical techniques in the three possible approaches, showing results from implant centers in the world in terms of functional gain, speech reception thresholds and word recognition scores. Data Synthesis The authors searched the MEDLINE database using the key term Bonebridge. They selected only five publications to include in this systematic review. The review analyzes 20 patients that received Bonebridge implants with different approaches and pathologies. Conclusion Bonebridge is a solution for patients with conductive/mixed hearing loss and SSD with different surgical approaches, depending on their anatomy. The system imparts fewer complications than percutaneous bone conduction implants and shows proven benefits in speech discrimination and functional gain.

Image-guided placement of the Bonebridge™ without surgical navigation equipment

PURPOSE

   Most of the current Bonebridge surgeries undergo preoperative simulation planning in a computer. However, surgeons usually use the landmarks on the bone surface to determine the location where to implant the device, using the simulation image in the computer only as a reference (conventional method). We developed an image-guided method for precisely replicating simulation surgery upon performing Bonebridge implantation.

METHODS

   Based on our previous development of the surface template-assisted marker positioning (STAMP) method for performing image-guided otologic surgery, we fabricated templates that fit only at the designated location on the patient's temporal bone surface. The Bonebridge STAMP (BB-STAMP) plate shows the exact location where to start drilling. The BB-STAMP was also combined with a perforator-guiding sleeve, so that the location, direction and depth of the cylindrical well could be precisely replicated as simulated. We also created a STAMP plate for confirmation that fits only after sufficient drilling at the correct location is finished. To evaluate the proposed methods, we performed simulation surgery on four cadaveric temporal bones and their 12 replicas (three each for four bones). The time used and the degree of mismatch between the simulated location and the drilled location were compared.

RESULTS

   A feasibility study was successfully conducted using the proposed BB-STAMP methods and the conventional method. The amount of time required for the procedure did not differ significantly between the surgical methods, although using the BB-STAMP and perforator guide was always quicker. The degree of mismatch between the simulation and resected models had tendency to be smaller when the surgery was guided by the BB-STAMP with or without a perforator guide, although the difference was not statistically significant.

CONCLUSIONS

   The proposed BB-STAMP is a promising method for replicating exactly what is performed during simulation without using a surgical navigation system.