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Background: The goal is to develop an intracochlear acoustic receiver (ICAR) for measurement of the sound pressure in the inner ear and in addition it is designed to be used as an implantable microphone for totally implantable cochlear implant systems. Critical ICAR specifications to be considered are the acoustical sensing performance, small dimensions, biocompatibility, hermeticity, reliability over time and low power consumption. Methods: The presented ICAR concept consists of a MEMS condenser microphone (MEMS CMIC) with a passive protective diaphragm sealing the MEMS CMIC against the liquid medium (perilymph) and enabling insertion into the cochlea. Experiments were performed in human and sheep temporal bones and during acute experiments in sheep. Results: The first ICAR prototypes have been used for intracochlear sound pressure measurements in human. The data thus obtained are in good agreement with the literature. A second ICAR prototype was further adapted for surgical insertion in the scala tympani in acute large animal experiments. A satisfactory agreement between sheep experiments in-vivo and in cadavers exist. Conclusions: A MEMS CMIC-based ICAR concept was developed to fulfill the major requirements for intracochlear sound pressure measurements in human and sheep temporal bones and in acute experiments in sheep. We conclude that the presented MEMS CMIC-based ICAR concept can be used for measurement of intracochlear fluid pressure and that this concept has potential as an acoustic receiver in totally implantable cochlear implants. [ABSTRACT FROM AUTHOR]

Aim of the study: This study evaluates the feasibility of the subcutaneous microphone for potential use in future totally implantable cochlear implants (TICI). Materials and methods: Ten post lingual native French speaking adult patients who had used and unilateral Nucleus cochlear implant for at least twelve months were selected. The subjects received an implantable subcutaneous microphone at the contralateral side. The microphone lead was connected to percutaneous plug to bring out the microphone signal. Multiple adaptive sound cleaning algorithms were added to subcutaneous microphone firmware and fitting software. The processed signal of the microphone was fitted as additional accessory to avoid changes to the CI map. The audiological performance with subcutaneous microphone was compared to that obtained with the external dual microphone. Hearing thresholds and speech recognition in quiet and noise were evaluated during 3 sessions on a 5 months period. Subjective sound quality (using comparative APHAB questionnaire and a study specific questionnaire) was investigated. Results: The average hearing threshold was 34.5 dB HL. The average word recognition score at 65 dB SPL was 84% and only 10% worse than dual external microphone configuration. The hearing performance in noise as well as the sound quality ratings (word score) showed an important significant improvement over previous studies with TICI. Body generated sounds became totally acceptable. Conclusions: A subcutaneous microphone is one readily available option for TICI and could meet the needs of patients for situations where the device will operate in invisible mode. On the basis of this study, the subcutaneous microphone architecture is expected to meet those needs and significant progress compared to previous studies has been made. Performance improvements can be mitigated by sophisticated pre-processing strategies, careful microphone fitting and optimise skin flap thickness. [ABSTRACT FROM AUTHOR]

Background: The generally accepted method to assess the functionality of novel bone conduction implants in a preclinical stage is to experimentally measure the vibratory response of the cochlear promontory. Yet, bone conduction of sound is a complex propagation phenomenon, depending on both frequency and amplitude, involving different conduction pathways., Objectives: The aim of this study is to validate the use of intracochlear sound pressure (ICP) as an objective indicator for perceived loudness for bone conduction stimulation. It is investigated whether a correlation exists between intracochlear sound pressure measurements in cadaveric temporal bones and clinically obtained results using the outcome of a loudness balancing experiment., Methods: Ten normal hearing subjects were asked to balance the perceived loudness between air conducted (AC) sound and bone conducted (BC) sound by changing the AC stimulus. Mean balanced thresholds were calculated and used as stimulation levels in a cadaver trial (N = 4) where intracochlear sound pressure was measured during AC and BC stimulation to assess the correlation with the measured clinical data. The intracochlear pressure was measured at the relatively low stimulation amplitude of 80 dBHL using a lock-in amplification technique., Results: Applying AC and BC stimulation at equal perceived loudness on cadaveric heads yield a similar differential intracochlear pressure, with differences between AC and BC falling within the range of variability of normal hearing test subjects., Conclusion: Comparing the perceived loudness at 80 dB HL for both AC and BC validates intracochlear pressure as an objective indicator of the cochlear drive. The measurement setup is more time-intensive than measuring the vibratory response of the cochlear promontory, yet it provides direct information on the level of the cochlear scalae., Competing Interests: Declaration of interest This work has been supported by Flanders Innovation and Entrepreneurship (IWT155047). TP is fully funded by Research Foundation Flanders (FWO 12Y6919N). GF, CB and JW are currently employees of Cochlear Ltd. GF is partly funded by Flanders Innovation and Entrepreneurship (HBC.2018.0184), NV has a senior clinical investigator fund of Research Foundation Flanders (FWO 1804816N)., (Copyright © 2022. Published by Elsevier B.V.)

Active transcutaneous bone conduction (BC) devices offer the benefit of improved power output compared to passive transcutaneous devices and remove the risk of skin infections that are more common in traditional percutaneous BC devices. Despite these advantages, more research is needed on implant location, device coupling, and their influence on device performance. This study is aimed at quantifying the extent to which certain parameters affect device output when using the Osia® system actuator. Parameters under study are (1) implant location, (2) comparison with the actuator of a state-of-the-art BC device, (3) bone undergrowth simulation, and (4) skull fixation. Five human cadaveric heads were implanted with the actuator at three different implant locations: (1) recommended, (2) posterior Osia® positions, and (3) standard Baha® position. At each location, the cochlear promontory velocity and the intracochlear pressure difference were measured. A percutaneous bone conduction actuator was used as a reference for the obtained measurements. Stimulation levels corresponded to a hearing level of 60 dB HL for frequencies between 250 and 6000 Hz. In addition, bone cement was used as a simulation for reactive bone growth. Results obtained in four heads indicate an improved power transmission of the transcutaneous actuator when implanted at the recommended position compared to the actuator of the percutaneous device on its respective recommended location when stimulating at an identical force level. A correlation was found between the promontory vibration and the actuator position, indicating that the same level of stimulation leads to higher promontory vibrations when the device is implanted closer to the ear canal. This is mainly reflected at frequencies higher than 1 kHz, where an increase was observed in both measurement modalities. At lower frequencies (<1 kHz), the power transmission is less influenced by the implant position and differences between the acquired responses are limited. In addition, when no rigid coupling to the skull is provided, power transfer losses of up to 30 dB can be expected., Competing Interests: CB was an independent researcher at the moment of the experiments and data analysis, but at the moment of manuscript preparation, CB has become an employee of Cochlear Ltd. GF and JW are employees of Cochlear Ltd., (Copyright © 2022 Guy Fierens et al.)

Making use of magnetic resonance imaging (MRI) for diagnostics on patients with implanted medical devices requires caution due to mutual interactions between the device and the electromagnetic fields used by the scanner that can cause a number of adverse events. The presented study offers a novel test method to quantify the risk of unintended output of acoustically stimulating hearing implants. The design and operating principle of an all-optical, MRI safe vibrometer is outlined, followed by an experimental verification of a prototype. Results obtained in an MRI environment indicate that the system can detect peak displacements down to 8 pm for audible frequencies. Feasibility testing was performed with an active middle ear implant that was exposed to several pulse sequences in a 1.5 Tesla MRI environment. Magnetic field induced actuator vibrations, measured during scanning, turned out to be equivalent to estimated sound pressure levels between 25 and 85 dB SPL, depending on the signal frequency. These sound pressure levels are situated well below ambient sound pressure levels generated by the MRI scanning process. The presented case study therefore indicates a limited risk of audible unintended output for the examined hearing implant during MRI.

Objective: To investigate the occurrence and progression of heterotopic ossification (HO) in patients treated by anterior cervical discectomy with arthroplasty. It was evaluated if HO affects clinical outcome and range of motion (ROM). Risk factors of HO was studied as well., Methods: Patients who underwent anterior cervical discectomy with arthroplasty for a cervical radiculopathy because of a herniated disc from the NECK and PROCON trial were analyzed for HO at 12 and 24 months postoperatively. HO was scored according to the McAfee-Mehren classification. The index ROM was defined by a custom developed image analysis tool, and global cervical ROM was measured by Cobb's angle. Clinical outcome was evaluated by means of the Neck Disability Index and the 36-Item Short Form Health Survey., Results: The occurrence of HO was 60% at 1 year, and it increased to 76% at 2-year follow-up. A total of 31% of patients were scored as high-grade HO at 1-year follow-up, and this percentage increased to 50% at 2-year follow-up. Clinical outcome does not correlate to HO grade, and no risk factor for high-grade HO could be identified. The ROM at the index level was significantly higher in low-grade HO group than those patients with high-grade HO, but in 15%-38% HO grade does not correspond to ROM., Conclusions: HO occurs in three fourths of the patients at 2 years after surgery, but does not necessarily correspond to clinical outcome, nor loss or preservation of ROM. The McAfee-Mehren classification should be combined with ROM evaluation to properly study HO., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Background: Motion preservation prostheses were introduced to prevent adjacent disc degeneration (ASD) and to diminish neck disability in the postsurgical follow-up. However, it is still a controversial issue, and the relationship between range of motion (ROM) and ASD has not been studied., Purpose: To compare the correlation between ROM of the cervical spine and the presence of radiological ASD after anterior discectomy. Clinical outcome was also correlated to ROM and ASD., Study Design: Retrospective cohort study., Methods: In all, 253 patients who underwent anterior discectomy for cervical radiculopathy due to a herniated disc were analyzed for segmental and global cervical ROM and the presence of ASD both preoperatively, and 12 and 24 months postoperatively. Patients who were included in two randomized, double-blinded trials comparing anterior cervical discectomy with arthroplasty, anterior cervical discectomy with intervertebral cage, or anterior cervical discectomy without intervertebral cage for one level disc herniation were analyzed. ROM was defined by a custom-developed image analysis tool. ASD was defined by decrease in disc height and anterior osteophyte formation on X-rays. Clinical outcome was evaluated by means of the Neck Disability Index (NDI)., Results: Two years postoperatively, no correlation was demonstrated between ROM and ASD. The incidence of ASD was comparable in the three groups, being 34% at baseline, and 58% at 2-year follow-up. Likewise, ASD progression was comparable in the three treatment arms. No correlation was demonstrated between ROM and NDI or ASD and NDI., Conclusions: Since ROM is not correlated to ASD, and clinical outcome is not correlated to ROM either, the relevance of continued ROM at the target level seems absent., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Goal: Intracochlear sound pressure (ICSP) measurements are limited by the small dimensions of the human inner ear and the requirements imposed by the liquid medium. A robust intracochlear acoustic receiver (ICAR) for repeated use with a simple data acquisition system that provides the required high sensitivity and small dimensions does not yet exist. The work described in this report aims to fill this gap and presents a new microelectromechanical systems (MEMS) condenser microphone (CMIC)-based ICAR concept suitable for ICSP measurements in human temporal bones., Methods: The ICAR head consisted of a passive protective diaphragm (PD) sealing the MEMS CMIC against the liquid medium, enabling insertion into the inner ear. The components of the MEMS CMIC-based ICAR were expressed by a lumped element model (LEM) and compared to the performance of successfully fabricated ICARs., Results: Good agreement was achieved between the LEM and the measurements with different sizes of the PD. The ICSP measurements in a human cadaver temporal bone yielded data in agreement with the literature., Conclusion: Our results confirm that the presented MEMS CMIC-based ICAR is a promising technology for measuring ICSP in human temporal bones in the audible frequency range., Significance: A sensor for evaluation of the biomechanical hearing process by quantification of ICSP is presented. The concept has potential as an acoustic receiver in totally implantable cochlear implants.

Purpose: Cervical arthroplasty is being used as an alternative for cervical fusion, but long-term follow-up results have rarely been reported. In this paper, we present 10-year follow-up results after implantation of the Bryan Cervical Disc Prosthesis in a single center., Methods: 89 patients underwent implantation of a single-level Bryan Cervical Disc Prosthesis to treat radiculopathy and/or myelopathy. Clinical (Neurological Success, Neck Disability Index (NDI), Neck- and Arm-Pain, and SF-36) and radiological follow-up was prospectively organized up to 10 years after surgery. Adverse events and second surgeries were recorded and evaluated., Results: Ten-year follow-up data were available for 72 (81%) patients. Maintenance or improvement of the neurological state was seen in 89% of patients after 10-year follow-up. SF-36 PCS scores improved significantly at all follow-up points. SF-36 MCS improvement was significant at 4 and 6 year, but not at 8- and 10-year follow-up. Significant improvement for NDI, and Neck- and Arm-Pain scores was found for the subgroup of patients in whom these data were available. Mean angular motion of the prosthesis at 10-year follow-up was 8.6°. Mobility of the device, defined as >2° of angular motion, was reached in 81% of patients. During the study period, 21 patients (24%) developed new or recurrent radiculopathy or myelopathy, the majority of these being treated conservatively. Seven patients (8%) required 8 additional spine surgeries to treat persistent or recurrent symptoms. Of these, 2 patients (2%) were reoperated at the index level and at 5 (6%) an adjacent level., Conclusion: In this study, favorable long-term clinical outcome after implantation of the Bryan Cervical Disc Prosthesis was seen, with the majority of prostheses remaining mobile after 10-year follow-up. However, still 6% of patients required adjacent level surgery.

This study aimed at evaluating the feasibility of an implanted microphone for cochlear implants (CI) by comparison of hearing outcomes, sound quality and patient satisfaction of a subcutaneous microphone to a standard external microphone of a behind-the-ear sound processor. In this prospective feasibility study with a within-subject repeated measures design comparing the microphone modalities, ten experienced adult unilateral CI users received an implantable contralateral subcutaneous microphone attached to a percutaneous plug. The signal was pre-processed and fed into their CI sound processor. Subjects compared listening modes at home for a period of up to 4 months. At the end of the study the microphone was explanted. Aided audiometric thresholds, speech understanding in quiet, and sound quality questionnaires were assessed. On average thresholds (250, 500, 750, 1k, 2k, 3k, 4k and 6 kHz) with the subcutaneous microphone were 44.9 dB, compared to 36.4 dB for the external mode. Speech understanding on sentences in quiet was high, within approximately 90% of performance levels compared to hearing with an external microphone. Body sounds were audible but not annoying to almost all subjects. This feasibility study with a research device shows significantly better results than previous studies with implanted microphones. This is attributed to technology enhancements and careful fitting. Listening effort was somewhat increased with an implanted microphone. Under good sound conditions, speech performance is nearly similar to that of external microphones demonstrating that an implanted microphone is feasible in a range of normal listening conditions.

Severe to profound mixed hearing loss is associated with hearing rehabilitation difficulties. Recently, promising results for speech understanding were obtained with a direct acoustic cochlear implant (DACI). The surgical implantation of a DACI with standard coupling through a stapedotomy can however be regarded as challenging. Therefore, in this experimental study, the feasibility of direct acoustic stimulation was investigated at an anatomically and surgically more accessible inner ear site. DACI stimulation of the intact, blue-lined and opened lateral semicircular canal (LC) was investigated and compared with standard oval window (OW) coupling. Additionally, stapes footplate fixation was induced. Round window (RW) velocity, as a measure of the performance of the device and its coupling efficiency, was determined in fresh-frozen human cadaver heads. Using single point laser Doppler vibrometry, RW velocity could reliably be measured in low and middle frequency range, and equivalent sound pressure level (LE) output was calculated. Results for the different conditions obtained in five heads were analyzed in subsequent frequency ranges. Comparing the difference in RW membrane velocity showed higher LE in the LC opened condition [mean: 103 equivalent dB SPL], than in LC intact or blue-lined conditions [63 and 74 equivalent dB SPL, respectively]. No difference was observed between the LC opened and the standard OW condition. Inducing stapes fixation, however, led to a difference in the low frequency range of LE compared to LC opened. In conclusion, this feasibility study showed promising results for direct acoustic stimulation at this specific anatomically and surgically more accessible inner ear site. Future studies are needed to address the impact of LC stimulation on cochlear micromechanics and on the vestibular system like dizziness and risks of hearing loss.

Recently, numerous studies have shown that human dynamics cannot be described accurately by exponential laws. For instance, Barabási [Nature (London) 435, 207 (2005)] demonstrates that waiting times of tasks to be performed by a human are more suitably modeled by power laws. He presumes that these power laws are caused by a priority selection mechanism among the tasks. Priority models are well-developed in queueing theory (e.g., for telecommunication applications), and this paper demonstrates the (quasi-)immediate applicability of such a stochastic priority model to human dynamics. By calculating generating functions and by studying them in their dominant singularity, we prove that nonexponential tails result naturally. Contrary to popular belief, however, these are not necessarily triggered by the priority selection mechanism., (© 2012 American Physical Society)

Background: Many short- and intermediate-term radiological and clinical studies on cervical arthroplasty with the Bryan Cervical Disc have been published, providing, most of the time, satisfactory results., Objective: To prospectively assess the intermediate and long-term radiographic characteristics of disk replacement surgery with the Bryan Cervical Disc and to correlate these results with clinical outcome., Methods: Range of motion was measured with a validated tool. Intervertebral disk degeneration was assessed with a quantitative scoring system. Heterotopic ossification was evaluated with a previously published scoring system. Device stability was investigated by measuring subsidence and anteroposterior migration. General clinical patient outcome was assessed with the Odom classification system., Results: Eighty-nine patients were initially included in this prospective long-term study. One patient was reoperated on at the index level and 4 were reoperated on at an adjacent level; those patients were not further analyzed. The mobility at the treated level was preserved in > or = 85% of our cases. The insertion of the prosthesis did not lead to an increase in mobility at the adjacent levels. The degeneration score increased at both adjacent levels. Heterotopic ossification was present in 34% to 39% of the patients, depending on the follow-up point. No cases of anteroposterior migration or subsidence were found. More than 82% of all patients had a good to excellent clinical outcome in the long run., Conclusion: The device maintains preoperative motion at the index and adjacent levels, seems to protect against acceleration of adjacent-level degeneration as seen after anterior cervical discectomy and fusion, and remains securely anchored in the adjacent bone mass in the long run. Heterotopic ossification was frequently seen. The vast majority of all patients had a good to excellent clinical outcome.

Degeneration of intervertebral discs and facet joints is one of the most frequently encountered spinal disorders. In order to describe and quantify degeneration and evaluate a possible relationship between degeneration and biomechanical parameters, e.g., the intervertebral range of motion and intradiscal pressure, a scoring system for degeneration is mandatory. However, few scoring systems for the assessment of degeneration of the cervical spine exist. Therefore, two separate objective scoring systems to qualitatively and quantitatively assess the degree of cervical intervertebral disc and facet joint degeneration were developed and validated. The scoring system for cervical disc degeneration consists of three variables which are individually scored on neutral lateral radiographs: "height loss" (0-4 points), "anterior osteophytes" (0-3 points) and "endplate sclerosis" (0-2 points). The scoring system for facet joint degeneration consists of four variables which are individually scored on neutral computed tomography scans: "hypertrophy" (0-2 points), "osteophytes" (0-1 point), "irregularity" on the articular surface (0-1 point) and "joint space narrowing" (0-1 point). Each variable contributes with varying importance to the overall degeneration score (max 9 points for the scoring system of cervical disc degeneration and max 5 points for facet joint degeneration). Degeneration of 20 discs and facet joints of 20 patients was blindly assessed by four raters: two neurosurgeons (one senior and one junior) and two radiologists (one senior and one junior), firstly based on first subjective impression and secondly using the scoring systems. Measurement errors and inter- and intra-rater agreement were determined. The measurement error of the scoring system for cervical disc degeneration was 11.1 versus 17.9% of the subjective impression results. This scoring system showed excellent intra-rater agreement (ICC = 0.86, 0.75-0.93) and excellent inter-rater agreement (ICC = 0.78, 0.64-0.88). Surgeons as well as radiologists and seniors as well as juniors obtained excellent inter- and intra-rater agreement. The measurement error of the scoring system for cervical facet joint degeneration was 20.1 versus 24.2% of the subjective impression results. This scoring system showed good intra-rater agreement (ICC = 0.71, 0.42-0.89) and fair inter-rater agreement (ICC = 0.49, 0.26-0.74). Both scoring systems fulfilled the criteria for recommendation proposed by Kettler and Wilke. Our scoring systems can be reliable and objective tools for assessing cervical disc and facet joint degeneration. Moreover, the scoring system of cervical disc degeneration was shown to be experience- and discipline-independent.

An anastomosis performed in calcified tissues tears up faster than in healthy tissues. This study develops and validates an in vitro non-destructive method to distinguish healthy from calcified aortic tissues. An uniaxial unconfined compression test is able to distinguish healthy from calcified aortas (p<0.01). The compressive E-modulus at a strain level of 10% is 227+/-34kPa for artificially calcified and 147+/-15kPa for healthy porcine aortic tissues. Calcified aortic tissues have a lower tensile strength than healthy porcine aortic tissues (p<0.05). The ultimate tensile strength is 1.34+/-0.18MPa and 1.55+/-0.31MPa for artificially calcified and healthy porcine aortic tissues respectively. Calcified aortic tissues have a lower resistance to tearing than healthy aortic tissues (p<0.05). The resistance to tearing is 1.78+/-0.33N/mm and 2.16+/-0.64N/mm for artificially calcified and healthy porcine aortic tissues respectively.