The reliability of hearing implants: report on the type and incidence of cochlear implant failures

Detecting and managing partial shorts in Cochlear implants: A validation of scalp surface potential testing

OBJECTIVE

To investigate the value of scalp surface potentials to identify and manage partial short circuits to ground in cochlear implant electrodes.

DESIGN

A retrospective review of patients with suspected partial short circuits.

MAIN OUTCOME MEASURE

Electrical output of individual electrodes was measured using scalp surface potentials for patients reporting a change in hearing function. Electrical output was compared to functional performance and impedance measurements to determine if devices with suspected partial short circuits were experiencing a decrease in performance as a result of reduced electrical output. Electrical output was checked in an artificial cochlea for two implants following explant surgery to confirm scalp surface potential results.

RESULTS

All patients with suspected partial short circuits (n = 49) had reduced electrical output, a drop in impedances to approximately ½ of previously stable measurements or to below 2 kΩ, an atypical electrical field measurement (EFI) and a decline in hearing function. Only devices with an atypical EFI showed reduced electrical output. Results of scalp based surface potentials could be replicated in an artificial cochlea following explantation of the device. All explant reports received to date (n = 42) have confirmed partial short circuits, with an additional four devices failing integrity tests.

CONCLUSION

Surface potential measurements can detect partial shorts and had 100% correlation with atypical EFI measurements, which are characteristic of a partial short to ground in this device. Surface potentials can help determine the degree to which the electrode array is affected, particularly when behavioural testing is limited or not possible.

Classification of cochlear implant complications using a modified Clavien-Dindo classification

OBJECTIVES

Cochlear implantation (CI) surgery is a highly effective procedure for severe to profound hearing loss, with a low complication rate. There are currently multiple grading systems for CI surgery complications, making comparison of outcomes difficult. We propose a modification to the Clavien-Dindo classification of complications, and use this modified classification to analyse our complications.

METHODS

Complications were classified as: I - Self-limiting complications requiring no treatment or simple pharmacological therapies; II - Complications requiring pharmacological interventions other than those permitted under the criteria for Grade I, or non-invasive radiological imaging; IIIa - Complications necessitating surgical, radiological or endoscopic intervention, but excluding implant explantation and/or reimplantation. IIIb - Complications necessitating implant explantation and/or reimplantation.

RESULTS

1053 patients were recorded as having had at least one cochlear implant inserted with 114 complications reported in 90 patients. The 114 complications were classified into the proposed classification with 18 (15.7%) as Grade I, 36 (31.5%) as Grade II, 17 (14.9%) as Grade IIIa and 43 (34.2%) as Grade IIIb.

DISCUSSION

We found a low complication rate, and were able to use the modified Clavien-Dindo classification system to analyse our data. We would strongly advocate for a uniform reporting system and propose this modification of a widely used system.

The Importance of a Preinsertion Integrity Device Test of Cochlear Implants

OBJECTIVES

The surgery of a cochlear implant is a complex interdisciplinary procedure with high quality standards to ensure patients safety and implant durability. An integrity test of the device prior to insertion is an additional tool to improve quality standards by detecting potentially malfunctioning implants without burdening the patient.

METHODS

At the Department of Otorhinolaryngology, University Hospital Frankfurt a. M. (Germany) since 2010 an integrity device test ("pre-insertion telemetry") has been performed prior to the implantation of a cochlear implant. The preinsertion telemetry measures the electrical impedances of the implant electrode contacts in conductive saline solution and thereby confirms regular bidirectional data transmission and electrode integrity. In the case of irregular results with suspected implant malfunction, the device was discarded during surgery and returned to the manufacturer for further technical review. Data and test results of the preinsertion telemetry and from rejected implants (manufacturers' reports) between January 2010 and December 2020 were analyzed.

RESULTS

From 2010 to 2020, 1,926 cochlear implants from three manufacturers were implanted at our institution. All implants had fully functioning bidirectional data transmission. 15 implants had irregular preinsertion telemetry results (electrode circuit failures) and were rejected during surgery. In 13 cases, the manufacturer confirmed implant malfunction. In the last 5 years, only one implant with irregular preinsertion telemetry was detected.

CONCLUSION

Preinsertion telemetry is strongly recommended as a quick and reliable integrity test of the device to confirm the functionality of a cochlear implant.

First Study in Men Evaluating a Surgical Robotic Tool Providing Autonomous Inner Ear Access for Cochlear Implantation

Image-guided and robot-assisted surgeries have found their applications in skullbase surgery. Technological improvements in terms of accuracy also opened new opportunities for robotically-assisted cochlear implantation surgery (RACIS). The HEARO^® robotic system is an otological next-generation surgical robot to assist the surgeon. It first provides software-defined spatial boundaries for orientation and reference information to anatomical structures during otological and neurosurgical procedures. Second, it executes a preplanned drill trajectory through the temporal bone. Here, we report how safe the HEARO procedure can provide an autonomous minimally invasive inner ear access and the efficiency of this access to subsequently insert the electrode array during cochlear implantation. In 22 out of 25 included patients, the surgeon was able to complete the HEARO^® procedure. The dedicated planning software (OTOPLAN^®) allowed the surgeon to reconstruct a three-dimensional representation of all the relevant anatomical structures, designate the target on the cochlea, i.e., the round window, and plan the safest trajectory to reach it. This trajectory accommodated the safety distance to the critical structures while minimizing the insertion angles. A minimal distance of 0.4 and 0.3 mm was planned to facial nerve and chorda tympani, respectively. Intraoperative cone-beam CT supported safe passage for the 22 HEARO^® procedures. The intraoperative accuracy analysis reported the following mean errors: 0.182 mm to target, 0.117 mm to facial nerve, and 0.107 mm to chorda tympani. This study demonstrates that microsurgical robotic technology can be used in different anatomical variations, even including a case of inner ear anomalies, with the geometrically correct keyhole to access to the inner ear. Future perspectives in RACIS may focus on improving intraoperative imaging, automated segmentation and trajectory, robotic insertion with controlled speed, and haptic feedback. This study [Experimental Antwerp robotic research otological surgery (EAR2OS) and Antwerp Robotic cochlear implantation (25 refers to 25 cases) (ARCI25)] was registered at clinicalTrials.gov under identifier NCT03746613 and NCT04102215.

Neuron Compatibility and Antioxidant Activity of Barium Titanate and Lithium Niobate Nanoparticles

The biocompatibility and the antioxidant activity of barium titanate (BaTiO₃) and lithium niobate (LiNbO₃) were investigated on a neuronal cell line, the PC12, to explore the possibility of using piezoelectric nanoparticles in the treatment of inner ear diseases, avoiding damage to neurons, the most delicate and sensitive human cells. The cytocompatibility of the compounds was verified by analysing cell viability, cell morphology, apoptotic markers, oxidative stress and neurite outgrowth. The results showed that BaTiO₃ and LiNbO₃ nanoparticles do not affect the viability, morphological features, cytochrome c distribution and production of reactive oxygen species (ROS) by PC12 cells, and stimulate neurite branching. These data suggest the biocompatibility of BaTiO₃ and LiNbO₃ nanoparticles, and that they could be suitable candidates to improve the efficiency of new implantable hearing devices without damaging the neuronal cells.

Investigation of the Effect of Abutment Angle Tolerance on the Stress Created in the Fixture and Screw in Dental Implants Using Finite Element Analysis

Today, an artificial tooth root called a dental implant is used to replace lost tooth function. Treatment with dental implants is considered an effective and safe method. However, in some cases, the use of dental implants had some failures. The success of dental implants is influenced by several biomechanical factors such as loading type, used material properties, shape and geometry of implants, quality and quantity of bone around implants, surgical method, lack of rapid and proper implant surface's integration with the jaw bone, etc. The main purpose of functional design is to investigate and control the stress distribution on dental implants to optimize their performance. Finite element analysis allows researchers to predict the stress distribution in the bone implant without the risk and cost of implant placement. In this study, the stresses created in the 3A.P.H.5 dental implant's titanium fixture and screw due to the change in abutment angles tolerance have been investigated. The results show that although the fixture and the screw's load and conditions are the same in different cases, the change of the abutment angle and the change in the stress amount also made a difference in the location of maximum stress. The 21-degree abutment puts the fixture in a more critical condition and increases the chance of early plasticization compared to other states. The results also showed that increasing the abutment angle to 24 degrees reduces the stress in the screw, but decreasing the angle to 21 degrees leads to increased screw stress and brings it closer to the fracture.

A retrospective review of cochlear implant revision surgery: a 24-year experience in China

PURPOSE

We aimed to analyse the reasons behind the need for cochlear implant revision surgeries, as well as the rate at which they occur, to reduce the revision surgery rate for non-device failures. We also aimed to elucidate the cumulative survival and device survival rates in different age groups.

METHODS

This retrospective single cohort study reviewed 4563 cochlear implant surgeries and 119 revision surgeries performed at a tertiary referral hospital in China between 1996 and 2019. Kaplan-Meier curves were used to calculate the cumulative survival and device survival rates.

RESULTS

The revision surgery rate was 2.61%. The reasons for revision included device (73.1%) and non-device (26.9%) failures. The most common reasons were hard device (47.1%) and non-device failure (28.6%). The 10- and 20-year cumulative survival rates were 96.8% and 96.7%, respectively. Younger children were more likely to undergo a second surgery.

CONCLUSION

This study is the longest study about revision surgery in China. Cochlear implantation is a reliable treatment. It has a low complication rate in patients with sensorineural hearing loss. Children have a higher revision rate than adults. Doctors should be aware of each complication and perform the appropriate procedure.

Device profile of the MED-EL cochlear implant system for hearing loss: overview of its safety and efficacy

INTRODUCTION

Patients suffering from severe to profound hearing loss or even deafness can achieve a hearing improvement with a cochlear implant (CI) treatment that is significantly higher than the results achieved with conventional hearing aids. The CI system consists of an implantable stimulator, which is inserted retro-auricularly into the mastoid, and an externally worn processor unit, which provides the pickup of sound and processing of acoustic information as well as the power supply for the stimulator and internal current sources. The stimulator has an electrode array that is inserted into the cochlea.

AREAS COVERED

This is a descriptive overview of MED-EL's multichannel CI system (MED-EL, Innsbruck, Austria), which was introduced to the European market in 1994. The continuing development of the implant as well as the external components is outlined and various other aspects (stimulation strategy, adaptation, results, reliability) are discussed.

EXPERT COMMENTARY

The strength of the company is the continuous pursuit of innovative ideas. This is evidenced by numerous innovations. The reliability of the implants has been continuously improved. The current SYNCHRONY models of the manufacturer show no indication of technically caused failures over an observation period of 5 years.