Advanced Bionics HiRes Ultra and Ultra 3D Series Cochlear Implant Recall: Time Course of Anomalies

Abstract

Objectives:
To estimate median survival time until the appearance of anomalies indicating a potential implant failure associated with fluid ingress in implanted cochlear implant (CI) devices of the initial version of Advanced Bionics HiRes Ultra and HiRes Ultra 3D series.

Study design:
Retrospective review.

Methods:
Cochlear implantation was performed in a standard fashion. Implant integrity was tested at follow-up visits by measuring impedance and electrically evoked compound action potential (ECAP). Additional tests such as electrical field imaging (EFI) were conducted by the manufacturer. Based on these tests, the presence or absence of an anomaly was classified.

Results:
Of the 349 devices implanted at this institution, 181 showed anomalies in accordance with the special failure mode and for this reason, 120 implants were already explanted. The median survival time without anomalies was 1062 days. So far, the suspicion of device failures has been confirmed in all cases in which a post-implantation analysis was already available.

Conclusions:
Regular tests at the follow-up visits are necessary to monitor the integrity of CIs.

Level of evidence:
3 Laryngoscope, 2022.

Full text

Advanced Bionics HiRes Ultra and Ultra 3D Series Cochlear Implant
Recall: Time Course of Anomalies
Lutz Gärtner, PhD ; Thomas Lenarz, MD
Objectives: To estimate median survival time until the appearance of anomalies indicating a potential implant failure
associated with fluid ingress in implanted cochlear implant (CI) devices of the initial version of Advanced Bionics HiRes Ultra
and HiRes Ultra 3D series.
Study Design: Retrospective review.
Methods: Cochlear implantation was performed in a standard fashion. Implant integrity was tested at follow-up visits
by measuring impedance and electrically evoked compound action potential (ECAP). Additional tests such as electrical field imaging
(EFI) were conducted by the manufacturer. Based on these tests, the presence or absence of an anomaly was classified.
Results: Of the 349 devices implanted at this institution, 181 showed anomalies in accordance with the special failure
mode and for this reason, 120 implants were already explanted. The median survival time without anomalies was 1062 days.
So far, the suspicion of device failures has been confirmed in all cases in which a post-implantation analysis was already
available.
Conclusions: Regular tests at the follow-up visits are necessary to monitor the integrity of CIs.
Key Words: advanced bionics, cochlear implant, device failure, electrical field imaging (EFI), electrically evoked
compound action potential (ECAP), HiRes Ultra, HiRes Ultra 3D, recall, survival time.
Level of Evidence: 3
Laryngoscope, 00:1–7, 2022
INTRODUCTION
On February 18, 2020, Advanced Bionics (a brand of
Sonova Holding AG, Stäfa, Switzerland) announced a volun-
tary recall of the initialversion(V1)ofits“HiRes Ultra”
and “HiRes Ultra 3D”cochlear implant (CI) devices.
1
The
reason given was that fluid ingress at the electrode has
occurred leading to interruption of stimulation, which in
turn caused a decrease in performance experienced by a
small percentage of recipients.
2
The V1 series can be identi-
fied by the serial number, which starts with a “1”followed
by six more digits.
At our clinic, anomalies in the affected CI series
were first noticed during a follow-up in April 2019 in a
HiRes Ultra Mid-Scala implant. On individual electrodes,
the impedance dropped, the current level to elicit a com-
fortable loudness perception (so-called M-level) increased,
the amplitude of the electrically evoked compound action
potential (ECAP) decreased, and speech recognition was
degraded.
3
This is a new pattern specific to this type of
failure. Between September 2016 and October 2019, we
implanted a total of 349 devices of the V1 series mentioned
above. In this retrospective study, the time course of device
anomalies and device failures is presented for the whole
cohort.
MATERIALS AND METHODS
Ethics Statement
This publication contains data collected during the clinical
routine and is approved by the ethics board of the Hannover Medi-
cal School (No. 1897-2013). The ethics board approval covers the
evaluation of all data acquired during the clinical routine. The
ethics committee waived the requirements for informed consent.
Subjects and Implants
At our clinic, the HiRes Ultra (V1) device was implanted
between September 2016 and November 2018, and the HiRes
Ultra 3D (V1) device was implanted between November 2018
and October 2019. Age at implantation was between 0.5 and
88.4 years. 74 implants were placed in children under 10 years of
age. Figure 1shows the time course of implantation regarding
the type of implant housing (“Ultra”and “Ultra 3D”) as well as
the type of electrode array (“Mid-Scala”and “SlimJ”). The follow-
ing numbers of CIs were implanted: Ultra Mid-Scala: 194; Ultra
SlimJ: 78; Ultra 3D Mid-Scala: 15; Ultra 3D SlimJ: 62.
Surgery
Cochlear implantation was performed in a standard fash-
ion.
4
A bone bed was drilled to insert the implant. A connecting
tunnel to the mastoid was created to insert the electrode.
The round window membrane was opened with a sharp cannula.
This is an open access article under the terms of the Creative
Commons Attribution-NonCommercial License, which permits use, distri-
bution and reproduction in any medium, provided the original work is
properly cited and is not used for commercial purposes.
From the Department of Otolaryngology (L.G., T.L.), Hannover
Medical School, Hannover, Germany.
Editor’s Note: This Manuscript was accepted for publication on
April 21, 2022.
The authors have no funding, financial relationships, or conflicts of
interest to disclose.
Send correspondence to Lutz Gärtner, PhD, Carl-Neuberg-Str.
1, 30625, Hannover, Germany. E-mail: gaertner.lutz@mh-hannover.de
DOI: 10.1002/lary.30151
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1
The Laryngoscope
© 2022 The Authors. The Laryngoscope
published by Wiley Periodicals LLC on
behalf of The American Laryngological,
Rhinological and Otological Society, Inc.

The electrode array was inserted atraumatically in a slow proce-
dure. In the case of a Mid-Scala electrode, the manufacturer’s
electrode insertion tool was used. The electrode carrier was fixed
in a bone slit in the posterior tympanostomy.
ECAP Measurements
This measurement proves the electrode-nerve interface and
is widely used to support fitting, especially in patients who can-
not give sufficient feedback on their auditory perception.
5
During
the clinical routine, ECAP was measured utilizing the Neural
Response Imaging (NRI) task within the clinical software
SoundWave (Advanced Bionics). The patient’s audio processor
with the coil placed over the implant was connected to a personal
computer via the CPI-3 (Clinical Programming Interface) inter-
face box. Default settings (32 averages, cathodic first stimulus,
case electrode as a reference, gain factor applied by the recording
amplifier: 300) were used.
Electrical Field Imaging
This measurement shows the longitudinal course of the elec-
tric field along the electrode array. A stimulus current Iis applied
on a given electrode contact and the intracochlear potential Uis
measured on all electrode contacts. To normalize the results, the
ratio U/I can be used as a generalized impedance value.
6
Cur-
rently, Electrical field imaging (EFI) is not available within the
clinical software. However, the manufacturer Advanced Bionics
carries out those measurements by using their “Electrical Field
Imaging and Modeling Tool”(EFIM), ver. 1.3.11 and since 2020 in
addition their “EFI Analysis Tool,”ver. 2.5. Results were assessed
by both the manufacturer and our staff.
Status of the Implanted Device Over Time
With the appearance of anomalies in several cases, we
informed our patients in May 2019 and conducted examinations
also in-between the regular follow-ups. In fact, these “V1 screen-
ings”were repeated at each visit and were not limited to patients
complaining about sound quality or deteriorated speech compre-
hension. Impedances, M-levels, and ECAP responses were mea-
sured using the clinical software SoundWave. On the same day,
the manufacturer Advanced Bionics performed additional mea-
surements, for example, EFI, to detect anomalies of the implant.
We analyzed the EFI measurement results independently
of the manufacturer and graded the status Sof the implant on
this basis. In case of doubt, ECAP measurements were taken into
account. Three categories were assigned as follows. S0: no anom-
aly observable, the EFI pattern did not show any sink, and the
electric field seems to decay with distance. S1a: slight anomaly
or anomaly on one or two electrode contacts. The EFI pattern
shows sinks which may be attributed to interacting channels.
S1b: anomaly on several electrode channels that may suggest
re-implantation.
Integrity Tests by the Manufacturer
Implanted devices were tested by Advanced Bionics at each
follow-up visit. Results were communicated to the clinic staff by
so-called “site visit reports”(SVR).
Explanted CIs were returned to Advanced Bionics for
examination. The “device failure analysis”(DFA) report, which
may take several months to complete, contains details about the
type of failure if one was found.
Reliability Reporting by the Manufacturer
The manufacturer’s reliability reporting is based on two dif-
ferent standards. The first methodology is in accordance with the
international standard ISO 5841-2,
7
the European consensus
statement on CI failures and explantations,
8
and the interna-
tional classification of reliability for implanted CI receiver stimu-
lators.
9
A patient who received the CI below the age of 18 years
is regarded as a child. The “cumulative survival rate”(CSR), also
labeled “cumulative survival percentage”(CSP), measures the
percentage of functioning devices at the given annual time inter-
vals after implantation.
In the United States, a second standard (CI86) was publi-
shed by the Association for the Advancement of Medical Instru-
mentation (AAMI).
10
Here, a patient who received the CI below
the age of 10 years is regarded as a child. The “cumulative
removal percentage”(CRP) measures the percentage of devices
that have been removed at given annually time intervals after
implantation.
Fig. 1. Overview of all cochlear implantations with Advanced Bionics HiRes Ultra and HiRes Ultra 3D devices (initial version, “V1”) over time.
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Kaplan–Meier Survival Analysis of Implanted
Devices With Anomalies
The new failure pattern, which has been observed with some
HiRes Ultra V1 and HiRes Ultra 3D V1 devices, may lead to impaired
speech comprehension and deteriorated sound quality, but still allows
for auditory perception without intermittencies. Therefore, the failure
might be difficult to detect and the necessity for re-implantation could
remain unrecognized. Since manufacturer’s reliability reports refer to
explants only, we were seeking a measure that describes the time
course of anomalies, whether they led to explantation or not. Kaplan–
Meier survival analysis
11
was used to estimate the probability that an
anomaly (status S1a or S1b) can be detected at a given time after sur-
gery. This probability has to be distinguished from the commonly used
reliability metrics CSR (or CSP).
Data were analyzed with the software IBM SPSS Statistics
27 (Armonk, NY). The parameter “time”was set as the difference
between day of measurement and the day of implantation. The
parameter “status”was given a value of “1”in case of any anomaly
(S1a or S1b), or a value of “0”when no anomaly (S0)was found. If no
anomaly was yet found, “time”refers to the measurementat the last
follow-up. The patient is labeled “right-censored”to express, that at
this time the device was fully functioning. If an anomaly was found,
“time”refers to the day, where the anomaly was detected for the
first time. In addition, three subgroups were analyzed separately,
which was accomplished by setting the “factor”inside Kaplan–
Meier analysis: (I) two-implant housing types (Ultra and Ultra 3D)
were included; (II) two electrode types (Mid-Scala and SlimJ) were
included; (III) two groups of implantees, referring to their age at
implantation (adults ≥10 years, children <10 years) were included.
Median survival time was estimated as the 50th percentile of the
survival function. Log-rank (Mantel-Cox) test was performed for
pairwise comparison within different subgroups.
RESULTS
The following analysis refers to 349 V1 series devices
implanted only in our clinic. The first V1 was explanted
in August 2017 for medical reasons due to wound healing
disorder in a young child. The second V1 was explanted
in April 2018 due to lacking ECAP responses on several
electrode contacts in a young child. In the latter case, a
failure of unknown origin was certified by the manufac-
turer and the device was rated against the CSR. Specific
patterns of the V1 anomaly were first recognized in April
2019 and described in a case report.
3
V1 screening started in May 2019 and so far more than
1100 EFI measurements have been conducted by the manu-
facturer and these were analyzed by him and our clinic staff.
Up to the end of March 2022, 121 V1 devices, corresponding
to 34.7%, were explanted at our clinic, mostly due to severe
anomalies (118 devices of status S1b, 2 devices of status S1a,
1 device for medical reasons as described above). The
explanted CIs were returned to the manufacturer for analy-
sis unless the patient disagreed.
No V1 screening tests have yet been performed on
24 implants since these patients did not follow our
repeated invitations for follow-up or already passed away.
Currently, DFA reports of explanted devices are
completed by the manufacturer in 80 cases. In 76 cases,
Advanced Bionics confirmed a device failure for the same
reason: electrode short in the electrode pocket. In two
cases, a failure of unknown origin was stated. In one case,
broken electrode wires were found as the cause of failure.
These 79 cases were rated against the CSR. One CI was
explanted for medical reasons (see above). Up until now,
our decision to re-implant was justified in all cases where
DFA reports are available.
Table Ishows the ratio of explanted versus implanted
V1 devices accumulated over time for the two different V1
implant housings (HiRes Ultra and HiRes Ultra 3D).
Kaplan–Meier survival analysis was performed with
the whole cohort of 349 V1 devices. The survival function
is shown in Figure 2. The median survival time was
1062 days, 95% confidence interval 90.5 days. In
TABLE I.
Cumulative Removal Percentage (CRP) Over Time.
Year
HiRes Ultra (V1) HiRes Ultra 3D (V1)
x/iCRP x/iCRP
Adults (≥10 years) 1 0/82 0.0% 0/64 0.0%
2 0/195 0.0% 3/64 4.7%
3 11/211 5.2% 10/64 15.6%
4 39/211 18.5% (13/64) (20.3%)
5 65/211 30.8%
6 (69/211) (32.7%)
Children (<10 years) 1 1*/28 3.6% 0/13 0.0%
2 2/57 3.5% 0/13 0.0%
3 11/61 18.0% 3/13 23.1%
4 24/61 39.3% (3/13) (23.1%)
5 34/61 55.7%
6 (36/61) (59.0%)
Note: The table shows also the exact cumulative number of explanted
(x) and implanted (i) devices up to the specified year since implantation
started. The values in parentheses are corresponding to the years that have
not yet been completed. All explantations were conducted due to V1 anoma-
lies with one exception marked by an asterisk (*), which was explanted due
to medical reasons. Patients are grouped regarding their age at implantation.
Fig. 2. Kaplan–Meier survival function for HiRes Ultra V1 and HiRes
Ultra 3D V1 series devices. Implants, which did not show any
anomalies so far (status S0), are right-censored (marked by a cross)
at the time of the last investigation. When an anomaly was
observed in an implant for the first time (status S1a or S1b), cumu-
lative survival drops. [Color figure can be viewed in the online issue,
which is available at www.laryngoscope.com.]
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TABLE II.
Statistical Data for All Subgroups.
Subgroup
I II III
Ultra Ultra 3D Mid-Scala SlimJ Adults (≥10 years)
Children
(<10 years)
Median survival time without
anomaly (days)
1093 1045 1015 1154 1130 980
95% confidence interval (days) 96.8 261.1 77.0 209.9 102.6 97.4
Number of devices 272 77 209 140 275 74
Number of devices with anomalies
(status S1a or S1b)
153 28 128 53 133 48
Period of implantation September 2016–
November 2018
November 2018–
October 2019
September 2016–
April 2019
September 2017–
October 2019
September 2016–
October 2019
September 2016–
August 2019
Note: Median survival time for the appearance of an anomaly was estimated by Kaplan–Meier analysis.
Fig. 3. Examples of E FI measurement results. The decay of the electric field is shown for each of the 16 electrode contacts alto-
gether. Eight different colors are used for this diagram. The blue shaded region just marks an impedance limit of 400 or 550 Ω,
respectively. Diagrams are from the software EFI Analysis Tool, ver. 2.5. (A) Inconspicuous findings, status S0; (B) Severe anomalies
on many electrode contacts, status S1b. Later, after re-implantation, a device failure was confirmed by the manufacturer. (C) Slight
impedance sinks are visible on E11 (black arrow). Due to anomalies in ECAP responses (see Fig. 4), this implant was graded status
S1a. (D) The same implant as shown in C, but 294 days later. A severe anomaly was found, status S1b. ECAP =evoked compound
action potential; EFI =electrical field imaging. [Color figure can be viewed in the online issue, which is available at www.
laryngoscope.com.]
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addition, analysis was done likewise for different sub-
groups. Results are shown in Table II. A log-rank test
was performed to assess whether significant differences
exist between the two types of implant housings (sub-
group I), the two types of electrode arrays (subgroup II),
and between adults and children (subgroup III). Results
show that survival distributions within the three sub-
groups do not differ significantly, subgroup I: χ
2
=1.528,
p=0.216; subgroup II: χ
2
=0.893, p=0.345; subgroup
III: χ
2
=2.537, p=0.111.
Examples of EFI measurements in three different V1
series CIs are shown in Figure 3. Usually, the electric field
is expected to decay with increasing distance to the stimu-
lating electrode (Fig. 3A). Impedances below a certain
limit are highlighted by a blue shaded region. Low imped-
ance and impedance sinks may indicate short circuits.
Fig. 4. ECAP Measurements of implant id 10162. Diagrams are from the software SoundWave, ver. 3.2.12. (A,B) ECAP responses on electrode
channel E11 (recording electrode E9). Stimulus strength is given in clinical charge units (CU). ECAP amplitude (EP) is the difference in voltage
between the negative and positive peaks, which are marked by dots. (C) The relative difference in ECAP amplitude between follow-up visits
after 114 and 674 days for all electrode contacts of the whole array. On channel 11, ECAP amplitude is reduced the most. Data are shown for
two different stimulus strengths, 200 and 250 CU, respectively. ECAP =evoked compound action potential. [Color figure can be viewed in the
online issue, which is available at www.laryngoscope.com.]
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We observed that each EFI anomaly was also accom-
panied by a decrease in ECAP amplitude or a change in
ECAP morphology. However, this was not always the
case in reverse. In rare cases, broad artifacts covered the
typical ECAP response, but the EFI pattern did not
reveal any channel interactions.
Nevertheless, ECAP measurements seem to be a valu-
able tool to discover device failures. The EFI measurement
in Figure 3C (674 days postoperatively) resembles the
example shown in Figure 3A. However, there are slight
impedance sinks visible on electrode E11, possibly indicat-
ing a short circuit. ECAP measurements show, that on E11
ECAP amplitude has decreased by about 50% in comparison
to a former measurement (114 days postoperatively) when
no impedance sink was visible on E11 (Fig. 4A,B). Nine
months later (968 days postoperatively), severe EFI anoma-
lies (status S1b) were found (Fig. 3D) and no ECAP response
could be observed up to a stimulus strength of 236 CU
(CU =manufacturer-specific clinical charge unit).
The relative difference in ECAP amplitude between two
appointments (114 and 674 days postoperatively, respec-
tively) is shown in Figure 4C for all electrode contacts. The
biggest change was observable on E11. Further investiga-
tions are necessary to confirm if consecutive ECAP measure-
ments can really predict the observed device failure. At least,
decreasing ECAP amplitudes and decreasing loudness per-
ception can be expected when the intended electrical stimulus
strength is compromised by short circuits.
DISCUSSION
In this retrospective study, we investigated the time
course of anomalies for the initial version (V1) of HiRes
Ultra and HiRes Ultra 3D CIs. The associated failure is
caused by fluid ingress nearby the ring electrode. Fluid
migrates into the electrode pocket of the implant, causing
conductive connections between some electrode leads. As a
result, the impedance on affected electrodes drops. Patients
may experience decreased loudness and the stimulation cur-
rent (M-Level) required for a pleasantly loud auditory per-
ception must then be increased. ECAP responses may
decrease in amplitude and be masked by artifacts. The fluid
does not reach the core of the implant, so intermittencies or
a complete shut-off do not occur. However, some patients
experience distorted sound, and speech comprehension may
be impaired, especially in noise.
Habituation is a crucial factor. If an anomaly occurred
very early, perhaps even immediately after implantation,
the patient will not perceive any impairment in speech rec-
ognition or sound quality because he or she has never got-
ten the opportunity to experience the full performance of
the implant. Therefore, an assessment of the status of the
implant based on speech understanding alone is insuffi-
cient. It would be interesting to analyze if speech compre-
hension scores correlate to the number and location of
affected electrode channels and corresponding parameters
like impedance and ECAP amplitude. This will be the sub-
ject of a subsequent study.
Since Advanced Bionics is on site at our clinic, V1 screen-
ing using EFI measurements could be performed at each
follow-up, regardless of whether the patient complained any
deteriorations or not. Our additional monitoring of imped-
ances and ECAP responses would be a measure that any cli-
nician or audiologist can perform themselves on a regular
basis to detect a potential anomaly. However, low impedances
alone are not usually regarded as an anomaly. Impedance
values can be affected by several mechanisms. After implan-
tation, fibrous tissue growth around the electrode array will
lead to an increase in impedance. On deactivated channels,
impedance generally increases as cells like macrophages and
fibroblasts deposit on the corresponding electrode contact as
a result of natural endogenous defense response. When the
channel is reactivated, the impedance decreases again due to
the electrical stimulation.
12,13
On the other hand, electrical
stimulation outside the compliance limit may also lead to an
increase in impedance.
14
The assessment of the status of the implant was essen-
tially based on the EFI measurements performed by the
manufacturer. This may induce some bias. However, the
measurement results were also reviewed by clinical special-
ists at our institution, and their classification did not always
agree with that of the manufacturer. Most CIs were
explanted only if, in addition to an EFI anomaly, one or more
other reasons were given as follows: a significant decrease in
speech comprehension; distorted sound perception; absence
of ECAP responses when the fitting was already based on
ECAP thresholds, as is oftenthe case in little children.
So far, each device with status S1 that was explanted,
was rated against CSR by the manufacturer after analysis.
This confirms our approach to deciding whether re-
implantation was necessary.
Kaplan–Meier survival analysis revealed no statisti-
cally significant difference in the median survival time
between the two types of electrode arrays. However, as of
the end of March 2022, anomalies (status S1a and/or S1b)
were found in 128 (61.2%) implants with Mid-Scala elec-
trode and in 53 (37.9%) implants with SlimJ electrode,
which suggests that Mid-Scala would be more susceptible
to anomalies. The apparent difference can be attributed
to the time difference from when implantation started.
We began with the HiRes Ultra Mid-Scala device in
September 2016 and 1 year later, implantations of HiRes
Ultra SlimJ started. Anomalies were initially noticed only
in Ultra Mid-Scala devices, and we considered possible
influences of surgical technique and/or electrode design.
Apparently, no other clinic had comparable issues at that
time, or regulatory authorities had not been notified by
other institutions. Later, also devices with SlimJ elec-
trode arrays showed anomalies.
Since the housing of Ultra and Ultra 3D only differs
in the design of the magnet, we would not expect any
impact on survival time. Indeed, no statistically signifi-
cant difference was found.
When we first recognized an uncommon course of CI
parameters (M-level, impedances, ECAP response) in
April 2019,
3
the manufacturer could not find any anomaly
by using EFI because some of the applied measurements
had no established test limits at that time. Meanwhile,
the EFI Analysis Tool will help to detect anomalies.
However, at least 2–3 electrodes must be affected to clas-
sify a possible device failure, depending on the specific
measurement.
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In their last global reliability report,
15
Advanced
Bionics refers to more than 12,100 HiRes Ultra V1 and
more than 6300 HiRes Ultra 3D V1 implants. Both
implant types have been removed from children about
twice as often as from adults due to device failures. As
shown in Table I, we also noticed this ratio. In contrast,
Kaplan–Meier analysis showed no significant difference
in the occurrence of anomalies between adults and chil-
dren. According to our experience, adults hesitate to get
re-implanted when the device is still working, even
though speech comprehension has deteriorated. Small
children will be re-implanted within a shorter period of
time after the appearance of severe anomalies to ensure
the best possible speech development.
Compared to Advanced Bionics’global reliability
report,
15
weseetwicetheCRP(TableI) after 4 years. There-
fore, one could speculate that the new implant failure mode
has not yet been detected in many institutions.
CONCLUSION
Continuous testing at follow-up visits is needed for
patients with CIs to monitor the full functionality of their
devices. Clinicians and audiologists should be alert for
new and unexpected failure patterns. In cases where
language development is not yet complete, re-implantation
must be considered early enough.
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