Cochlear implant receiver/stimulator fixation with and without drilling; a single blind randomized controlled study

Cochlear implantation is a surgical procedure that requires careful planning
and execution. The correct electrode array placement in the cochlea is crucial
for optimal functionality of the device. This array is connected to the
receiver/stimulator, which is placed under the temporalis muscle, in close
proximity to the ear pinna. During cochlear implant (CI) positioning, the R/S
device should be placed close enough to the pinna, without possible
interference of the microphone in the behind-the-ear device laying (partially)
on top of the R/S device. Fixation of the device on the skull is also important
because if the device migrates towards the ear, it could cause pain or
discomfort to the patient and it could have an effect on the position of the
electrode array in the cochlea. The latter is suggested but not proven.
Surgical experts and manufacturers still reach for consensus on the correct
fixation method of the R/S device, that is to say, the method that least
endanger optimal CI functionality while also having the least intra- and
postoperative risks.
There are currently up to eleven different fixation methods being applied in
practice. In our clinic, the technique used for fixation requires drilling out
a part of the bony cortex of the skull (respecting a thin medial layer without
exposing dura mater), where the R/S device will be placed (the bony bed
technique). Another widely used technique is fixation of the device under the
periosteum and temporal muscle by creating a tight pocket (the subperiosteal
tight pocket technique). This technique has the advantage of a smaller incision
(less invasive operation), shorter operational time, and it eliminates risks of
complications that could occur when drilling out a bony bed (such as dural
damage). Creating the subperiosteal pocket might also require less manipulation
of the temporalis muscle (compared to the mentioned bony bed technique),
thereby minimizing the risk of postoperative hematoma even more.
We conducted a literature review to compare the migration rates between these
two techniques and the results were inconclusive due to a lack of
methodologically high quality studies. Thus there is no quality evidence to
support the superiority of either technique.

The primary objective of this study is to compare the migration rates of the
two fixation techniques (bony bed vs. subperiosteal pocket), and assess the
feasibility of the techniques, thereby assuring the stability of the implant
with the least patient burden. Our secondary objective is a difference in
patient-experienced burden using the validated COMPASS questionnaire

Single blind, randomized controlled trial. Patients are randomized into one of
two groups, the bony bed (group A) and the subperiosteal tight pocket technique
group (group B), with stratification for age (18-50 years, >50 years).
Stratification is applied in both study groups.

The R/S device of the CI will be fixated according to the respective group the
patient has been allocated in. All patients will undergo a Cone Beam CT (CBCT)
scan within 48 hours after surgery and at 3 and 12 months postoperatively.
Patients will fill out the PROM at 3 and 12 months postoperatively.

The burden patients will experience by participating in this study will be
undergoing three CBCT scans postoperatively and filling out a questionnaire
twice. Patients will be scheduled to undergo these scans on the same day as a
regular appointment with the audiologist of speech therapist so an extra visit
to the hospital will not be necessary. The scan exposes the patient to
radiation, albeit a reduced exposure compared to a conventional CT scan.