Cochlear implant receiver/stimulator fixation with and without drilling; a 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.
Therefore we propose to investigate the migration rates of the two fixation techniques (bony bed vs. subperiosteal tight pocket).

Subperiosteal tight pocket fixation technique is not inferior to the bony bed fixation technique on migration of the receiver/stimulator at 12 months.

Baseline (postoperative), 1 week, 4 weeks, 8 weeks, 3 months and 12 months after CI surgery.

Subperiosteal tight pocket fixation technique.