Atraumatic cochlear implant insertion techniques (so-called ‘soft surgery’) are now standard practice in most centres for all cases (no longer just for attempted hearing preservation cases). This has led to several studies examining cochlear trauma and electrode insertion force. In this study, the authors used a microsensor attached to a model cochlea to compare intracochlear pressure changes (recording maximum amplitude change and peak frequency deviation) between a number of insertion techniques. All cases were with an Advanced Bionics 1J electrode using the insertion tool via a 1.5mm round window opening at a speed of 0.2mm/sec. The conditions tested were: freehand (no support to hand or elbow); one-point support (left hand used to support the right); two-point support (left hand supporting right and elbow resting on table); semi-automated insertion (insertion tool held but electrode advanced with a linear actuator) with one-point support; semi-automated insertion with two-point support; and fully automated insertion (insertion tool fixed to a retractor and linear actuator used to advance the electrode). Unsurprisingly, the two-point support minimised amplitude changes and frequency deviations compared to other manual techniques; this is an important conclusion that can be applied more widely to other otological procedures. Interestingly, the freehand two-point technique out-performed the semi-automated two-point technique. However, the fully automated technique scored best in all conditions. While the exact clinical effects of intra-cochlear pressure changes remain unknown, fully automated insertions may one day be routine clinical practice.

Effects of different insertion techniques of a cochlear implant electrode on the intracochlear pressure.
Todt I, Ernst A, Mittmann P.
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Stephen James Broomfield

University Hospitals, Bristol, UK.

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