Influence of surgeon experience on the incidence of tip fold-over with slim preformed cochlear implant electrodes

To assess whether increasing experience with implantation of a thin preformed electrode array for perimodiolar insertion reduces the incidence of tip fold-over (TFO).

The retrospective study included 100 patients who received a cochlear implant (CI) with the Slim Modiolar (SM) electrode array (Cochlear, Sydney, Australia) at a university CI centre between November 2015 and December 2022. Postoperative radiological imaging was performed to verify electrode position. Surgical reports and radiological images were reviewed and the incidence of TFO was analyzed for three experienced CI surgeons. In addition, the incidence of intraoperative measurements showing evidence of electrode malposition and the mean duration of surgery over time were documented.

129 SM implantations in 100 patients were included. In seven cases (5.4%) TFO was radiologically detected and successfully revised. In eight cases (6.2%), electrophysiological measurements indicated misplacement and the position was corrected during the same surgery. For one surgeon, five out of 67 implantations (7.5%) were affected by TFO, with the frequency of this complication decreasing over time. The average surgery time for all surgeons was 122.2 (± 44.2) minutes, with two surgeons showing a decrease over time.

The results show a tendency that the SM electrodes can be implanted with a lower complication rate and faster over time. Therefore, it can be assumed that the implantation of the SM electrode requires a certain amount of practice, even for experienced surgeons. As intraoperative electrophysiological measurements detected 71.4% of all radiologically confirmed TFOs, their use is highly recommended.