Surgical Considerations for Partial Cochlear Implant Insertion

Validation of the accuracy of a preoperative planning tool in predicting electrode position for individualized partial cochlear implant (CI) insertions.

This retrospective study was conducted at a tertiary university hospital and included ten patients who underwent cochlear implantation with MED-EL FLEX electrode arrays. Insertion depths were individually planned using a previously proposed virtual implantation tool, employing preoperative cone-beam CT imaging and audiological data. A target insertion angle was derived from each patient's audiogram using the audiogram and CBCT data, and the corresponding insertion depth was calculated. Postoperative imaging was used to reconstruct the actual electrode position, which was compared with the preoperative prediction. Anatomic parameters and surgical access metrics, including round window angle (RWA) and visual angle (VA), were assessed to investigate potential influences on prediction accuracy.

Predicted and actual electrode positions showed high concordance, with a median insertion depth of 20.01 mm (planned) versus 19.08 mm (actual) and a median insertion angle of 344.96 degrees (planned) versus 354.60 degrees (actual). Bland-Altman analysis demonstrated small systematic deviations and good overall agreement. RWA and VA did not significantly impact prediction accuracy.

The used virtual planning tool, initially developed for full insertions, can reliably guide individualized partial electrode insertions. These findings support their clinical applicability for hearing-preservation CI strategies and highlight the need for precise anatomical assessments and high-quality imaging in surgical planning.