Estimation of insertion depth angle based on cochlea diameter and linear insertion depth: a prediction tool for the...

Area of Science:

• Otolaryngology
• Biomedical Engineering
• Neurosurgery

Background:

• Cochlear implant electrode array insertion depth angle is influenced by cochlear size and linear insertion depth (LID).
• The recommended LID for the CI422 implant varies between 20-25 mm.
• Accurate prediction of insertion depth angles is crucial for avoiding over-insertion and preserving low-frequency residual hearing.

Purpose of the Study:

• To investigate the influence of cochlear size and LID on the insertion depth angle of the CI422 cochlear implant electrode array.
• To develop a predictive tool for estimating insertion depth angles using preoperative cochlear diameter and LID.
• To aid surgeons in optimizing electrode array placement for residual hearing preservation.

Main Methods:

• Utilized postoperative high-resolution 3D-radiographs from Flat Panel Computed Volume Tomography (FPCT) in 37 CI422 recipients.
• Measured insertion depth angle, linear insertion depth (LID), and cochlear basal turn diameter from FPCT images.
• Analyzed correlations between cochlear diameter, LID, and insertion depth angle.

Main Results:

• Identified a wide variation in insertion depth angles (306° to 579°).
• Observed a positive correlation between linear insertion depth (LID) and insertion depth angle.
• Found a negative correlation between cochlear diameter and insertion depth angle.

Conclusions:

• Preoperatively measured cochlear diameter and selected linear insertion depth (LID) can serve as predictors for the final insertion depth angle.
• This predictive capability can assist surgeons in achieving desired electrode array placement.
• Optimized placement may enhance the preservation of residual hearing in cochlear implant recipients.