The Effect of Ultra-slow Velocities on Insertion Forces: A Study Using a Highly Flexible Straight Electrode Array

Area of Science:

• Biomedical Engineering
• Neurosurgery
• Otolaryngology

Background:

• Minimizing insertion forces during cochlear implant (CI) surgery is crucial for reducing patient trauma and preserving residual hearing.
• Previous research indicates that ultra-slow insertion velocities, below manual capabilities, can significantly lower insertion forces with certain electrode arrays (EAs).

Purpose of the Study:

• To characterize insertion forces generated by a flexible straight electrode array (EA) at slow and ultra-slow velocities.
• To determine if ultra-slow insertion velocities reduce insertion forces independently of other surgical variables.

Main Methods:

• Five flexible straight electrode arrays (EAs) were tested in an artificial scala tympani model.
• Insertion forces were recorded at automated, continuous velocities ranging from 0.03 mm/s to 1.6 mm/s.

Main Results:

• An ultra-slow velocity of 0.03 mm/s yielded median insertion forces of 0.010 N at 20 mm and 0.026 N at 24.3 mm.
• These forces were 24-29% of those measured at 1.6 mm/s.
• Reducing velocity from 0.4 mm/s to 0.03 mm/s decreased insertion forces by 50%, independent of insertion depth and trial number.

Conclusions:

• Ultra-slow insertion velocities effectively decrease insertion forces for the tested electrode array, irrespective of insertion depth.
• The findings suggest that ultra-slow velocities can reduce insertion forces by at least 60% compared to humanly feasible continuous velocities (≥0.9 mm/s).