In-Vitro Study of Speed and Alignment Angle in Cochlear Implant Electrode Array Insertions

Abstract

The insertion of the electrode array is a critical step in cochlear implantation. Herein we comprehensively investigate the impact of the alignment angle and feed-forward speed on deep insertions in artificial scala tympani models with accurate macro-anatomy and controlled frictional properties. Methods: Motorized insertions (n=1033) were performed in six scala tympani models with varying speeds and alignment angles. We evaluated reaction forces and micrographs of the insertion process and developed a mathematical model to estimate the normal force distribution along the electrode arrays. Results: Insertions parallel to the cochlear base significantly reduce insertion energies and lead to smoother array movement. Non-constant insertion speeds allow to reduce insertion forces for a fixed total insertion time compared to a constant feed rate. Conclusion: In cochlear implantation, smoothness and peak forces can be reduced with alignment angles parallel to the scala tympani centerline and with non-constant feed-forward speed profiles. Significance: Our results may help to provide clinical guidelines and improve surgical tools for manual and automated cochlear implantation.

Cochlear Size Assessment Predicts Scala Tympani Volume and Electrode Insertion Force- Implications in Robotic Assisted Cochlear Implant Surgery

“…Our findings were reflected in a study recently published by Aebischer et al (19). The authors reported higher insertion forces with higher insertion speed across six different ST models (19). This was reflected in our study as well.…”

“…Earlier reports by Kontorinis et al and Landry et al indicated that higher insertion speed was associated with higher insertion forces ( 17 , 18 ). Our findings were reflected in a study recently published by Aebischer et al ( 19 ). The authors reported higher insertion forces with higher insertion speed across six different ST models ( 19 ).…”

“…In this study, the quasi-linear positive correlation between ST volume and A-and B-values enabled creation of a predictive algorithm to facilitate pre-operative prediction of ST indicated that higher insertion speed was associated with higher insertion forces (17,18). Our findings were reflected in a study recently published by Aebischer et al (19). The authors reported higher insertion forces with higher insertion speed across six different ST models (19).…”

Cochlear Implant Electrode Impedance as Potential Biomarker for Residual Hearing

“…Consequently, most losses of residual hearing occurred intraoperatively or in the early postoperative phase. Reasons can be a traumatic electrode insertion (9,23,24) or an inflammatory response with resulting scar tissue formation (12)(13)(14). In addition, the presence of the electrode array can influence the mechanical properties of the cochlea and, thus, residual hearing thresholds (25,26).…”

Suitable Electrode Choice for Robotic-Assisted Cochlear Implant Surgery: A Systematic Literature Review of Manual Electrode Insertion Adverse Events

“…Intra-cochlear electrode insertion is considered one of the crucial steps of a successful CI surgery. In particular, studies have suggested that slow steady insertion (achieved more easily with robotic insertion) can reduce pressure changes within the cochlea ( 5 , 6 ), reduce insertion forces ( 7 ), and increase the likelihood of an in-axis insertion into ST and improve hearing outcomes ( 8 ). Robotic-assisted cochlear implant surgery (RACIS) aims to optimize this insertion process by (1) computer control of insertion speed and by applying insertion forces more steadily and smoothly, (2) defining the angle with which the electrode is inserted into the ST, and (3) improving the estimated insertion depth to minimize trauma and provide better hearing outcomes.…”