Impact of Insertion Speed, Depth, and Robotic Assistance on Cochlear Implant Insertion Forces and Intracochlear Pressure: A Scoping Review

Abstract

Cochlear implants are crucial for addressing severe-to-profound hearing loss, with the success of the procedure requiring careful electrode placement. This scoping review synthesizes the findings from 125 studies examining the factors influencing insertion forces (IFs) and intracochlear pressure (IP), which are crucial for optimizing implantation techniques and enhancing patient outcomes. The review highlights the impact of variables, including insertion depth, speed, and the use of robotic assistance on IFs and IP. Results indicate that higher insertion speeds generally increase IFs and IP in artificial models, a pattern not consistently observed in cadaveric studies due to variations in methodology and sample size. The study also explores the observed minimal impact of robotic assistance on reducing IFs compared to manual methods. Importantly, this review underscores the need for a standardized approach in cochlear implant research to address inconsistencies and improve clinical practices aimed at preserving hearing during implantation.

Keywords: angular depth; cochlear implantation; cochlear trauma; electrode design; hearing preservation; insertion approach; insertion depth; insertion forces; insertion speed; intracochlear pressure; robotic assistance.

Figure 2

Impact of insertion speed on insertion forces and intracochlear pressure. (A) Studies were performed on cadaveric specimens [11,52]. The study of intracochlear pressure was evaluated using a nonparametric regression technique called Locally Weighted Scatterplot Smoothing (LOWESS). (B) Studies performed in artificial cochlea models [11,18,27,31,34,40,43,51,53]. The impact of insertion speed on insertion force is displayed in the logarithmic y-axis; hence, the linear regression lines appear curved. The color corresponds with the study, and the points and error bars represent mean and standard deviation, except in the case of cadaveric intracochlear pressure measurement, where these represent the median and interquartile range.

Figure 1

PRISMA flowsheet showing number of search results. The figure was generated using the PRISMA Flow Diagram tool [32].

Figure 3

Impact of insertion depth on the IFs measured in cadaveric specimens (A) [10,11,38,39,44,45,48,57] and in artificial cochlea models (B) [11,13,14,18,23,28,29,37,39,40,41,42,43,44,46,47,51,53,58] with angular insertion depth in degrees and insertion distance in mm. (B-II) has y-axis with a logarithmic scale. The color corresponds with the study, and the points and error bars represent the mean and standard deviation.

Figure 4

Impact of robotic insertion on mean maximal IFs measured in cadaveric specimens (I) [10,11,26,38,39,44,45,48,57] and artificial cochlea models (II) [11,13,14,18,23,28,29,37,39,40,41,42,43,44,46,47,51,53,58]. Unweighted two-sample t-tests were used for both diagrams with no significant difference found (box charts not weighted). Red line—median; black box—interquartile range; red crosses—outliers.

Figure 5

Impact of robotic insertion on pressure measurements in artificial cochlea models [19,20,22,30,31,34,35,36]. Unweighted two-sample t-tests were used for (I,III,IV), with significant differences found in mean pressure measurements (box charts not weighted, p < 0.001). A weighted t-test was used for (II), highlighting a significant difference between manual and robotic insertion (p = 0.011). Red line—median; black box—interquartile range; red crosses—outliers.

Figure 6

Distribution of trauma occurrences by angular insertion depth, surgical approach, and cochlear implant type in human cadaveric cochlear implantation studies: (I) comparison of cochleostomy (CO) and round window (RW) approaches. (II) evaluation of lateral wall (LW) and perimodiolar (PM) cochlear implants. Trauma locations are categorized by angular insertion depth in degrees: 0–50; 50–100; 100–150; 150–200; 200–250; above 250 degrees. Trauma levels follow the Eshraghi et al. scale [12]. Bubble size and accompanying number indicate the number of trauma occurrences.