Ex Vivo Evaluation of a Minimally Invasive Approach for Cochlear Implant Surgery

Abstract

Drilling a minimally invasive access to the inner ear is a demanding task in which a computer-assisted surgical system can support the surgeon. Herein, we describe the design of a new micro-stereotactic targeting system dedicated to cochlear implant (CI) surgery and its experimental evaluation in an ex vivo study. Methods: The proposed system consists of a reusable, bone-anchored reference frame, and a patient-specific drilling jig on top of it. Individualization of the jig is simplified to a single counterbored hole drilled out of a blank. For accurate counterboring, the setup includes a manufacturing device for individual positioning of the blank. The system was tested in a preclinical setting using twelve human cadaver donors. Cone beam computed tomograph (CBCT) scans were obtained and a drilling trajectory was planned pointing towards the basal part of the cochlea. The surgical drill was moved forward manually and slowly while the jig constrained the drill along the predetermined path. Results: Drilling could be performed with preservation of facial nerve in all specimens. The mean error caused by the system at the target point in front of the cochlea was 0.30 mm ± 0.11 mm including an inaccuracy of 0.09 mm ± 0.03 mm for counterboring the guiding aperture into the jig. Conclusion: Feasibility of the proposed system to perform a minimally invasive posterior tympanotomy approach was shown successfully in all specimens. Significance: First evaluation of the new system in a comprehensive ex vivo study demonstrating sufficient accuracy and the feasibility of the whole concept.

Drilling accuracy evaluation of a mouldable surgical targeting system for minimally invasive access to anatomic targets in the temporal bone

“…2021 [ 10 ] MSF 0.24 0.09 0.36 0.51 10 TBS 2022 Rau et al . 2022 [ 11 ] MSF 0.51 0.35 1.10 1.56 11 TBS 2023 present study SD standard deviation, IGS image-guided surgery system, TBS temporal bone specimen, ABM artificial bone material …”

“…Depending on their level of sophistication, these concepts are tested in different laboratory settings with increasing proximity to intraoperative conditions [23]. Initially, the positioning accuracy is determined in more technical settings [12,24], followed by drilling experiments in bone-substitute material ("in vitro", [10,18,19]) and in human temporal bone specimens ("ex vivo" [11,17,[25][26][27]) before finally reaching the stage of "in vivo" testing of the procedure [4,28]. Three previously presented approaches [14,16,21] have already reached clinical application demonstrating successful implementation of minimally invasive cochlear implantation surgery in patients.…”

“…In spite of those promising results, image-guided and/or robot assisted approaches for minCIS are relatively new research topics with several technologies still at an early stage of development [ 22 ]—far from having evolved to a well-established clinical standard [ 11 , 23 ]. Common drawback of all these procedures for minimally invasive approaches on the lateral skull base is that none of them have shown any superior clinical benefit so far.…”

“…systems [7,8], customized surgical targeting systems a.k.a. microstereotactic frames [4,[8][9][10][11][12][13][14] or robotic systems [6,[15][16][17][18][19][20]. Recently, research has evolved to the description of first successful implantations in patients via a single drill tunnel through the mastoid [13,14,16,21].…”

Robotics for Cochlear Implantation Surgery: Challenges and Opportunities

“…No injuries to the facial nerve were observed, but sacrifice of the chorda tympani was necessary in one specimen due to a narrow facial recess. Human error in adjusting the moldable template was also reported in one case, which prompted researchers to look into additional security measures in the future (58).…”