The "pull-back technique" for the 532 slim modiolar electrode
23 April 2019 (online)
The distance between the modiolus and the electrode array (EA) is one factor that has become the focus of many discussions. Positioning the EA closer to the spiral ganglion, with the goal of reducing the current spread, has been shown to improve hearing outcomes. The perimodiolar EAs can be complemented with an extra careful surgical maneuver called the “pull-back technique”. The purpose of this study is to investigate the intracochlear movements and pull-back technique for the new recently developed 532 slim modiolar electrode.
In 5 temporal bones a decapping procedure was performed. The EA was inserted and the intracochlear movements were microscopically examined and digitally captured. Three situations were analyzed: the initial insertion, the over-insertion and the pull-back position. The position of the three white markers (WM) of the EA in relation to the round window (RW) was evaluated when performing this three actions.
The initial insertion achieved an acceptable perimodiolar position of the EA, but a gap was still observed between the mid-portion of the array and the modiolus (first WM was seen in the RW). When we inserted the electrode a little deeper the mid-portion of the array was pushed away from the modiolus (second and third WM were seen in the RW). After applying the pull-back technique the gap observed during the initial insertion disappeared, resulting in an optimal perimodiolar position (first WM was once again visible in the RW).
This temporal bones study demonstrated that when applying the pull-back technique for the 532 slim modiolar electrode, a closer proximity to the modiolus was achieved when the first WM of the EA was visible in the round window.