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. 2022 Apr;17(2):72-77.
doi: 10.1016/j.joto.2021.12.001. Epub 2021 Dec 16.

Methods for measuring pre-, intra-, and postoperative skin thickness for cochlear implants

Lena Zaubitzer  1 , Elena Schaefer  1 , Elisabeth Wallhaeuser-Franke  1 , Johannes Burkart  1 , Katrin Herrmann  2 , Beatrice Walter  1 , Angela Schell  1 , Claudia Scherl  1 , Jérôme Servais  1 , Daniel Haeussler  1
Affiliations

Methods for measuring pre-, intra-, and postoperative skin thickness for cochlear implants

Lena Zaubitzer et al. J Otol. 2022 Apr.

Abstract

Objective: This study was conducted to determine whether there is a reliable method for measuring the thickness of the retroauricular skin before, during, and after cochlear implantation, which allows the assessment of the optimal force of the external magnet of the cochlear implant (CI).

Methods: The retroauricular skin thickness of 83 patients who received a CI was measured using three different methods. The thickness was measured on pre- and postoperative CT images, as well as intraoperatively. The magnet category chosen by the surgeon was recorded when the implant was switched on and during the first follow-up visit. Correlation analyses were performed on the different skin thickness measurements and between the skin thickness and magnet strength categories.

Results: Only six patients required an exchange of the magnet until the follow-up. Although the median absolute thickness differed significantly between the three measures (p < 0.0001), their thickness values showed highly significant correlations (Pearson's r = 0.457-0.585; p < 0.01). In addition, magnet strength, was significantly correlated with the flap thickness determined pre-, post-, and during surgery. The lowest correlation with magnet strength was found in the intraoperative needle method.

Conclusion: All three measurements methods provided a suitable base for determining the ideal magnetic force. However, of particular interest were the pre- and postoperative CT measurements. The first enabled the early assessment of the required magnetic strength and thus a timely postoperative supply, whereas the latter helped to estimate the need for magnetic strength reduction during follow-up care and the feasibility of an early swith-on.

Keywords: Cochlear implant; Flap thickness; Headpiece; Magnet strength.

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Conflict of interest statement

The Author(s) declare(s) that there is no conflict of interest.

Figures

Fig. 1
Fig. 1
Measurements of skin thicknesses on preoperative CT images skin thickness was measured along a straight line that was drawn orthogonally to the skull bone (red line) into the center of the implanted magnet (green line).
Fig. 2
Fig. 2
Measurements of skin thicknesses on postoperative CT images skin thickness was measured along a straight line that was drawn orthogonally to the skull bone (red line) into the center of the implanted magnet (green line).
Fig. 3
Fig. 3
Results of the three different measurement methods.
Fig. 4
Fig. 4
Correlation between preoperative, postoperative measurement and the needle methods (95%-CI of the fitted curve is shown by the red area).
See this image and copyright information in PMC

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