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. 2015:2015:574209.
doi: 10.1155/2015/574209. Epub 2015 Jul 5.

Cochlear Dummy Electrodes for Insertion Training and Research Purposes: Fabrication, Mechanical Characterization, and Experimental Validation

Affiliations

Cochlear Dummy Electrodes for Insertion Training and Research Purposes: Fabrication, Mechanical Characterization, and Experimental Validation

Jan-Philipp Kobler et al. Biomed Res Int. 2015.

Abstract

To develop skills sufficient for hearing preservation cochlear implant surgery, surgeons need to perform several electrode insertion trials in ex vivo temporal bones, thereby consuming relatively expensive electrode carriers. The objectives of this study were to evaluate the insertion characteristics of cochlear electrodes in a plastic scala tympani model and to fabricate radio opaque polymer filament dummy electrodes of equivalent mechanical properties. In addition, this study should aid the design and development of new cochlear electrodes. Automated insertion force measurement is a new technique to reproducibly analyze and evaluate the insertion dynamics and mechanical characteristics of an electrode. Mechanical properties of MED-EL's FLEX(28), FLEX(24), and FLEX(20) electrodes were assessed with the help of an automated insertion tool. Statistical analysis of the overall mechanical behavior of the electrodes and factors influencing the insertion force are discussed. Radio opaque dummy electrodes of comparable characteristics were fabricated based on insertion force measurements. The platinum-iridium wires were replaced by polymer filament to provide sufficient stiffness to the electrodes and to eradicate the metallic artifacts in X-ray and computed tomography (CT) images. These low-cost dummy electrodes are cheap alternatives for surgical training and for in vitro, ex vivo, and in vivo research purposes.

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Figures

Figure 1
Figure 1
Cross-section of dummy electrodes: standard fabrication procedure (a) and fabrication using filament with reduced length (b).
Figure 2
Figure 2
Samples of PET and FEP filament (a), fabricated dummy electrode F24 01 (b). The stimulation contacts (not connected) and the tracker wire are included to facilitate localization of the electrode in CT images. The opaque PET filament is not visible in this picture.
Figure 3
Figure 3
Overview of the experimental setup for automated insertion studies and components involved.
Figure 4
Figure 4
Initial position and orientation of the implant with respect to the phantom.
Figure 5
Figure 5
Insertion force curves measured during five consecutive insertions of the same FLEX28 electrode.
Figure 6
Figure 6
Mean insertion forces of three similar FLEX28 electrodes.
Figure 7
Figure 7
FLEX20 insertion force model.
Figure 8
Figure 8
FLEX24 insertion force model.
Figure 9
Figure 9
FLEX28 insertion force model.
Figure 10
Figure 10
Insertion force comparison between commercially available FLEX20 electrode (black curve) and PET filament dummy (red curve).
Figure 11
Figure 11
Insertion force comparison between commercially available FLEX24 electrode (black curve) and PET filament dummy (red curve).
Figure 12
Figure 12
Insertion force comparison between commercially available FLEX28 electrode (black curve) and dummy electrodes characterized by PET filament (red, blue, and magenta curves), FEP filament (cyan curve), and PET filament with reduced length (yellow curve).
Figure 13
Figure 13
Documentation of the insertion procedure at characteristic insertion depths (see also Figure 12) for FLEX28 and three different dummy electrode types. Due to the opaque material of the dummy electrodes, the position of the tip is indicated by a red circle.

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