Comprehensive literature review on the application of the otological surgical planning software OTOPLAN® for cochlear implantation

Abstract

Background: The size of the human cochlear, measured by the diameter of the basal turn, varies between 7 and 11 mm. For hearing rehabilitation with cochlear implants (CI), the size of the cochlear influences the individual frequency map and the choice of electrode length. OTOPLAN® (CAScination AG [Bern, Switzerland] in cooperation with MED-EL [Innsbruck, Austria]) is a software tool with CE marking for clinical applications in CI treatment which allows for precise pre-planning based on cochlear size. This literature review aims to analyze all published data on the application of OTOPLAN®.

Materials and methods: The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were applied to identify relevant studies published in the PubMed search engine between January 2015 and February 2023 using the search terms "otoplan" [title/abstract] OR "anatomy-based fitting" [title/abstract] OR "otological software tool" [title/abstract] OR "computed tomography-based software AND cochlear" [title/abstract].

Results: The systematic review of the literature identified 32 studies on clinical use of OTOPLAN® in CI treatment. Most studies were reported from Germany (7 out of 32), followed by Italy (5), Saudi Arabia (4), the USA (4), and Belgium (3); 2 studies each were from Austria and China, and 1 study from France, India, Norway, South Korea, and Switzerland. In the majority of studies (22), OTOPLAN® was used to assess cochlear size, followed by visualizing the electrode position using postoperative images (5), three-dimensional segmentation of temporal bone structures (4), planning the electrode insertion trajectory (3), creating a patient-specific frequency map (3), planning of a safe drilling path through the facial recess (3), and measuring of temporal bone structures (1).

Conclusion: To date, OTOPLAN® is the only DICOM viewer with CE marking in the CI field that can process pre-, intra-, and postoperative images in the abovementioned applications.

Keywords: Anatomy based fitting; Cochlear duct length; Computed tomography-based software ear/cochlear; Computer simulation; Imaging modalities (MRI, computer tomography [flat-panel volume CT]).

Fig. 1

Flowchart depicting the literature review process using the guidelines of Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA)

Fig. 2

Exemplary representation of the preoperative planning of a cochlear implantation and visualization of an implanted electrode with direct cochlear access pathway. Measurement of the cochlea using the corresponding parameters in the “cochlear view,” generated by rotation around the body axes. Axial view (a), coronal view (b), sagittal view (c), and three-dimensional visualization of the temporal bone, ossicles, and facial nerve (d). Blue double arrow diameter, green double arrow width, and red double arrow height. Postoperative image of a direct cochlear access (DCA) pathway with an electrode inside (e). (e From the open access publication of Jablonski et al. 2021 [27] © Jablonski et al.; CCBY4.0; https://creativecommons.org/licenses/by/4.0/)

Fig. 3

Visualization of a postoperative position control and determination of the individual electrode contacts. The evaluation in the three body planes is shown—axial (a), coronal (b), sagittal (c)—and the 3D representation of the implant (d). By moving the lines in the three body planes, each electrode can be individually controlled in the center position. blue arrow diameter line, green arrow width line, red arrow height line

Fig. 4

Exemplary representation of a patient-fitted electrode insertion with respect to electroacoustic stimulation

Fig. 5

Mastoid thickness measurement on axial (a) and coronal (b) planes

Fig. 6

Suboptimal view of the cochlea where the size was measured in the oblique coronal plane (a) and in the axial plane (b). (a From Grover et al. [23], reproduced with permission © Springer Nature, all rights reserved; b from Mertens et al. [38], © G. Mertens et al.; CCBY4.0; https://creativecommons.org/licenses/by/4.0/)