Real-Time Light-Guided Vocal Fold Injection: Ex Vivo Feasibility Study in a Canine Model

    Vocal fold paralysis is a well-known complication of thyroidectomy. The transcricothyroid(CT) membrane approach is a good option for office-based vocal fold injection(VFI). However, because the needle tip is invisible during injection using CT approach, precise localization requires high level of experience, and mastering this approach involves steep learning curve. To overcome current limitations, we conceptualized a novel technique: real-time light-guided VFI(RL-VFI), which enables simultaneous VFI under direct visualization of the lighted needle tip. Herein, we aimed to verify the feasibility of RL-VFI in cadaveric canine model, simulating the setting of office-based VFI, as well as to explore its clinical usefulness.

    Customized prototype device was developed. It consisted of three parts: light source,controller,and injector. Light source comprised laser diodes of two wavelengths(635nanometers[nm], red; 532nm, green). Four types of injector were developed using 40-mm needles of 23- and 25-gauge and optic fibers of 50 and 100?m. ex vivo canine larynx was prepared for the experiment. Flexible laryngoscopy system was used to examine canine vocal folds.

    Various routes from three insertion points (3mm, 10mm,and 17mm from the midline) were validated using the device. Regardless of the injection routes, the location of the needle tip was accurately indicated by light. RL-VFI was feasible under light guidance without difficulties. Moreover, precise and simultaneous re-injection could be performed at the intended point using the device.

    CONCLUSION:We introduced RL-VFI in an ex vivo canine larynx, simulating the setting of office-based VFI. Clinical application of RL-VFI will improve safety and precision of CT approach, as well as expand its applications.


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