Novel Dissection Station for Endolaryngeal Microsurgery and Laser Surgery: Development and Dissection Course Experience

Material and Methods

Larynx Box

We constructed a dissection station box ( Figure 1 ) from CO₂ laser-resistant material called Makrolon (Bayer Material-Science, Leverkusen, Germany). It is composed of linear polycarbonate resins and low-viscosity, high-performance thermoplastics, which completely absorb the laser energy. The polycarbonate is bought as flat plates or cylindrical tubes and thereafter cut into the required forms. The cylindrical container of 25-cm diameter is fixed with liquid bicarbonate glue on a footplate of the same material, measuring 40 cm in length and 30 cm in width. The laryngeal support hosted by the dissection station consists of a plate of 130 mm in length and 64 mm in width, with 4 incisions on each side to fix the straps, which securely fix the specimen. It is articulated in all 3 dimensions for optimal positioning as a function of the laryngeal specimen used. Required material thickness is 8 mm for the straight parts and 4 mm for the tube. The specimen remains accessible during the whole procedure through the cap on top of the box. An external articulated arm mounted on the footplate serves as holder of the laryngoscope, measuring 75 × 65 mm and with a height of 112 mm. The position (height and inclination) of the laryngoscope may be adjusted by the 2 screws. A rubber diaphragm covers the opening for the laryngoscope (40 mm in diameter). There are 4 rubber feet on the base of the station to prevent it from slipping. Total height of the device is 26.7 cm. Details on the construction are shown in Figure 2 . For optimal exposure and an ergonomic setting, the position of the laryngoscope and the laryngeal support may be amended when required. The transparent material allows constant verification of the accurate placement of the specimen, laryngoscope, and instruments during training. Moreover, it guarantees a hygienic work environment, since it can easily be cleaned and disinfected after use (even by a machine). Moreover, the lightweight larynx box (approximately 1.5 kg) is portable and may therefore be used in different facilities.

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Figure 1.

A-C, Multiple views of the ready-to-use dissection station constructed from polycarbonate resins. The laryngeal specimen and the laryngoscope are fixed on articulated arms permitting an ergonomic dissection.

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Figure 2.

Construction details. A, Internal articulated holder of the laryngeal specimen. B, External articulated holder of the laryngoscope. C, Cylindrical box measuring 25 cm in diameter and fixed on a plate, 30 × 40 cm.

The production cost is <300 euros. The Patent Cooperation Treaty has patented the dissection station as a CO₂ laser box for surgical simulation (patent 43828).

Dissection Course and Larynx Box Evaluation

In January 2016, we evaluated the dissection station during an international dissection course on the laryngotracheal framework, which was run in the Department of Otorhinolaryngology–Head and Neck Surgery at University Hospital of Modena, Italy with 24 participants.

For optimal teaching during dissection, we used our larynx box equipped with a laryngoscope with an integrated 0° endoscope (Karl Storz, Tuttlingen, Germany) connected to a portable screen with a light source (Karl Storz), which was placed in front of the dissector ( Figure 3A ). The panoramic view of the larynx offered by the endoscope allowed a thorough understanding of the anatomic structures and the teaching steps involved in the different interventions.

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Figure 3.

Endoscopic setup. A, Dissection course setup with a laryngoscope containing a 0° endoscope connected to a portable screen. B, Sample dissection. C, Overview of the dissection station in use.

Since the ovine model has been described to be suitable for laryngology training, ⁶ we used the larynges of 6-month-old lambs from the local butchery. Our Institutional Review Board approved the use of fresh ex vivo ovine laryngotracheal specimens in the larynx box. Animal welfare and slaughtering are subject to regular veterinary inspection and regulations for alimentary use. All participants were trained in cordectomy, arytenoidectomy, posterior cordotomy, and supraglottoplasty ( Figure 3 ).

After the course, each participant completed a questionnaire to subjectively evaluate the larynx box and its suitability for surgical training. We evaluated tissue properties, reliability of dissection, level of difficulty, as well as the general properties of our dissection station, such as specimen position, laryngeal exposure, suitability of the station, and whether the experience gained during the dissection would translate into clinical practice. For each question, the participants gave a rating from 1 (very poor) to 10 (excellent).

CO₂ Laser Training

The use and safety of the larynx box with use of the CO₂ laser were evaluated in our laboratories. Makrolon is also used in the production of laser protection glasses and is therefore considered to be laser safe. Moreover, polycarbonates are flame retardants and provide additional safety when used with a CO₂ laser. As expected, we did not note any damage or alterations to the dissection station during its use with the CO₂ laser.

After setting up the box as described, we performed the same exercises with cold instruments (cordectomy, arytenoidectomy, posterior cordotomy, and supraglottoplasty) using a Leica F40 microscope and a CO₂ laser ( Figure 4 ). All participants wore standard eye protection glasses as routinely used during CO₂ laser surgery.

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Figure 4.

Microscopic setup. A, Example of CO₂ laser dissection of an ovine larynx. B-D, Different angles and overview of the dissection station in use with a microscope.

Results

We assessed the suitability of our novel dissection station among 24 specialized laryngologists, with a mean experience of 14 years (range, 3-35 years). The participants came from 8 countries.

The feedback from the participants was very positive, with a mean general impression of 9.5 points (out of 10) and a mean recommendation score of 9.6 for further use. The larynx box was shown to be very convenient for surgical training, with a high rate of approval and a highly recognized utility in transforming the taught surgical steps into daily practice (9.5).

Figure 5 summarizes all results concerning the questions put to the participants during the dissection course.

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Figure 5.

Dissection course survey. Subjective performance of the larynx box is shown as x-y plot. Scores range from 0 (very poor) to 10 (excellent). Values are represented as mean ± SD.

During CO₂ laser dissection, the larynx box appeared to be safe, and no material alterations were observed. All surgeons easily performed the proposed endolaryngeal interventions.

Discussion

The system for endolaryngeal surgery presented in this study is a lightweight, safe Makrolon construction containing adjustable holders for a laryngeal specimen of any kind (human, animal) and with any laryngoscope. These precisely adjustable parts provide a realistic laryngeal exposure simulation. Moreover, the dissection station is relatively small, portable, and easy to clean and disinfect. It may be integrated without any drawbacks in an already-existing dissection and training laboratory (eg, temporal bone dissection laboratory containing a microscope) or brought to the operating room or any other facility suitable for surgical training.

Moreover, our dissection station permits use with CO₂ lasers. The polycarbonate resins used for the box absorb the laser energy, representing no danger to the environment. Therefore, the Patent Cooperation Treaty approved it for use with a CO₂ laser. The use of the CO₂ laser in endolaryngeal surgery represents an important aspect of modern surgical approaches and has its own learning curve. ¹² In our experience, training in the use of a CO₂ laser can be easily performed on fresh tissue via the described dissection station. The trainee may improve his or her understanding of tissue reactions to the application of CO₂ laser and therefore gain useful experience and not just in the handling of the instruments. Since the larynx box may be brought to the operating room or a temporal bone dissection laboratory, we may take advantage of already-existing infrastructure for education, which limits additional costs.

In 1997, Paczona presented a larynx holder composed mainly of a wooden box. ⁸ In 2012, Nasser et al presented a wooden system for education in phonomicrosurgery. ³ In our opinion, the choice of a highly durable polycarbonate resin material has several advantages over wood—namely, its weight, the possibility to clean and disinfect it, and its safety with use of CO₂ lasers. Moreover, in a wooden box, the position of the specimen, the instruments, and the laryngoscope may not be assessed during dissection without opening it. Specially designed dissection stations, including custom-made laryngoscopes^9,10 or even a wall-mounted laryngoscope, ⁴ are suitable for permanent installation in a dissection laboratory, but they are heavy and therefore not easily portable, as required during dissection courses, for example. With the system described (larynx box, 0° endoscope fixed to the laryngoscope, and portable screen with integrated light source), a dissection course may be organized with reasonable material expense at any suitable venue.

The same advantage applies to the use of CO₂ lasers, since they may not be available at every dissection laboratory. Moreover, in open designed dissection stations, the use of CO₂ lasers cannot be considered safe, as when used in a closed box made of certified material. The airway manikin with an integrated porcine larynx developed in 2012 by Nixon et al ¹¹ presents the advantage of simulating laryngeal exposure on a manikin rather than adjusting the different holders, as in all other stations (including that described here). Nevertheless, the cost-effectiveness of this model remains an issue, since these airway models are expensive, although the authors did not mention its price. Moreover, they cited the risk of fire with use of the CO₂ laser. In our opinion, dissection in the laboratory should be safe and without any compromise.

As for the use of synthetic models, ¹³ the animal model appears to be superior in terms of tissue quality and tactile feedback to the operator during dissection. Furthermore, the range of possible interventions taught on a real larynx is higher than on a synthetic model, which in fact is not as cost-effective as an animal model. ¹⁴ The use of widely available and cheap animal larynges is, in our opinion, a valuable aspect in terms of providing a lifelike educational experience.

We designed the tool described here and used during the dissection course, but we did not evaluate it. This represents a limitation of the study as compared with, for example, Dedmon et al, ⁴ who validated their simulator. Further evaluation by setting up a standardized educational program using our novel dissection station will be the subject of further research.

Conclusion

We designed and validated a highly developed dissection station for endolaryngeal surgery. The lightweight and transparent larynx box is suitable for any kind of laryngeal specimen, and any surgical intervention can be taught at reasonable cost. Moreover, it is safe and suitable for use with CO₂ lasers. Validation among experienced surgeons revealed its suitability as a teaching tool in endolaryngeal microlaser and laser surgery.

Author Contributions

Francesco Mattioli, conception and design, device construction, data acquisition, training dissection, critical revision and final approval; Livio Presutti, conception and design, senior training dissection supervision, critical revision of the manuscript and final approval; Marco Caversaccio, conception and design, interpretation of the data, critical revision of the manuscript and final approval; Marco Bonali, conception and design, training dissection, figure edition, critical revision and final approval; Lukas Anschuetz, conception and design, data acquisition and analysis, training dissection, manuscript edition and revision, final approval.

Disclosures

Competing interests: Lukas Anschuetz, research fellowship from the Bangerter-Rhyner Foundation, Bern, Switzerland, and from Karl Storz GmbH, Tuttlingen, Germany. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Sponsorships: None.

Funding source: None.