Learning Modern Laryngeal Surgery in a Dissection Laboratory

1. Collection of the Specimens

1. Take lamb and porcine innards from animals slaughtered for meat products.
   NOTE: Innards should be supplied by a reliable butcher who has complied with current health standards.
2. Collect the larynx together with the base of the tongue and the first five tracheal rings, in order to give stability to the specimen. Leave the remaining innards with the butcher, especially the brain and spinal cord, to avoid infective tissue.
3. Thoroughly wash the specimen and put it in a numbered box for tracking.
4. Use the specimen right away or freeze it at -18 °C and defrost it at least 24 h before the dissection.

2. Preparation of the Laboratory

1. If possible, use a sector table with a proper sink, easily washable before and after use.
2. Procure a surgical light or a traditional lamp providing sufficient illumination.
3. Put a barrier across the table at the halfway point to split it into two stations.
   NOTE: This allows for more apprentices to work at the same time and protects them from the laser beam.
4. Procure a special waste container where the specimen and used parts will eventually be discarded. Close the container, label it with the specific European Waste Catalogue (EWC) code, and dispose of it according to the institution's protocols.
5. Optionally, set the air conditioning to offset heat from all of the machinery working and maintain a steady temperature in the room.

3. Preparation of the Endoscopic Station

1. Put the specimen on a proper support, positioning the laryngoscope at the end of the surgical table (Figure 1).
   NOTE: The stand support is the one proposed by Delfo Casolino and Andrea Ricci Maccarini and is made of a metal folding structure with adjustable transverse bars²³. The stand support is equipped with a holder for a laryngoscope and a chassis for specimen positioning.
2. For the safety of the attendants, position an open wood box around the station in order to absorb potential improperly directed laser beams.
   NOTE: Recently the literature has reported a new validated station, approved for CO₂ laser surgery, called LarynxBox. This transparent structure is entirely made by polycarbonate resin, which can safely absorb all the misdirected laser beams^14,24 and could be a replacement for the wooden structure described above.
3. Insert the laryngoscope inside the specimen, expose the desired surgical target (i.e., supraglottic, arytenoid, glottic plane, etc.) and fix the laryngoscope to the support by tightening the proper screw.
   NOTE: Be sure for safety and for the precision of the surgery to firmly fix both the laryngeal specimen and the laryngoscope to the metal structure. If not, use dedicated needles or tape to steadily secure the specimen to the station.
4. Choose the proper laryngoscope for the selected laryngeal region. For example, use a wide and curved laryngoscope for the supraglottic region (i.e., Lindholm operating laryngoscope), a straight and narrow one for the vocal folds (i.e., Dedo operating laryngoscope).
5. For exposure of the vocal folds in the porcine specimen, embed the tip of the laryngoscope anterior to the arytenoid cartilages, pushing these structures in a lateroposterior direction, in order to open and put tension on the vocal folds.
6. Place a suction system inside the specimen, from above or below, in order to extract the laser fumes.
7. Put and fix in position a wet gauze inside the inferior tracheal extremity of the larynx, in order to avoid the emission of CO₂ laser from the inferior part of the specimen. In the same way, place a wet gauze at the superior border of the larynx in order to protect the areas not involved in the dissection.
8. Connect the operating microscope to the CO₂ laser, and place it on the right side of the table.
9. Ensure that the surgeon and all the participants wear safety goggles before turning on the CO₂ laser.
10. Put the endoscope or the exoscope in front of the laryngeal specimen in order to guarantee that the attendants get the same perspective as that of the first operator.
    NOTE: Make sure to put the endoscope or the exoscope above the CO₂ laser source in order to avoid a collision between the laser and the instrumentation.
11. Use an endoscope holder to maintain the optic system in place. Ensure that all the components are fixed and stable in their position for safety and for the surgical dissection.
12. Put the 4k or full high definition (FHD) monitor on the left side of the table, linked to the microscope or to the endoscopic camera.
13. Prepare a microlaryngoscopy set of surgical instruments on a table, beside the first surgeon.
    NOTE: The set should at least contain laryngeal forceps, scissors and spreader, telescope with light cable, ball end suction device, laryngeal hook, laryngeal needle, gauzes.
14. Start the dissection.

4. Preparation of the Open Surgery Station

1. Place the specimen on the other end of the sector table, inside an open box.
2. Prepare the open laryngeal surgery set on a table beside the operating field.
   NOTE: The set should at least be composed of scissors, a pair of forceps (traumatic and atraumatic), dissector, scalpels, pin cutter, hook, needle holder, and stitches.
3. Adjust the surgical light so it is on the surgical field.
4. Optionally, set the CO₂ fiber laser device.
5. Optionally, put a conventional two-dimensional (2D) camera or a three-dimensional (3D) exoscope above the surgical field and connect it to a 2D/3D monitor.
   NOTE: The tutor and the other surgeons can watch what the operator is doing and provide guidance while wearing polarized glasses.

5. (Optional) Broadcast the Dissection

1. Set up an ambient camera, capable of filming all of the room.
2. Link the two monitors, used in the dissections, to a workstation.
3. Broadcast the signal to an external room to extend the procedure to the public, to make comments, or guide the dissection remotely.

6. Endoscopic Dissection

1. Start with a bilateral vestibulectomy in order to improve the view on the glottic plane. Turn on the CO₂ laser and use a 6−10 W power, SuperPulse or UltraPulse mode, a length of 0.8−1.5 mm and a depth of 1−2 points. Use the micromanipulator in order to move the laser pointer and micro forceps in order to grab the mucosa while performing the vestibulectomy.
2. Once the vestibulectomy is performed, inject 2 mL of a NaCl solution (0.9%) into Reinke's space in order to highlight the mucosa.
3. Perform the superior cordotomy: using the CO₂ laser or the microscissors incise the mucosa longitudinally along the superior and lateral aspect of the vocal cord. Grasp the mucosa with forceps and dissect Reinke's space in order to identify the underlying vocalis muscle.
4. Perform a bilateral cordectomy, from type I to V, based on the goal of the dissection, according to the European Laryngological Society (ELS) classification by Remarcle et al.²⁵.
   NOTE: If a porcine model is used for endoscopic dissection, it is not possible to perform a type II cordectomy, because the vocal ligament is absent. Cordectomies can be performed both by CO₂ laser (4−6 W, Super or Ultrapulse mode, a length of 0.8−1.5 mm, and a depth of 1−2 points) or by cold surgical instrumentations (endoscopic microforceps and microscissors).
5. Once the cordectomy is performed, extract the surgical specimen and place it on a working table. Try to define the anatomical landmarks (e.g., anterior, posterior, and deep aspects).
6. Approach the paraglottic spaces and dissect the region for any anatomical purpose, paying attention to the anatomical landmarks and limits.
7. Perform supraglottic laryngectomies from I to IVb according to the classification of Remacle et al.²⁶ and approach the pre-epiglottic space.
   NOTE: It must be kept in mind that porcine larynges have larger arytenoids and a smaller epiglottis than in humans.

7. Open Dissection I (OPHL)

1. Dissect the strap muscles along the midline using scissors and forceps.
2. Remove the prelaryngeal tissue.
3. For larynx skeletonization, rotate the larynx contralaterally and perform, using scissors or a scalpel, an incision of the inferior constrictor muscle bilaterally along the lateral aspect of the thyroid cartilage. This procedure can also be performed with a CO₂ fiber laser²⁷, if available. Protect the superior laryngeal pedicle by retracting the larynx medially and downwards, then section the thyrohyoid ligament. Bilaterally dissect the pyriform sinus from the thyroid cartilage and the paraglottic space, as far as the inferior cornu of the thyroid cartilage.
4. Dissect the cricothyroid muscle and section the inferior cornu of the thyroid cartilage bilaterally to protect the recurrent laryngeal nerve.
5. Manually fracture the thyroid cartilage along the midline. Push with the thumbs on the laryngeal prominence while pulling forward the lateral laminae of the cartilage.
6. Using a scalpel, make the superior access along a line parallel to the superior border of the thyroid cartilage through the pre-epiglottic space. Remove the pre-epiglottic space. Modify the superior access according to the selected type of OPHL, following the ELS classification⁶.
7. Using a scalpel, make the inferior access between the cricoid ring and the first tracheal ring. Modify the inferior access according to the selected type of OPHL, following the ELS classification⁶.
8. Complete the dissection: using scissors or scalpel perform bilaterally the vertical incisions in order to connect the superior and the inferior accesses. Cut the ary-epiglottic folds, the false vocal cords, the true vocal cords, and the subglottic region. Modify the lines of incision according to the selected type of OPHL, following the ELS classification⁶.
9. Perform the pexy: apply four polyglactin 910 stitches for OPHL types I and II, and six for OPHL type III, of which one median double, between the cricoid cartilage and the hyoid bone, passing through the base of the tongue. Ensure to make the passage of the lateral stitches adherent to the superior aspect of the hyoid bone in order to not damage the lingual artery.
   NOTE: The inferior structure will vary based on the type of OPHL performed (thyroid cartilage for OPHL type I, cricoid cartilage for OPHL type II, first tracheal ring for OPHL type III).
10. Optionally, check the result in the inside-out technique using a 0° endoscopic telescope.

8. Open Dissection II (Total Laryngectomy)

1. Remove the infrahyoid muscles using the scissors.
2. Divide the thyroid gland isthmus and move the lobes off the trachea, cricoid, and inferior constrictor muscles.
3. Rotate the larynx contralaterally and incise the inferior constrictor muscle along the lateral aspect of the thyroid cartilage using scissors or scalpel. Expose the pyriform sinus bilaterally. Release the greater cornu of the thyroid cartilage on both sides.
4. Dissect bilaterally the pyriform sinus from the thyroid cartilage and the paraglottic space.
5. Dissect the suprahyoid muscles from the hyoid bone following the superior border of the bone.
   NOTE: Because in human patients the hypoglossal nerve and lingual artery are located at a depth below the greater cornu of the hyoid bone, simulate the maneuver by cutting the muscle insertion close to the medial aspect of the cornu.
6. Perform the pharyngotomy through the valleculae, the pyriform sinus, or the postcricoid area. The choice of entry point is based on the size of the tumor. Use the scissors or the scalpel for this step.
7. For inferior access, use the scalpel to incise the trachea between two tracheal rings and extend the tracheal incision posterolaterally.
8. To perform the laryngectomy in the craniocaudal direction, begin from the epiglottis and proceed through the pharyngotomy. Using the scissors, cut the aryepiglottic folds then proceed through the lateral wall of the pyriform sinus. Incise the postcricoid mucosa transversely, dissecting the plane between the trachea and the esophagus. Remove the larynx.
9. To perform the laryngectomy in a retrograde manner, use the scissors to transect the posterior membranous tracheal wall, dissecting above the trachea from the anterior esophageal wall. Incise the hypopharyngeal mucosa below the upper border of the cricoid lamina. Extend the incision to the pyriform sinus and remove the larynx.
10. Perform the primary closure of the pharynx using interrupted absorbable sutures or barbed sutures in the horizontal direction.
    NOTE: The sutures should be located submucosally on the external surface in order to avoid granulation and possible fistulas. The primary closure of the defect can be achieved easily if at least 2 cm of pharyngeal mucosa is preserved, otherwise a flap has to be harvested.