Recognition of the main landmarks on the skin (Fig. 4.2) is probably the most simple and fundamental step in all surgical head and neck procedures. Identification by palpation of laryngeal framework in sheep animal model is quite similar to human. In order to start the procedure, it is useful to identify superficial landmarks (Fig. 4.2):

Make a vertical incision about 13 cm in order to show the superficial fascia that covers muscles of the neck. Incision could be performed with 10 or 15 blades. In this step the main goal is to elevate only a cutaneous and subcutaneous flap. When all superficial fascias are exposed, surgeons have to dissect it on the midline with surgical scissors or blade. After this, to allow a good exposition of the main structures below, it is useful to suture subcutaneous tissue at the lateral skin in its upper and lower part (Fig. 4.3).

When the dissection of the superficial layers is completed, it is important to identify the main structures of laryngeal framework and muscles that surround it (Fig. 4.4).

After the identification of thyroid and cricoid cartilage with ruler and dermographic pen, sign the midline. As described in comparison anatomy, the position of anterior commissure (AC) in sheep larynx is quite similar to humans; the AC is located at the midpoint of the line between the thyroid notch and inferior border of the thyroid cartilage (Fig. 4.5).

Normally the length of vertical incision depends on extension of stenosis evaluated in preoperative endoscopic examination. The incision performed with 15 scalpels typically extends through the lower third of the thyroid cartilage (preserving the anterior commissure), the cricothyroid membrane, the anterior cricoid arch, and the upper two tracheal rings. It is useful to preserve the cricothyroid muscles. Full laryngofissure could increase the risk of destabilizing the laryngeal framework. Measure the length and width of the desired anterior expansion graft. It is mandatory to avoid off-midline incision in order to prevent incision and damage of vocal folds (VFs) (Fig. 4.6).

At the beginning you can try the same surgical step creating a tracheo-fissure in the lower trachea, to get confidence in this technique (Fig. 4.7).

In human procedure from 1970, several grafting materials were tested:

Costal cartilage is considered the best grafting material, due to its rigidity and availability in large quantities [2, 7].

Thyroid cartilage is preferred as graft material following an anterior cricoid split in premature neonates who have failed multiple extubation attempt [8].

For surgical training it is possible to use Fig. 4.8.

The Eraser, in our opinion is the better material for surgical training because is simple to shape and has low cost.

The shaping start on one side of the eraser or the perichondrial side in case of cartilage graft; a boat-shaped template is drawn to match exactly the anterior laryngeal defect, preserving superior, inferior, and lateral flanges (Fig. 4.9).