Recognition of the main landmarks on the skin (Fig. 7.2) 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. 7.2):

Make a vertical incision about 13 cm in order to show the superficial fascia that covers muscles of the neck (Fig. 7.3). 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 fascia is exposed, the surgeon has to dissect it on the midline with surgical scissor or blade. After this, to allow a good exposition of the main structures below is useful to suture subcutaneous tissue at the lateral skin in its upper and lower part (Fig. 7.3).

When the dissection of the superficial layers is completed, it is important to identify the main structures of laryngeal framework and muscles surrounding it (Fig. 7.4).

The anatomic difference between human and sheep is well described in anatomical chapter. Our goal is to perform a correct dissection plane by plane in order to respect and identify the structures.

Infrahyoid muscles are retracted laterally, resulting in optimal exposure of the lower edge of the thyroid cartilage over its entire width.

It is useful to suture the bigger muscles to subcutaneous layer in order to maintain a wide surgical field. This step simulates the strap muscle dissection on the midline performed in the human procedure in order to expose the hyoid bone and trachea. Sheep thyroid has not an isthmus, so it is not necessary to split the thyroid gland on the midline (Fig. 7.5a).

Now, it is possible to identify all the landmarks (Fig. 7.5b):

The dissection of the trachea (Fig. 7.6) is done only anteriorly and slightly laterally without identifying the recurrent laryngeal nerves (RNLs). Surgical pearls to avoid RNLs injury are: