162 THE HEAD AND NECK 



membrane) is exposed in the interval between them. Through 

 this area the surgeon performs the operation of laryngotomy, 

 which may be carried out as an emergency operation when 

 some foreign body lodges in the larynx, or as a preliminary step 

 in extensive operations on the jaws or mouth. The incision is 

 vertical as it passes through the superficial structures, but the 

 actual opening in the ligament is made transversely. In this 

 way injury to the crico-thyreoid artery is avoided, and the 

 cartilages can be separated widely to facilitate the introduction 

 of the laryngotomy tube. Unlike a tracheotomy tube, which is 

 circular on section, a laryngotomy tube is oval so as to fit accur- 

 ately into the narrow gap between the cricoid and thyreoid 

 cartilages. Laryngotomy is not performed in children owing 

 to the extreme narrowness of the crico-thyreoid ligament. 



In the operation of Thyreotomy, or splitting of the thyreoid 

 cartilage, great care must be exercised to avoid injuring the 

 vocal folds. The operation is performed through a vertical 

 median incision, which passes between the depressor muscles of 

 the hyoid and the anterior jugular veins of the two sides. A 

 small opening is made in the crico-thyreoid ligament above the 

 crico-thyreoid artery, and the thyreoid cartilage is split with 

 scissors. In advanced age, calcification of the cartilage may 

 render the use of a Gigli saw necessary. It is introduced below, 

 and passed up through the rima glottidis and brought out through 

 a second small opening in the thyreo-hyoid membrane. 



Laryngectomy. In excision of the larynx the best approach 

 is obtained by a median incision, which commences at the hyoid 

 bone, and is carried downwards beyond the isthmus of the 

 thyreoid gland. A short transverse incision is made at each end, 

 and two flaps, consisting of skin, superficial fascia, and platysma, 

 are turned laterally. The superficial layer of depressor muscles 

 (p. 154) is divided, and the sterno-thyreoid is cut across low 

 down. This procedure exposes the thyreoid gland below and 

 on each side of the larynx. The pretracheal fascia is incised 

 along the medial border of the upper pole of the gland on each 

 side, and the isthmus is divided between ligatures. In this 

 part of the operation the superior thyreoid arteries (p. 167) must 

 be carefully preserved. The gland can now be separated from 

 the larynx and the trachea, which is exposed lying on the 

 anterior surface of the oesophagus. The trachea is separated 

 from the oesophagus by blunt dissection as high up as the lower 

 border of the inferior constrictor. The recurrent (laryngeal) 



