Penetrating Neck Injury
The neck is inherently vulnerable to penetrating injury as large vascular structures, and the airway, lie relatively superficial to the skin. It has little native protection from ballistic projectiles with the exception of the spinal cord, which is covered by vertebrae throughout its length. The structures at highest risk are the great vessels, namely the paired carotid arteries and internal jugular veins. These structures run in parallel with one another in conjunction with the vagus nerve, and any injury to one vessel should be assumed to have damaged the other until proven otherwise. The vessels increase in size and run deeper as they travel towards the mediastinum, making direct compression, as well as surgical access, more difficult. Surface markings for these vessels are the anterior border of the sternocleidomastoid (SCM) muscle, as it runs from the mastoid down to insert into the medial third of the clavicle. The trachea starts immediately under the larynx and is palpable for the first one or two rings in most individuals with the neck extended. The cricothyroid membrane is found by running a finger below the thyroid cartilage and is easily penetrated to gain access to the airway at a point below the vocal cords. Surgical tracheostomy is undertaken usually by cutting a window into the trachea at the level of the second or third tracheal rings. Pertinent anatomy includes the isthmus of the thyroid gland, and the laryngeal nerves that run bilaterally between trachea and oesophagus (Fig. 18.1).
