The human neck contains numerous vital structures. Both blunt and penetrating injuries can damage structures from many organ systems. The challenge is to treat immediate, life-threatening complications of neck injury, such as airway compromise and hemorrhage, and also to recognize subtle signs of serious pathology.
The neck is anatomically defined by triangles, zones, and fascial planes. Each sternocleidomastoid muscle separates the neck into two descriptive triangles, anterior and posterior (Figure 1). The posterior triangle is bordered by the anterior surface of the trapezius, posterior surface of the sternocleidomastoid muscle, and the middle third of the clavicle. The anterior triangle is formed by the borders of the sternocleidomastoid muscle, inferior mandible, and midline of the neck. Most vital structures are contained within the anterior triangle.
The anterior triangle is further subdivided into three horizontal zones (Figure 2), which have historically determined whether a patient undergoes mandatory surgical exploration or further diagnostic evaluation.1 Using this classification system, the index of suspicion for injury to a particular structure is dictated by the zone (Table 1). Classically, zone II injuries undergo surgical exploration; zone I and III wounds undergo further evaluation. This zone-based approach assumes a direct correlation between the site of the external wound and damage to deep structures; however, the trajectory of the penetrating object can be difficult to determine clinically, and nearly half traverse multiple zones.2-4
Table 1 Anatomic Zone and Structures of the Anterior Neck |Favorite Table|Download (.pdf)
Table 1 Anatomic Zone and Structures of the Anterior Neck
Clavicles to the cricoid cartilage
Proximal carotid vertebral arteries
Major thoracic vessels
Cricoid cartilage to the angle of the mandible
Carotid and vertebral arteries
Angle of the mandible and the base of the skull
Distal carotid and vertebral arteries
Finally, the neck is divided into fascial planes (Figure 3). The platysma is a thin muscle that stretches from the facial muscles to the thorax, demarcating superficial from deep wounds. Wounds that do not penetrate the platysma are not life threatening. The platysma muscle is enclosed within superficial fascia anteriorly and deep fascia posteriorly. The deep fascia is comprised of the investing, pretracheal, and prevertebral fascia and the carotid sheath.5 These fascial layers compartmentalize neck structures and, thus, can prevent exsanguination by confining hematomas. Conversely, increased pressure from expanding hematoma or edema can compromise the airway. Further, the layers can serve as a conduit for ...