ANATOMY OF THE NECK

The neck contains a number of important structures all in close proximity. The carotid artery and the internal jugular vein are juxtaposed immediately deep to the sternocleidomastoid muscle. The pharynx and its junction with the esophagus at the level of the cricopharyngeus musculature are immediately deep to the larynx and the trachea. The thyroid gland and the associated parathyroids are located in the anterior neck overlying the upper trachea. The thoracic duct is well protected as it traverses the neck and enters the jugular-subclavian system in the left neck deep to the sternocleidomastoid muscle. The cervical vertebra and the spinal cord are the most posterior structures except for the long cervical musculature.

The neck is conventionally divided into a series of triangles.¹ Most surgical discussions center on the anatomy of the anterior triangles which encompass the area between the sternocleidomastoid muscles. Functionally, the neck is divided into three zones (Figure 1). The boundaries for zone 1 include the cricoid cartilage (superiorly), the thoracic inlet (interiorly), and the sternocleidomastoid (laterally). Its surgical significance is the fact that this zone encompasses the major cervicothoracic vasculature, along with components of the aero-digestive tract. Zone III is the horizontal region of the neck cephalad to the angle of the mandible which superior border is the base of skull. It is important to note that the internal carotid artery which is cephalad to the angle of the mandible is not readily accessible surgically, necessitating special maneuvers to achieve vascular control (e.g., surgical dislocation of the mandible). However, zone II (the area between the cricoid cartilage and the angle of the mandible), is readily accessible with the most direct surgical approach being achieved with an incision along the anterior border of the sternocleidomastoid muscle (Figure 2).

Figure 1 Zones of the neck for injury stratification.

(Drawing by Doris Holloman.)

Figure 2 Incisions for operative exposure of penetrating neck injuries.

(Drawing by Doris Holloman.)

INITIAL EVALUATION

The initial evaluation of the patient suffering neck injury should be dictated by the Advanced Trauma Life Support® guidelines. Such guidelines provide a management framework to expeditiously identify life-threatening injuries and appropriately prioritize treatment. Presentations which warrant urgent surgical intervention, usually referred to as “hard signs” (Table 1) of neck injury, include subcutaneous emphysema, expanding and/or pulsatile hematoma, or brisk bleeding from the wound. All are overt findings suggestive of a major vascular or aero-digestive tract injury. Diagnostic studies are not essential for these presentations. Optimal airway management is always the first priority.

Table 1 Signs of Penetrating Neck Injury

Without the “hard signs” of injury and, consequently, a need for immediate surgical intervention, a more selective or expectant approach can be initiated. The armamentarium of this selective approach include esophagoscopy, esophagography, laryngoscopy/tracheoscopy, arteriography, or Doppler ultrasonography. Although subtle findings (so-called “soft signs”—see Table 1) such as difficulty speaking or change in voice tone could prompt such a selective evaluation, the major controversy centers around whether patients with zone II injury and no “hard findings” should undergo selective management or just observation (expectant management).

A detailed neurologic examination is required for all cervical injuries. Penetrating wounds should never be explored locally. This maneuver should only be done in the operating theater as part of a formal neck exploration. In order to limit patient gagging and coughing, insertion of nasogastric tubes or nasal tracheal suctioning should be withheld, if possible, until the induction of anesthesia in the operating theater.

AERO-DIGESTIVE INJURY

Simultaneous injuries of the airway and digestive tract are not uncommon due to the close proximity of the trachea and esophagus in the neck. According to Asensio and associates,² aero-digestive tract injuries are seen in 10% of penetrating injuries. As highlighted previously, optimal airway management is the top priority.

In a patient who requires urgent airway management, the translaryngeal endotracheal approach is still the best option, particularly when it is performed by skilled practitioners.³ The role of the surgical airway should always be considered when approaching any patient who might have a difficult airway for conventional management. However, someone who is an expert with airway management should make an attempt at rapid translaryngeal endotracheal intubation. The surgical airway of choice in a true emergency setting is a cricothyroidotomy. A tracheostomy should only be considered in the adult when there is an urgent need for an airway in a patient who you suspect might have a partial laryngo-tracheal separation. Even in that setting, an attempt should be made, if possible, by an airway expert to perform a careful translaryngeal endotracheal intubation (Figure 3).

Figure 3 Neck wound sustained during an altercation. Note that the airway is established by direct intubation of the lacerated trachea through the wound. Maintaining the patient in the sitting position until intubation is accomplished facilitates airway exposure and minimizes the risk of drowning in secretions.

After achieving airway control, and if a selective management approach is chosen, the available modalities include flexible fiber-optic laryngoscopy, flexible esophagoscopy, flexible bronchoscopy and contrast esophagography. Using a water-soluble contrast agent and multiple views of the esophagus, extravasation can be safely excluded. The 85% sensitivity and specificity of this study can be increased to near 100% by the addition of esophagoscopy.⁶ With increased experience with flexible fiber-optic scopes and enhanced technology, dependence on the use of contrast studies has lessened. Visualization of the proximal 3–5 cm of the cervical esophagus immediately inferior to the cricopharyngeal constrictor is critical for this area can be easily missed during scope insertion and withdrawal. This area has to be specifically inspected.

While direct laryngoscopy should be used to determine if there is a laryngeal injury, fiber-optic bronchoscopy is used for detection of a tracheal or bronchial injury. Alternatively, computed tomography (CT) scan of the neck may identify injuries that require further investigation or operative intervention.

If a tracheal injury is found, it should be repaired by interrupted absorbable suture reapproximating the lacerated trachea after appropriate debridement of devitalized tissue. An accompanying tracheostomy is often not needed unless there is a complex injury.

For suspected laryngeal injuries, fiber-optic endoscopy is the diagnostic procedure of choice and can be combined with surgical exploration depending on the preference of the evaluating team and the suspicion for more severe injury. Laryngeal injury, including the thyroid cartilage, vocal cords, and the arytenoid processes, may require specialized reconstruction. The grading system (Table 2) advocated by Bent et al.⁵ details their retrospective experience over an 18-year period with laryngeal injuries. The emphasis is on securing an adequate airway and addressing all associated life-threatening injuries. With laryngeal injuries, airway control is best obtained by performing a tracheostomy. Treatment delay in laryngeal injuries beyond 48 hours can lead to inferior results. However, the delay often reflects the fact that the patient is severely injured and is unable to undergo definitive management. Mucosal coaptation and fracture reduction should be performed at the time of initial exploration.

Table 2 Laryngeal Injury Classification

Source: Bent JP, Silver JR, Porubsky ES: Acute laryngeal trauma: a review of 77 patients. Otolaryngol Head Neck Surg 109:441–449, 1993.

Injury to the cervical esophagus can be difficult to diagnose and result in the development of a fulminant mediastinitis. Weigelt and associates⁶ reported only 7 of 10 injured patients with signs or symptoms of the esophageal injury. The authors noted that there is a false-negative rate of approximately 20% for either endoscopy or esophagography. When the two procedures were combined in evaluation, the false-negative rate decreased to 0%. Armstrong et al.⁷ reported a retrospective series of 23 patients with penetrating cervical esophageal injury. Contrast esophograms were only 62% sensitive, while rigid esophagoscopy was 100% sensitive. With advanced fiber-optic technology and greater operative experience, flexible endoscopy has essentially supplanted rigid esophagoscopy.

Most esophageal injuries require the basic surgical principles. Minimal debridement precedes primary closure, which should be done in two layers. An inner absorbable is followed by an outer nonabsorbable suture layer. For concomitant tracheal and esophageal wounds, interposition of viable endogenous tissues, such as muscle flaps, is essential. Complications of treatment, such as esophageal stenosis, tracheo-esophageal fistula, and infection are frequent.

Injury to the pharynx, often subtle, requires simple primary repair and drainage.

SOFT TISSUE INJURY

Care of the soft tissue follows the same principles of debridement of devitalized skin. Although primary closure can be done, constructing a flap or free tissue graft may be required in order to provide adequate soft tissue coverage, especially in large, open wounds. Penetrating wounds to the thyroid are best controlled by suture ligature although lobectomy may be warranted depending on the degree of hemorrhage, devascularization, and tissue destruction. Identified injuries to major nerves of the neck or brachial plexus should be tagged for future repair.

THORACIC DUCT INJURY

Injury at the base of the left neck risks laceration of the thoracic duct. Soft tissue injury and bleeding make identifying this injury difficult. Therefore, the classic chylous drainage may not be readily apparent at the time of initial surgical exploration.

VASCULAR INJURY IN THE NECK