Neck Zones in Medical Practice
The neck is divided into three anatomic zones based on bony and cartilaginous landmarks: Zone I extends from the clavicles/sternal notch to the cricoid cartilage, Zone II extends from the cricoid cartilage to the mandibular angle, and Zone III extends from the mandibular angle to the skull base. 1
Anatomic Boundaries
Zone I (Inferior Zone): Extends from the clavicles and sternal notch superiorly to the cricoid cartilage 1
- This is the most inferior zone and contains the thoracic outlet vessels, subclavian vessels, vertebral arteries, trachea, esophagus, and thyroid gland
- Surgical access is most challenging in this zone due to bony constraints of the thoracic inlet
Zone II (Middle Zone): Extends from the cricoid cartilage inferiorly to the angle of the mandible superiorly 1
- This is the largest and most commonly injured zone
- Contains the carotid arteries, internal jugular veins, pharynx, larynx, esophagus, recurrent laryngeal nerves, and spinal cord
- Historically, this zone was most accessible for surgical exploration 1
Zone III (Superior Zone): Extends from the angle of the mandible inferiorly to the skull base superiorly 1, 2
- This is the most superior zone and surgical access is limited by the mandible and skull base
- Contains the distal internal carotid artery, vertebral arteries, and cranial nerves IX-XII
- Injuries here are difficult to expose surgically 2
Clinical Relevance and Evolution of Management
The traditional zone-based approach to penetrating neck trauma is being replaced by a "no-zone" approach that focuses on clinical signs and imaging findings rather than anatomic location. 1, 3, 4, 5
Historical Zone-Based Management
- Traditionally, Zone II injuries underwent mandatory surgical exploration 1
- Zone I and III injuries were evaluated with angiography and other imaging before deciding on surgical intervention 1, 2
- This approach led to high rates of non-therapeutic explorations and associated complications 4, 5
Modern "No-Zone" Approach
- The American College of Radiology now recommends a selective approach based on clinical signs (hard vs. soft signs) rather than anatomic zones alone 1, 3
- CT angiography (CTA) has sensitivity of 90-100% and specificity of 98.6-100% for detecting vascular injuries, enabling safe selective management regardless of zone 3, 6, 4
- This approach reduces unnecessary invasive procedures while maintaining patient safety 4, 5
Key Clinical Pitfall
While anatomic zones remain useful for describing injury location and understanding surgical access challenges, they should not dictate management algorithms in the modern era. 3, 4, 5 The presence or absence of hard signs (active hemorrhage, expanding hematoma, hemodynamic instability, airway compromise) determines the need for immediate surgical exploration, not the zone of injury 3, 7.