This diagram shows the relationship of the musculoskeletal compartment, encircled by prevertebral fascia, and the encircling investing fascia encompassing the broad flat muscles. Within the investing layer is the anterior visceral compartment and flanking areolar carotid sheaths with their neurovascular contents. The strap muscles are surrounded by an intermediate fascial layer. Between the prevertebral fascia and the visceral compartment is a continuous space from the base of the skull down into the mediastinum. Infection can ascend and descend in this space and air from an injured respiratory tree of esophagus can dissect up into the subcutaneous tissues of the head and neck.
The superior thoracic aperture is formed by the first thoracic vertebra, first ribs, manubrium and superimposed clavicles. The slope of the aperture places the arch of the subclavian artery higher than that of the vein. The transition between axillary and subclavian portions of those vessels is at the lateral border of the first rib. A variety of structures and anomalies can compress the neurovascular structures causing a “thoracic outlet” syndrome. Resection of the first rib can relieve symptoms for proper indications. Ultrasound guided central venous cannulation avoids many of the pifalls of blind puncture. Injury to the well-protected first ribs indicates major force and associated vascular injuries should be suspected.
Segments of the carotid arteries are divided at the level of the cricoid cartilage and angle of the mandible into zones I-III. While zone II injuries can be exposed directly with little difficulty, zone I injuries may necessitate sternotomy for safe proximal control. Zone III injury, or more commonly high internal carotid occlusive disease, may require temperomandibular (TM) joint dislocation for exposure.