4.1 General Information

• C3–C7 are defined as the subaxial spine.

• Majority of flexion/extension of the neck and lateral bending occur here:

  • Maximal flexion occurs at C4/C5 and C5/C6.

  • Maximal lateral bending occurs at C2/C3, C3/C4, and C4/C5.

• Lordotic curvature: 16 to 25 degrees.

• Landmarks:

  • C2/C3: lower border of mandible.

  • C3: hyoid bone.

  • C4: thyroid cartilage.

  • C6: cricoid cartilage.

4.2 Bony Anatomy

(Fig. 4.1)

• Vertebral body:

  • Concave superiorly.

  • Convex inferiorly.

• Uncinate process:

  • Directly interacts with adjacent vertebral body above.

  • Contain articular surfaces.

• Pedicle:

  • Angled medially and superiorly.

  • Pedicles smaller than those in thoracic and lumbar spine.

• Transverse process:

  • Contains transverse foramen:

    • All cervical vertebrae have transverse foramen.

    • Anterior to nerve root groove.

    • Allow for passage of vertebral artery.

  • C6 transverse process (Chassaignac’s tubercle) is palpable.

• Lamina:

  • Bridge between lateral masses and spinous process.

• Lateral mass:

  • Lateral to junction between pedicle and lamina.

  • Contains the superior and inferior articular processes:

    • Creates the facet joint with the adjacent vertebral articular processes.

    • Superior articular facets exhibit posteromedial orientation, transitioning to posterolateral with caudal progression:

      • Supports more flexion/extension.

• Spinous process:

  • Bifid from C3 to C5.

  • C7 exhibits largest spinous process.

4.3 Ligamentous Anatomy

• Anterior ligamentous complex:

  • Anterior longitudinal ligament (ALL):

    • Traverses along anterior surface of vertebral bodies.

    • Resists extension.

  • Annulus fibrosis of the intervertebral disk.

• Middle ligamentous complex:

  • Posterior longitudinal ligament (PLL):

    • Traverses along posterior surface of vertebral bodies.

    • Resists flexion.

  • Annulus fibrosis.

• Posterior ligamentous complex:

  • Facet capsules:

    • Support facet joint for adjacent vertebra articulation and resist distractive forces.

  • Interspinous and supraspinous ligament:

    • Traverse between spinous processes:

      • Midline avascular plane.

    • Continuous with the ligamentous nuchae above C7.

  • Ligamentum flavum:

    • Deepest structure posteriorly prior to reaching spinal canal.

    • Connects the laminas of adjacent vertebrae.

4.4 Muscular Anatomy

• Fascial layers ( Fig. 4.2 ):

  • Platysma:

    • Superficial muscle.

  • Superficial layer of deep cervical fascia:

    • Contains anterior neck muscles (except longus colli) and trapezius posteriorly.

  • Prevertebral layer of deep cervical fascia:

    • Contains all posterior neck muscles deep to trapezius.

    • Covers ALL and longus colli.

  • Pretracheal fascia:

    • Contains thyroid and trachea.

  • Carotid sheath:

    • Contains carotid artery, internal jugular vein, and vagus nerve (cranial nerve X).

• Muscular layers:

  • Anterior neck muscles ( Fig. 4.3; Tables 4.1 and 4.2 ):

    • Divided into two regions: anterior neck and anterior cervical triangle:

      • Anterior cervical triangle primarily functions to move the hyoid bone.

  • Posterior neck muscles:

    • Divided into three regions: posterior neck, occipital triangle, and suboccipital triangle:

      • Posterior neck ( Table 4.3, Figs. 4.4, 4.5 ).

      • Occipital triangle ( Table 4.4, Fig. 4.6 ):

        • Borders: sternocleidomastoid (SCM; anterior), trapezius (posterior), and omohyoid (inferior).

      • Suboccipital triangle:

        • Borders: formed by the muscles it contains.

        • See Chapter 3.