4.1 General Information

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  C3–C7 are defined as the subaxial spine.

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

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

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

  
  
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  Lordotic curvature: 16 to 25 degrees.

  
  
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  Landmarks:

  
  
  
  
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    C2/C3: lower border of mandible.

    
    
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    C3: hyoid bone.

    
    
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    C4: thyroid cartilage.

    
    
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    C6: cricoid cartilage.

4.2 Bony Anatomy

(Fig. 4.1)

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  Vertebral body:

  
  
  
  
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    Concave superiorly.

    
    
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    Convex inferiorly.

  
  
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  Uncinate process:

  
  
  
  
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    Directly interacts with adjacent vertebral body above.

    
    
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    Contain articular surfaces.

  
  
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  Pedicle:

  
  
  
  
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    Angled medially and superiorly.

    
    
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    Pedicles smaller than those in thoracic and lumbar spine.

  
  
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  Transverse process:

  
  
  
  
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    Contains transverse foramen:

    
    
    
    
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      All cervical vertebrae have transverse foramen.

      
      
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      Anterior to nerve root groove.

      
      
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      Allow for passage of vertebral artery.

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

  
  
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  Lamina:

  
  
  
  
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    Bridge between lateral masses and spinous process.

  
  
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  Lateral mass:

  
  
  
  
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    Lateral to junction between pedicle and lamina.

    
    
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    Contains the superior and inferior articular processes:

    
    
    
    
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      Creates the facet joint with the adjacent vertebral articular processes.

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

      
      
      
      
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        Supports more flexion/extension.

  
  
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  Spinous process:

  
  
  
  
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    Bifid from C3 to C5.

    
    
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    C7 exhibits largest spinous process.

4.3 Ligamentous Anatomy

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  Anterior ligamentous complex:

  
  
  
  
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    Anterior longitudinal ligament (ALL):

    
    
    
    
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      Traverses along anterior surface of vertebral bodies.

      
      
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      Resists extension.

    
    
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    Annulus fibrosis of the intervertebral disk.

  
  
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  Middle ligamentous complex:

  
  
  
  
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    Posterior longitudinal ligament (PLL):

    
    
    
    
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      Traverses along posterior surface of vertebral bodies.

      
      
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      Resists flexion.

    
    
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    Annulus fibrosis.

  
  
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  Posterior ligamentous complex:

  
  
  
  
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    Facet capsules:

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

    
    
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    Interspinous and supraspinous ligament:

    
    
    
    
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      Traverse between spinous processes:

      
      
      
      
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        Midline avascular plane.

      
      
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      Continuous with the ligamentous nuchae above C7.

    
    
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    Ligamentum flavum:

    
    
    
    
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      Deepest structure posteriorly prior to reaching spinal canal.

      
      
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      Connects the laminas of adjacent vertebrae.

4.4 Muscular Anatomy

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  Fascial layers ( Fig. 4.2 ):

  
  
  
  
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    Platysma:

    
    
    
    
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      Superficial muscle.

    
    
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    Superficial layer of deep cervical fascia:

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

    
    
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    Prevertebral layer of deep cervical fascia:

    
    
    
    
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      Contains all posterior neck muscles deep to trapezius.

      
      
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      Covers ALL and longus colli.

    
    
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    Pretracheal fascia:

    
    
    
    
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      Contains thyroid and trachea.

    
    
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    Carotid sheath:

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

  
  
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  Muscular layers:

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

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

      
      
      
      
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        Anterior cervical triangle primarily functions to move the hyoid bone.

    
    
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    Posterior neck muscles:

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

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

        
        
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        Occipital triangle ( Table 4.4, Fig. 4.6 ):

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

        
        
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        Suboccipital triangle:

        
        
        
        
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          Borders: formed by the muscles it contains.

          
          
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          See Chapter 3.