Anatomy of the Axis   



- See:
      - Development & Anomalies of Axis
      - Dens Frx:
      - Extension Teardrop Frx of C2
      - Hangman's Frx
      - Normal Variants:

 

- Discussion:
    - C2 provides rotation at its superior articulation w/ C1, & limited flexion, tilt, & rotation at its inferior articulation w/ C3;
    - body of C2 is the largest of the cervical vertebrae;
    - superior articulations are on the lateral masses;
    - superior projection of the odontoid is stabilized to the C1 ring by transverse and alar ligaments;
    - lateral masses of C2 have aperture for accepting transversing vertebral artery;
    - axis is transverse vertebra w/ its superior articular facets located anterior and its inferior facets located posterior;
    - isthmus (the pedicles) between these joints is prone to frx;
    - prominent spinous process of C2 is palpable beneath of occiput;

- Normal Variants of Dens:
    - rare but may be misinterpreted as a fracture;
    - dens may be completely absent, hypoplastic, or incompletely fused to body of C2 (lesion called Os Odontoideum)
         - Os Odontoideum is smaller than normal dens & is fixed to anterior ring of C1; - the 2 move as a unit;
              - subluxation and instability are common


Effect of C1-C2 rotation on canal size.

Radiology of postnatal skeletal development. XII. The second cervical vertebra.

Computed axial tomography in C1-C2 trauma.

Axis fractures: a comprehensive review of management and treatment in 107 cases.



Original Text by Clifford R. Wheeless, III, MD.

Last updated by Data Trace Staff on Thursday, December 22, 2011 1:21 pm