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