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Occipital-Atlanto-Axial Injuries

- Discussion:
    - highest percentage of missed injuries occur in this region;

- Exam:
    - Torticollis:

- Radiographs:
    - Atlanto-occipital Disassociation
          - C1-C2 interspinous space should not be greater than 10 mm;
          - occipital condyles should articulate w/ lateral masses of C1, but this relationship cannot be evaluated on single lateral film;
    - Atlanto-axial Subluxation
          - ADI in children (< 10 yrs) < 3.5 mm; (see pediatric C-spine)
          - ADI in adults < 3 mm;
                - an anterior shift of C1 on C2 of more than 3-5 mm implies injury to transverse ligament (see atlanto-axial subluxation;
                - shift > 5 mm implies injury transverse & alar ligaments;
          - SAC:
                - > 18  mm - normal;
                - 15-17 mm - grey zone;
                - < 14  mm - cord compression;
    - Atlas (Jefferson frx)
    - Odontoid Frx / Hangman frx)

    - Wachenheim's line
          - used to determine anterior / posterior subluxation
          - this line is drawn down posterior surface of clivus & its inferior extension should barely touch posterior aspect of odontoid tip;
          - this relationship does not change in flexion and extension;
          - if this line runs behind the odontoid, posterior subluxation has occured and vice versa;
    - Posterior relationships are assessed by a line extending from the posterior foramen magnum to the posterior laminae of C1;
          - this line may curve gently, but should not have a sig step off

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