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Flexion and Extension Views of C-spine

- See:
      - Anterior Subluxation:
      - Ligamentous Instability:

- Discussion:
    - the flexed view is usually most helpful in detecting ligamentous injury that is not apparent on the neutral view
    - determines the integrity of the supporting soft tissues and ligaments, as well as the stability of a known injury
           - subluxations may be the sequelae of ligamentous tears w/o frxs;
           - this malalignment may only be apparent w/ the dynamic study;
    - typically, this view is ordered at 7 to 10 days post injury when C-spine is less tender;

- Flexion View:
    - ADI in children should be less than 3.5 mm;
    - ADI in adults should be less than 3 mm;
    - alignment of cervical canal should assume gentle kyphosis
    - interspinous and interlaminar distances should remain symmetric, while facet joint & intervetebral spaces should not widen;
    - vertebral body angulation / translation:
         - patterns of instability include:
                - 1.7 mm or greater of disk widening;
                - 3.5 mm of translational displacement (vetebral body subluxation should be no greater than 1 mm as compared to extension view);
                - angulation between two adjacent vertebra of 11 deg more than contiguous cervical vertebrae;
                - measurements are made from each inferior endplate;

- Extension View:
    - mild lordosis;
    - as result of compression and rotation compenents, there is unilateral articular pillar frx, subluxation of contralateral facets, disruption of 
         anterior longitudinal ligament, & mild anterior displacement of the involved body;

- Assessment of RA:
    - need to observe any abnormal movements of the
C1-C2 level;
    - distance > 3mm between anterior arch of Atlas & front of odontoid process is abnormal as is a distance of 3-5 mm between posterior 
           borders of adjacent subaxial vertebrae;

- Contraindications:
    - altered state of consciousness (closed head injury, intoxication, or combativeness);
    - documented neurologic deficit;
    - inability of patient to flex and extend the neck w/o assistance;

- Technique:
    - views are aligned identical to the lateral of the cervical spine
    - patient flexes and extends their own neck under the supervision of the requesting physician;
    - no manual flexion/extension should be applied;
    - adequate amount of flexion is necessary for test to be meaningful;
    - support head w/ lead-gloved hand or small pillow after flexed posture is actively achieved by the patient in the supine position