Anterior Subluxation (Hyperflexion Sprain) & Wedge Frx

- See: Hyperflexion Injuries

- Discussion:
    - partial or complete tear of posterior ligaments w/ varying degrees in widening of the interspinous and interlaminar spaces, as well as 
         subluxation, but not dislocation of Facet Joint;
    - hyperflexion sprain injury may include mild anterior subluxation of involved vertebral body;
    - this subluxation may be so subtle that it may only be appreciatted on lateral films obtained in flexion;
    - that stable injuries to Anterior column include compression frx of < 25% loss of vertebral body height & anteroinferior avulsion frxs 
         where the fragment width is < 20% of vertebral body width;
    - that unstable injuries to Anterior column include compression frxs w/ > 25% loss of ht indicating posterior ligament rupture, and 
         fractures thru vertebrae;
    - frx lines seen on lateral radiographs or CT scans, which extend thru vertebral body centrum in coronal plane represent 
         anterior column failure;
- Subluxation in RA:
    - anterior subluxation occurs as the result of Facet Joint disease and is most commonly seen at C5/6 level, which is level of greatest mobility;
    - any level may be affected, however, and it is common to see several levels showing anterior subluxation in a stepwise fashion;
    - subaxial involvement in R.A. in less common than atlantoaxial lesions;
- Powers Ratio:
    - identifies anterior subluxation and is described as ratio of BC/OA
    - BC is distance from basion to midvertical portion of posterior laminar line of the Atlas;
    - OA is distance from opisthion to midvertical portion of posterior surface of anterior ring of Atlas;
    - if this ratio is greater than 1, anterior subluxation exists

Upper cervical instability in rheumatoid arthritis.

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

Last updated by Data Trace Staff on Thursday, December 22, 2011 11:57 am