- Discussion:
    - instability = cephalic displacement of posterior sacroiliac complex of at least 5-15 mm on inlet and outlet views;
    - look for gap (rather than impaction) posteriorly, & frx of 5th lumbar transverse process or avulsion of sacrospinous ligament;

- Pertinent Radiographs:
      - AP view
      - Inlet and Outlet Views
      - Judet View

- Push-Pull Views:
    - used to evaluate dynamic displacement of the pelvis;
    - these views are obtained as in outlet view with the examiner pushing on the femur for one view and pulling on it for the other;

- Sacroiliac Views:
    - used to visualize the sacroiliac joints;
    - pt is positioned as for Judet views w/ central beam directed toward sacroiliac joint;
    - only CT scan of the pelvis gives well detailed image of SI joint;
    - neither the iliac or obturator oblique radiographs shows this well;

- Lateral View:
    - required if sacral frx is suspected;
    - technique is identical to lateral view of lumbar spine except that it is centered on the sacrum;

- Arteriography:
    - indicated for patients w/ concomitant pelvic frx and hemodynamic instability, especially when there is frx displacement thru the greater sciatic notch

Pelvic and Lower Extremity Trauma--Symposium: The Role of Standard  Roentgenograms in the Evaluation of Instability of Pelvic Ring Disruption.

The role of standard roentgenograms in the evaluation of instability of  pelvic ring disruption.