Sacroiliac joint (AP oblique view)
The AP Oblique view of the sacroiliac joint is one projection that makes up the sacroiliac series. Both sides of the SIJs are examined for comparison.
- patient positioned supine on the imaging table with legs extended
- elevate the side of interest approximately 25 to 30 degree 2
- the patient’s body should be adjusted to allow the body’s long axis to be parallel to the long axis of the x-ray table.
- AP projection
- perpendicular to the image receptor, centring 2.5 cm medial to the elevated anterior superior iliac spine 2
- laterally to include the entire sacroiliac joint of interest
- superiorly and inferiorly to include the entire joint
- 18 cm x 24 cm
- 75 kVp
- 25-30 mAs
- 100 cm
Image technical evaluation
- the sacroiliac joint farthest from the IR should be demonstrated open
- the degree of obliquity required to display the SIJ can vary greatly among patients
- radiolucent support such as a sponge can be used to help elevate the hip and thorax to maintain position
- a 20-25° cephalad angle centring 2.5 cm medial and 4 cm distal to the elevated anterior superior iliac spine may better demonstrate the sacroiliac joint free from foreshortening 2
- 1. Carver ECarver B. Medical imaging. 2nd ed. Edinburgh: Churchill Livingstone; 2006.
- 2. Frank E, Long B, Smith B, Merrill V. Merrill's atlas of radiographic positioning & procedures. 12th ed. Jeanne Olson;.