Is the acquisition of a separate view of the sacroiliac joints in the prone position justified in patients with back pain?

One hundred consecutive patients in whom radiographs of the sacroiliac joints had been requested concurrently with radiographs of the lumbar spine and/or pelvis were reviewed to ascertain the diagnostic value of the sacroiliac radiograph. In 92 patients, radiographs of the lumbar spine or pelvis provided complete visualization of the sacroiliac joints, 81 of which were judged normal, six abnormal, and five equivocal. Review of the specific sacroiliac radiographs confirmed the six abnormal cases, and resulted in one equivocal case being judged abnormal. In no case did the sacroiliac joint radiograph result in a normal diagnosis being changed to abnormal. Where the sacroiliac joints appear normal on a lumbar spine or pelvic radiograph, there is no diagnostic benefit, and a considerable radiation penalty, from the performance of additional radiographs specific to those joints.