Radiographic diagnosis of sacroiliitis--are sacroiliac views really better?

OBJECTIVE: To determine whether detailed oblique radiographs of the sacroiliac (SI) joints provide significant diagnostic advantage to a single AP projection of the pelvis in establishing the presence and severity of sacroiliitis. METHODS: Radiographs (both AP pelvis and detailed oblique projections) of 445 right SI joints and 442 left SI joints were obtained from patients with an established diagnosis of a seronegative spondyloarthropathy, and interpreted for severity. Data for the right and left SI joints were analyzed, comparing interpretations of severity based on AP pelvis projections with oblique views. RESULTS: Analysis of these data showed an agreement rate between AP views and SI views of 89.7% for the right SI joint radiographs and 86.4% for the left SI joint. There was no instance in which a patient with "unequivocal abnormalities"of the SI joints on the AP pelvis was read as having "normal" SI views. Similarly, there were no cases in which "normal" SI joints on AP pelvis films were read as having unequivocal abnormalities on SI views. CONCLUSION: In this group of patients with seronegative spondyloarthropathies, there was very close agreement between severity score of sacroiliitis from AP pelvis radiographs and SI joint views. We conclude that in most circumstances, the AP pelvis film will yield the diagnosis of sacroiliitis without the additional radiation exposure and expense related to specific SI joint radiographs.