Imaging findings of sacroiliac joints in spondyloarthropathies and other rheumatic conditions.

Purpose: The authors sought to evaluate the role of the different imaging techniques in the study of sacroiliac joints in patients with spondyloarthropathies (SpA) and other rheumatic conditions and to assess potential pitfalls in the radiological diagnosis.

Materials And Methods: Forty-three consecutive patients with sacroiliitis as the predominant symptom of a rheumatic disorder were retrospectively studied. Radiography, computed tomography (CT) and magnetic resonance (MR) imaging were performed. The following imaging findings were evaluated: bone marrow oedema, intra-articular effusion, synovial reaction, joint-space widening, bone sclerosis or hyperostosis, subchondral erosions and, in final stages, joint-space narrowing and ankylosis. All images were independently reviewed by two musculoskeletal radiologists.

Results: Radiography demonstrated bone sclerosis in 10 patients (23%), subchondral erosions in 15 (34%), jointspace widening in 8 (18%), joint-space narrowing in 17 (39%) and ankylosis in 3 (6%). CT examination showed sclerosis of the sacroiliac joint in 17 patients (41%), subchondral erosions in 21 (53%), joint-space widening in 22 (53%), joint-space narrowing in 18 (43%) and ankylosis in 7 (17%). At MR, we found bone marrow oedema in 25 patients (92%), intra-articular effusion in 26 (96%), synovial reaction in 21 (77%) and joint-space widening in 5 (18%).

Conclusions: Radiological study of the sacroiliac joints in patients with different rheumatic disorders represents a problem of difficult diagnostic evaluation due to the complexity of the anatomical region and the variability of radiographic findings. The integrated use of conventional radiography, CT and MR imaging is suggested to avoid misdiagnosis.