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. 2021 May 28;81(2):237–242. doi: 10.1136/annrheumdis-2021-220136

Figure 3.

Figure 3

Imaging examples. (A) Female patient with osteitis condensans (23 years old, HLA-B27 negative, normal CRP). Radiography suggests bilateral erosions and joint space blurring (arrows) with mild sclerosis. However, cross-sectional imaging shows no erosions but some bone marrow oedema (arrows) and sclerosis (arrowheads) consistent with the final diagnosis. (B) Male patient with axSpA (53 years old, HLA-B27 positive, long history of back pain). Radiography shows only mild blurring of the joint space (arrowheads) and capsular calcification (arrow) and was deemed negative by all readers. However, MR and CT show extensive ankylosis (arrowheads) with preservation of only a small portion of the joint space, suggesting advanced axSpA. (C) Female patient with mechanical joint disease (34 years old, HLA-B27 negative, normal CRP). Radiography and T1W MR show extensive sclerosis (arrowheads) and irregularities (arrows) on the left side, MR-STIR extensive bone marrow oedema (arrowheads) and joint fluid (arrow). Both were misclassified by the readers as positive for axSpA. In this patient, only CT ruled out erosions (arrow) and confirmed the diagnosis of osteitis condensans and iliosacral complex as an anatomical variant. (D) Male patient with axSpA (40 years old, HLA-B27 positive, normal CRP). Radiography shows only minor irregularities (arrows) and was deemed negative. MR shows small cysts (arrows) and minor irregularities (arrowhead) as well as some bone marrow oedema on STIR but was judged negative by two of the three readers. Only CT shows very tiny erosions, confirming the diagnosis of axSpA (arrows). axSpA, axial spondyloarthritis; CRP, C reactive protein; STIR, short-tau inversion recovery; XR, X-ray.