Radiography
Pelvic X-rays Magnetic resonance imaging Pelvic X-rays The modified New York criteria describe the grading of the SIJ on pelvic X-rays. [26,27] Sclerosis, erosions, joint space widening or ankylosis of SIJ are features of established disease, and may take years to develop. Changes compatible with a classification of axSpA are grade 2 (or higher) changes bilaterally or grade 3 (or higher) un
Pelvic X-rays
The modified New York criteria describe the grading of the SIJ on pelvic X-rays.[26,27] Sclerosis, erosions, joint space widening or ankylosis of SIJ are features of established disease, and may take years to develop. Changes compatible with a classification of axSpA are grade 2 (or higher) changes bilaterally or grade 3 (or higher) unilaterally. Degenerative changes of SIJ are common.
Magnetic resonance imaging
A non-contrast MRI of the SIJs is key to diagnosing early disease, as it is more specific and sensitive than plain radiographs. Interpretation of MRI by a radiologist with expertise in axial imaging is recommended. A ‘positive MRI’ has the following requirements:
- bone marrow oedema (BMO) on a T2-weighted sequence sensitive for free water (such as short tau inversion recovery (STIR) or T2FS) or bone marrow contrast enhancement on a T1-weighted sequence (such as T1FS post-Gd)
- inflammation clearly present and located in a typical anatomical area (subchondral bone)
- MRI appearance must be highly suggestive of SpA.
Maharaj, A. B., et al. (2024). South African Rheumatism and Arthritis Association 2024 guidelines for the management of axial spondyloarthritis. South African Medical Journal, 114(10), e2668.