Background/Purpose: To assess the prevalence of inflammatory and structural lesions on MRI of the sacroiliac joints (SIJ) in patients with peripheral spondyloarthritis (PSpA) in a very early stage of the disease.

Methods: Baseline data originated from the double-blind RCT with golimumab in 60 patients (CRESPA), who were diagnosed with PSpA and had a symptom duration <3 months. MRI SIJ was performed at baseline. Peripheral arthritis, dactylitis or enthesitis combined with ≥1 SpA feature (uveitis, psoriasis, IBD, preceding infection, HLAB27 or sacroiliitis on imaging) was necessary for inclusion. However, all patients already fulfilled the classification criteria without data on imaging of the SIJ. Bone marrow edema (BME) of the SIJ was quantified using the Spondyloarthritis Research Consortium of Canada (SPARCC) scoring system. Besides BME of the SIJ, all MRIs were also scored for other inflammatory lesions such as enthesitis and capsulitis. Structural MRI lesions of the SIJ such as subchondral sclerosis, erosions, periarticular fat and ankylosis were also assessed. Hip evaluation consisted of the presence of joint effusion, BME, enthesitis and cortical aberrations.

Results:  Although not the reason for encounter, 7 out of 60 patients reported ever having inflammatory back pain (IBP) at inclusion or in the past, with median Visual analogue scores (VAS) of 2.0 (range 0.0- 9.0) for back pain. Overall, 35% of patients (21/60) exhibited BME of the SIJ and fulfilled the definition of a positive MRI by ASAS, with median SPARCC score of 8.0 (range 2.0-37.0). Only 3 out of 7 patients with IBP exhibited BME on MRI SIJ. Therefore, almost 86% of patients (18/21) with active sacroiliitis did not exhibit symptoms of IBP. Median VAS back pain in patients with sacroiliitis compared to patients without sacroiliitis respectively reached 2.0 and 1.0 (P=NS). Pelvic enthesitis was present in 23.8% (5/21) of patients with an ASAS positive MRI SIJ and in 10.3% (4/39) of patients with negative MRI. None of the patients exhibited enthesitis of the L5 spinous process, iliac crest, anterior superior iliac spine or ramus pubis. None of the patients exhibited thorax enthesitis.

Conclusion: Even in early diagnosed peripheral SpA patients, over 1/3 exhibited BME suggestive of acute sacroiliitis and structural lesions of the SI joints. Our findings underscore the importance of sacroiliitis as the cornerstone feature within the SpA-concept, even in asymptomatic patients.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/the-prevalence-of-inflammatory-and-structural-lesions-on-mri-of-the-sacroiliac-joints-in-patients-with-very-early-peripheral-spondyloarthritis/