Abstract
BackgroundStudies have shown that structural lesions may be present in patients with non-radiographic axial spondyloarthritis (nr-axSpA). However, the relevance of structural lesions in these patients is unclear, particularly without signs of inflammation on magnetic resonance imaging (MRI). We assessed the presence of structural lesions at baseline on MRI in the sacroiliac joints (SIJ) of patients with nr-axSpA with and without SIJ inflammation on MRI.MethodsBone marrow edema (BME) was assessed on short tau inversion recovery (STIR) scans from 185 patients with nr-axSpA, by two independent readers at baseline using the Spondyloarthritis Research Consortium of Canada (SPARCC) score. Structural lesions were evaluated on T1 weighted spin echo scans, with readers blinded to STIR scans, using the SPARCC MRI SIJ structural score. Disease characteristics and structural lesions were compared in patients with SIJ BME (score ≥2) and without SIJ BME (score <2).ResultsBoth SIJ BME and structural lesions scores were available for 183 patients; 128/183 (69.9%) patients had SIJ BME scores ≥2 and 55/183 (30.1%) had scores <2. Frequencies of MRI structural lesions in patients with vs without SIJ BME were: erosions (45.3% vs 10.9%, P < 0.001), backfill (20.3% vs 0%, P < 0.001), fat metaplasia (10.9% vs 1.8%, P = 0.04), and ankylosis (2.3% vs 1.8%, P = ns). Significantly more patients with both SIJ BME and structural lesions were male and/or HLA-B27 positive than patients with only SIJ BME. Mean (SD) spinal scores (23 discovertebral units) were significantly higher in patients with SIJ structural lesions than without: 6.5 (11.5) vs 3.3 (5.1), respectively, P = 0.01.ConclusionsIn patients with nr-axSpA, SIJ structural lesions, particularly erosions, may be present on MRI when radiographs are normal or inconclusive, even in patients negative for MRI SIJ inflammation. They may reflect more severe disease with greater spinal inflammation.Trial RegistrationClinicalTrials.gov, NCT01258738. Registered on 9 December 2010.
Highlights
Studies have shown that structural lesions may be present in patients with non-radiographic axial spondyloarthritis
sacroiliac joints (SIJ) bone marrow edema (BME) data were available for 183 patients; 128/183 (69.9%) patients had SIJ BME and 55/183 (30.1%) did not
Relative frequencies of magnetic resonance imaging (MRI) structural lesions in patients with versus without SIJ BME were: erosion (58/128, 45.3% vs 6/55, 10.9%; P < 0.001), backfill (26/128, 20.3% vs 0/55, 0%; P < 0.001), fat metaplasia (14/128, 10.9% vs 1/55, 1.8%; P = 0.04), and ankylosis (3/128, 2.3% vs 1/55, 1.8%; P = nonsignificant) (Fig. 2)
Summary
Studies have shown that structural lesions may be present in patients with non-radiographic axial spondyloarthritis (nr-axSpA). The relevance of structural lesions in these patients is unclear, without signs of inflammation on magnetic resonance imaging (MRI). The Assessment of SpondyloArthritis international Society (ASAS) classification system for axSpA is based on whether patients meet clinical criteria or imaging criteria [6,7,8]. According to the ASAS classification criteria, bone marrow edema (BME)/osteitis on MRI is a requirement for patients with nr-axSpA who meet the criteria via the MRI arm [8]. This may occur nonspecifically, and some patients with nraxSpA do not have MRI evidence of inflammation [1, 2]
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