Patients with nonradiographic axial spondyloarthritis (nr-axSpA) may have sacroiliac joint (SIJ) structural lesions even in cases where there are normal radiographs with no sign of inflammation on magnetic resonance imaging (MRI), according to recent research published in Arthritis Research & Therapy.
“The results of this study demonstrate that structural lesions on MRI, particularly erosions, may occur in nr-axSpA when radiographs are normal or inconclusive, and even in the absence of SIJ [bone marrow edema (BME)] on MRI,” Walter P. Maksymowych, MD, from the Department of Medicine at the University of Alberta in Edmonton, Canada, and colleagues wrote in their study.
Dr Maksymowych and colleagues evaluated BME in 185 patients who underwent short tau inversion recovery MRI scans, where 2 readers used the Spondyloarthritis Research Consortium of Canada, a score that accounts for erosion, backfill, fat metaplasia, and ankyloses, to assess BME from the short tau inversion recovery scans.
Two different readers who were blinded to the short tau inversion recovery scans analyzed the structural lesions in T1-weighted spin echo scans using the MRI SIJ structural score for the Spondyloarthritis Research Consortium of Canada, and results were compared between MRIs with and without SIJ BME.
A Spondyloarthritis Research Consortium of Canada score ≥2 was associated with the presence of BME, whereas a score of <2 was associated with the absence of BME.
Of the 183 patients with complete SIJ BME and structural lesion data, 69.9% (n=128) had a BME score ≥2, whereas 30.1% of patients (n=55) had scores <2. Erosions occurred in 45.3% of patients with SIJ BME compared with 10.9% of patients without SIJ BME (P <.001).
There were 20.3% of patients with SIJ BME who had backfill compared with 0% of patients without BME (P <.001). Patients with SIJ BME had fat metaplasia in 10.9% of cases compared with 1.8% of cases in patients without SIJ BME (P =.04), and patients had ankylosis in 2.3% of cases in the SIJ BME group compared with 1.8% of patients without SIJ BME.
Patients in the SIJ BME group were more likely to be male, Human Leukocyte Antigen B27-positive, and have greater spinal (6.5 vs 3.3) and 23 discovertebral unit scores (11.5 vs 5.1) compared with patients without SIJ BME (P =.01).
Summary and Clinical Applicability
SIJ structural lesions may signal more severe nr-axSpA disease progression, and earlier identification could lead to intervention before more advanced inflammation occurs. These study results suggest plain radiographs may not be identifying all patients in whom SIJ structural damage is present.
“It has been suggested that there is a window of opportunity for disease modification with anti-inflammatory agents by treating acute inflammatory lesions before bone formation pathways are triggered in more complex inflammatory lesions,” Dr Maksymowych and colleagues wrote.
“Consequently, the presence of structural lesions in the SIJ may help select patients for intervention with [anti-tumor necrosis factor] agents early in the disease course.”
The researchers noted the difficulty in interpreting T1weighted spin echo MRIs in cases of erosion and heterogeneous lesions and the lack of a control population.
Dr Maksymowych is a paid consultant for AbbVie, Amgen, Lilly, Janssen, Pfizer, Sanofi, and UCB and is the chief medical officer of CaRE Arthritis Ltd. Dr Dougados is a consultant for and has received funding and grants from AbbVie, Lilly, Merck, Pfizer, Sanofi, and UCB. Dr Jones, Marshall, and Bukowski are paid employees of, and stock owners in Pfizer. Szumski is a paid employee of inVentiv Health.
Maksymowych WP, Wichuk S, Dougados M, et al. MRI evidence of structural changes in the sacroiliac joints of patients with non-radiographic axial spondyloarthritis even in the absence of MRI inflammation [published online June 6, 2017]. Arthritis Res Ther. doi: 10.1186/s13075-017-1342-9