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Sacroiliac MRI Lesions Set Apart axSpA and Other Back Pain
The analysis of structural lesions in sacroiliac joints using MRI showed distinct patterns of structural changes across multiple groups, with patients with axial spondyloarthritis (axSpA) showing higher rates of erosions and fatty lesions than other groups without axSpA. Inflammatory and structural lesions occurred simultaneously in those with axSpA.
METHODOLOGY:
Researchers assessed differences in the structural lesions appearing on sacroiliac joint MRIs in 172 participants (mean age, 30.1-34.3 years) from two projects comparing patients with axSpA with those without.
They included patients with axSpA (n = 47) and those without axSpA comprising patients with chronic back pain (n = 47), women with postpartum back pain (n = 7), runners (n = 24), and healthy individuals (n = 47).
Two trained, calibrated readers independently inspected the sacroiliac joint MRIs for erosions, fatty lesions, sclerosis, and ankylosis.
A scoring system similar to that of the Spondyloarthritis Research Consortium of Canada scoring method was used for the assessment.
Several structural lesion cutoffs were identified and tested as suggested by two working groups, with specific definitions for three or more erosions, three or more fatty lesions, and five or more erosions and/or fatty lesions. The frequency of patients meeting the cutoffs was assessed within different subgroups.
TAKEAWAY:
Structural lesions were identified in 79% of patients with axSpA and 13% of those without axSpA, with erosions (75% vs 9%) and fatty lesions (40% vs 4%) showing the most marked differences and sclerosis (13% vs 3%) and ankylosis (15% vs 2%) showing smaller group differences.
Erosions were also prevalent in women with postpartum back pain (57%), and fatty lesions were the most prevalent in healthy individuals (6%).
Significant differences were noted across groups for fatty lesions ( P < .001), erosions ( P < .001), and ankylosis ( P = .016); however, sclerosis showed no significant variation. The proposed cutoff definitions performed well in differentiating axSpA from non-axSpA.
< .001), erosions ( < .001), and ankylosis ( = .016); however, sclerosis showed no significant variation. The proposed cutoff definitions performed well in differentiating axSpA from non-axSpA. In the axSpA group, an overlap of 72%-79% was observed between structural lesions and inflammation, while non-axSpA subgroups showed a significantly lower rate of overlap. However, 4%-29% of patients in the non-SpA subgroup compared with only 6% in the axSpA group had structural lesions without inflammation.
IN PRACTICE:
"We are convinced that if structural lesions ought to be part of axSpA classification criteria, the implementation of cut-offs for these lesions should be considered. Nevertheless, for a comprehensive understanding of the possible added value of structural lesions, it is crucial to look at the prevalence of structural lesions in the absence of inflammation," the authors wrote.
SOURCE:
This study was led by Zohra Kerami, Amsterdam UMC Locatie AMC, Amsterdam, the Netherlands. It was published online on May 28, 2025, in RMD Open .
LIMITATIONS:
The sample sizes were notably small for some subgroups. Additionally, comprehensive clinical and demographic information was lacking for healthy individuals, women with postpartum back pain, and runners. Data on previous pregnancies and the interval between MRI and delivery were not collected systematically, which limited the analysis of pregnancy-related effects.
DISCLOSURES:
This study did not receive any specific funding. Few authors reported receiving consultancy fees, research support, and/or speaking fees and honoraria for lectures or participation in advisory boards from various pharmaceutical companies. One author reported being an associate editor and another reported being an owner of Joint Imaging BV.
