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MRI detected sacroiliac joint erosions effectively in patients with ankylosing spondylitis
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Erosions of the sacroiliac joints in patients with ankylosing spondylitis can be detected through magnetic resonance imaging and were substantial and comparable to bone marrow edema, according to recent study results.
Researchers randomly selected 60 patients, 30 with ankylosing spondylitis (AS) and 30 control patients, including 15 with nonspecific back pain and 15 healthy volunteers. Four readers independently assessed the patients’ semicoronal T1SE and short tau inversion recovery (STIR) sequences of their sacroiliac joints (SIJ) on magnetic resonance imaging (MRI) scans.
Erosions, extended erosion (EE) and backfill (BF) were recorded based upon standardized MRI methodology. Researchers defined EE as erosion that “extends continuously across the entire length of at least 1 SIJ quadrant of the iliac and/or sacral subchondral bone,” and BF as “complete loss of iliac or sacral cortical bone with refilling of the excavated area by tissue.” Kappa statistics and intraclass correlation coefficients (ICC) were used to assess the reproducibility of specific MRI lesions for all patients.
Two or more readers detected SIJ erosions in all AS patients and in five control patients with nonspecific back pain and in one healthy volunteer. Four readers recorded a median of 8.6 erosions in the iliac quadrants (IQR=6.9) and 2.1 in the sacral joint portion (IQR=2.9) of the SIJ in all 30 AS patients (P<.0001). Researchers recorded kappa values for erosion (0.72), EE (0.73) and BF (0.63) in all 60 patients and for all four readers. ICC values were: erosion (0.79), EE (0.72) and BF (0.55). The kappa and ICC values for bone marrow edema were 0.61 and 0.93, respectively.
“This systematic, standardized and controlled evaluation of SIJ MRI scans in AS patients demonstrated that the reliability between 4 readers for detection of erosion on SIJ MRI was substantial and comparable to BME,” researchers concluded. “In contrast to BME and [fat infiltration], erosion occurred significantly more frequently on the iliac side. … further assessment in prospective studies is required to understand the characteristics of these variants and their role in the evolution of sacroiliitis.”
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