Background/Purpose:

Magnetic resonance imaging (MR) plays an important role in the evaluation of inflammatory and structural changes in axial spondyloarthritis (axSpA) patients. Prior research suggests subchondral fatty marrow is an imaging precursor to ankylosis. The ability to predict new bone formation in patients with axSpA may have treatment implications. The goal of the current study is to evaluate imaging and clinical factors associated with subchondral sacroiliac joint (SIJ) fatty marrow.

Methods:

A retrospective analysis of 91 AxSpA patients who underwent a lumbar spine or pelvis MR with axial and coronal T1 in addition to fluid sensitive sequences was performed. Images were reviewed by a radiologist and evaluated for findings of both active and structural disease in addition to disease distribution. Bone marrow edema was quantified using the Spondyloarthritis Research Consortium of Canada (SPARCC) quadrant based approach method. Clinical variables including gender, age, race, disease duration and classification, current or prior Tumor Necrosis Factor alpha inhibitor (TNFi) therapy, HLA-B27 status, history of uveitis, inflammatory bowel disease and psoriasis were collected. Univariable analyses with c2 and Student’s t-Test were performed on dichotomous and continuous variables.  Multivariable logistic regression was performed after adjusting for gender and disease duration.

Results:

Of the 91 patients, 76 (83.5%) demonstrated sacroiliac (SI) joint abnormalities on MR with 90.8% of these demonstrating bilateral and 56.6% demonstrating symmetric changes. Distribution of abnormalities included bone marrow edema in 56.7% with a SPARCC score of 7.30 ± 11.53, erosions in 44.7%, fatty marrow in 52.3% and ankylosis in 19.7% of patients.  Covariates independently associated with fatty marrow change included disease duration ≥10 years (OR 3.5, 95% CI [1.05-11.9], p=0.04), psoriasis (OR 29.1, 95% CI [1.34-633.5], p=0.032) and symmetric sacroiliitis (OR 4.36, 95% CI [1.30-14.59], p=0.02). There was no association with TNFi therapy (Table 1).

Conclusion:

Our data demonstrates fatty marrow replacement is associated with longer disease duration (≥10 years) and the presence of psoriasis in addition to the imaging finding of symmetric disease distribution.  Additional studies are warranted to explore the role of psoriasis in the development of chronic sacroiliitis and ankylosis.

Table 1. Multivariable analysis after adjustment for gender and disease duration

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/imaging-and-clinical-factors-associated-with-subchondral-sacroiliac-fatty-marrow-in-axial-spondyloarthritis/