Background/Purpose: Axial psoriatic arthritis (PsA) is the only one of the PsA manifestations, still not clearly defined, with no currently available universally acceptable clinical and imaging criteria.¹ MAXIMISE, the first RCT which has proven efficacy of a bDMARD in the management of axial manifestations of PsA, provides a dataset of MRIs in a population of PsA patients (pts) with a clinical diagnosis of axial disease and may address the gap in determining the role of MRI in diagnosis and classification of axial PsA.² So far, structural lesions such as fat lesions, which were shown to follow resolution of inflammation in the spine of pts with axial spondyloarthritis (axSpA) ³ or the presence of degenerative changes (DCs) which may delay or confound the diagnosis of axial PsA have not been assessed in any PsA cohort with axial involvement. This post-hoc exploratory analysis of baseline MRIs from the MAXIMISE trial² investigated: (1) the post-inflammatory changes by FAt Spondyloarthritis Spine Score (FASSS) ⁴, (2) the inflammatory changes in the posterior spinal elements (spinal process) and (3) the prevalence of DCs. ⁵

Methods: The baseline spinal-MRIs (T1 and STIR) for pts from the MAXIMISE trial fulfilling the pre-defined clinical criteria for active axial disease (BASDAI ≥4, spinal pain (VAS) ≥40 and inadequate response to ≤ 2 NSAIDs, N=485) were re-read. FASSS is a scoring method which addresses the spectrum of fat lesions according to anatomical localization and phenotypic diversity with a sum score ranging from 0 to 456 for the 23 disco-vertebral units (DVUs) ⁴. Spinal process inflammation (SPi) was documented. The degenerative changes i.e., Modic 1, Modic 2, Schmorl’s node with or without bone marrow oedema (BME), disc degeneration (herniation or marginally located high intensity zone), erosion, sclerosis, Pfirrmann changes, were also included in the reading protocol.^{3, 5}

Results: For approximately 80% of the pts, no fat lesions were identified (Figure 1a). The mean (SD) FASSS at baseline for the overall population was 1.8 (5.7), 0.2 (1.2), 1.0 (3.6) and 0.6 (1.9) for the whole spine, cervical, thoracic, and lumbar regions, respectively. SPi were documented for 11.1% of the patients. Approximately 63% of the pts had at least one type of DC (Figure 1b). The most prevalent DCs for the overall population were: Pfirrmann changes (grade ≥3), 51.1%; disc degeneration, 36.7%; Modic 1 or Modic 2, 22.1%; Schmorl’s node with or without BME, 11.8 %. The proportion of pts with specific changes in the spinal sub-locations are presented in Table 1.

Conclusion: Re-reading the baseline MRIs from the MAXIMISE trial, the largest cohort of PsA pts with active axial disease diagnosed by clinical criteria, revealed fat lesions and DCs for approximately 20% and 63% of the pts, respectively, while SPi occurred much less frequently. These data shed light into the imaging characteristics of patients with PsA and axial manifestations.

References:

1. Feld J, et al. Nat Rev Rheumatol. 2018;14:363–71.
2. Baraliakos X, et al. Ann Rheum Dis. 2020;80(5):582–90.
3. Baraliakos X, et al. Ann Rheum Dis. 2014:73(10):1819-25
4. Pedersen SJ, et al. Arthritis Res Ther. 2013;15(6):R216.
5. de Bruin F, et al. Rheumatology. 2016;55(1):56-65.

Figure 1: (a) Prevalence of FASSS categories (b) Prevalence of degenerative changes DC, degenerative change; FASSS, FAt Spondyloarthritis Spine Score

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/post-inflammatory-and-degenerative-changes-in-patients-with-psoriatic-arthritis-and-axial-manifestations-post-hoc-analysis-from-a-double-blind-randomized-phase-3b-trial/