Background/Purpose: To compare the prevalence of inflammatory posterior arch abnormalities (IPAA) on lumbar spine MRI between spondyloarthritis patients (SpA) and low back pain patients (LBP).

Methods: Design : Monocentric cross-sectional case-controlled study. Patients : SpA patients fulfilling the 2009 ASAS criteria who had a lumbar spine MRI were retrospectively selected from medical files. Chronic LBP patients with a lumbar spine MRI planned in the Toulouse Hospital Radiology Center were prospectively selected if they had no argument for a symptomatic back pain (e.g. tumor, infection,..). MRI : STIR and T1 sagittal images from 3 and 1.5 Tesla MRI going up to T8-T9 stages were reviewed by two experienced rheumatologists, blinded from the diagnosis and clinical data. IPAA (i.e.: pedicle edema, transverse and spinous process edema, interspinous process edema, costo-transverse or zygapophyseal joint arthritis) were collected in the two groups. Analyses : The prevalence of IPAA between SpA and LBP patients were compared by Chi2 or Fisher’s exact test. Clinical data (age, sex, disease duration, BASDAI, CRP, BASFI) were compared in the SpA group according to the presence/absence of IPAA by Chi2 or Wilcoxon tests.

Results: Ninety-five patients were included in each group. Inter and intra-observer agreement was excellent (κ=0.938). The prevalence of all IPAA was not significantly different between SpA and LBP groups (55.9% in SpA group versus 69.5% in LBP group, p = 0.97). On the other hand, there was a significant difference in the prevalence of costo-transverse joint arthritis, pedicle edema, transverse and spinous process edema between the two groups (prevalence of these anomalies in SpA group: 27% versus 8% in LBP group, p = 0.006). Costo-transverse joint arthritis and transverse process edema have a specificity and a positive predictive value of 100% for the diagnosis of SpA, with sensitivity of 17% and 3.2% respectively. Patients with IPAA in SpA group had a longer disease duration (11 years versus 8 years, p=0.02), higher CRP level (medians : 11 versus 3, p=0.0002), more often a MRI sacroiliitis (84% versus 47%, p=0.001), more often psoriasis (27% versus 10.2%, p=0.04) but received less NSAIDs (42% versus 69%, p=0.01) compared to patients without IPAA.

Conclusion: Costo-transverse joint arthritis, pedicle edema and transverse process edema are more frequent and specific for the diagnosis of SpA. IPAA are frequently associated with biological inflammation and MRI sacroiliitis.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/prevalence-of-inflammatory-posterior-arch-abnormalities-on-lumbar-spine-mri-in-spondyloarthritis-patients-compared-to-low-back-pain-patients/