Effect of Age on Active and Structural Magnetic Resonance Imaging Lesions in Sacroiliac Joints of Healthy Individuals and Patients With Nonspecific Back Pain

Objective: To assess the effect of increasing age on the frequency of inflammatory and structural magnetic resonance imaging (MRI) lesions in the sacroiliac joints (SIJ) in 3 independent cohorts of healthy individuals and patients with nonspecific back pain (NSBP).

Methods: We assessed MRI SIJ lesions in 3 cohorts (A, B, and C) of healthy individuals (cohort A, n = 79; cohort B, n = 78) and patients with NSBP (cohort A, n = 87; cohort C, n = 46) aged ≤ 45 years referred with back pain suspicious of axial spondyloarthritis (axSpA). MRI lesions were recorded on consecutive slices in SIJ quadrants or halves through the cartilaginous SIJ. Lesions were ascertained by 2-7 central readers according to standardized lesion definitions. Lesions recorded concordantly by the majority of readers were analyzed according to age categories (18-29, 30-39, and 40-50 yrs) and previously reported data-driven MRI cutoffs indicative of inflammatory or structural lesions typical of axSpA.

Results: Only 3.8% (in both cohort A and cohort B) of healthy individuals and 5.7% (cohort A) and 4.3% (cohort C) of patients with NSBP had erosion in ≥ 1 SIJ quadrant, and progressive increases of erosion with age categories were not evident. None of the healthy individuals and 2.3% and 4.3% of cohort A and cohort C, respectively, of the patients with NSBP showed erosion in ≥ 3 SIJ quadrants, the cutoff indicative of axSpA; not a single individual met this cutoff in the highest age category. Fat metaplasia was slightly increased with age among healthy individuals and patients with NSBP in cohort A, but not in cohorts B or C.

Conclusion: SIJ MRI data from healthy individuals and NSBP controls did not indicate progressive increases in structural lesions with increasing age categories when standardized definitions for axSpA lesions were adopted. MRI cutoffs for structural lesions denoting axSpA discriminated equally well between axSpA and NSBP across all age categories.