What Level of Inflammation Leads to Structural Damage in the Sacroiliac Joints? A Four‐Year Magnetic Resonance Imaging Follow‐Up Study of Low Back Pain Patients

Abstract

Objective. Sacroiliac (SI) joint bone marrow edema (BME) is considered to be pivotal in the detection of early spondyloarthritis. However, the link between BME and development of spondyloarthritis-related bone remodeling remains unclear. This study was undertaken to investigate the evolution of BME and structural lesions in the SI joints over time.Methods. Baseline and 4-year follow-up magnetic resonance imaging scans were conducted in 604 patients ages 18-40 years who were referred with low back pain to an outpatient spine clinic. Eight SI joint regions were scored for BME and categorized as absent, limited (<25% of subcortical bone region), intermediate (25-50%), or extensive (>50%). Structural lesions including erosions and fat lesions were scored as absent or present.Results. SI joint BME was seen at either time point (baseline or at 4 years) in 41% of participants but was persistent at both time points in only 16% of participants. Structural SI joint lesions developed according to the extent of BME at baseline: limited, intermediate, and extensive BME (as compared to absent BME) were independently associated with erosion at follow-up with odds ratios (ORs) of 3, 5, and 46, respectively, and with fat lesions (ORs 3, 7, and 33, respectively). In regions with limited and intermediate BME at baseline, 60% and 50% had resolved by follow-up, respectively, while only 2% and 7% had evolved into extensive BME by follow-up.Conclusion. While extensive SI joint BME was a strong independent predictor of development of structural lesions, limited and intermediate BME were mostly transient and only rarely evolved into extensive BME or structural lesions. These findings enhance our understanding of the natural development of SI joint lesions and indicate different progression patterns for limited/intermediate versus extensive BME, possibly due to different etiologies.

Anatomic Distribution of Sacroiliac Joint Lesions on Magnetic Resonance Imaging in Patients With Axial Spondyloarthritis and Control Subjects: A Prospective Cross‐Sectional Study, Including Postpartum Women, Patients With Disc Herniation, Cleaning Staff, Runners, and Healthy Individuals

“…However, in a post hoc analysis of women who had previously given birth in the groups of disc herniation, cleaning staff, and long‐distance runners, we found very limited BME, fat lesions, and sclerosis and no erosion, backfill, and ankylosis, which suggests that SI joint findings on MRI in postpartum women may diminish over time. This is in agreement with the observation of Arnbak et al (25), who observed that small and intermediate SI joint BME lesions on MRI in patients with low back pain were mostly transient and rarely developed into extensive BME or structural lesions such as fat lesions and erosion.…”

Spondyloarthritis on the Move: Biomechanical Benefits or Harm

“…In summary, these studies further confirm that pregnancy and extensive physical activity are possible non-SpA-related causes of low-grade sacroiliac joint BME, as was earlier observed for obesity and age-related degeneration [41]. This low-grade BME was shown to have a different progression compared to extensive BME in a study including 604 unselected low back pain patients including an unknown proportion of SpA patients.…”

“…In this group, low-grade BME was prevalent but mostly transient, and only rarely developing into extensive BME or structural lesions. In contrast, extensive BME strongly predicted the development of new structural lesions in the same region [41].…”

Early axial spondyloarthritis according to the ASAS consensus definition: characterisation of patients and effectiveness of a first TNF inhibitor in a large observational registry

“… 30 Extensive sacroiliac bone marrow oedema is also a strong predictor of the development of structural lesions, in contrast to limited or intermediate inflammatory lesions. 31 Male sex was shown to be a predictor of future sacroiliac inflammation detected by MRI in patients with IBP of short duration. 18 It is also known to be a predictor of treatment response in both radiographical 32 and non-radiographical 33 axSpA and to be associated with accelerated radiographical progression at the levels of the sacroiliac joints 34 and the spine.…”