Anatomical Variation at the Sacroiliac Joints in Young Adults: Estimated Prevalence by CT and Concomitant Diagnostics by MRI

Presentation Format: Oral presentation.

Purpose or Learning Objective: (1) To estimate the prevalence of anatomical variation at the sacroiliac joints (SIJs) in young adults by computed tomography (CT) and (2) to analyze the diagnostic ability of magnetic resonance imaging (MRI) to detect the variants and concomitant MRI findings that could be misdiagnosed as inflammatory changes.

Methods or Background: The study sample was composed of CT examinations of 155 individuals aged 18 to 40 years and prospectively collected comparative SIJ MRI examinations of 49, who also filled out a questionnaire on back pain and underwent a clinical examination. The CTs and MRIs were analyzed by two musculoskeletal radiologists regarding seven SIJ variants and additional bone marrow edema (BME) and fatty marrow deposition by MRI.

Results or Findings: The interobserver agreement of both CT and MRI was good or very good for most variants. Mean age of the 155 individuals was 28 years, 99 (64%) were men; 88 (57%) had at least one SIJ variation, and most frequent were dysmorphic cartilaginous joint facets (dysmorphic CF) (n = 33), bipartite iliac bony plate (n = 27), accessory SIJ (n = 24), and iliosacral complex (n = 18), with a female predominance in all variants. The ability of MRI to detect SIJ variants was satisfying, except for crescent-like iliac bony plate and semicircular defects, which were rare. Dysmorphic CF, accessory SIJ, and iliosacral complex were frequently observed in individuals with BME, which might imitate inflammatory changes, located either in relation to the variant(s) or at so-called load-related areas.

Conclusion: Anatomical SIJ variation is frequent in young adults. Most of the variants were detectable by MRI, and three SIJ variants were often observed when BME was present.

Publication History

Article published online:
03 June 2021