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Table 3 Prevalence of four atypical SIJ morphologies, transitional vertebra and disc degenerative changes. Furthermore, BME and/or structural changes in relation to these. N (%) if not otherwise stated

From: Differences in topographical location of sacroiliac joint MRI lesions in patients with early axial spondyloarthritis and mechanical back pain

  axSpA (n = 25) MBP (n = 59)
Any atypical SIJ morphology 20 (80%) 53 (90%)
Accessory SIJ 9 (36%) 27 (46%)
 With BMEa 6 (67%) 7 (26%)
 With structural changesb 4 (44%) 9 (33%)
Iliosacral complex 15 (60%) 35 (59%)
 With BMEa 10 (67%) 5 (14%)
 With structural changesb 5 (33%) 1 (3%)
Dysmorphic cartilaginous facets 10 (40%) 22 (37%)
 With BMEa 10 (100%) 18 (82%)
 With structural changesb 9 (90%) 9 (41%)
Bipartite iliac bony plate 1 (4%)* 15 (25%)
 With BMEa 0 1 (7%)
 With structural changesb 0 0
Transitional vertebra 2 (8%) 3 (5%)
 With BMEa 2 (100%) 1 (33%)
 With structural changesb 2 (100%) 3 (100%)
Disc degeneration (0–3) 1.6 1.7
Disc extrusion (disc degeneration = 3) 6 (24%) 16 (27%)
Vertebral corner changes (BME/FMD) 3 (12%)* 1 (2%)
Vertebral end plate changes (BME/FMD) 6 (24%) 20 (34%)
  1. axSpA axial spondylarthritis, BME bone marrow edema, MBP mechanical back pain, N number, SIJ sacroiliac joint
  2. *p < 0.05 for the test for between-group differences
  3. a Percent of atypical morphologies accompanied by BME
  4. b Percent of atypical morphologies with structural changes in form of FMD and/or sclerosis in relation to an atypical morphology