Table 2.
Anatomic distribution of bone marrow edema in the SI joint quadrants on MRIa
| Upper ilium | Lower ilium | Upper sacrum | Lower sacrum | |||||
|---|---|---|---|---|---|---|---|---|
| Anterior | Posterior | Anterior | Posterior | Anterior | Posterior | Anterior | Posterior | |
| Positive MRI of the SI joints (n = 64) | 44 (68.8) | 34 (53.1) | 48 (75.0) | 53 (82.8) | 39 (60.9) | 37 (57.8) | 37 (57.8) | 43 (67.2) |
| Negative MRI of the SI joints (n = 108) | 4 (3.7) | 7 (6.5) | 18 (16.7) | 16 (14.8) | 5 (4.6) | 7 (6.5) | 3 (2.8) | 4 (3.7) |
| Healthy participants (n = 47) | 2 (4.3) | 2 (4.3) | 10 (21.3) | 18 (38.3) | 4 (8.5) | 2 (4.3) | 3 (6.4) | 6 (12.8) |
| Patients with axial SpA (n = 47) | 39 (83.0) | 34 (72.3) | 41 (87.2) | 41 (87.2) | 33 (70.2) | 36 (76.6) | 33 (70.2) | 35 (74.5) |
| Controls with chronic back pain (n = 47) | 2 (4.3) | 4 (8.5) | 11 (23.4) | 5 (10.6) | 3 (6.4) | 3 (6.4) | 1 (2.1) | 2 (4.3) |
| Runners (n = 24) | 4 (16.7) | 1 (4.2) | 1 (4.2) | 2 (8.3) | 2 (8.3) | 1 (4.2) | 1 (4.2) | 2 (8.3) |
| Women with postpartum back pain (n = 7) | 1 (14.3) | 0 (0) | 3 (43.0) | 3 (43.0) | 2 (28.6) | 2 (28.6) | 2 (28.6) | 2 (28.6) |
a
Magnetic resonance images (MRIs) that indicated sacroiliitis according to the Assessment of SpondyloArthritis international Society (ASAS) definition were considered positive. Those that did not meet the ASAS definition were considered negative. Values are the number (%). SI = sacroiliac; SpA = spondyloarthritis.