Number and proportion of lesions on MRI and PET/MRI for the SIJ and the spine. Values are n (%) unless otherwise specified.
| Lesions | BME | FD | p | BME + FD | p | PET | Erosions | Sclerosis | Ankylosis | |
|---|---|---|---|---|---|---|---|---|---|---|
| SIJ | Total (%), n = 104 | 46 (44.2) | 44 (42.3) | NS | 18 (17.3) | — | 48 (46.2) | 34 (32.2) | 20 (19.2) | 10 (9.6) |
| Total (%) + PET | 35 (67.1) | 15 (34.1) | < 0.001 | 13 (72.2) | NS*, 0.005** | — | 21 (61.8) | 11 (55) | 0 | |
| Sole total (%) | 28 (60.9) | 26 (59.1) | NS | — | — | 11 (22.9) | 6 | 4 | 0 | |
| Sole total (%) + PET | 22 (78.6) | 2 (7.7) | < 0.001 | — | — | — | 1 (16.7) | 2 (50) | 0 | |
| Spine | Total (%), n = 1196 | 118 (9.9) | 218 (18.2) | < 0.001 | 69 (9.9) | — | 65 (5.4) | — | — | — |
| Total (%) + PET | 35 (29.7) | 41 (18.8) | NS | 28 (40.6) | < 0.001*, 0.019** | — | — | — | — | |
| Sole total (%) | 49 (41.5) | 149 (68.3) | < 0.001 | — | — | 17 (26.2) | — | — | — | |
| Sole total (%) + PET | 7 (14.3) | 13 (8.7) | NS | — | — | — | — | — | — |
↵* p value of the positive PET/MRI as compared with sole BME lesions without any other concomitant lesions in the corresponding spinal part.
↵** p value of the positive PET/MRI as compared with sole FD lesions without any other concomitant lesions in the corresponding spinal part. MRI: magnetic resonance imaging; PET: positron emission tomography (positive finding on PET/MRI indicated by focal 18F-F uptake); SIJ: sacroiliac joints; BME: bone marrow edema; FD: fat deposition; 18F-F: 18F-labeled fluoride; NS: not significant; Total: number of lesions in the corresponding spinal part; Total + PET: number of lesions in the corresponding spinal part in combination with focal 18F-F uptake; Sole total: number of lesions without any other concomitant lesions in the corresponding spinal part; Sole total + PET: number of lesions without any other concomitant lesions in the corresponding spinal part in combination with focal 18F-F uptake.