Aim: To determine which signs are the most accurate in the diagnosis of sacroiliitis with MRI.
Material and methods: 40 consecutive patients with inflammatory low back pain underwent MRI at 1.5 T with FSE T2 and SE T1 weighted-images before and after Gadolinium-DOTA injection. 22 patients were suffering from spondylarthropathy while the other 18 patients constituted the control group. Each examination was interpreted by two independent observers who analysed 11 different signs.
Results: Intra and inter observer reproducibility were high (respectively 76% and 70%). Inter observer reproducibility was excellent for bone marrow edema (89%) but low for bone productions (38%). Three lesions displayed a high positive predictive value: ligamentous contrast enhancement (86%), bone marrow edema (80%) and bone erosions (70%). Intra articular enhancement of the sacro-iliac joint was a less sensitive sign than bone marrow edema.
Conclusion: This study confirms the excellent positive predictive value of MRI for an early diagnosis of active sacroiliitis. Bone marrow edema seems to be a more pertinent sign than intra articular enhancement.