Enteropathic arthritis in the sacroiliac joint. Imaging and differential diagnosis

A new high resolution computed tomography (HRCT) scoring system of sacroiliac joint (SIJ) involvement in enteropathic arthritis is introduced.

SIJ's of 100 patients were studied. A total of 25 patients presented with pain syndrome, 25 with suspicious seronegative spondylarthritis, 25 with inflammatory bowel diseases and 25 without joint or bowel diseases, as a control group. HRCT was carried out in all 100 patients. For comparison, a plain film radiography (PFR), conventional CT (slices of 10 mm) and bone scan were used.

Quantitative differences: In the pain syndrome group, there were no erosions identified neither intraarticular calcifications. Disc degeneration was seen in 12/25 cases. In 4/25 patients, vacuum phenomena appeared in the SIJ. In 3/25 patients, ventral capsular calcification occurred in the ventral sacroiliac ligament (anterior capsule complex). In the seronegative spondylarthritis group, 16/25 patients had positive findings, while PFR documented erosions only in 3/25 cases. In the bowel diseases group, erosions were detected in 17/25 cases with HRCT, while the plain film was positive only in three cases and in seven cases the findings were questionable. Intraarticular calcification with erosion was documented in three cases and in seven cases without erosion. The bone scan was positive in 7/25 of this cases, but in 5/7 there was mismatching with HRCT. Important new finding was the HRCT detected erosion which was not detected on BS but was obvious on Anti-Granulocyte-Antibody scintigraphy. In the control group, only degenerative changes were seen in 4/25 cases and no erosions.

HRCT is: (1) the reliable imaging of definitive (often 'cold stage') sacroileitis; (2) gives optimal detection of erosion; and (3) appears to be the only method in the documentation of calcifications in the posterior ligamental portion of the SIJ.