Analysis of CT Scan for Sacroiliac Joint in Ankylosing Spondylitis

Objective To investigate the rule to choose the candidates for sacroiliac joints CT scan in patients with ankylosing spondylitis(AS) and the analysis of their images. Methods All the 980 cases suspected AS by clinical appearances and /or laberary tests were candidates. Their conventional radiology and CT scan features were studied and compared. Results Positive cases were 502 by X ray and 579 by CT. During the five parts of 0-Ⅳ degree sacroiliac joints diagnosed by X ray film, CT results were consistent in 43%, 35%, 48%, 71%, and 78% separately. According to CT findings, X ray could improve the diagnosis by 1-3 grades. Conclusion CT scan is much better than X ray film in finding out minute changes, making an earlier diagnosis of the sacroilitis and getting a precise grading because of its higher resolution power for small signs. For patients with significant X ray abnormalities CT scan does not seem to be necessary in only getting a diagnosis.