CT Evaluation of Subluxation of Sacroiliac Joint in Diagnosing Ankylosing Spondylitis

Objective To investigate CT sign of subluxation of sacroiliac joint, and to evaluate the sign in diagnosing ankylosing spondylitis (AS).Materials and Methods Thirty-four cases with CT-proved AS (study group) and 23 healthy individuals (control group) were collected. The level of sacroiliac subluxation was measured on axial CT scans. Through statistic analysis, the diagnostic standard of sacroiliac subluxation was formulated. Using this standard, 20 cases who were clinically diagnosed as ankylosing spondylitis but had normal CT findings were reviewed.Results Sacroiliac subluxation of different degree was seen in 73.5% of study group patients, in 40% patients with suspected AS and in 21.7% of control group subjects. The level and frequency of sacroiliac joint subluxation in study group was higher than that in control group. Treatment for AS was effective in 8 cases with sacroiliac subluxation.Conclusion Sacroiliac subluxation plays an important role in making early CT diagnosis of ankylosing spondylitis.