X-Ray Techniques in the Diagnosis of Sacroiliitis in Patients with Ankylosing Spondylitis

Background:

The aim of the study was to improve X-ray diagnosis of sacroiliitis in ankylosing spondylitis by using oblique projections.

Patients and Methods:

The study included 35 patients (26 males, 9 females, aged 1840 years; average age 30.0 + 5.3 years; joint functional failure stage IIV) with bilateral sacroiliitis and 15 control subjects. All the patients had X-ray in the direct and oblique projections. In the direct projection, patient was on his back, and the beam was perpendicular to the surface of the body. In this case, the direction of X-ray beam was at an angle with the joint space. Additionally, we performed X-rays in the oblique projection, for each sacroiliac joint separately, with the patient turning 30 to the horizontal plane. The beam was parallel to the sacroiliac joint space. The width of the joint space, changes of articular surfaces (sclerosis, erosions), and the symmetry of the lesions were analyzed. All findings were verified by CT.

Results:

On the direct X-ray, bilateral sacroiliitis was found in 38 patients, of them, 33 cases were true positive and 5 were false positive. Two cases were false negative yielding a diagnostic accuracy of88%. On the oblique X- ray, sacroiliitis was noted in 35 patients, of them, 33 cases were true positive and 1 was false positive and three cases were false negative, yielding a diagnostic accuracy of 92%. The sensitivity of the direct projection radiography was 94%, and its specificity was 67%. The sensitivity of the oblique projection was 91% and its specificity was 93%.

Conclusions:

The oblique X-ray is more informative for the diagnosis of sacroiliitis and assessment of changes in the sacroiliac joints.