Background Sensitivity and specificity of conventional radiographs of the sacroiliac joints (SI-joints) for assessing sacroiliitis is limited. Low dose CT may better visualise SI joints than plain radiographs and is associated with lower radiation exposure.
Objectives Evaluation of the diagnostic role of low dose computed tomographies (CTs) of the SI-joints in assessing patients with chronic low back pain and low to moderate suscipition of axial SpA.
Methods 51 Patients who presented to our clinic in a routine clinical setting for evaluation of chronic back pain of unknown origin and in whom x-rays of the SIJ were inconclusive underwent low dose CTs of the SI-joints. 7 patients also underwent magnetic resonance imaging (MRI) of the SIJ. We retrospectively analysed in how many patients low-dose CT helped to establish a diagnosis.
Results 51 patients (47.1% male, 53.1% HLA-B27 positive, mean age 48.2 years (SD 10.3), mean disease duration 9.3 years (SD 7.9)) were retrospectively assessed. Only 36.4% presented with inflammatory back pain (IBP).
Using low dose CTs of the SI-joints, finally:
A) in 66.7% (34/51) of patients sacroiliitis was excluded, among them degenerative changes of SI-joints were found in 17.6% (9/51) of patients. In nearly all of these patients axial SpA was excluded.
B) In 9.8% (5/51) a diagnosis of ankylosing spondylitis (AS) could be confirmed by CT.
C) In 23.5% (12/51) of patients chronic sacroiliitis (mostly sacroiliitis unilaterally grade 2) was found however these findings were not sufficient to fulfil the modified New York criteria. Amongst others based on these findings in most of these patients a diagnosis of “undifferentiated axial spondyloarthritis” was made. In one of these patients MRI could not be performed because of claustrophobia.
Conclusions In this group of slightly older chronic back pain with moderate suspicion of axial SpA only low-dose CT of the SI-joints helped to exclude axial SpA. Low dose CT which is associated with a lower radiation exposure may be used as an alternative to MRI in this population.
Disclosure of Interest None Declared