Early recognition of sacroiliitis by magnetic resonance imaging and single photon emission computed tomography

To evaluate the role of magnetic resonance imaging (MRI) and single photon emission computed tomography (SPECT) in the detection of sacroiliitis in patients with clinical features of inflammatory back disease but without conventional radiographic changes.

Twenty-four patients with inflammatory low back pain (ILBP) and normal or suspicious changes of sacroiliitis (New York criteria: 0-1) on conventional radiography, in addition to 12 control subjects were studied. MRI, bone and SPECT scans of the sacroiliac (SI) joints were obtained and interpreted without knowledge of patient identification. MRI scans were scored according to the modified New York criteria and examined for the presence of joint fluid, abnormalities in articular cartilage and in the underlying marrow signal. A quantitative and qualitative assessment of radiopharmaceutical uptake in the SI joints was derived from planar bone scan films and SPECT scans.

MRI detected features of scaroiliitis in 54% of patients with ILBP and in 17% of controls (p = 0.07). Quantitative and qualitative analysis of planar bone scan films did not reveal any differences between the 2 patient groups. In contrast, SPECT scanning identified sacroiliitis in 38% of patients with ILBP compared to none in controls (p = 0.05). When MRI and SPECT scanning were combined there was evidence of sacroiliitis in 63% of patients with ILBP and in 17% of controls (p = 0.025).

MRI and SPECT bone scanning provide objective and complementary evidence of sacroiliitis in patients with clinical features of inflammatory spinal disease in the absence of conventional radiographic changes.