Radiological and Magnetic Resonance Imaging Findings in the Sacroiliac Joints in Patients with early Spondylarthropathy

Objective: To compare the radiological (X-ray) and magnetic resonance imaging (MRI) findings in the sacroiliac (SI) joints in patients with early spondylarthropathy (SpA). Methods: Forty consecutive HLA B27 antigen positive patients with early SpA and inflammatory low back pain (LBP) were studied. Their SI joints were investigated by posterior anterior plain X-ray and MRI. Results: The X-ray and MRI examinations gave similar results in the SI joints in 24 patients, whereas they differed in 16, this difference being significant (p = 0.007). In those 16 patients, in whom the findings differed, the X-ray findings were normal but MRI showed sacroiliitis which was bilateral in 13 and unilateral in 3 patients. The kappa coefficient between these investigations was 0.346, showing poor agreement. Conclusion: These results indicate that MRI may considerably improve the diagnosis of sacroiliitis in HLA B27 antigen positive patients with early SpA and inflammatory LBP.