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