Evaluation of magnetic resonance imaging and radionuclide bone scan in early spondyloarthropathy

Abstract

Introduction Spondyloarthropathy (SpA) comprises a small percentage of low backache (LBA) and presents with inflammatory pain. Sacroiliitis in SpAs forms the basis of diagnosis, and may take 7–8 years to become visible in plain radiographs. In order to achieve significant modification of the course of the disease it is imperative to make an early diagnosis, identify risk factors for aggressive disease and initiate the therapy right at outset. Magnetic resonance imaging (MRI) is a promising modality to pick up inflammation and structural damage early in the course of the disease. Objective To assess the role of MRI and radionuclide bone scan in patients with early SpA of less than 2 years. Methods Patients with inflammatory LBA, defined according to the Calin criteria and satisfying the European Spondyloarthropathy Study Group (ESSG) criteria for SpA of less than 2 years duration, were included. Controls had mechanical LBA. A detailed clinical assessment and assessment of disease activity and functional impairment was done with validated measures. Radiological assessment included conventional radiograph of the pelvis, radionuclide scan and MRI of sacroiliac joints (SI joints). The sensitivity, specificity and predictive value of each modality in contributing to the diagnosis of SpA were assessed. Results Assessment of 132 SI joints in 33 patients (Age 31 ± 6.14 years, M:F 24:9) and 33 controls (Age 31.8 ± 7.21 years, M:F 27:5) was done. The mean disease duration of cases was 10.7 (± 6.97) months. Conventional radiograph failed to pick up sacroiliitis in any of the cases. Positive bone scan was present in 27 patients (21 bilateral sacroiliitis, 6 unilateral sacroiliitis). Bone scan had a sensitivity of 81.8% and a specificity of 88%. MRI abnormality was present in 29 patients (50 joints, bilateral in 21 and unilateral in 8) and in none of the controls. This accounted for a sensitivity of 87.9% and a specificity of 100%. The MRI changes included bone marrow oedema (89%), synovial enhancement (55%), subchondral oedema (41%), erosions (51%) and sclerosis (28%). Both inflammatory and structural changes in MRI showed positive correlation with Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) ( P = 0.034, 0.02) and erythrocyte sedimentation rate (ESR) ( P = 0.02, 0.001). Conclusions In patients with early SpA of less than 2 years duration, conventional radiographs did not pick up sacroiliitis; however, both the radionuclide scan and MRI were useful.