MAGNETIC RESONANCE IMAGING (MRI) IN THE EVALUATION OF JUVENILE RHEUMATOID ARTHRITIS (JRA)

Radiologic evaluation of JRA is limited by the predominance of cartilage in the child's joint and by reluctance to subject children to xrays. We assessed the relative efficacy of MRI in evaluating joint disease in 16 JRA children. Mean age was 11.2 years (range 7-20.5 years), and mean duration of disease was 5.2 years (range 2-8.5 years). Although onset mode varied all had severe and active polyarthiristis. MRIs on 15 knees and 12 hips demonstrated effusions in 6 hips, synovial hypertrophy in 5 knees and popliteal cysts in 6 knees, none of which were visible on corresponding xrays. Avascular necrosis, suspected in the hips of one child, was noted by MRI in two hips and one knee. Joint frgments, not seen on xray, were found in 3 knees and one hip. Cartilage loss was more severe than could be seen on xray in 9/12 hips and 5/15 knees. One child with clinically normal hips and only osteopenia on hip xray showed 50% loss of cartilage by MRI. Hypoplastic or absent menisci were found in 10/15 knees and may provide explanation for the jiont instability so frequently present. In contrast, premature fusion of growth plates, seen in the xrays of hips and knees of one patient, were not well visualised by MRI. We conclude that MRI may provide a non-invasive and highly sensitive means of assessing both early and advanced joint disease in JRA.