Background Juvenile idiopathic arthritis is a chronic inflammatory disease with the challenge of bone and cartilage destruction early in life. Assessment of damage in JIA is therefore of pivotal interest for preceding the long-term disease course in patients with JIA. In particular, the polyarticular JIA is considered being a highly destructive disease. Magnetic resonance imaging (MRI) in adult rheumatoid arthritis patients is known to detect erosions already in early stages. Since in JIA the knowledge on the impact of arthritis on bone structure during the course of the disease is still limited, additional studies are needed to dissect the reversible inflammatory changes from the usually irreversible destructive change in the joints of children (1-3)
Objectives To test, whether suspect erosions in JIA patients detected by MRI are indeed associated to structural damage to the cortical bone
Methods Twelve children with a median age of 15.87±2.66 years, 10 with polyarthritis and two with psoriatic arthritis received MRI and conventional computed tomography (CT) of the same wrist. Mean disease duration was 2.16 years. All patients were treated with NSAIDs and subcutaneous methotrexate. Due to the relatively small patient cohort a descriptive statistical approach was chosen.
Results Overall 1248 surfaces were evaluated both in MRI and CT; 27 erosions were detected by MRI and 46 erosions by CT. Erosions predominated in the capital bone, lunar bone and the second metacarpophalangeal joint. The ulnar styloid, the scaphoid, the carpometacarpal joint, and the 2nd, 4th and 5th metacarpophalangeal joints were not affected. Of the 27 erosions detected in MRI, 23 were confirmed as being true bone erosions in the CT while 4 lesions were identified as vessel channels but not erosions. Widths of erosions in the MRI varied from 0.34 to 7.34mm, and depths from 0.98 to 5.35mm. In the CT widths ranged from 0.57 to 4.22 mm, and depths from 0.72 to 5.36mm. Details of sensitivity, specificity as well as positive and negative predictive value (PPV/NPV) see table 1.
Conclusions MRI bone erosions in patients with JIA mostly correspond to cortical breaks detected by conventional CT suggesting structural bone damage in patients with JIA.
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Disclosure of Interest None declared