MRI FINDINGS IN THE KNEE IN JUVENILE IDIOPATHIC ARTHRITIS: EXPERIENCE WITH A NEWLY DEVELOPED JUVENILE ARTHRITIS MRI SCORING SYSTEM (JAMRIS)

R. Hemke1, M. Maas1, M. van Veenendaal2, J. van den Berg2 3, J. Swart3, K. Dolman3, J. Anink2, T. Kuijpers2, M. van Rossum2 3 1Department of Radiology, Academic Medical Center; 2Department of Pediatric Rheumatology, Emma Children's Hospital, Academic Medical Center; 3Department of Pediatric Rheumatology, Jan van Breemen Institute, Amsterdam, Netherlands

Background: MR imaging is superior to clinical examination in detecting inflammatory changes in the joint and is more sensitive than US or plain radiography to demonstrate joint damage. Former studies have shown that open-bore MRI bilateral knee investigations without sedation are feasible in children with JIA. As to date, it is unclear which specific articular and extra-articular manifestations of JIA are notable in the MRI assessment of disease activity and disease outcome in the knees, the most commonly involved joint in JIA.

Objectives: To evaluate a standardized assessment method for the findings in the knee in JIA by using a newly developed literature-based Juvenile Arthritis MRI Scoring System (JAMRIS).

Methods: In this prospective cohort study both knees of 51 children (mean age 12 years [range 5-16]) were examined using an open-bore MRI (1.0T). Clinical indications for MRI were: (group I) clinical arthritis in ≥ 1 joints for > 6 weeks suggestive for JIA (22 pts); (Group II) evaluation of disease activity in clinically active disease before change of therapy (12pts) and (Group III) inactive disease > 6 months (17 pts). All patients had a rheumatologic work-up including the ACR-Pedi core-set and bilateral X-rays of the target joints.

The imaging protocol consisted of T1, T2 and T2-fatsat sequences in all three anatomical directions and lasted for a maximum of 75 minutes. No intravenous contrast was used. A literature-based MR scoring system was constructed (JAMRIS), focused on structural damage, anatomical location of pathology and signal intensity changes. One expert radiologist evaluated all MRI studies, blinded to clinical status.

Results: The MRI examinations were successfully completed by all 51 patients. The following JAMRIS items were observed: Synovial hypertrophy was seen in 27 (26%) of the 102 knees. Hydrops of the suprapatellar bursa was seen in 72 (71%), effusion in the lateral recess was seen in 39 (38%), Baker's cyst in 22 (21%) and effusion anterior to the anterior cruciate ligament (ACL) was seen in 63 (62%) of the 102 knees. Erosions were seen in 5 (5%), subcortical bone marrow edema in 31 (30%) and epiphyseal bone marrow edema in 24 (24%) of the 102 knees. Cartilage lesions were seen in 13 (13%) and tendinopathy/internal derangement in 6 (6%) knees. Abnormalities of the infrapatellar fat pad were seen in 68 (67%) of the knees and popliteal lymph nodes in 77 (75%) of the 102 knees.

Conclusion: Effusion anterior to the ACL is a new common phenomenon observed upon MR imaging of the knee in JIA. Hydrops in the bursa suprapatellaris, abnormalities of the infrapatellar fat pad and popliteal lymph nodes are also common MR findings. Bone erosions and tendinopathy/internal derangement were noted infrequent. Soft tissue abnormalities were not seen and hence removed from our scoring list. The JAMRIS scoring system enables to describe systemically the findings in the knee in JIA. Further validation and correlation with clinical and radiological assessments are presently conducted.

Disclosure of Interest: None declared

Citation: Ann Rheum Dis 2010;69(Suppl3):632

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