IN-VITRO MAGNETIC-RESONANCE MICROIMAGING OF EXPERIMENTAL OSTEOARTHRITIS IN THE RAT KNEE-JOINT

Objective. To visualize articular changes during iodoacetate induced o steoarthritis (OA) of the rat knee using high resolution magnetic reso nance imaging (MRI). Methods. All images were acquired on a 8.5T micro imager on ex vivo rat knees. After optimization studies, 3D spin echo sequences were used with TR 1200 ms and TE 15 ms; 40 sagittal images w ere obtained with a resolution of 400 x 60 x 60 mu m. OA lesions were achieved by injecting 3 mg iodoacetate in the right knee joint (Day 0) . Progression of OA changes was studied at Days 5, 10, 15, 20, 30, 90 and corresponding radiographs and histological sections were obtained. Results, Spin echo images of the normal rat knee clearly visualized c ortical bone, calcified menisci, patella, and cruciate ligaments as da rk regions. Cartilage and muscles appeared as intermediate signer. In some cases a trilaminar appearance of cartilage and growth plate was d epicted. This appearance persisted at Day 5, although cartilage presen ted a marked loss of proteoglycans. After Day 10 the menisci appeared irregular and inhomogeneous. After Day 15, MRI showed important altera tions of articular cartilage, predominant on weight bearing areas of f emoral condyles. Osteophytic remodeling was also seen around the patel la. From Day 20 to Day 90 anatomical changes progressively affected ep iphyseal bone, leading to subchondral cysts and loss of its regular tr abecular structure. Conclusion. High field MRT provides a sensitive me thod for investigating ex vivo focal erosions of cartilage and establi shed osteochondral remodeling in experimental OA in the rat. In this m odel, microimaging provides more information about early modifications of cartilage and soft tissue than radiographic exploration, in good c orrelation with histological data.