| PrefaceMRI is the most important modality to evaluate articular cartilage noninva-sively. Many researchs pay attention to the study of articular cartilage. However , recent studies emphasize on the technique of MR imaging and morphology of articular cartilage. The study of articular cartilage will tend to evaluate the function of cartilage and the relationship between morphology and function in future.This is the fist research to study the changes of articular cartilage in nature history of experimental pyogenic arthritis with various MR sequences and related the MRI presentations with histophathologic, biochemical changes, in order to find the relationship between them.In addition, this is the fist research to study clinical cases of pediatric pyogenic arthritis in order to evaluate articular cartilage in early stage. Because pyogenic arthritis in children will lead to severe sequelae in growth and founction of bone and joint if diagnosis and treatment were delayed, moreover, initial clinical presentations were always occult, early diagnosis was difficult made before laboratory examination. The results will be used to assess the destructional degree of cartilage, evaluate prognosis and response to therapy.PurposeTo study the MR imaging appearances of articular cartilage before significant morphologic changes in experimental pyogenic arthritis and to compare the findings with histopathology and biochemical changes in the nature history of py-ogenic arthritis.To summariz the MR imaging characteristics of pediatric pyogenic arthritis and evaluate the diagnosis value of MR imaging in pediatric pyogenic arthritis and pay attention to the changes of articular cartilage in pyogenic arthritis.Materials and MethodsForty canine knees were used for experiment, four knees of random animals served as a normal control, thirty - six knees of the other animals were each in-tra - articular injected with 2ml of Staphylococcus aureus suspension (108 organisms/ml). Afer injection, at 3, 7, 10, 14, 19, 21, 24, 27, 31 days , MRI of pyogenic arthritis joints were performanced with Elscint Prestige 2. OT system. Axial, saggital and coronal images were obtained with SE -T1WI, FSE-T2WI / FSE-PDWI, FS-FSE-T2 WI, STIR sequences. Signal intensity and thickness of cartilage were measured. After animals sacrificed, the samples of femoral condyle were then fixed, decalcified, saggital sectioned and stained, using HE, toluidine blue, the cartilage of tibial plateau were used to measure proteo-glycan content.We collected ten cases of acute pyogenic arthritis. Clinical symptoms involved fever, joint ache, swelling and limited activity. The time from finding symptoms to performing MR imaging ranged from 2 to 22 days ( mean, 12 days). Involved joints were as follows; knee(n =7) , shoulder(n =2) , hip(n = 1). Of all patients, 9 were male and 1 was female; their ages ranged from 4. 5 months to 12 years (mean, 5 years). All patients were studied with computed radiography(FCR AC - 3CS/ID) , MR( Elscint Prestige 2. OT MR) on SE -T1WI , FSE - T2WI/FSE - PDWI and STIR. Axial, saggital and coronal images were obtained, additional computed tomography ( Marconi MX8000 CT) for three patients. All images were reviewed by two musculoskeletal radiologists who were experienced in musculoskeletal imaging. We analyzed diverse MR imaging findings of acute pyogenic arthritis in terms of articular cartilage changes, bone erosion, ligament and joint capsule changes, joint fluid. We payed attention toobserve articular cartilage abnormalities, involving the changes of signal intensity and morphology.ResultsAfter intra - articular injection, from 3 to 7 day the morphology on MRI were normal; from 10 to 31 days, articular cartilage became changing,the fist sign is irregular surface(1 degree) , from 24 days 2 degree was observed without 3 degree. At 19 days and after then thickness of cartilage decreased (P <0. 05) and articular suface became irregular without defect. From 7 day the signal intensity of cartilage in pyogeni...
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