The MR Study Of Articular Cartilage Of Two Different Rabbit Osteoarthritis Models In The Knee Joint

Objective:To explore the value of MRI in assessing the main pathologic changes of articular cartilagematrix(collagen and proteoglycan) of osteoarthritis．Methods:Thirty New Zealand white rabbits were randomly divided into A, B, C three groups.12rabbits were selected in both experimental group A and B.0.5ml0.4%collagenase II (2mg) or0.5ml1.6%papain(8mg) was injected into the right knee joint cavity of group A and Brespectively, The same drugs were injected4days later in both two groups. The equivalentdilution was injected into the left knee joint cavity as control.6rabbits were selected as the blankcontrol group.6(4) weeks after the last injection, the A (B) group’s OA model is establishedcompletely. The bilateral knee joints of rabbits of three groups were scanned with T2WI,3D FSSPGR, T2mapping and T1mapping in sagittal plain. T2, T1values of the lateral femoral condylecartilage and the femoral condyle cartilage thickness were measured by post-processing software.The femurs were pathologically examined. T2, T1values and the cartilage thickness werecompared within and between groups.Results:①It is pathologically confirmed that the two different rabbit models of early osteoarthritiswere established successfully by intra-articular injection of collagenase II, papain. Nosignificant changes were observed on conventional MRI sequences.②Group A: T2and T1value of the right side(48.10±3.92ms;1041.3±81.9ms)were higherthan the left side(35.68±1.57ms;694.4±43.9ms), and the difference was statisticallysignificant (P=0.000;0.000);③Group B:The T1value of the right side(992.6±65.5ms) were higher than the leftside(689.3±53.0ms), and the difference was statistically significant (P=0.000), The T2valueof the right side(36.37±1.69ms) and the left side(35.69±1.77ms) showed no significantdifferences(P=0.353);④T heT2values of the right side in group A was higher than group B, and the differencewas statistically significant (P=0.000); The T1values of the right side in group A and groupB showed no significant difference(P=0.160);⑤The cartilage thickness showed no significant difference within and betweengroups(P>0.05).Conclusion: The T2mapping and T1mapping are more sensitive than the conventional MRI sequences tofacilitate the early diagnosis of osteoarthritis and reflects the changes of cartilage matrix. Morespecifically, T2value was able to provide information about the changes of collagen, whereas T1value was affected by both collagen and proteoglycan.