Clinical Application And Evaluation Of MRI T₂-mapping Of Patellar Cartilage In Patients With Knee Osteoarthritis

ObjectivesTo compare T₂ value of patellar cartilage grouped by radiographic stage of patello femoral osteoarthritis(OA) and by body mass index(BMI) in order to explore its diagnostic value in OA.Methods84 subjects(29 men,55 women;mean age,53.6 years;range,26～72 years)were enrolled in the study.One side or both sides of knee joint conformed to the knee joint OA diagnosis which the China Medical Association Orthopedics Branch promulgated in 2007.Standing lateral radiographs centered on the knee for every subject.84 subjects were scanned using four echo spin-echo sequence and the conventional MRI sequences such as T₁ weighed Imaging(T₁WI),fat-suppression proton density weighted imaging(FS-PDWI) and the three dimensional fat-suppressed gradient-recalled echo(3D-FS-SPGR).The knee joint of partial subjects were scanned using CT.84 subjects were divided into the normal group,the mild osteoarthritis group,and the severe osteoarthritis group according to kellgren-Lawrance(K-L),into the normal group,the overweight group and the obese group according to the body mass index(BMI).The T₂ values of the patellar cartilage were measured and were analyzed with SPSS 17.0.Results1.The radiographs of 84 subjects met the data analysis.The MR imaging of seven knee joints were not qualified to carry on the data analysis because of motion artifacts.2.Normal group had mean T₂ value of(37.6±4.5) ms,while mild OA and severe OA had mean T₂ value of(49.8±6.2) ms and(51.9±8.6) ms.The significance was found between the normal group and the mild osteoarthritis group or the severe osteoarthritis group(P＜0.05).No significance was found between mild osteoarthritis group and severe osteoarthritis group(P＞0.05).3.The cartilage of eleven subjects was not found obvious morphologic change. The early OA subjects had mean T₂ value(48.8±4.6) ms.The significance was found between the normal group and the early OA group(P＜0.05).4.Normal group had mean T₂ value of(38.7±7.4) ms,while overweight group and obese group had mean T₂ value of(45.7±6.4) ms and(51.1±7.9) ms.The significance was found between normal group and overweight group or obese group (P＜0.05 among the three group).BMI had a significant effect on T₂ value(P＜0.001).Conclusion1.The significance was found between the normal group and mild OA group or the severe osteoarthritis group,no significance was found between mild OA group and severe OA group.The changes of T₂ value provide an important means for the diagnosis of OA.2.T₂ relaxation time of knee joint cartilage can indicate component abnormally with quantitative measure in articular cartilage of early osteoarthritis group without morphology change,and has a high value in early diagnosis. 3.The differences of T₂ values with BMI signify structural changes within the patellar cartilage and that BMI may be considered a potential factor for increase of T₂ values.We may delay the osteoarthritis patient's condition through the control of body weight.