Quantitative Evaluation Of Bone And Cartilage In Knee Osteoarthritis Using Multimodality Imaging

Objective: To explore subchondral trabecular bone microstructural features,and to determine the relationship between cartilage and trabecular bone in the osteoarthritic knee using 3T MRI and synchrotron radiation micro-computer tomography from human to animal experiments.Methods: 1、Eighty subjects were prospectively enrolled in our study and divided into three groups on the basis of criteria(control group,mild OA group and severe group).3D Balanced Fast Field Echo(3D–FFE)images were obtained by 3T MRI to quantify trabecular bone structure,and FatSat 3D Fast Field Echo(3D–FFE)images were acquired to assess cartilage thickness.Trabecular bone parameters,including bone volume fraction(BVF),erosion index(EI)and the trabecular plate-to-rod ratio(SCR),and trabecular thickness were evaluated using digital topological analysis.Subchondral bone and cartilage parameters between different groups were compared,and their correlations were analyzed.2、On the first part,the number of severe OA were increased,and totally 92 subjects were enrolled in this study.We used the same method to image trabecular bone and cartilage.Further,the trabecular bone in twelve sites of the knee joint was evaluated using digital topological analysis,and the cartilage thickness in four sites was calculated.Subregional trabecular bone and cartilage parameters between groups were compared,and their correlations were analyzed.3、Twelve mature New Zealand rabbits were used and subjected to surgery using the improved Hulth method.Further,they were equally divided into four groups based on various time(control group,W4,W8,W12).3D-vibe sequence was used to image cartilage,and synchrotron radiation micro-computer tomography was used to image trabecular bone.In addition,the level of CTX-Ⅱ,α-CTX in serum was analyzed by ELISA.The dynamic change of cartilage,subchondral trabecular bone,biomarker between groups were compared and their correlations were analyzed.4、Three cylindrical cartilage-bone plugs were harvested from the joint of human knee,and were performed by SR-micro CT.Further,the processed SR-micro CT images were compared with pathologic pictures.Then we analyzed the size,shape,orientation of chondrocytes and orientation of collagen framework.Results: 1、In mild OA,the gross trabecular bone feature in two femoral condyles was deteriorated showing a lower(BVF,a lower SCR,lower trabecular thickness and a higher EI(P<0.001).In severe OA,BVF was further decreased.2、Within both femoral condyles,the subregional trabecular bone structure deteriorated in mild OA,showing a lower BVF(0.15 to 0.12,P<0.05),higher EI(2.25 to 2.28,P <0.01),and a lower SCR(6.22 to 5.96,P<0.05).Within medial and lateral tibia,deterioration in the trabecular bone was also observed,demonstrating a lower BVF(0.15 to 0.12 P <0.05)and a higher EI(2.25 to 2.61,P<0.05).Extensive correlations were found between the medial cartilage thickness and subregional trabecular parameters.There was mainly a positive correlation with both femoral BVFs(r >0.3,P <0.05),and a negative correlation with the tibia SCR(r <-0.2,P <0.05).3、Four week after surgery,the α-CTX level was increased,and BVF,trabecular thickness was decreased(P=0.013,0.038).Eight week after surgery,the CTX-Ⅱ level and T2 Values was increased.T2 values was positively correlated with serum α-CTX,CTX-Ⅱ(P <0.001),and negatively correlated with trabecular bone BVF and trabecular thickness(P=0.026,0.018).4、The size,shape,distribution of chondrocytes and orientation of collagen framework can be clearly demonstrated on reconstructed images of SR-microCT.Conclusion: 1、In the early stage of OA,trabecular bone osteoporotic changes were observed in both femoral condyles and the tibia.Based on a strong correlation with the medial cartilage thickness,the trabecular structural topological analysis may be useful for elucidating OA onset,progression and monitoring treatment.2、Serum α-CTX,CTX-Ⅱ combined with imaging parameters can be used to reflect and monitor dynamic change of cartilage and subchondral trabecular bone.3、SR-micro CT with phase-contrast can demonstrate a true cellular resolution for human articular cartilage.