The MR Quantitative Evaluation Of The Repair Tissue Of Osteochondritis Dissecans(OCD) Following Microfracture Treatment

Part I:Histological and MR quantitative analysis of repair tissue following microfracture treatment for knee joint osteochondritis dissecans models in rabbitsPurpose:To quantitatively analyze the histological and MR performances of repair tissue (RT) following microfracture for knee joint osteochondritis dissecans(OCD) models in rabbits at different time points, make comparisons with the RT performances of joint debribement, explore the efficiency of the microfracture treatment for OCD, discuss the matching between histological basis and MR performance, and provide clinical suggestions on optimizing the post-op OCD follow-up with MR.Materials and Methods:Twenty-seven New Zealand Rabbits were randomly assigned into3groups (sacrificed at the end of3weeks,5weeks and7weeks post-op respectively),9in each group. For each rabbit, one knee joint was made into OCD model. In each group,6were for microfracture treatment, and the other3were for joint debridement as control. MR scan, which mainly included sequences of3D double echo steady state sequence (3D-DESS) and T2-mapping, was taken at3weeks,5weeks and7weeks post-op. The thickness index and T2value index of RT were calculated and T2-mapping of repair region was drafted. Then the operation sites were removed to make histological sections of H-E, Masson and Safranin-O staining. The modified O’Driscoll score system was employed to make semi-quantitative evaluation on the histological performance of RT. Comparisons were made with respect to MR and histological findings between two treatments at each time point using unpaired Studen t tests. Effects of two treatments were evaluated longitudinally by comparing the results of three time points using a one-way ANOVA, with significance defined as P<0.05.Results:The post-op thickness indexes of two groups increased gradually, T2value indexes decreased, and O’driscoll scores increased gradually. At each time point, the thickness index of microfracture was higher than that of debridement group(3-week:0.743±0.048vs0.624±0.013,t=4.077;5-week:0.813±0.031vs0.734±0.015,t=4.107;7-week:0.972±0.064vs0.777±0.039, r=4.782; P<0.05), and the defects of microfracture in7-week group were almost fully covered while the defects of the debridement in7-week group were not. The T2value index of microfracture group was lower than that of debridement group at3-week point(1.338±0.043vs 1.510±0.009,t=6.583,P<0.05), but it was higher than that of debridement group at5-week and7-week points (5-week:1.284±0.097vs1.116±0.068, t=2.663;7-week:0.916±0.036vs0.843±0.016,t=3.283; P<0.05). The O’Driscoll score of microfracture group was higher than that of joint debridement at every time point (3-week:7.167±0.753vs4.667±0.577,t=5.000;5-week:9.833±1.169vs7.667±0.577,t=2.960;7-week:11.167±0.753vs8.333±1.155, t=4.520; P<0.05). For microfracture group, the RT was mainly repaired by fibrocartilage and got matured gradually with more production of well-distributed collagen fibrils; while for joint debridement group, the RT was mainly repaired by fibrous and scar tissue.Conclusion:The study revealed that the post-op repairing thickness and tissue composition of microfracture for OCD were greater than that of joint debridement; MR3D-DESS and T2-mapping could show the thickness and tissue composition of the RT after OCD treatments, provide effective evaluation of repairing conditions, and of great importance on the OCD post-op follow-up. Part II:The MR quantitative evaluation of the repair tissue of ankle osteochondritis dissecans(OCD) following microfracture treatmentPurpose:investigate the differences of the quantitative MR and clinical outcomes between the short-term and middle-term follow-up of the ankle OCD after microfracture treatment, and analyze the correlation between the quantitative MR and clinical outcomes, so as to evaluate the efficacy of the quantitative MR to follow-up the repairing conditions of ankle joint OCD after microfracture.Materials and methods:Collected48patients of ankle joint OCD who had took microfracture treatment from the sports medicine department of Huashan Hospital, gave them MR scans for ankle joint and evaluated their clinical outcomes. The MRI sequences mainly included3D-DESS, T2-mapping, T2-STIR, which were used to respectively measure the thickness index, T2index of repair tissue(RT) and the volume of bone marrow edema (BME) under RT. The clinical outcomes were evaluated by the American Orthopaedic Foot and Ankle Society (AOFAS) scoring system, these patients were divided into two groups. Group I for3-12months post-op,27patients in total, with the mean follow-up time8.3±0.7months; Group II for12-24months post-op,21patients in total, with the mean follow-up time16.4±1.2months. The independent samples t test are used to compare the differences of quantitative MR (thickness index, T2index, BME volume) and AOFAS scores between the two groups; and pearson correlation was used to analyze the correlation between quantitative MR and AOFAS scores. The difference would be statistically significant if P<0.05.Results:After microfracture treatment for ankle joint OCD, the quantitative MR showed that the thickness index of RT in group II was higher than that in group I (0.827±0.096vs0.691±0.112,t=-4.434, P<0.05), T2index was lower than group I (1.096±0.168vs1.401±0.125, t=1.222, P<0.05), BME volume was lower than group I (0.454±0.318vs0.972±0.940,t=2.674, P<0.05) and AOFAS scores was higher than group I (86.904±6.418vs77.148±9.376,t=4.079, P<0.05). The clinical outcomes of90%patients in group II were good or excellent.The thickness index, T2index and BME volume were all correlated with AOFAS scores (pearson correlation indexes were r=0.416, r=-0.475, r=-0.353respectively, P<0.05), the BME was not correlated with thickness index nor T2index (P>0.05).Conclusion:The short-term and middle-term follow-up results of microfracture treatment for ankle joint OCD suggested that the detect region was filled gradually, the RT got matured gradually, the BME region under the RT was reducing, and the clinical symptoms was relieved. Quantitative MR was correlated with clinical outcomes. The quantitative MR3D-DESS, T2-mapping, T2-STIR could comprehensively evaluate the repairing conditions of ankle joint OCD after microfracture treatment from the respects of repaired thickness, biochemical structure of RT and BME under RT. The BME was not correlated with thickness index nor T2index, which was insufficient of being an independent indicator to evaluate the conditions of RT. But the timely intervention and the reducing of BME could relieve the patients’ clinical symptoms.