兔膝关节剥脱性骨软骨炎微骨折及关节清理术后修复的组织学及MR定量对比分析

Histological and MR quantitative analysis of repaired tissue following microfracture treatment for knee joint osteochondritis dissecans in rabbit models

目的与关节清理术对比，研究微骨折治疗关节剥脱性骨关节炎（OCD）的有效性，探讨MR检查结果对应的组织学基础，指导临床更好地应用MR检查结果进行OCD术后的随访。方法新西兰大耳兔27只，按照随机区组法分成3组，各9只，分别于3、5、7周取材，选单侧膝关节制作OCD模型，6只行微骨折术（微骨折组），3只关节清理作为对照（关节清理组）。于术后3、5、7周分别行MR扫描，成像序列主要为3D双回波稳态序列（3D-DESS）、T2-mapping，计算修复厚度指数和T2指数、绘制T2-mapping；截取手术部位制作组织学切片，包括HE染色、Masson染色，采用O’driscoll改良法进行组织学半定量评分。单因素方差分析比较不同时间点修复的组织学及MR表现，独立样本t检验比较微骨折组和关节清理组在各相同时间点的组织学及MR表现。结果微骨折组和关节清理组术后修复厚度指数逐渐增加（F值分别为33．940、28．841，P值〈0．05），T2指数逐渐减低（F值分别为80．183、206．206，P值〈0．05），O’driscoll评分逐渐增高（F值分别为29．867、17．167，P值〈0．05）。各个时间点，微骨折组厚度指数均大于关节清理组（3周时分别为0．743±0．048和0．624±0．013，t=4．077；5周时分别为0．813±0．031和0．734±0．015，t=4．107；7周时分别为0．972±0．064和0．777±0．039，t=4．782；P值均〈0．05），7周时，微骨折组基本完全填充，关节清理组未完全填充。微骨折组3周时的T2指数低于关节清理组（分别为1．338±0．043和1．510±0．009，t=6．583，P〈0．05），5周和7周时的T2指数大于关节清理组（5周时分别为1．284±0．097和1．116±0．068，t=2．663；7周时分别为0．916±0．036和0．843±0．016，t=3．283；P值均〈0．05）。微骨折组各个时间点O’driseoll评分均高于关节清理组（3周时分别为7．167±0．753和4．667±0．577，t=5．000；5周时分别为9．833±1．169和7．667±0．577，t=2．960；7周时分别为11．167±0．753和8．333±1．155，t=4．520；P值均〈0．05）。微骨折组以纤维软骨修复，逐渐成熟，生成的胶原纤维增多、分布均匀；关节清理组最终以纤维瘢痕修复。结论OCD微骨折术后修复厚度和组织构成均优于关节清理；MR3D-DESS、T2-mapping能分别反映OCD术后修复组织的厚度、组织构成，能有效评估修复情况，对临床OCD术后的随访具有重要价值。

Objective To quantitatively analyze the histological and MR images of repaired tissue （RT） following microfracture for knee joint osteochondritis dissecans （OCD） in rabbit models at different time points,make comparisons with the RT performances of joint debribement, explore the efficiency of the microfracture treatment for OCD. Methods Twenty-seven New Zealand rabbits were randomly assigned into3 groups （ sacrificed at the end of 3,5 and 7 weeks post-operation respectively） , with 9 in each group. For each rabbit,one knee joint was made into an OCD model. In each group ,6 were for microfracture treatment, and the other 3 were for joint debridement as control. MR scan, which mainly included sequences of 3D double echo steady state sequence （3D-DESS） and T2-mapping, was taken at 3,5 and 7 weeks post- operation. The thickness index and T2 value index of RT were calculated and T2 -mapping of repaired region was drafted. Then the operation sites were removed to make histological sections of HE and Masson staining. The modified O＇Driscoll score system was employed to make semi-quantitative evaluation for the histological performance of RT. Comparisons were made with respect to MR and histological findings between two treatments at each time point using unpaired Student t test. Effects of two treatments were evaluated longitudinally by comparing the results of three time points using one-way ANOVA. Results The post-operation thickness indexes of two groups increased gradually（ F = 33. 940,28. 841, P 〈 0. 05 ） , T2 value indexes decreased （ F = 80. 183,206. 206, P 〈 0. 05 ） , and O＇ driseoll scores increased gradually （ F = 29. 867,17. 167, P 〈 0. 05 ）. At each time point, the thickness index of microfracture was higher than that of debridement group（3-week：0. 743 ±0. 048 vs 0. 624 ±0. 013 ,t =4. 077 ;5-week：0. 813 ±0. 031 vs 0. 734 ± 0. 015 ,t = 4. 107 ; 7-week ： 0. 972 ± 0. 064 vs 0. 777 ± 0. 039, t = 4. 782 ; P 〈 0. 05 ）, and the defects of microfracture in 7-week group were almost fully recovered while the defects of the debridement in 7-week group were not. The T2 value index of microfracture group was lower than that of debridement group at 3-week point（ 1. 338 ±0. 043 vs 1. 510 ± 0. 009, t = 6. 583, P 〈 0.05 ）, but it was higher than that of debridement group at 5-week and 7-week points（5-week： 1. 284 ± 0. 097 vs 1.116 ± 0. 068, t = 2. 663 ;7-week ：0. 916± 0. 036 vs 0. 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. 753 vs 4. 667 ± 0. 577, t = 5. 000;5-week： 9. 833 ± 1. 169 vs 7. 667 ± 0. 577, t = 2. 960 ; 7-week ： 11. 167 ± 0. 753 vs 8. 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. Conclusions The post-operation repairing thickness and tissue composition of microfracture for OCD are superior to that of joint debridement. MR 3 D-DESS and T2-mapping can show the thickness and tissue composition of the RT after OCD treatments, provide effective evaluation of repairing conditions, and they are of great importance on the OCD post-op follow-up.