运动对骨软骨骨折转归影响的MRI表现与MMP-13表达

观察运动对骨软骨骨折(OCF)转归影响的MRI表现及MMP-13在膝骨折片覆盖软骨中的表达。方法随机选用30只月龄及体质量相近的健康新西兰大白兔,雌雄不限:实验组20只建立兔膝股骨髁OCF模型;假手术对照组10只。所有模型均不进行内固定及外固定。术后即进行术侧膝关节间歇主动活动(IAM)与间歇被动活动(IPM);术后1、2周分别从实验组中随机抽取10只实验兔行MRI检查、大体观察、组织学检查,假手术对照组10只于术后2周行上述检查。MRI扫描序列包括:TSE-T1WI、TSE-T2WI、T2WI/SPAIR、3D/WATSc/FFE/T1WI。结果术后1、2周,骨折线均清晰,OCF片移位14(14/20);骨片覆盖软骨术后2周较术后1周损伤重(P<0.05);骨折区成纤维细胞数术后2周较术后1周多(P<0.05)。术后第2周,股骨髁骨折处骨质增生,MRI示薄层低信号,骨片内部分骨小梁坏死;骨片覆盖软骨MMP-13表达,术后2周较术后1周表达程度明显增高(P<0.05),对照组仅2(2/10)只轻度表达。结论运动可使兔股骨髁关节表面OCF愈合不佳,术后2周变化类似剥脱性骨软骨炎的特点;OCF后骨片覆盖软骨MMP-13表达升高,对临床治疗OCF及评价预后具有重要意义。

Effect of Movement on Osteochondral Fracture Outcomes Evaluated by MRI and MMP-13 Expression

Objective To evaluate the effect of movement on osteochondral fracture outcomes using MRI,and to investigate the expression of MMP-13 in the covering cartilage of bone flap.Methods Thirty New Zealand rabbits of similar age and weight were chosen in this study.Osteochondral fracture of femoral condyle of the knee joint was induced in 20 rabbits(experimental group) and sham operation was performed in another 10 rabbits(control group).Rabbits in experimental group were not treated by internal or external fixation,but were allowed intermittent active motion(IAM) and intermittent passive motion(IPM).Ten experimental rabbits were randomly chosen to receive MRI,histological examination,and gross examination 1 and 2 weeks after operation,respectively.Rabbits in control group received these examinations 2 weeks after operation.MRI sequences included TSE-T1WI,TSE-T2WI,T2WI/SPAIR and 3D/WATSc/FFE/T1WI.Results Fracture lines were clear and displaced osteochondral fragment was seen in 14 of the 20 experimental rabbits 1 and 2 weeks after operation.Moreover,osteochondral fracture resulted in more damage to covering cartilage of bone fragment and greater number of fibroblasts 2 weeks after operation than 1 week after operation(P<0.05).The fracture of the femoral condyle presented obvious hyperosteogeny and MRI showed a thin layer of low signal intensity.Some bone trabeculae in bone fragment showed necrosis.In experimental group,the expression of MMP-13 in the covering cartilage of bone fragment detected at 2 weeks after operation was significantly higher than that detected at 1 week after operation(P<0.05).In control group,MMP-13 expression was only found in 2 rabbits.Conclusion The movement leads to poor healing of osteochondral fracture of femoral condyle in rabbits.The MRI and pathological features of osteochondral fracture are similar to osteochondritis dissecans 2 weeks after operation.The increased MMP-13 expression in covering cartilage of bone flap after osteochondral fracture is of great significance for clinical treatment and prognostic evaluation of osteochondral fracture.