Abstract：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.
2012, Vol. 52 
