Braking Time Effects On Rabbit Knee Joint Cartilage Injury And Repair

Objective To investigate the effects of immobilization for different time on injury andrepair after releasing immobilization of articular cartilage.Methods 49 male New Zealand white rabbits were randomly divided into seven groups (n =7): group A1, group A2, group A3,group B1, group B2, group B3,group C. The left posteriorlimbs of rabbits were immobilized in full extension by a plaster cast. Group A1,A2 and A3 wereimmobilized for 4 weeks, group B1,B2 and B3 were immobilized for 6 weeks,group A2 andgroup B2 moved independently for 4 weeks after releasing immobilization, group A3 and groupB3 moved independently for 8 weeks after releasing immobilization, group C received notreatment.In each group, one rabbit was selected randomly for HE staining and safranin "O"staining.The other six rabbits were measured the range of the knee motion,observed the generalmorphology and the expressions of collagenⅡmRNA and aggrecan mRNA of chondrocytesby Real-time PCR.Results (1)Compared with the group C,the ranges of knee motion of the group A1 and B1were significantly reduced(P<0.01),and the group B1was smaller than the groupA1(P<0.01).Compared with the group A1,the range of knee motion of the group A3 wasincreased(P<0.01).Compared with the group B1,the range of knee motion of the group B3 wasincreased(P<0.01). The range of knee motion of the group B3 was smaller than the groupA3(P<0.01).The range of knee motion of the group A3and B3 were smaller than the groupC(P<0.01).(2)General and histological morphology observation,After immobilization,thedegenerative changes of articular cartilage were found.And the degeneration of articular cartilagereversed in varying degrees after released the immobilization and free movement.(3)Comparedwith the group C,the expressions of collagenⅡand aggrecan mRNA of the group A1 and B1were significantly reduced(P<0.01),and the group B1 was lower than the groupA1(P<0.01).Compared with the group A1,the expression of collagenⅡand aggrecan mRNA ofthe group A3 was increased(P<0.01),but the difference of group A1 and A2 was nosignificant(P>0.05).Compared with the group B1,the expression of collagenⅡand aggrecanmRNA of the group B3 was increased(P<0.01),but the difference of group B1 and B2 was nosignificant(P>0.05).The expression of collagenⅡand aggrecan mRNA of the group B3 waslower than the group C(P<0.01),but the difference of group C and A3 was nosignificant(P>0.05).Conclusion With the knee immobilization time extension ,the cartilage damage willincrease ; The cartilage damage caused by short-term immobilization will repair by itself afterreleased the immobilization and repair rate will slow down with the time of the immobilizationprolonged.