| Main roles of the posterior cruciate ligament (PCL) are to controll the posterior translation of tibia and to regulate the rotation of tibia. Lateral meniscus is a vital part of the knee,which can absorp shock, transmiss stress and stabilize the knee. In this study, Chapter one:strainings changes in different sites of lateral meniscus caused by PCL deficiency or rupture are observed through biomechanical approach to investigate biomechanical effect of deficiency or rupture of PCL on lateral meniscus. Chapter two:histological changes of meniscus and expression of MMP-1,MMP13&TIMP-1 in lateral meniscus are observed for investigating roles of MMP-1,MMP13&TIMP-1 in the degradation of lateral meniscus. Chapter three:the circumferentia displacement of lateral meniscus after PCL deficiency or rupture is measured, so as to provide theoretical evidence about whether deficiency or rupture of PCL has effects on the lateral meniscus. This study have very important meanings for the protection of lateral meniscus and the avoidance of osteoarthritis after PCL injury. OBJECTIVE To investigate biomechanical effect of rupture of PCL on lateral meniscus.METHOD Strainings of lateral meniscus anterior horn, caudomedial part and posterior horn in all fresh normal adult knee joint specimens including 12 specimens of intact PCL,6 of antelateral bundle(ALB) rupture,6 of postmedial bundle(PMB) rupture and 12 of complete rupture PCL are tested when the knee joints are loaded 200N,400N,600N,800N and 1000N at 0°,30°,60°and 90°of flexion.RESULT 1. At 0°of knee flexion, Strainings of anterior horn, caudomedial part& posterior horn are all negative values, pressing strainings. Strainings of lateral meniscus'anterior horn, caudomedial part and posterior horn show no significant difference between PMB rupture group and PCL complete rupture group,intact PCL group and ALB rupture group under the load of 200N and 400N,P>0.05, strainings of anterior horn, caudomedial part in PMB rupture group and PCL complete rupture group are bigger than that in intact PCL group and ALB rupture group,which have significant difference, P<0.05, strainings of posterior horn in PMB rupture group and PCL complete rupture group is smaller than intact PCL group and ALB rupture group, which have significant difference, P<0.05; significant difference is showed among all the groups under the loads of 600N,800N,1000N,P<0.05, under the same load and angle of flexion, the correlation of the absolute value of straining in every group of lateral meniscus'anterior horn and caudomedial part increases in this way of PCL complete rupture group> PMB rupture group>ALB rupture group>PCL intact group,and posterior horn increases in this way of PCL complete rupture group< PMB rupture group 0.05, Anterior horn& caudomedial part in PCL complete rupture group& ALB rupture group are negative values, pressing strainings, in PCL intact group& PMB rupture group are positive values, pulling strainings, which have significant difference, P<0.05, posterior horn in PCL complete rupture group& ALB rupture group are positive values, pulling strainings, in PCL intact group& PMB rupture group are negative values, pressing strainings, which have significant difference, P< 0.05; significant difference is showed among all the groups under the load of 600N,800N, 1000N,P<0.05, under the same load and angle of flexion, the correlation of the absolute value of straining in every group increases in this way of PCL complete rupture group>ALB rupture group,PCL intact group> PMB rupture group.3. At 60°and 90°of flexion, anterior horn &caudomedial part in PCL complete rupture group& ALB rupture group are negative values, pressing strainings, in PCL intact group& PMB rupture group are positive values, pulling strainings; posterior horn in PCL complete rupture group& ALB rupture group are positive values, pulling strainings, in PCL intact group& PMB rupture group are negative values, pressing strainings. There is significant difference among all the groups under the load of 200N,400N,600N,800N,1000N,P<0.05. under the same load and angle of flexion, the correlation of the absolute value of straining in every group increases in this way of PCL complete rupture group>ALB rupture group, PCL intact group>PMB rupture group.CONCLUSION 1.PCL complete rupture is likely to cause abnormal strainings in all regions of lateral meniscus under different load and angle of flexion.2. Under the load of 200N and 400N, ALB rupture at 0°of flexion and PMB rupture at 30°of flexion have no effect on strainings in all regions of lateral meniscus.3. Under the load of 600N,800N and 1000N, ALB rupture at 0°of flexion and PMB rupture at 30°of flexion have obvious effect on strainings in all regions of lateral meniscus.4. Abnormal strainings in all regions of lateral meniscus can be caused by PMB rupture at 0°,60°,90°of flexion and ALB rupture at 30°,60°and 90°of flexion under different load. OBJECTIVE To study histological effects on lateral meniscus and roles of MMP1,MMP13&TIMP-1 in the secondary injury of the lateral meniscus after rupture of PCL.METHOD Lateral meniscus of 60 rabbits matched mode pairs in experiment side which PCL were transected and in control side which PCL were intact, at the 4th,8th,12th,16th,24th week,execute 12 rabbits randomly,then to observe lateral meniscus in general view and through HE staining and through immunohistological staining, to detect expressions of MMP1,MMP13&TIMP-1.RESULT 1. The observation in general view showed that with times lateral meniscus of experiment group gradually wore,even ruptured, presenting yellow color and bad elasticity.2. With times the observation of histology shows uneven surface of meniscus,loose tissue, disorders of collagen fibers, infiltration of inflammatory cell,interstitial edema and deformation of intracytoplasm mitochondrion in the chondrocytes. Histological evaluation of the degeneration in fibrocartilage of meniscus in both groups:The scores at 4th,8th,12th,16th,24th week were higher in the experimental group than those in the control group,showing significant difference, P<0.05; the scores of experimental group at 12th,16th,24th week was higher than that at 4th and 8th week, showing significant difference, P< 0.05,but there is no significant difference between the 4th and 8th week, P> 0.05.3. At the 4th,8th,12th,16th,24th week,expressions of MMP1,MMP13&TIMP-1 are higher in experimental group than that in control group, showing significant difference, P< 0.05.4. In experimental group, the expression of MMP 1 is higher at (12w,16w,24w) than that at(4w,8w),showing significant difference, P< 0.05,; but there is no significant difference between 4w and 8w, P> 0.05. there is no significant difference among 12w,16w,24w, P> 0.05.5. In experimental group, there is no significant difference between 4w and 8w, there is no significant difference between 12w and 16w, P> 0.05; the expression of MMP 13 is higher at (12w,16w) than that at (4w,8w)& (24w),showing significant difference among 12w&4w,12w&8w,12w&24w,16w&4w, 16w&8w,16w&24w, P< 0.05.6. In experimental group,the expression of TIMP-1 is obviously higher at 12w than any other weeks, P< 0.05, there is no significant difference among 4w,8w,16w& 24w, P> 0.05.CONCLUSION 1. Rupture of PCL can cause the degeneration of lateral meniscus with times.2. MMP-1 displays rising firstly then expressing consistently after the rupture of PCL; MMP 13, TIMP-1 displays high expression firstly then low expression in advanced stage after the rupture of PCL.3. MMP-1,MMP13,TIMP-1 can be observed as an index for the injury of lateral menicus after the rupture of PCL. The high expression of MMP-1,MMP13,TIMP-1 hints that the physiopathological mechanism triggered by MMP-1,MMP13,TIMP-1 is maybe one cause of the degeneration of lateral meniscus after the rupture of PCL.OBJECTIVE To explore the effect of PCL rupture on lateral meniscus circumferentia displacement and the correlation between the degree of PCL rupture and circumferentia displacement.METHOD The circumferentia displacement of lateral meniscus in all fresh normal adult knee joint specimens including 12 specimens of PCL intact,6 of anterolateral bundle(ALB) rupture,6 of postmedial bundle rupture(PMB) and 12 of complete rupture PCL are tested when the knee joints loaded 200N,400N,600N,800N,1000N at 0°,30°,60°and 90°of flexion. RESULT 1.The range of circumferentia displacement of lateral meniscus distributes between 0.5-2.6mm in PCL intact group.2. At 0°of knee flexion, under the loads of 200N,400N, the circumferentia displacement of lateral meniscus between PCL complete rupture group and PMB rupture group, PCL intact group and ALB rupture group shows no significant difference, P>0.05, the circumferentia displacement in PCL complete rupture group and PMB rupture group is bigger than in PCL intact group and ALB rupture group,showing significant difference, P<0.05; there is significant difference among each group under the load of 600N,800N,1000N, P<0.05.3. at 30°and 60°of flexion,under the loads of 200N and 400N, the circumferentia displacement of lateral meniscus between PCL intact group and PMB rupture group, PCL complete rupture group and ALB rupture group shows no significant difference, P>0.05, the circumferentia displacement in PCL complete rupture group and ALB rupture group is bigger than in PCL intact group and PMB rupture group,showing significant difference, P<0.05; Under the loads of 600N,800N and 1000N, the circumferentia displacement among every group shows significant difference at 30°and 60°of flexion, P<0.05.4. At 90°of flexion,under the loads of 200N, the circumferentia displacement of lateral meniscus between PCL intact group and PMB rupture group, PCL rupture group and ALB rupture group shows no significant difference at 90°of flexion,P>0.05, the circumferentia displacement in PCL complete rupture group and ALB rupture group is bigger than in PCL intact group and PMB rupture group,showing significant difference, P<0.05; Under the loads of 200N,600N,800N and 1000N the circumferentia displacement among every group shows significant difference at 90°of flexion, P<0.05.CONCLUSION l.The physiological circumferentia displacement of lateral meniscus is between 0.5mm and 2.6mm.2.The circumferentia displacement of lateral meniscus in ALB rupture group at flexed position of the knee becomes much bigger than that in PCL intact group.3.The circumferentia displacement of lateral meniscus in PMB rupture group at extended position of the knee becomes much bigger than that in PCL intact group.4.The circumferentia displacement of lateral meniscus becomes much bigger at all position of the knee when the PCL is ruptured completely.5.The abnormal circumferentia displacement of lateral meniscus after PCL rupture hints that PCL rupture maybe a factor which causes the degeneration of lateral meniscus.
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