| The posterior cruciate ligament (PCL) provides dynamic stability to knee by preventing posterior translation of the tibia relative to the femur. The role of medial meniscus is shocks absorption,stress transmission, and stabilization of the knee joint. They influence each other in maintaining the stability of knee joint. With the development of MRI and arthroscope, early diagnosis and treatment of PCL injury turns to be easily achieved, Additionally, some studies have shown that the beginning of arthritis within a PCL-deficient knee could be caused by abnormal kinematics, but it is little known whether deficiency of PCL effects on the medial meniscus. Therefore, more comprehension of the histological effect and biomechanics effect of PCL rupture on medial meniscus is of great value and meaning on prevention and cure of medial meniscus injury and osteoarthrosis caused by PCL rupture. In this study,straining changes in several sites of medial meniscus caused by PCL injury is observed through biomechanics approach; histological changes of meniscus and expression of MMP1, MMP13and TIMP1 in medial meniscus are observed so as to investigate the function of MMP1, MMP13 and TIMP1 in degeneration of medial meniscus; circumferentia displacement of medial meniscus after PCL injury is measured, so as to provide theoretical evidence whether deficiency of PCL effects on the medial meniscus. OBJECTIVE The effect of PCL injury in several sites of medial meniscus by measuring biomechanics is observed so as to explore the mechanism of medial meniscus injury after PCL rupture.METHOD The straining of medial meniscus anterior horn, caudomedial part and posterior horn in all fresh normal adult knee joint specimens including 12 specimens of complete PCL,6 of anterolateral bundle (ALB) rupture,6 of posteromedial bundle (PMB)rupture 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 1.①The straining of medial meniscus anterior horn, caudomedial part and posterior horn are negative values (pressing strainings) at 0°of flexion.②The straining of medial meniscus anterior horn, caudomedial part and posterior horn shows no significant difference among all the groups under the loads of 200N at 0°of flexion,P >0.05;③The straining of medial meniscus anterior horn, caudomedial part and posterior horn shows no significant difference between PMB rupture group and PCL complete rupture group, between complete PCL group and ALB rupture group under the load of 400N and 600N at 0°of flexion,P>0.05;④significant difference is showed among all the groups under the loads of 800N and 1000N at 0°of flexion,P<0.05, under the same load and angle of flexion, the correlation of the absolute value of straining in every group of medial meniscus anterior horn and caudomedial part increases in this way of PCL complete rupture group > PMB rupture group> ALB rupture group> complete PCL group,and of posterior horn increases in this way of PCL complete rupture group< PMB rupture group 0.05.③The straining of medial meniscus anterior horn,caudomedial part and posterior horn shows significant difference in all groups under the load of 800N and 1000N at 30°,60°of flexion,P<0.05. The absolute value of anterior horn straining(pressing straining) in ALB rupture group< PCL complete rupture group, the absolute value of anterior horn straining(pulling straining) in complete PCL group>PMB rupture group. The correlation of the absolute value of caudomedial part straining in every group increases in this way of PCL complete rupture group> ALB rupture group>PMB rupture group > complete PCL group.The the absolute value of posterior horn straining(pulling straining) in ALB rupture group< PCL complete rupture group, The the absolute value of posterior horn straining(pressing straining) in complete PCL group>PMB rupture group.3.①The straining of medial meniscus anterior horn in complete PCL group and PMB rupture group are pulling strainings at 90°of flexion,and in ALB rupture group and PCL complete rupture group are pressing strainings at 90°of flexion.The straining of medial meniscus caudomedial part in all groups are pressing strainings at 90°of flexion.The straining of medial meniscus posterior horn in complete PCL group and PMB rupture group pressing strainings, and in ALB rupture group and PCL complete rupture group are pulling strainings at 90°of flexion.②The straining of medial meniscus anterior horn,caudomedial part and posterior horn shows significant difference in all groups under different load at 90°of flexion,P<0.05. The absolute value of anterior horn straining(pressing straining) in ALB rupture group< PCL complete rupture group, The absolute value of anterior horn straining(pulling straining) in complete PCL group> PMB rupture group. The correlation of the absolute value of medial meniscus caudomedial part straining in every group increases in this way of PCL complete rupture group> ALB rupture group>PMB rupture group> complete PCL group.The absolute value of posterior horn straining(pulling straining) in ALB rupture group< PCL complete rupture group. The absolute value of posterior horn straining(pressing straining) in complete PCL group>PMB rupture group.CONCLUSION 1.Under the load of 200N PCL complete rupture, PMB rupture at 0°of flexion cause no effect on the straining in all regions of medial meniscus.2.Under the load of 400N,600N and 800N, PCL complete rupture and PMB rupture at 0°of flexion is likely to cause abnormal straining in all regions of medial meniscus.3. Under the load of 200N,400N and 600N, ALB rupture at 0°of flexion and PMB rupture at 30°,60°of flexion cause no effect on the straining in all regions of medial meniscus.4. Under the load of 800N and 1000N, ALB rupture at 0°of flexion and PMB rupture at 30°, and 60°of flexion cause apparently effect on the straining in all regions of medial meniscus.5. Abnormal straining in all regions of medial meniscus can be caused by ALB rupture at 30°,60°,90°of flexion and PMB rupture at 90°of flexion under different load.6. Abnormal straining in all regions of medial meniscus can be caused by PCL rupture at 30°,60°,90°of flexion under different load.OBJECTIVE Study the effect on medial meniscus which was caused by rupture of PCL.METHOD Medial meniscus of 48 rabbits matched mode pairs both in experiment side which PCL were transacted and control side, at the 4th,8th,12th,16th and 24th week, execute 12 rabbits randomly, then to observe medial meniscus in general and through HE staining and immunohistochemisty staining, detect the expression of MMP1, MMP13 and TIMP1.RESULT 1. The observation in general showed that along with the increase of the time medial meniscus of experiment group gradually wore, even ruptured, presenting yellow and bad elasticity.2. Along with the increase of the time the observation of histology shows uneven surface of meniscus, loose tissue, disorder of collagen fibers, 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 the 4th,8th,12th, 16th and 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 the 24th week group> 16th week group> 8th week group> 4th week group,showing significant difference, P<0.05.3. At the4th,8th,16th and 24th week, expression of MMP1, MMP13 and TIMP1 is higher in experimental group than that in control group,showing significant difference, P<0.05.4. In experimental group, expression of MMP1 is higher at the 8th than that at 4th week, showing significant difference, P<0.05, expression of MMP1 is higher at the 16th and 24th week than that at 4th and 8th week, showing significant difference, P<0.05, and there is no significant difference between the 16th and 24th week,P>0.05.5. In experimental group, expression of MMP13 is higher at the 8th and 16th week than that at 4th and 24th week,showing significant difference, P<0.05, expression of MMP13 is higher at the 24th week than that at 4th week, showing significant difference, P<0.05,but there is no significant difference between the 8th and 16th week, P>0.05. 6. In experimental group, expression of TIMP1 is higher at the 8th week than that at 4th,16th and 24th week,showing significant difference, P< 0.05; expression of TIMP1 is higher at the 16th week than that at 4th and 24th week, showing significant difference, P＜0.05, but there is no significant difference between the 4th and 24th week, P>0.05. CONCLUSION 1. Rupture of PCL could cause the degeneration of medial meniscus.2. A regularity of expression of MMP13 andTIMP1 is displayed that the expression is increasing in primal stage and decreasing in advanced stage after rupture of PCL.3. A regularity of expression of MMP1 is displayed that the expression is increasing in primal stage and keeping high level in advanced stage after rupture of PCL.4. MMP1, MMP13,TIMP1 play an important role in the degeneration of medial meniscus.OBJECTIVE To explore the effect of PCL rupture on medial meniscus circumferentia displacement and the correlation between the degree of PCL rupture and circumferentia displacement.METHOD The circumferentia displacement of medial meniscus in all fresh normal adult knee joint specimens including 12 specimens of complete PCL,6 of anteriolateral bundle(ALB) rupture,6 of posteromedial bundle rupture(PMB) and 12of complete rupture PCL are tested when the knee joints loaded 200N,400N,600N,800N and 1000N at 0°,30°, 60°and 90°of flexion.RESULT 1. At 0°of flexion and under the loads of 200N,400N and 600N, the circumferentia displacement of medial meniscus between PCL complete rupture group and PMB rupture group shows no significant difference, P>0.05; between complete PCL group and ALB rupture group shows no significant difference, P>0.05; the circumferentia displacement of medial meniscus in PCL complete rupture group and PMB rupture group>complete PCL group and ALB rupture group, P< 0.05. There is significant difference among each group under the load of 800N and 1000N at 0°of flexion, P<0.05, the correlation of the circumferentia displacement of medial meniscus in every group increases in this way of PCL complete rupture group> PMB rupture group> ALB rupture group> complete PCL group.2. Under the loads of 200N,400N and 600N, the circumferentia displacement of medial meniscus between complete PCL group and PMB rupture group, PCL complete rupture group and ALB rupture group shows no significant difference at 30°,60°of flexion, P>0.05, the circumferentia displacement of medial meniscus in PCL complete rupture group and ALB rupture group> complete PCL group and PMB rupture group, P<0.05.Under the loads of 800N and 1000N, the circumferentia displacement among every group shows significant difference at 30°,60°of flexion, P<0.05, the correlation of the circumferentia displacement of medial meniscus in every group increases in this way of PCL complete rupture group> ALB rupture group>PMB rupture group> complete PCL group.3. Under the loads of 200N,400N,600N,800N and 1000N the circumferentia displacement among every group shows significant difference at 90°of flexion, P<0.05, the correlation of the circumferentia displacement of medial meniscus in every group increases in this way of PCL complete rupture group> ALB rupture group>PMB rupture group > complete PCL group.CONCLUSION 1. The circumferentia displacement of medial meniscus in ALB rupture group at flexed position of the knee joint becomes bigger than that in complete PCL group.2.The circumferentia displacement of medial meniscus in PMB rupture group at straight position and 90°flexed position of the knee joint becomes bigger than that in complete PCL group.3.The circumferentia displacement of medial meniscus becomes big at all position of the knee joint when the PCL is ruptured completelyAALL the above may draw a conclusion that early reestablishment of the PCL help to maintain the stability of knee after PCL injury. |
