PCL Bundles' Classification And The Mechanical And Histological Influence On The Medial Tibial Plateau After PCL Ruptured

Along with the development of sports and communication, the incidence of injury of posterior cruciate ligaments (PCL) increases, of which a considerable portion are partial injury of PCL.Clinical results manifest that the incidence of catilage degeneration in the medial chamber of tibiofemoral joint is higher than normal, however, the machanism is unclear. It may be explained by a biomechanical mechanism or a biological one or both of them together.It is also unknown how the biomechanical mechanism or the biological mechanism act or whether partial injury of PCL could influence the catilage degeneration in the medial chamber of tibiofemoral joint.It is urgent to solve these questions so as to provide theoretical evidence for making proper plans for PCL injury and how to prevent catilage degeneration after PCL injury.Meanwhile,clinical data also shows that the PCL reconstruction has a high failure rate owing to the graft's stress concentration.Therefore, many researchers pay attention to the anatomy and function of PCL fiber bundles,but a lot of experts begin to realize that the PCL is not made of completely separate fiber bundles, but a fiber continuum, therefore,the functional research of PCL fiber becomes the hot spot.however,most of the contemporary research on the functional research of PCL fiber is through the gross observation of the tension mode of PCL fiber bundles or the measurement of distance between the insertions of each PCL fiber bundes, which can not reflect the subtle functional change of PCL fiber bundes or cause much damage to the anatomical structure of the knee.So it is necessary to design a experiment that can reflect the subtle functional change of PCL fiber bundes and destroy PCL and other structures of the knee as less as possible.In our research the strain gages designed by ourselves would be placed on the surface of each PCL fiber bundle to measure the strain change on each fiber bundle.Then the data would be analysed by cluster analysis to classify the fiber bundles.Furthermore,we will measure the strain on the anterior,middle and posterior parts of the medial tibial plateau after cutting the partial or whole PCL. Meanwhile, the histological change and expression of MMP-13 and TIMP-1 in the medial tibial plateau cartilage of rabbits would be studied by HE staining, toluidine blue staining and immunohistochemical methods.Objective:To investigate the biomechanical function and intrinsic correlation of the PCL bundles in order to provide biomechanical evidence for the later experimental research and clinical therapy.Methods:12 fresh cadaveric knees from adult human beings were used. Selected the bilateral anterior part of the PCL femoral insertion and the bilateral posterior part of the PCL tibial insertion as the measurement parts which respectively correspond to:anteromedial area fiber bundle (anteromedial bundle),anterolateral area fiber bundle (anterolateral bundle),posteromedial area bundle (posteromedial bundle) and posterolateral area bundle (posterolateral bundle). The strain on the PCL bundles was measured when the knees were applied with 1000N axial loading force in 0°,30°,60°,90°positions. The bundles were functional classified by cluster analysis.Results:1.In 0°position, the strain on the posteromedial and posterolateral bundles was significantly larger than the anteromedial and anterolateral bundles (P<0.05), while there was no significant difference between the posteromedial and posterolateral bundles (P>0.05) and so did the anteromedial and anterolateral bundles (P>0.05); In 30°,60°nd 90°position, the strain on the anteromedial and anterolateral bundles was significantly larger than the posteromedial and posterolateral bundles (P<0.05), while there was no significant difference between the anteromedial and anterolateral bundles (P>0.05) and so did the posteromedial and posterolateral bundles (P>0.05).2.The strain on the anteromedial and anterolateral bundles gradually increased by degrees as the knee flexed from 0°to 90°and all the difference were significant (P <0.05). The strain on the posteromedial bundle was largest in 0°position while smallest in 30°position and the difference between 0°and 30°position were significan (P<0.05);The strain in 90°position was larger than in 30°position and the differences were significant (P<0.05); There were no significant differences between the strain of any other two positions (P>0.05). There were no significant changes of the strain on the posterolateral bundle among different angles (P>0.05).3.Cluster analysis classfied the anteromedial and anterolateral bundle as one class and the posteromedial and posterolateral bundles as the other class.Conclusion:1.A11 the four area fiber bundles of PCL maintain certain tension during the whole range of motion.2. The posteromedial and posterolateral area bundles mainly maintain stability of the knee in extended positions while the anteromedial and anterolateral area fiber bundles mainly maintain stability of the knee in flexed positions.3. The strain on the anteromedial and anterolateral area fiber bundles vary drastically while strain on posterolateral area bundles change littlely during the whole range of motion.4. Cluster analysis classfied the anteromedial and anterolateral bundle as one class and the posteromedial and posterolateral bundles as the other class.5.With Combined consideration of the biomechanical property, cluster analysis results and the relative position at the femoral insertion of the four area fiber bundles of PCL,PCL may be classified into the anterolateral functional fiber bundle and the posteromedial functional fiber bundle.Objective:To investigate the biomechanical influences of partial and total PCL rupture on the medial tibial plateau and provide theoretic evidence for prevention and cure of osteoarthritis.Methods:12 fresh cadaveric knees from adult human beings were divided into PCL intact group(12 samples),ALB broken group(6 samples),PMB broken group(6 samples) and PCL totally broken group(6 samples). The knees were applied with 0-1000N axial loading force when they flexed to 0°,30°,60°,and 90°.The strain on the anterior, middle and posterior part of the medial tibial plateau were respectively measured and analysed.Results:1. In 0°position:①Strain on the anterior,middle and posterior parts were all compressive.②With 200N and 400N axial loading, on all the anterior,middle and posterior parts,strain between PCL intact group and ALB broken group and strain between PMB broken group and PCL totally broken group were neither significantly different(P>0.05),while the absolute value of strain in PMB broken group and PCL totally broken group were significantly larger than PCL intact group and ALB broken group on the anterior and middle parts(P<0.05) and were significantly smaller than PCL intact group and ALB broken group on the posterior part(P<0.05).③With 600N,800N and 1000N axial loading, on all the anterior,middle and posterior parts, the differences among ALB broken group, PMB broken group and PCL totally broken group were not significant(P>0.05),while the absolute value of strain in all these three groups were significantly larger than PCL intact group on the anterior and middle parts (P<0.05) and were significantly smaller than PCL intact group on the posterior part(P<0.05).2. In 30°position:①Strain on the anterior,middle and posterior parts were all compressive.②With 200N and 400N axial loading, on all the anterior,middle and posterior parts, the differences among PCL intact group,ALB broken group and PMB broken group were all not significant(P>0.05),while the absolute value of strain in all these three groups were significantly smaller than PCL totally broken group on the anterior and middle parts (P<0.05) and were significantly larger than PCL totally broken group on the posterior part(P<0.05).③With 600,800N and 1000N axial loading, on all the anterior,middle and posterior parts, strain between PCL intact group and PMB broken group and strain between ALB broken group and PCL totally broken group were neither significantly different(P>0.05), while the absolute value of strain in ALB broken group and PCL totally broken group were significantly larger than PCL intact group and PMB broken group on the anterior and middle parts (P<0.05) and were significantly smaller than PCL intact group and PMB broken group on the posterior parts(P<0.05).3.In 60°nd 90°positions:①Strain on the anterior part was tensile while strain on the middle and posteror parts were compressive.②With 200N and 400N axial loading, on all the anterior, middle and posterior parts, the differences among PCL intact group,ALB broken group and PMB broken group were all not significant(P>0.05),while the absolute value of strain in all these three groups were significantly larger than PCL totally broken group on the anterior and posterior parts (P<0.05) and were significantly smaller than PCL totally broken group on the middle part(P<0.05).③With 600N,800N and 1000N axial loading, on all the anterior,middle and posterior parts, strain between PCL intact group and PMB broken group and strain between ALB broken group and PCL totally broken group were neither significantly different(P>0.05), while the absolute value of strain in ALB broken group and PCL totally broken group were significantly smaller than PCL intact group and PMB broken group on the anterior and posterior parts (P<0.05) and were significantly larger than PCL intact group and PMB broken group on the middle parts(P<0.05).Conclusion:1.PCL total rupture may cause abnormal load on all parts of the medial tibial plateau with any axial loading in all the positions.2.With 200N and 400N axial loading, in extended positions ALB rupture may not cause abnormal load on any part of the medial tibial plateau,while PMB rupture may cause abnormal load on all parts of the medial tibial plateau;In flexed positions, neither ALB nor PMB isolated rupture may cause abnormal load on any part of the medial tibial plateau.It suggests that With low axial loading PMB act as the stabilizer in extended position, while in flexed positions both ALB and PMB play a role as the stabilizer.3. With 600N,800N and 1000N axial loading, PMB rupture may not cause abnormal load on any part of the medial tibial plateau in any position and ALB ruptre may not cause abnormal load on any part of the medial tibial plateau in extended position while cause abnormal load on all parts of the medial tibial plateau in flexed positions.It suggests that With large axial loading PMB play little stabilizing role in any position and ALB mainly act as a stabilizer in flexed positions. Objective:To explore whether PCL rupture could cause cartilage degenaration of medial tibial plateau and the biological mechanism for cartilage degenaration and further provide theoretical evidence for clinical diagnosis and therapy of osteoarthritis by studying changes in tissue structure and expression of MMP-13 and TIMP-1 in the medial tibial plateau cartilage after the PCL of rabbits were cut.Methods:48 male rabbits were randomly divided into four groups. All underwent unilateral PCL cut in posterior leg and the contralataral as the control randomly.HE staining, toluidine blue staining and immunohistochemical methods were carried out.Changes in tissue structure and expression of MMP-13 and TIMP-1 in the medial tibial plateau cartilage were observed and analyzed at 4,8,16,24 weeks after the PCL of rabbits were severed.Results:1.Gross observation:As the time went on, the color change,decreased gloss,the abrased surface and even ulcer and osteophyte occurred on medial tibial plateau cartilage.2.HE staining and toluidine blue staining:The rough surface,cell hypertrophy,cell hyperplasia,cell cluster,abnormal cell disposition and inequable staining occurred one after another since since 8 weeks after operation.Since 8 weeks the Mankin score of medial tibial plateau cartilage in experimental groups was significently higher than the control group(p<0.05). In experimental groups,the Mankin score increased continuously from 4 weeks to 24 weeks after operation and the difference was significant(p<0.05) while the Mankin score in contral group change little(P>0.05).3. MMP-13 expression:All the experimental groups had higher MMP-13 expression than that in control groups (P<0.05). In experimental groups, MMP-13 expressed significantly lower in 4-week group than that in 8,16,24-week groups (p<0.05) and expressed significantly higher in 8-week group than that in 4,16,24-week groups(p<0.05). There were no signifigant differences among the control groups (P>0.05).4. TIMP-1 expression:In 4,8,16-week groups the experimental groups had higher TIMP-1 expression than that in control groups (P<0.05) while in 24-week group there was no signifigant differences between the experimental group and the control group(P>0.05). In experimental groups, TIMP-1 expressed significantly lower in 24-week group than that in 4,8,16-week groups (p<0.05);There was no signifigant differences between 8-week group and 16-week group(P>0.05).TIMP-1 expressed significantly higher in 8-week group and 16-week group than that in 4,24-week groups (p<0.05). There were no signifigant differences among the control groups(P>0.05).Conclusion:1.PCL rupture may cause cartilage degeneration on the medial tibial plateau. 2.The increased expression Of MMP-13 and TIMP-1 suggest that MMP-13 and TIMP-1 may participate in cartilage degeneration on the medial tibial plateau after PCL rupture.