Study On The Biomechanical And Histological Effects Of Rupture ACL On The Femoral Lateral Condyle

The anterior cruciate ligament(ACL) is a stable structure whose main role is controlling the antedisplacement of tibial and regulating the rotation of tibial.ACL deficiency always results in the secondary injuries of articular cartilage and meniscus,followed by the severe degeneration of the knee joint in the end.For the sake of preventing the development of osteoarthrosis and the injury of femoral lateral condyle,it is important to understand the histological and biomechanics mechanism of the effect on femoral lateral condyle,which directly relates to the early diagnosis, clinical decision and appraisement of ACL injury.At present,the researching about the effect of ACL injury mostly concentrates on the degeneration of articular cartilage and reconstruction of ACL after complete rupture of ACL,and few on the effect on biomechanics and histology of lateral condyle.In this study,straining changes of the anterior part,middle part and posterior part on the lateral condyle caused by ACL injury were analyzed by way of biomechanics approach,as well as histological evaluation of cartilage in femoral lateral condyle and expression of IL-1βand MMP13 in cartilage,which provides theoretical evidence for the formation of the secondary injury of the femoral lateral condyle following the ACL injury. Chapter 1 The biomechanical study of ACL bundles' functional classificationObjective:To investigate the functional bundle division of the ACL, to provide the theoretical evidence for ACL reconstruction.Method:In this experiment the specimens were 6 normal knee joints of adult male.The bilateral areas in front of the ACL tibial insertion and the bilateral areas at the back of the ACL femoral insertion were chosen as the four straingauge point,which correspond to anteromedial bundle, anterolateral bundle,posteromedial bundle and posterolateral bundle respectively.The strain of each bundle under the load of 800N were measured when the knee joint position at 0°,30°,60°,90°angle respectively,followed by the cluster analysis to explore the functional division of the ACL.Results:1.①When the knee located at 0°,the strain of ACL anterolateral bundle and posterolateral bundle were bigger than anteromedial and posteromedial bundle,p＜0.01.However,there were no significant difference between the anterolateral bundle and posterolateral bundle,as well the anteromedial and posteromedial bundle,p＞0.05.②When the knee located at both 30°and 90°,the strain of ACL anteromedial bundle and posteromedial bundle were bigger than anterolateral and posterolateral bundle,p＜0.05.However,there were no significant difference between the anterolateral bundle and posterolateral bundle,as well the anteromedial and posteromedial bundle,p＞0.05.③When the knee located at 60°,the strain of each bundle were ordered from maximum to minimum as follows:posteromedial bundle, anteromedial bundle,posterolateral bundle and anterolateral bundle. There were significant difference among the four bundles,p＜0.05.2.①The strain of the anteromedial bundle coincided with the strain of the posteromedial bundle.Ranking from maximum to minimum,the strain of these two bundles at different knee positions were 90°,60°, 30°,0°.There were significant difference among the four bundles, p＜0.05.②For the strain of the anterolateral bundle,there were no significant difference at the knee positions,p＞0.05.③The strain of the posterolateral bundle reached its peak at the position angle at 60°, p＜0.05;its bottom at the position of 30°,p＜0.05;position angle at 0°and 90°respectively,for the strain of the posterolateral bundle,both of them were moderate and there was no significant difference between them,p＞0.05.3.Cluster analysis:The anteromedial bundle and the posteromedial bundle can be regarded as the same kind of bunch by way of cluster analysis.And so do the anterolateral bundle and the posterolateral bundle.Conclusion:When the knee at the position angle at 0°,the strain of the anterolateral bundle and the posterolateral bundle were bigger than the medial ones.However,when the knee at the other bended positions, the strain of the anteromedial bundle and the posteromedial bundle were bigger the lateral ones.Therefore,we could draw a conclusion that the lateral bundles maintain the stability mainly when the knee straightens and the medial ones mainly keep the stable when the knee flexes. Combined with the cluster analysis,the ACL can be regarded as two functional bundles:the anteromedial bundle and the posterolateral bundle. Chapter 2 The biomechanical influence of ACL ruptures on the femoral lateral condyleObjective:To investigate the biomechanical influences of ACL rupture on the femoral lateral condyle and provide theoretic evidence for early ACL repair.Methods:10 fresh cadaveric knees from adult human beings were divided into ACL intact group(10 samples),AMB broken group(5 samples),PLB broken group(5samples) and ACL total broken group(10 samples).The knees were applied with 200N～800N axial loading force when they flexed 0°,30°,60°,90°.The strain on the femoral lateral condyle was measured in different loading force along with the position angles.Result:1.In 0°position,under the load of 200N and 400N,for the straining of the anterior part,middle part and posterior part on the femoral lateral condyle,there were no significant difference between PLB rupture group and ACL complete rupture group,as well as complete ACL group and AMB rupture group,P＞0.05;under the loads of 600N and 800N,there was significant difference between the anterior part and posterior part on the femoral lateral condyle,P＜0.05,while the straining of middle part on the femoral lateral condyle showed no significant difference among all the groups under the loads of 600N and 800N,P＞0.05;under the same load and angle of flexion,the correlation of the absolute value of straining in every group of the anterior part and middle part on the femoral lateral condyle increased as follows:ACL complete rupture group＞PLB rupture group＞AMB rupture group＞ complete ACL group.But the posterior part on the femoral lateral condyle increased as follows:complete ACL group＞AMB rupture group＞PLB rupture group＞ACL complete rupture group.2.In 30°position,under the load of 200N and 400N,for the straining of the anterior part,middle part and posterior part on the femoral femoral lateral condyle,there were no significant difference between AMB rupture group and ACL complete rupture group,as well as complete ACL group and PLB rupture group,P＞0.05;under the load of 600N and 800N,there were significant differences among the four groups.Under the same load and angle of flexion,the correlation of the value of straining in each group increased as the follows:ACL complete rupture group＞AMB rupture group＞PLB rupture group＞complete ACL group.3.In 60°position,under the load of 200N and 400N and 600N and 800N,for the straining of the anterior part and middle part and posterior part on the femoral lateral condyle,there were significant difference among four groups,P＜0.05;under the same load and angle of flexion, the correlation of the value of straining in each group increased as the follows:ACL complete rupture group＞AMB rupture group＞PLB rupture group＞complete ACL group.4.In 90°position,under the load of 200N and 400N and 600N and 800N,for the straining of the anterior part and middle part and posterior part on the femoral lateral condyle,there were significant difference among four groups,P＜0.05.under the same load and angle of flexion, the correlation of the value of straining in each group of the anterior part on the femoral lateral condyle increased as follows:ACL complete group＞PLB rupture group＞AMB rupture group＞complete rupture group. while each group of middle part and posterior part on the femoral lateral condyle increased as follows:ACL complete rupture group＞AMB rupture group＞PLB rupture group＞complete ACL group.Conclusion:ACL total rupture may cause abnormal straining on the femoral lateral condyle.The AMB rupture showed the various straining of the anterior part,middle part and posterior part on the femoral lateral condyle at 30°and 60°and 90°of flexion.The PLB rupture showed the various straining of the anterior part and posterior part on the femoral lateral condyle at 0°of flexion. Chapter 3 Study on the histological influence of ACL rupture on the femoral lateral condyleObjective:To explore the histological variety of femoral lateral condyle followed by rupture of ACL.Method:Lateral meniscus of 48 rabbits were matched as experiment side and control side,ACL rupture used for experiment side.At the 1st, 3rd,6th and 8th week,12 rabbits were executed randomly,followed by naked-eye observation of lateral meniscus and by way of HE staining,as well immunohistochemistry staining to detect the expression of IL-1βand MMP13.Result:1.Gross observation:with longer time,the lateral condyle cartilage had the color changed,the gloss decreased,the surface abrased and even had different depth ulcer on the cartilage.2.Histological observation:3^rd week late,in the experiment side, fibrous degeneration of cartilage surface layer occurred,along with middle layer rupture,chaotic arrangement of chondrocyte,irregular tidal line with blood capillary and more clustered chondrocytes.For the Mankin scores,there was significant difference between the experiment side and control side,P＜0.05.3.In experiment side,IL-1βexpressed significantly higher in 3^rd week,6^th week than that in 1^st week,8^th week respectively,p＜0.05,in which IL-1βexpressed higher in 8^th week than that in 1^st week,P＜0.05; there was no significant difference between 3^rd week and 6^th week.While compared to control side,in 1^st,3^rd,6^th and 8^th week respectively,there were more higher IL-1βexpression respectively,P＜0.05. 4.In experiment side,MMP-13 expressed significantly higher in 3^rd week,6^th week than that in 1^st week,8^th week respectively,p＜0.05,in which MMP-13 expressed higher in 8^th week than that in 1^st week, P＜0.05;there was no significant difference between 3^rd week and 6^th week.While compared to control side,in 1^st,3^rd,6^th and 8^th week respectively,there were more higher MMP-13 expression respectively, P＜0.05.Conclusion:ACL rupture may cause cartilage degeneration on the femoral lateral condyle.A regularity of expression of IL-1βand MMP13 show the increasing expression in primal stage and decreasing in late stage after ACL rupture.The increased IL-1βand MMP-13 expression suggest that IL-1β,MMP-13 may participate in cartilage degeneration on the femoral lateral condyle after ACL rupture.