Study On The Anatomic Relationship Of ACL And PCL And The Effect Of ACL Rupture On The Biomechanics Of PCL

ACL(anterior cruciate ligament)and PCL(Posterior cruciate ligament)are the main structures which maintain the stability when the knee joint flex,extend and revolve.ACL plays an important role in controlling the tibia antedisplacement and adjusting the function of revolve.PCL mainly maintain the action of roll and glide onto tibial plateau of condyles of femur when knee flex and extend.Especially,PCL are important in the knee locked mechanism which aroused by the action that tibial plateau intort when knee extend.ACL and PCL together keep the normal roll and glide between tibia and femur.With the increase of traffic accidents and the popularity of competitive sports,the combined ligaments injuries of knee are increasing.Among them,ACL injury combined with MCL injury are most frequent,followed by PCL injury combined with MCL injury.ACL with LCL trauma and ACL,PCL and MCL --three ligaments combined injuries are also reported sometimes. But there are few studies focus on the effect on the PCL after ACL ruptured.If ruptured ACL are not treated in time,the knee structure changes so that the load and stress are redistributed which lead to the damage of the other structrues(eg.PCL)and the unstability and function disorder of knee.The anatomic relationship between ACL and PCL is the base of the study of their biomechanics and injury mechanism.To make clear the effect of ACL rupture on the biomechanical characteristics of PCL are not only useful to the prevention and cure of the followed PCL injury after ACL ruptured but also benefit to the reestablishment of the ACL.ChapterⅠThe study on anatomy and anatomic relationship of ACL and PCLObjective To investigate the anatomic characteristics of the ACL and PCL and explore the relationship between the two.The result will provide basic anatomic evidence for the study that investigating the effect of the ACL rupture on the biomechanics of the PCL.Method:The specimens in this experiment are 6 normal knee joints of adult male.Saw asunder the femur intercondyloid fossa in sagittal plane and observe the gross shape and form of the ACL and PCL.Then, measuring the length of the anteromedial part of ACL,the posterolateral part of ACL,the posteromedial part of PCL and the anterolateral part of PCL and measuring the transverse diameter and vertical diameter of the insertions of both ACL and PCL on tibia and femur when the knee joint located at 0°,30°,60°,90°respectively.At last,calculate the area of the insertions of ACL and PCL using Photoshop software and other selective area calculated software.Results:1.Morphological results:The area of ACL insertion on tibia is bigger than that on femur while the insertion area of PCL on tibia is smaller than the area on femur.There are synovium linked between ACL and PCL.Although there are some evidence in surface showing the ligaments may divide,the inner fibers of both ACL and PCL connect interlacedly and hard to be separated.2.Length calculated result:①The length of the anteromedial part of ACL is longer than the posterolateral part no matter the knee at what location(p＜0.05).The length of the anteromedial part of ACL at different locations can be ordered as 90°,0°,30°,60°from maximum to minimum.The difference of length of any two locations is of significance(p＜0.05).The maximum length of posterolateral part of ACL appears at the location of 0°and the minimum length of posterolateral part occurs at the location of 90°(p＜0.05),the moderate lengths at the location of 30~°nd 60°have no significant difference(p＞0.05).②The length of the anterolateral part of PCL is longer than the posteromedial part no matter the knee at what location (p＜0.05).The length of the anterolateral part:the length at 30°and 60°are longer than that at 0°(p＜0.05);the length at 90°are longer than that at 30°(p＜0.05),but with no significant difference of that at 0°and 60°(p＜0.05); the length at 30°and 60°are not significant different(p＜0.05).The length of the posteromedial part of PCL:The length at 30°are longer than that of 60°and 90°(p＜0.05),but with no significant difference of that at 0°.And the length at 0°,60°,90°are not significant different(p＞0.05).③The anterolateral part of PCL is longer than the anteromedial part of ACL at all locations(p＜0.05).Similarly,the posteromedial part of PCL is longer than the posterolateral part of ACL at all locations with significant difference (p＜0.05).3.Area calculated result:①The area,transverse diameter and vertical diameter of ACL insertion on tibia are bigger than those counterparts on femur,the difference are of significance(p＜0.01).②The area and vertical diameter of PCL insertion on femur are bigger than those counterparts on tibia,the difference are of significance(p＜0.01),the transverse diameter are with no significant difference(p＞0.05).③The area, transverse diameter and vertical diameter of PCL insertion on femur are larger than those of ACL insertion on femur,the difference are of significance(p＜0.05).④The area,transverse diameter and vertical diameter of PCL insertion on tibia are smaller than those of ACL insertion on tibia,the difference are of significance(p＜0.05).Conclusion The posterolateral part of ACL and the posteromedial part of PCL are relatively longer when the knee at 0°,which suggest the posterolateral part of ACL and the posteromedial part of PCL play their role when the knee locates at straighten position.And the anteromedial part of ACL and the anterolateral part of PCL are longer at the position of 90°,which suggest them exert their role when the knee flex.The above suggestions with the fact there are bundles linked the ACL and PCL encourage a suggestion that the ruptured ACL influence the biomechanic characteristics of PCL.ChapterⅡThe effect of the A CL rupture on the biomechanics of the PCLObjective To investigate the effect of the ACL rupture on the biomechanics of the PCL and therefore to provide the theory guidance about prevention,early diagnosis and treatment of PCL injury which occur after the ACL rupture.Method The specimens in this experiment are 6 normal fresh knee joints of adult male.At first,all the 6 specimens were classified as the group with intact ACL.Then,the ACL of 6 specimens were ruptured so that they were regareded as the group with the ACL ruptured.The strain measuring point are located at the medial and lateral of the PCL insertion on femur,which represent the posteromedial bundle and anterolateral bundle respectively.Test the strain of the two bundles of PCL under the load of 200N at different angle(0°,30°,60°,90°).Results:1.results of the intact ACL group:①At 0°and 30°,the strain of the posteromedial bundle of PCL are bigger than the strain of the anterolateral bundle(p＜0.05).At 60°and 90°,the strain of the posteromedial bundle of PCL are smaller than the strain of the anterolateral bundle(p＜0.05).②At 0°,30°,60°and 90°,with the increasing angle of the knee flex,the strain of the anterolateral bundle of PCL increase.The difference of each two angle are significant(p＜0.01).And the strain of the posteromedial are ordered from maximum to minimum as 30°,0°,60°, 90°(p＜0.01).2.results of the ruptured ACL group:①At 0°and 30°,the strain of the posteromedial bundle of PCL are bigger than the strain of the anterolateral bundle(p＜0.05).At 60°and 90°,the strain of the posteromedial bundle of PCL are smaller than the strain of the anterolateral bundle(p＜0.05).②At 0°,30°,60°and 90°,with the increasing angle of the knee flex,the strain of the anterolateral bundle of PCL increase.The difference of each two angle are significant(p＜0.01).The results of posteromedial bundle are more complicate:the strain at 0°and 30°have no significant difference(p＞0.05).But the strain at these two angle are bigger than the rest two(60°and 90°).And the strain at 60°are bigger than the strain at 90°with the significant difference(p＜0.05).3.Comparison of the above two group:①When the knee at the 0°and 90°,the strain of the anterolateral bundle and the strain of the posteromedial bundle with the ruptured ACL are bigger than that with the intact ACL(P＜0.05).But at the 30°and 60°,the differences of the two bundles are not significant in two group(p＞0.05).Conclusion:When knee at straighten position and 30°,the posteromedial bundle of PCL keep in tension while anterolateral bundle relax.And when the knee flex to 60°or 90°,the strain of anterolateral bundle of PCL increase and exceed that of posterolateral bundle.These facts suggests the posteromedial bundle may be the main bundle which keep the knee stable when at straighten position while the anteromedial bundle maintain the stability when knee flex.From 0°to 90°,with the increasing degree of the knee flex,the strain of the anterolateral bundle of PCL increases correspondingly.The fact shows the characteristics of the anterolateral bundle of PCL.The strain of posteromedial bundle reachs its peak at 30°which needs further research.After ACL ruptured,the strain of PCL raise up when knee at 0°position.This appearance may be caused by the hyperextension injury of knee.When the knee with ruptured ACL flexed to the 90°position,the strain of PCL increase.This may represent the PCL has a close relationship with the stability of flex and intort.