Biomechanics Study On The Effect Of Anterior Cruciate Ligament Rupture On Medial Collateral Ligament

ACL(anterior cruciate ligament)and MCL(medial collateral ligament) are the main structures which maintain the stability of the knee joint and are the most vulnerable structures in the knee.ACL plays an important role in controlling the tibia antedisplacement and adjusting the function of revolve.MCL mainly against valgus load of the knee and limit external rotation of the tibia.The mechanical functions of ACL and MCL are interrelated,with combined ACL and MCL injuries comprising the most proportion of all multiligament knee injuries.With the increase of the study tests about interdependent functions of ACL and MCL,there are few studies focus on the anatomic relationship of ACL and MCL,and the effect on the MCL after ACL ruptured.With the development of MRI, arthroscope,early diagnosis and treatment of ACL injury turns to be easily achieved.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 structures(e.g.MCL) and the unstability and function disorder of knee.It is significant of reconstructing ACL, handling the complicating injury of MCL and recovering the stability of knee joint so as to prevent the development of osteoarthrosis.The anatomic relationship between ACL and MCL 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 MCL are not only useful to the prevention of the followed MCL injury after ACL ruptured but also benefit to the reestablishment of the ACL.This research intends to observe the anatomy features of ACL and MCL,to study the respectively biomechanics effect of the MCL made by ACL complete and partial rupture,so as to assist the reestablishment of ACL rupture. ChapterⅠThe study on anatomy of ACL and MCLObjective To investigate the anatomic characteristics of ACL and MCL.The result will provide basic anatomic evidence for the study that investigating the effect of ACL rupture on the biomechanics of MCL.Method The specimens in this experiment are 6 normal knee joints of adult male.First,observing the gross shape and form of ACL and MCL.Then,measuring the length of the anteromedial part of ACL, the posterolateral part of ACL and MCL when the knee joint located at 0°,30°,60°,90°respectively and measuring the transverse diameter and vertical diameter of the attachments of both ACL and MCL on tibia and femur.At last,calculate the area of the attachments of ACL and MCL using photoshop software and other selective area calculated software.Results:1.Morphological results:The area of ACL and MCL attachment on tibia is bigger than that on femur.The inner fibers of ACL connect interlacedly and hard to be separated.The femoral attachment of MCL is centered in a small depression slightly proximal and posterior to the center of the medial epicondylehad,and MCL have two separate attachments on the tibia.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°and 60°have no significant difference (P＞0.05).②The length of MCL is(94.6±4.2)mm,(95.3±4.6)mm, (96.7±3.4)mm,(97.4±5.2) mm when the knee joint located at 0°,30°,60°,90°respectively.3.Area calculated result:①The area,transverse diameter and vertical diameter of ACL attachment on tibia are bigger than those counterparts on femur,the difference are of significance(P＜0.01).②The area and vertical diameter of MCL attachment on are tibia bigger than those counterparts on femur,the difference are of significance (P＜0.01),the transverse diameter are with no significant difference (P＞0.05).Conclusion The posterolateral part of ACL is relatively longer when the knee at 0°,and the anteromedial part of ACL is longer at the position of 90°;The knee more flexing,MCL more intensional.The area of MCL femur are smaller than the area of MCL tibia attachment.ChapterⅡThe effect of ACL rupture on the biomechanics of MCLObjective To investigate the effect of the ACL rupture on the biomechanics of the MCL and therefore to assist the reestablishment of 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.To test the straining of three parts of MCL (femoral part,medial part and tibial part) when the knee joints loaded on 200N,400N,600N,800N at straighten 0°,flection 30°,60°,and 90°.Then separated the specimens into AMB rupture group and PLB rupture group, test again.At last,another bundle was cut off,this specimens are ACL complete rupture group and test again.Results:1.Results of the intact ACL group:①At 0°and 60°,the tensile train of the femoral part of MCL are smaller than the strain of the other parts(P＜0.05).②At 30°,the compressive train of the femoral part of MCL are bigger than the strain of the other parts(P＜0.05).③At 90°, the tensile train of the femoral part of MCL are smaller than the strain of the other parts,showing significant difference(P＜0.05).2.Results of the AMB group:①At 0°,the tensile strain of the AMB group are similar the strain of the intact ACL group(P＞0.05).②At 30°,the medial and tibial part of MCL showed to be tensile strain when the same part of MCL in intact ACL group showed to be compressive strain,showing significant difference(P＜0.05).③At 60°,the femoral part of MCL showed to be compressive strain when the same part of MCL in intact ACL group showed to be tensile strain,showing significant difference(P＜0.05).④At 90°,the medial part and the femoral part of MCL showed to be are the compressive strain when them in intact ACL group showed to be tensile strain,the tensile strain of the AMB group and the intact ACL group showing significant difference(P＜0.05).3.Results of the PLB group:①The strain of the medial part of MCL are bigger than the other parts at 0°,30°,60°,90°.②At 0°,the PLB group showed to be the tensile strain when the intact ACL group showed to be compressive strain(P＜0.05).③At 30°,the tensile strain of the PLB group are similar the strain of the intact ACL group(P＞0.05).④At 60°,the PLB group showed to be the compressive strain when the intact ACL group showed to be tensile strain. The medial and tibial part showing significant difference(P＜0.05).⑤At 90°,the PLB group showed to be the compressive strain when the intact ACL group showed to be tensile strain.Comparison of the above two group,showing significant difference(P＜0.05).4.Results of the ACL rupture group:①At 0°,the ACL rupture group showed to be the tensile strain when the intact ACL group showed to be compressive strain (P＜0.05).②At 30°and 60°,the strain of the ACL rupture group shoued significant difference with the strain of the intact ACL group at medial part(P＜0.05).③At 90°,the ACL rupture group showed to be the compressive strain when the intact ACL group showed to be tensile strain, showing significant difference(P＜0.05).Conclusion:1.The intact ACL group,MCL showed to be tensile strain and should to be tensional at 0°,60°,90°.No change about the biomechanics of MCL happen after AMB rupture,however the knee more flexing,MCL more loose.MCL showed to be compressive strain and should to be loose after PLB rupture.MCL showed to be compressive strain and should to be loose after ACL complete rupture at 0°,30°,90°. 2.At 90°,the biomechanics of MCL will be change after ACL part/ complete rupture.