| Objective : To determeine the effect on the knee after the posterlateral structure(PLS) and Posterior crucate ligament (PCL) were sectioned . Analyse the difference after the isolated or combined section of PCL and PLS . To investigate the role of external rotatory stability of the knee after the reconstruction of the two structures were performed . Compare the result after PCL isolated recontruction and PCL –PLS combined recontruction .Method :6 Fresh cadaveric knees were used . There are around 20cm femur and tibia in length from the knee joint ,and the specimens with intact fascia and capsule and all free of previous ligament tear and macroscopic osteoarthrosis . The femur was fixed relative to the base of the robot while the tibia fixture was attached to a free rotatable holder .The external rotation of the tibial were measured with 5Nm tibial torque . All knees were tested in full extension, 30o,60o,90o of flexion . Each knee was initially tested with the intact fascia .The fllowing tests were performed after transection of the PCL ,PFL ,FCL ,PT . Identical tests were also performed after each step . we used autogenous hamstring tendon to reconstruct the PCL ,and the Achilles tendon reconstruct the PFL and PT, and the tenodesis of the biceps femoris tendon to repair FCL. The external rotation angle of tibial must be test for 3 times after each step . At last ,all the data were calculated throw statistical analysis , then produced the chart and table . Results :The external tibial rotation in intact knees was least at zero degree and greatest at 90 degrees of flextion .There were fast increases at zero to 30 and 60 to 90 degrees .The isolated sectioning of the PCL did not result in a sigificant external rotation( P＞0.05 ).Sectioning of PFL showa significant increase of 3.0±0.17 and 2.8±0.05 degrees in external rotarion at 60 and 90 degree of flextion ( P ＜ 0 .01). After sectioning FCL (PCL+PFL+FCL), a significant increasing external rotarion in all position can see( P ＜ 0 .01). It was 17.8±0.141 degrees at 30 degree of flextion , and 3.8±0.09 degrees were increased than intact knee at 30 degree.When Sectioned all structure (PCL+PFL+FCL+PT) , there was a greatest significantly increased external rotation in all position ( P ＜ 0.01 ). It was 23.5±0.45 degree at 30 degree of flextion , and 9.5±0.42 degrees were increased than intact knee at 30 degree , 6.7±0.14 degrees were increased compared with FCL section at 30 degree .The isolated PCL reconstruction did not affect the external rotation. It was 21.2±0.45 degrees at 30 degree of flextion .There was a sigificant decrease in external rotation compared with PT section (P < 0.01),such as 2.3±0.60 degrees decreased at 30 degree .Whereas , the combined PCL—PLS reconstruction reset the knee to realy physiological laxity patterns . It shows that there was a significant change in external rotation compared with intact knees(P < 0.05). It were 0.4±0.15 degrees increased at 30 degree compared with intact knees and 0.9±0.02 degrees were decreased at 60 degree. Conclusion :The major structures of the PSL include the PT,LCL,PFL. They have great important role to resist excessive varus and external rotation forces. Every ligament have their own biomechanical property,but they act together to provide stability of the knee .PCL have great function to resist posterior tibial translation. Isolated PCL sections produced an increase in posterior tibial translation and no change in external rotation . Complex injury of PCL and PSL can produce instability in external rotation and greater increase in posterior tibial translation,it can also change the force in the knee .From this study we can see that PT have the important role to resist external rotation . It has connective attachment to popliteus muscle. Popliteus muscle tensioning make internal tibial rotation .It may lost the ablity to produce internal tibial rotation and resist external tibial rotation while PT sectioned ,and oth...
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