Establishment Of Pig Knee Joint Meniscus Posterior Horn Injury Model And Biomechanical Test

Objective :1.Establish a model of pig knee joint meniscus injury and observe the change of meniscus stress distribution after medial meniscus posterior angle injury 。 2.The biomechanical method was used to investigate the progress of meniscus injury under the influence of different knee flexion angles,pressure loads and circulation times on the three types of meniscus injury types of horizontal,longitudinal and radial fissure。 Methods: 1.CT and MRI images of the mature adult pig hindlimb knee joint were selected,and the obtained image data were imported into mimics software to construct a three-dimensional virtual model of knee joint and meniscus structure,simulating the meniscus stress and analyzing the inner side.The change of the meniscus stress after the meniscus injury and the extent of the specimen meniscus damage load。2.The posterior horns of the medial meniscus of the hind limbs of 9 fresh adult pigs were made into three different types of damage: horizontal split,longitudinal split and radiative split.The damage length was 4 mm,and each type of damage was 3 cases.Electro-hydraulic servo fatigue test was performed.The pressure load of the machine is set to 20% 40% 60% of the specimens of the meniscus fracture strength load.The in vitro biomechanical test is carried out at three levels;the number of cycles is set to 600 times,1200 times,2400 times;the flexion fixed angle of the knee joint of the specimen Divided into three levels of 30°,90°,120°;according to the orthogonal experimental design table,the specimens were divided into 9 groups,under the different parameters,the meniscus crack expansion of each group was observed,and the variance analysis of orthogonal experimental design data was used.Compare the differences。 Result: 1.The maximum stress of the meniscus is 19.668 Mpa,and the meniscus reaches the critical load of failure.Therefore,20% 40% 60% of the fracture strength load was used for in vitro biomechanical test(i.e.200 N 400N 600 N axial load).2.The results of biomechanical research show that the type of meniscus damage has the greatest influence on crack growth.According to the comparison of the samples before the experiment,three kinds of meniscus damage cracks,horizontal crack,longitudinal crack and radiation crack,all extend;among them,horizontal crack is better than longitudinal crack and radiation crack,with statistical significance(P < 0.05);longitudinal crack is better than radiation crack.When the pressure load is 400 N,the effect of crack propagation is the greatest;with the increase of the number of cycles,the crack propagation increases gradually,and the trend of increase is enlarged;when the knee joint flexion is 90 degrees,the meniscus crack propagation is the greatest.Conclusion: 1.the three-dimensional finite element model of pig knee joint was successfully constructed,which laid a foundation for studying the mechanism of meniscus injury of pig knee joint.2.The horizontal fissure is most likely to expand in the posterior horn of the medial meniscus of the knee joint,radial fissures are not easy to expand.