有限元分析立定跳远状态时不同摆臂动作和触地姿势的膝关节损伤

Finite element analysis of knee joint injury under different arm swinging modes and touchdown postures in standing long jump

背景:立定跳远是人体跳跃时常采用的标准动作,同时也是下肢爆发力训练的主要项目之一。大量研究表明,起跳过程中的摆臂动作及触地时足部采用外八姿态能够增加跳跃距离,但鲜有研究关注触地过程中的膝关节损伤。目的:探讨立定跳远不同摆臂动作和触地姿势下双侧半月板和股骨软骨的应力及应力分布特征。方法:招募8名男性大学生进行立定跳远试验,试验中分自由摆臂和限制摆臂起跳、踝关节正常姿态和“外八”姿态触地4种情况,采集跳跃过程中的运动学数据和地面反作用力,通过逆动力学计算获取膝关节反力作为边界条件和荷载。基于1名受试者的膝关节MRI图像,建立膝关节三维有限元模型,对立定跳远触地过程进行数值模拟。结果与结论:(1)摆臂动作与踝关节姿态对膝关节运动学特征的影响存在交互作用,限制摆臂与改变踝关节触地姿态均会对膝关节在矢状面、额状面上的运动学特征产生显著影响(P<0.001,P<0.001);(2)限制摆臂+正常姿态触地与自由摆臂+正常姿态触地时的双侧软骨接触较为均匀,限制摆臂+外八姿态触地和自由摆臂+外八姿态触地的应力集中均发生在软骨内侧而外侧接触较少,内侧软骨较外侧受到更大的冲击;摆臂动作+外八姿态触地时,股骨软骨接触应力峰值(8.89 MPa)和半月板接触应力峰值(10.71 MPa)均较低;限制摆臂+外八姿态触地时,股骨软骨接触应力峰值(13.11 MPa)和半月板接触应力峰值(11.23 MPa)均较高;(3)结果显示,正确的摆臂动作配合适当程度的踝关节“外八”姿态落地,能够减小膝关节的损伤风险;当踝关节以“外八”姿态触地并限制跳跃过程中的摆臂动作时,会使股骨软骨的接触应力显著增大,可能提高膝关节损伤风险。

BACKGROUND:Standing long jump is a standard action often used in human body jumping,and it is also one of the main items of lower limb explosive force training.A large number of studies have shown that the arms swing movement in the take-off process and the use of the toe-out posture of the foot when touching the ground can increase the jumping distance,but few studies have paid attention to the knee joint injury during the touchdown process.OBJECTIVE:To study the stress distribution characteristics of the bilateral meniscus and femoral cartilage under different arm swinging modes and touchdown postures in standing long jump.METHODS:Eight male college students were recruited for the standing long jump test.The kinematic data and ground reaction force were collected under the condition of free and limited swing arms,ankle joint normal posture and toe-out posture touching the ground.The knee reaction force was obtained as the boundary condition and load by inverse dynamic calculation.Based on the MRI images of a subject’s knee joint,a three-dimensional finite element model of the knee joint was established to simulate the landing process of a standing long jump.RESULTS AND CONCLUSION:(1)There was an interaction between arm swing and ankle posture on knee kinematics.Limiting the swing arm and changing the contact posture of the ankle joint would have a significant impact on the kinematics characteristics of the knee joint in the sagittal plane and frontal plane(P<0.001,P<0.001).(2)When the limited swing arm+normal posture touchdown and the free swing arm+normal posture touchdown,the bilateral cartilage contact was more uniform.The stress concentration of the limited swing arm+toe-out posture touchdown and the free swing arm+toe-out posture touchdown occurred on the inner side of the cartilage and the stress on the outer side was less.The inner cartilage was more impacted than the outer side.The peak contact stresses of femoral cartilage(8.89 MPa)and meniscus(10.71 MPa)were lower when the swing arm combined with toe-out touched the ground,while the peak contact stresses of femoral cartilage(13.11 MPa)and meniscus(11.23 MPa)were higher when the swing arm combined with toe-out was limited.(3)These findings indicate that the correct arm swing and the appropriate toe-out posture landing can reduce the risk of knee joint injury.When the ankle joint touches the ground in toe-out posture and limits the arm swing during jumping,the contact stress of the femoral cartilage will be significantly increased,possibly increasing the risk of knee joint injury.