Effect of Component Impulsive Loading on Relative ACL Strain

描述（由申请人提供）：膝关节前交叉韧带（ACL）损伤经常改变活跃人群的生活方式。最近，无论选择何种治疗，这些损伤的长期后果都变得更加清晰。退行性关节炎是最常见的结果，发生在损伤后7年内（Pinczewski 2002）。据估计，2005年在美国手术治疗了300，000例ACL撕裂（AOSSM 2006），因此需要更好地预防这些损伤。这项建议解决了迫切需要更好地了解ACL损伤的机制，希望改善风险因素监测和预防计划。许多ACL损伤发生在跳跃时单脚着地或跑步和切割时。目前还没有系统研究脉冲载荷的方向如何影响ACL应变。我们计划使用尸体结构，首先确定ACL应变如何受到对膝关节施加压缩和力矩的脉冲载荷方向的影响。膝关节最初将通过预张紧的股四头肌、内侧和外侧腘绳肌和腓肠肌等效物以15？的初始角度限制，但膝关节可以在负载下屈曲。在AIM 1中，我们将检验以下假设：与涉及等效仅屈曲力矩的矢状对称载荷相比，向膝关节施加外翻、内旋或外旋力矩的2*BW冲击力将增加峰值ACL应变。在AIM 2中，我们将检验以下假设：AIM 1外翻和轴向旋转力矩分量的叠加导致ACL峰值应变大于相似幅度的屈曲力矩。在AIM 3中，将对假设进行检验，即在矢状面外载荷组件的4*BW脉冲载荷下，ACL断裂的风险高于矢状面对称载荷。在AIM 4中，我们将检验这样一个假设，即当膝关节对冲击载荷做出反应时，拉伸腘绳肌等效肌肉可以降低ACL峰值应变。飞行员数据表明，当足够的髋关节屈曲伴随着与跳跃着陆相关的膝关节屈曲时，可以诱导这种拉伸;缺乏这种拉伸会导致ACL应变增加。将在重复测量设计中使用成对膝关节对三个假设进行检验。载荷传感器将用于测量膝关节上方和下方的3-D脉冲载荷，并将使用测力传感器测量肌肉力量。将使用Certus系统测量股骨和胫骨的三维运动学。ACL相对应变将使用差动可变磁阻传感器测量。将使用多达120个尸体膝关节。

DESCRIPTION (provided by applicant): Anterior cruciate ligament (ACL) injuries of the knee frequently alter the lifestyle of active people. Recently, the long-term consequences of these injuries have become clearer regardless of the treatment chosen. Degenerative arthritis is the most common outcome, occurring in as little as seven years post injury (Pinczewski 2002). With an estimated 300,000 ACL tears surgically treated in the U.S. in 2005 (AOSSM 2006) there is a need to better prevent these injuries. This proposal addresses the urgent need to better understand the mechanism of ACL injury in hopes of improving both risk factor surveillance and prevention programs. Many ACL injuries occur when landing on one foot from a jump or when running and cutting. There are no systematic studies of how the direction of the impulsive loading affects ACL strain. We plan to use a cadaver construct to first determine how ACL strain is affected by the direction of an impulsive load that applies both compression and a moment to the knee joint. The knee will initially be constrained at an initial angle of 15¿ via pretensioned quadriceps, medial and lateral hamstring and gastrocnemius muscle- equivalents, but the knee can flex under load. In AIM 1 we will test the hypothesis that a 2*BW impulsive force that applies valgus, internal or external axial rotation moments to the knee will increase peak ACL strain compared with a sagittally-symmetric loading involving an equivalent flexion-only moment. In AIM 2 we will test the hypothesis that superposition of the AIM 1 valgus and axial rotation moment components results in greater peak ACL strain than a flexion moment of similar magnitude. In AIM 3 the hypothesis will be tested that there is a higher risk for ACL rupture under a 4*BW impulsive loading with an out-of-sagittal plane loading component than with sagittally-symmetric loading. In AIM 4 we will test the hypothesis that peak ACL strain can be reduced by stretch of the hamstring muscle-equivalents as the knee flexes in response to impulsive loading. Pilot data suggest that such stretch can be induced when adequate hip flexion accompanies the knee flexion associated with a jump landing; absence of such stretch results in increased ACL strain. Three hypotheses will be tested using paired knees in a repeated measures design. Load transducers will be used to measure the 3-D impulsive loading above and below the knee, and muscle forces will be measured using load cells. 3-D kinematics of the femur and tibia will be measured using the Certus system. ACL relative strain will be measured using a differential variable reluctance transducer. Up to 120 cadaver knees will be used.