Effect of Component Impulsive Loading on Relative ACL Strain

描述(申请人提供)：膝关节前十字韧带(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，这些伤害的长期后果都变得更加清楚。退行性关节炎是最常见的结果，发生在损伤后短短七年内(Pinczewski 2002)。据估计，2005年美国有300,000例前交叉韧带撕裂接受手术治疗(AOSSM 2006)，因此有必要更好地预防这些损伤。这项建议解决了更好地了解前交叉韧带损伤机制的迫切需要，希望改善危险因素监测和预防计划。许多前交叉韧带损伤发生在单脚着地跳跃或跑步和割伤的时候。目前还没有关于冲击载荷方向如何影响前交叉韧带应变的系统研究。我们计划使用身体结构来首先确定冲击载荷的方向如何影响前交叉韧带的应变，脉冲载荷对膝关节既施加压缩又施加力矩。膝关节最初将通过预紧股四头肌、内侧和外侧腿筋和腓肠肌等效物被约束在15°的初始角度，但膝关节在负荷下可以弯曲。在目标1中，我们将检验这样一种假设，即施加外翻、内轴或外轴旋转力矩的2*BW的冲击力与包含相同的仅屈曲力矩的矢状对称载荷相比，会增加最大的ACL应变。在AIM 2中，我们将检验这样的假设，即AIM 1外翻和轴向旋转力矩分量的叠加导致的最大前交叉韧带应变大于类似量级的屈曲力矩。在AIM 3中，将检验这一假设，即在4*BW冲击载荷下，矢状面外载荷分量比矢状面对称载荷下有更高的前交叉韧带断裂风险。在AIM 4中，我们将验证这样的假设，即当膝关节对脉冲负荷作出反应时，伸展腿筋肌肉等效物可以减少峰值前交叉韧带应变。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，可以诱导出这样的伸展；如果没有这样的伸展，会导致前交叉韧带拉伤的增加。三个假设将在重复测量设计中使用成对膝盖进行检验。载荷传感器将被用来测量膝盖上方和下方的3-D脉冲载荷，肌肉力量将使用载荷传感器来测量。股骨和胫骨的三维运动学将使用Certus系统进行测量。ACL相对应变将使用差动可变磁阻传感器进行测量。将使用多达120个身体膝盖。

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.