Effect of 3-D Compound Impulsive Loading on Relative ACL Strain

描述(由申请人提供)：这项建议解决了目前的一个知识鸿沟：为什么女性比男性更容易受到前交叉韧带损伤的影响2到8倍。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。在01-03年间，我们使用一个固定的身体结构来确定引起最大峰值前交叉韧带应变的脉冲复合3-D载荷的方向：压缩+屈曲力矩+胫骨内轴力矩。我们现在寻求资金，使用这一具有非线性股四头肌拉伸刚度的身体测试结构，来确定在上述复合脉冲载荷情景下，性别对前交叉韧带峰值相对应变的影响。每个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-肌腱等效物放置在15度的初始屈曲角度，使膝关节在脉冲负荷下能够弯曲。在目标1中，我们将在22个大小匹配的男性和女性膝关节上检验这一假设，即性别不影响由于2*BW冲力和上述复合脉冲载荷而导致的最大ACL相对应变。飞行员的数据显示，女性膝盖的前交叉韧带拉伤更大。在AIM 2中，为了进一步阐明损伤机制，我们将使用重复测量设计和22个大小匹配的膝盖来检验以下假设：与外侧优势肌力相比，内侧优势股四头肌和腿筋膝关节肌力显著增加ACL峰值相对应变，尤其是在女性。试点数据表明情况的确如此。在AIM 3中，我们将使用重复测量设计在10膝上检验假设，即将女性股四头肌等效肌与较硬的男性股四头肌对换可以显著降低复合冲击载荷下女性膝关节的最大前交叉韧带应变；在10膝男性膝上，相应的效果不会达到显着水平。试点数据表明，情况确实如此。这项研究的见解将有助于解决更好地了解性别在前交叉韧带损伤机制中的作用，以改进危险因素监测和预防计划的迫切需要。 公共卫生相关性：这项研究的目标是更好地了解导致前交叉韧带损伤在女性中比男性更常见的机制。考虑到女性前交叉韧带的横截面积较小，在目标1中，我们将使用完全配备器械的身体膝盖来验证模拟跳跃着陆时女性前交叉韧带的峰值应变大于相同大小的男性的假设。在目标2中，我们将测试这样的假设，即当腿部内外穿过膝盖的肌肉力量不平衡时，这种张力在女性中会升高。在AIM 3中，我们将检验这样一个假设，即增加女性股四头肌的拉伸硬度可以显著降低峰值前交叉韧带应变。这项研究的见解将有助于提高旨在降低前交叉韧带损伤风险的预防计划的有效性，特别是在女性中。

DESCRIPTION (provided by applicant): This proposal addresses a current knowledge gap: why women are 2 to 8-fold more susceptible to ACL injury than men. Many ACL injuries occur when landing on one foot from a jump or when running and cutting. In Years 01-03 we used an instrumented cadaver construct to identify the direction of the impulsive compound 3-D loading that causes the largest peak ACL strain: compression + flexion moment + internal tibial axial torque. We now seek funds to use this cadaver testing construct, complete with non-linear quadriceps tensile stiffness, to determine the effect of gender on peak ACL relative strain under the above compound impulsive loading scenario. Each knee will initially be positioned at an initial flexion angle of 15 degrees via pretensioned quadriceps, medial and lateral hamstring and gastrocnemius muscle-tendon equivalents that allow the knee to flex under the impulsive load. In AIM 1 we will test the hypothesis in 22 male and female knees from size-matched cadavers that gender does not affect the peak ACL relative strain due to a 2*BW impulsive force and the above compound impulsive loading. Pilot data suggest ACL strain is larger in female knees. In AIM 2, to further delineate the injury mechanism, we will use a repeated measures design and 22 size-matched knees to test the hypothesis that medially-dominant quadriceps and hamstring knee muscle forces significantly increase peak ACL relative strain compared to laterally-dominant muscle forces, especially in females. Pilot data suggest this to be the case. In AIM 3 we will use a repeated measures design to test the hypothesis in 10 knees that swapping out the female quadriceps muscle-equivalent with a stiffer male counterpart will significantly reduce the peak ACL strain in the female knee under the compound impulsive loading; in 10 male knees the corresponding effect will not achieve significance. Pilot data suggest this is indeed the case. Insights from this research will help address the urgent need to better understand the role of gender in the mechanism of ACL injury to improve both risk factor surveillance and prevention programs. PUBLIC HEALTH RELEVANCE: The goal of this research is to better understand the mechanisms causing ACL injuries to be more common in women than men. Given the smaller cross-sectional area of the female ACL, in AIM 1 we will use fully instrumented cadaver knees to test the hypothesis that the peak ACL strain during a simulated jump landing is larger in females than males of the same size. In AIM 2 we will test the hypothesis that this strain is elevated in the female when the muscle forces crossing the knee on the inside and outside of the leg are not balanced. In AIM 3 we will test the hypothesis that increasing the tensile stiffness of the female quadriceps muscle significantly reduces peak ACL strain. Insights from this research should be useful for improving the efficacy of prevention programs designed to reduce the risk of ACL injury, particularly in females.