FALL BIOMECHANICS AND HIP FRACTURE RISK

以他们的频率衡量，对生活质量和经济的影响 成本，髋部骨折是一个危机比例的公共卫生问题。这个 髋部骨折发病率随年龄呈指数增长，加上 已证实的与年龄相关的骨密度和强度下降导致 普遍认为，与年龄相关的骨质丢失或骨质疏松症是 髋部骨折发生率的最重要决定因素。然而，有些人已经 表明老年人跌倒倾向的增加是 最重要的病因。最近，直通瀑布监控系统 身体股骨的研究和体外强度测试表明， 从站立高度坠落的能量大约是站立高度的16倍。 在体外使髋关节骨折所需的能量。此外，大多数下跌者 他们摔断了臀部，倒在一边，直接落在臀部，然后做 不要用伸出的手来打破跌倒。这些发现表明 除了跌倒的发生率增加外， 跌倒本身很可能是髋部骨折发生的主要原因。 老年人。虽然之前的研究已经确定了这些宿主和 引发跌倒的环境因素，以前的工作都没有集中在 跌倒力学在老年人髋部骨折病因中的作用 老年人。我们假设反射介导的跌倒(其中神经肌肉 响应机制处于活动状态)导致坠落构型和影响 在以下情况下，髋部骨折风险显著降低的作用力 与跛行跌倒(其中神经肌肉反应机制是 缺席)。为了探索这一假设，我们将使用一个迅速流离失所的 在年轻的成年志愿者中启动安全跌落的蹦床。机器人的运动学 将使用高速视频监控反射调节的跌倒和跛行跌倒： A)青年志愿者；b)仪表化车祸假人；以及 C)老年身体标本。我们的第二个假设是臀部撞击 坠落产生的力可以从一个简单的非损伤性的 做实验。这一“骨盆释放”实验使我们能够描述 车身节段构型(有效质量)和 软组织覆盖在髋部通过确定弹簧常数和 系统简单质量-弹簧-阻尼器模型的阻尼系数。这 实验将在男性和女性志愿者中进行，代表 几种潜在影响配置的年龄和体型范围 无论有没有肌肉活动。的预测准确度 然后将评估坠落撞击速度的实际值的模型 使用身体坠落测试。最后，为……提供理论框架 理解和推广实验坠落和 在骨盆释放实验中，我们将制定一系列的分析 坠落和撞击的模型。这些将从简单的集中质量开始 表示法，并扩展到两个和三个元素的铰接段。 我们还将采用15段动态模型(最初是为 汽车碰撞模拟)到坠落的研究。模型预测 将通过与实验坠落和身体进行比较来验证 影响，然后用于探索条件，如反应时间和 腿部力量下降，导致高危跌倒 老年人。我们期待着秋季的这些实验和分析研究 力学有助于更好地理解那些导致 以髋部骨折的高风险摔倒，从而设计出更多 有效的干预策略以减少髋关节发病率的增长 老年人中的骨折。

As measured by their frequency, influence on quality of life and economic cost, hip fractures are a public health problem of crisis proportions. The exponential increase with age in hip fracture incidence, coupled with demonstrated age-dependent reductions in bone density and strength have led to the widely held view that age-related bone loss, or osteoporosis, is the most important determinant of hip fracture incidence. However, some have suggested that the increased propensity for falls among the elderly is the most important etiologic factor. Recently, through falls surveillance studies and in-vitro strength tests of cadaveric femora, we have shown that the energy available in a fall from standing height is about sixteen times the energy required to fracture the hip in-vitro. Moreover, most fallers who fracture their hip fall to the side, land directly on the hip and do not use the outstretched hand to break the fall. These findings suggest that in addition to the increased incidence of falling, the mechanics of the fall itself may well dominate the occurrence of hip fracture in the elderly. While previous research has determined those host and environmental factors which initiate falls, no previous work has focused on the role of fall mechanics in the etiology of hip fracture among the elderly. We hypothesize that reflex-mediated falls (in which neuromuscular response mechanisms are active) result in fall configurations and impact forces which represent a significantly decreased risk for hip fracture when compared to limp falls (in which neuromuscular response mechanisms are absent). To explore this hypothesis we will use a rapidly displaced trampoline to initiate safe falls in young adult volunteers. Kinematics of reflex-mediated and limp falls will be monitored using high-speed video in: a) young adult volunteers; b) an instrumented automotive crash dummy; and c) elderly cadaveric specimens. Our second hypothesis is that hip impact forces resulting from a fall can be predicted from a simple non-injurious experiment. This "pelvis-release" experiment allows us to characterize the combined influence of body segment configuration (the effective mass) and soft tissues overlying the hip by determining the spring constants and damping factors for simple mass-spring-dashpot models of the system. This experiment will be conducted with male and female volunteers representing a range of ages and body types for several potential impact configurations and both with and without muscle activity. The predictive accuracy of the model at realistic values of fall impact velocity will then be evaluated using cadaver drop tests. Finally, to provide a theoretical framework for understanding and extending the results of both the experimental falls and the pelvis-release experiments, we will develop a series of analytical models for falling and impact. These will begin with simple lumped mass representations and extend to two- and three-element articulated segments. We will also adapt a 15-segment, dynamic model (developed originally for automotive crash simulations) to the study of falling. Model predictions will be validated by comparison to the experimental falls and to cadaver impacts, and then used to explore conditions such as reaction times and decreased lower extremity strength which lead to high-risk falls in the elderly. We expect these experimental and analytical studies of fall mechanics to lead to an improved understanding of those factors which lead to falls with a high risk of hip fracture and thus to the design of more effective intervention strategies to reduce the growing incidence of hip fractures among the elderly.