FALL BIOMECHANICS AND HIP FRACTURE RISK

跌倒生物力学和髋部骨折风险

• 批准号: 2079969
• 负责人: WILSON C HAYES
• 金额: $ 29.59万
• 依托单位: BETH ISRAEL DEACONESS MEDICAL CENTER
• 依托单位国家: 美国
• 财政年份: 1994
• 资助国家: 美国
• 起止时间: 1994-02-01 至 1996-07-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/2079969
• 关键词: adult human (21+); aging; biomechanics; body height; body movement; electromyography; female; gender difference; hip fractures; human subject; male; mathematical model; neuromuscular function; osteoporosis; postmortem; psychomotor reaction time; reflex; young adult human (21-34)

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.

通过其频率来衡量，对生活质量和经济的影响 成本，髋部骨折是一个危机程度的公共健康问题。 这 髋部骨折发生率随年龄呈指数增长，加上 已证明骨密度和强度随年龄的减少导致 人们普遍认为，与年龄相关的骨质流失或骨质疏松症是 髋部骨折发生率最重要的决定因素。 然而，有些人有 表明老年人跌倒倾向增加的原因是 最重要的病因。 近日，通过跌倒监测 对尸体股骨的研究和体外强度测试，我们表明 从站立高度跌落时可获得的能量约为十六倍 体外髋部骨折所需的能量。 而且，大多数跌倒者 髋部骨折的人摔倒在一边，直接用髋部着地，然后做 不要用伸出的手去阻止坠落。 这些发现表明 除了跌倒发生率增加之外， 跌倒本身很可能主导髋部骨折的发生 老年。 虽然之前的研究已经确定了那些宿主和 引发跌倒的环境因素，以前的工作尚未关注 跌倒力学在髋部骨折病因学中的作用 老年。 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）导致跌落配置和影响 代表髋部骨折风险显着降低的力量 与跛行跌倒相比（其中神经肌肉反应机制是 缺席的）。 为了探索这个假设，我们将使用快速位移的 蹦床以启动年轻成年志愿者的安全跌倒。 运动学 将使用高速视频监测反射介导的跌倒和跛行跌倒： a) 年轻的成年志愿者； b) 仪表化汽车碰撞假人；和 c) 老年尸体标本。 我们的第二个假设是髋部冲击 跌倒产生的力可以通过简单的非伤害性预测 实验。 这个“骨盆释放”实验使我们能够表征 身体节段配置（有效质量）和的综合影响 通过确定弹簧常数和覆盖臀部的软组织 系统的简单质量-弹簧-阻尼器模型的阻尼因子。 这 实验将由代表一个群体的男性和女性志愿者进行 几种潜在影响配置的年龄和体型范围 以及有或没有肌肉活动。 的预测准确度 然后将评估坠落冲击速度实际值的模型 使用尸体跌落测试。 最后，提供一个理论框架 理解并扩展实验跌倒和 骨盆释放实验，我们将开发一系列分析 坠落和冲击模型。 这些将从简单的集中质量开始 表示并扩展到二元和三元铰接段。 我们还将采用 15 段动态模型（最初开发用于 汽车碰撞模拟）来研究跌倒。 模型预测 将通过与实验跌倒和尸体的比较来验证 影响，然后用于探索诸如反应时间和 下肢力量下降，导致跌倒的高风险 老年。 我们期望秋季的这些实验和分析研究 机制，以提高对导致这些因素的理解 跌倒时髋部骨折的风险很高，因此需要设计更多 有效的干预策略可降低髋关节发病率的上升 老年人骨折。