Effect of prosthesis stiffness on impact force during in vivo step loads and gait

假体刚度对体内步态负载和步态冲击力的影响

基本信息

批准号：
9030953
负责人：
Steven A. Gard
金额：
--
依托单位：
JESSE BROWN VA MEDICAL CENTER
依托单位国家：
美国
项目类别：
财政年份：
2014
资助国家：
美国
起止时间：
2014-11-01 至 2016-10-31
项目状态：
已结题

项目摘要

Shock absorption is an inherent function of the able-bodied locomotor system. Able-bodied ambulators are not typically consciously aware of shock attenuation, but lower-limb prostheses users are often acutely aware of the jarring impact forces that can occur when they take a step with their prosthesis. These impact forces are transmitted through the prosthesis to the residual limb, making walking uncomfortable and even painful. Components with reduced stiffness are commonly prescribed in lower-limb prostheses to change the mechanical response of the prosthesis to an applied load, providing shock absorption and reducing forces transmitted to the residual limb during gait. However, contrary to expectations, these components do not generally decrease ground reaction force (GRF) loading peaks during gait, a commonly used indicator of shock absorption. Previous reports of increased subject preference for reduced-stiffness components indicate that these components are influencing the limb-prosthesis system. However, this influence has not been documented consistently in any biomechanical gait parameter. Currently, the difference in prosthetic stiffness required to overcome the passive contributions in total limb stiffness and enact a change in the impact force profiles is unknown. Therefore, it is important to evaluate the effect of changes in prosthetic stiffness in vivo and in a controlled impact environment. Furthermore, only manufacturer-recommended stiffness levels for any of these reduced-stiffness components have been previously evaluated. It is also important to determine if prosthesis users actively modulate total limb stiffness during walking in response to changes in prosthesis stiffness, preserving some minimum magnitude of impact force when reduced-stiffness components are incorporated into their prostheses. The purpose of this proposed study is to systematically vary the stiffness of a transtibial prosthesis and measure the force response during in vivo impact loading and gait. Impact forces will be measured as the prosthetic stiffness is systematically varied while using a novel in vivo impact-testing protocol that reduces the ability of the prosthesis user to influence impact forces. These data will then be compared with a quantitative gait analysis performed over the same prosthetic stiffness levels. This proposed study will be the first to perform a systematic evaluation of the impact force-prosthetic stiffness relationship. Reduced prosthetic stiffness is hypothesized to decrease impact force magnitudes during impact testing. GRF loading peaks are not expected to change between prosthetic stiffness conditions, indicating an active compensation strategy by the prosthesis user during gait. The proposed study is intended to lay the groundwork for a more complete understanding of how prosthetic components function in vivo. First, it would corroborate subjective data that indicates that reduced-stiffness components are capable of overcoming the low stiffness of the soft tissue of the residual limb and influencing the limb-prosthesis system, even in the absence of documented biomechanical changes during walking. Furthermore, the anticipated results would indicate that subjects are able to accommodate to changes in prosthetic component stiffness, requiring further investigations to identify, better understand, and develop components that can capitalize upon these adaptive mechanisms. Finally, these results would inform clinical practice and prosthetic design by indicating which levels of reduced prosthetic stiffness are effective at reducing impact forces within the residual limb and prosthesis as a whole.

减震是健全运动系统的固有功能。身体健全的步行者不是通常有意识地意识到震动衰减，但下肢假肢使用者通常会敏锐地意识到当他们用假肢迈出一步时可能会产生刺耳的冲击力。这些冲击力是通过假肢传播到残肢，使行走不舒服甚至疼痛。下肢假肢中通常会使用刚度降低的部件来改变假体对所施加负载的机械响应，提供减震和减少力步态时传递至残肢。然而，与预期相反，这些组件并没有通常会降低步态期间的地面反作用力 (GRF) 负载峰值，这是一种常用的冲击指标吸收。先前关于受试者对降低刚度组件的偏好增加的报告表明，这些组件正在影响假肢系统。然而这种影响并没有被在任何生物力学步态参数中都有一致的记录。目前，假肢刚度的差异克服肢体总僵硬的被动贡献并改变冲击力所需的个人资料未知。因此，评估体内假体刚度变化的影响非常重要并在受控影响环境中。此外，对于任何产品，只有制造商推荐的刚度水平这些刚度降低的部件的结构之前已进行过评估。确定是否假肢使用者在行走过程中主动调节肢体总硬度，以响应假肢的变化刚度，当降低刚度的组件时，保留一些最小的冲击力大小融入他们的假肢中。这项研究的目的是系统地改变跨胫骨假体的刚度和测量体内冲击载荷和步态期间的力响应。冲击力将被测量为假肢刚度系统地变化，同时使用一种新颖的体内冲击测试方案，减少了假肢使用者影响冲击力的能力。然后将这些数据与定量数据进行比较在相同的假肢刚度水平上进行步态分析。这项拟议的研究将是第一个对冲击力与假肢刚度关系进行系统评估。缩小假肢假设刚度可以降低冲击测试期间的冲击力大小。 GRF 负载峰值为预计假体刚度条件之间不会发生变化，表明主动补偿策略假肢使用者在步态中。拟议的研究旨在为更全面地了解假肢如何发挥作用奠定基础。成分在体内发挥作用。首先，它将证实主观数据表明刚度降低组件能够克服残肢软组织的低刚度并影响即使在行走过程中没有记录生物力学变化的情况下，肢体假肢系统也会受到影响。此外，预期结果表明受试者能够适应环境的变化假肢部件的刚度，需要进一步研究来识别、更好地理解和开发可以利用这些自适应机制的组件。最后，这些结果将为临床提供信息通过指出哪些程度的降低假肢刚度是有效的来进行实践和假肢设计减少残肢和假肢整体的冲击力。