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

减震是健全的运动系统的固有功能。健全的救护车不是 通常有意识地意识到震动衰减，但下肢假肢使用者经常敏锐地意识到 当他们带着假肢走一步时，可能会产生震动的冲击力。这些冲击力是 通过假肢传递到残肢，使行走不舒服，甚至疼痛。 刚度降低的部件通常用于下肢假肢中，以改变假肢的刚度。 假体对所施加载荷的机械响应，提供减震和减小力 在步态中传递到残肢。然而，与预期相反，这些组件不 通常会降低步态期间的地面反作用力（GRF）载荷峰值，这是一种常用的冲击指标 吸收先前关于受试者对刚度降低部件偏好增加的报告表明， 这些部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一致记录。目前，假肢刚度的差异 需要克服总肢体刚度的被动贡献，并改变冲击力 Profiles是未知的。因此，在体内评价假体刚度变化的影响是很重要的 在可控的撞击环境中。此外，对于任何 这些刚度降低的部件的性能之前已经进行了评估。同样重要的是要确定， 假肢使用者在行走过程中响应于假肢的变化主动调节总肢体刚度 刚度，当刚度降低的部件 植入他们的假肢 本研究的目的是系统地改变经胫骨假体的刚度， 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 假体刚度系统地变化，同时使用一种新的体内冲击测试方案， 假体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。 步态分析在相同的假肢刚度水平。这项拟议的研究将是第一个 对冲击力-假体刚度关系进行系统评价。复位假体 假设刚度在冲击测试期间减小冲击力的大小。GRF加载峰值为 预计不会在假体刚度条件之间发生变化，表明通过以下方式采取主动补偿策略： 假肢使用者在步态中。 这项拟议的研究旨在为更全面地了解假体如何 成分在体内起作用。首先，它将证实主观数据表明，减少刚度 部件能够克服残肢软组织的低刚度， 假肢系统，即使在没有记录的生物力学变化，在行走。 此外，预期结果将表明，受试者能够适应 假体组件刚度，需要进一步的研究，以确定，更好地理解， 可以利用这些自适应机制的组件。最后，这些结果将告知临床 实践和假体设计，指出降低假体刚度的水平在 从而减小残肢和假肢作为整体内的冲击力。

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.