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

减震是健全的运动系统固有的功能。健全的救护车不是 通常有意识地意识到冲击衰减，但假肢使用者往往敏锐地意识到 当他们用假肢迈出一步时，可能会产生不和谐的冲击力。这些冲击力是 通过假肢传播到残肢，使行走不适，甚至疼痛。 在下肢假体中，通常会开出刚度降低的部件，以改变 假体对外加载荷的机械反应，提供减震和减震力 在步态过程中传播到残肢。然而，与预期相反，这些组件并不 通常会降低步态中的地面反作用力(GRF)负荷峰值，这是一种常用的休克指标 吸收。先前关于受试者对降低刚度部件的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 在任何生物力学步态参数中记录一致。目前，假体僵硬的差异 克服肢体总刚度的被动贡献并改变冲击力所需的 配置文件未知。因此，在活体内评估假体硬度变化的效果是很重要的。 并在受控的冲击环境中。此外，只有制造商推荐的任何 在这些降低的刚度组件中，以前已经评估过。同样重要的是确定 假肢使用者在行走过程中主动调整肢体总硬度，以响应假肢的变化 刚度，当降低了刚度的部件 整合到他们的假肢中。 这项拟议的研究的目的是系统地改变经胫骨假体的硬度和 测量在活体冲击载荷和步态时的力响应。冲击力将被测量为 在使用一种新的体内冲击测试方案时，假肢的刚度可以系统地变化，该方案可以降低 假肢使用者影响冲击力的能力。然后将这些数据与量化的 步态分析在相同的假体僵硬水平上进行。这项拟议的研究将是第一个 对撞击力-假体刚度关系进行系统评估。简化假体 在冲击试验过程中，假定刚度会降低冲击力的大小。GRF加载峰值为 预计不会在假体僵硬条件之间改变，表明主动补偿策略 假肢使用者在步态过程中。 这项拟议的研究旨在为更全面地了解假体是如何 这些成分在体内发挥作用。首先，它将证实表明刚度降低的主观数据 假体能够克服残肢软组织僵硬程度低，影响 假肢系统，即使在行走过程中没有记录生物力学变化的情况下也是如此。 此外，预期的结果将表明受试者能够适应 假体部件硬度，需要进一步研究以确定、更好地理解和开发 能够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，通过指出哪些水平的减少假体僵硬是有效的 整体减少残肢和假体内的冲击力。

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.