Boutwell Erin, Stine Rebecca, Gard Steven
1 Northwestern University Prosthetics-Orthotics Center, Chicago, IL, USA.
2 Jesse Brown VA Medical Center, Chicago, IL, USA.
Prosthet Orthot Int. 2017 Apr;41(2):178-185. doi: 10.1177/0309364616640945. Epub 2016 Jul 9.
Reduced-stiffness components are often prescribed in lower-limb prostheses, but their efficacy in augmenting shock absorption has been inconclusive.
To perform a systematic variation of longitudinal prosthetic stiffness over a wide range of values and to evaluate its effect on shock absorption during gait.
Repeated-measures crossover experiment.
Twelve subjects with a unilateral transtibial amputation walked at normal and fast self-selected speeds. Longitudinal prosthetic stiffness was modified by springs within a shock-absorbing pylon: normal (manufacturer recommended), 75% of normal (medium), 50% of normal (soft), and rigid (displacement blocked). The variables of interest were kinematic (stance-phase knee flexion and pelvic obliquity) and kinetic (prosthetic-side ground reaction force loading peak magnitude and timing).
No changes were observed in kinematic measures during gait. A significant difference in peak ground reaction force magnitudes between medium and normal ( p = 0.001) during freely selected walking was attributed to modified walking speed ( p = 0.008). Ground reaction force peaks were found to be statistically different during fast walking, but only between isolated stiffness conditions. Thus, altering longitudinal prosthesis stiffness produced no appreciable change in gait biomechanics.
Prosthesis stiffness does not appear to substantially influence shock absorption in transtibial prosthesis users. Clinical relevance Varying the level of longitudinal prosthesis stiffness did not meaningfully influence gait biomechanics at self-selected walking speeds. Thus, as currently prescribed within a transtibial prosthesis, adding longitudinal stiffness in isolation may not provide the anticipated shock absorption benefits. Further research into residual limb properties and compensatory mechanisms is needed.
低刚度组件常用于下肢假肢，但它们在增强减震方面的效果尚无定论。
在广泛的数值范围内对假肢纵向刚度进行系统变化，并评估其对步态中减震的影响。
重复测量交叉实验。
12名单侧经胫骨截肢患者以正常和自我选择的快速速度行走。通过减震塔内的弹簧改变假肢纵向刚度：正常（制造商推荐）、正常的75%（中等）、正常的50%（柔软）和刚性（位移受阻）。感兴趣的变量包括运动学（站立相膝关节屈曲和骨盆倾斜）和动力学（假肢侧地面反作用力加载峰值大小和时间）。
步态期间运动学测量未观察到变化。在自由选择行走过程中，中等刚度和正常刚度之间的地面反作用力峰值存在显著差异（p = 0.001），这归因于行走速度的改变（p = 0.008）。在快速行走期间，发现地面反作用力峰值在统计学上存在差异，但仅在孤立的刚度条件之间。因此，改变假肢纵向刚度在步态生物力学方面没有产生明显变化。
假肢刚度似乎对经胫骨假肢使用者的减震没有实质性影响。临床相关性在自我选择的行走速度下，改变假肢纵向刚度水平对步态生物力学没有显著影响。因此，按照目前经胫骨假肢的规定，单独增加纵向刚度可能无法提供预期的减震益处。需要对残肢特性和代偿机制进行进一步研究。
