The influence of powered prostheses on user perspectives, metabolics, and activity: a randomized crossover trial

Abstract

Background Powered prosthetic ankles provide battery-powered mechanical push-off, with the aim of reducing the metabolic demands of walking for people with transtibial amputations. The efficacy of powered ankles has been shown in active, high functioning individuals with transtibial amputation, but is less clear in other populations. Additionally, it is unclear how use of a powered prosthesis influences everyday physical activity and mobility. Methods Individuals with unilateral transtibial amputations participated in a randomized clinical trial comparing their prescribed, unpowered prosthesis and the BiOM powered prosthesis. Participants’ metabolic costs and self-selected walking speeds were measured in the laboratory and daily step count, daily steps away from home, and walking speed were measured over two weeks of at-home prosthesis use. Participants also rated their perception of mobility and quality of life and provided free-form feedback. Dependent measures were compared between prostheses and the relationships between metabolic cost, perception of mobility, and characteristics of walking in daily life were explored using Pearson’s correlations. Results Twelve people were randomly allocated to the powered prosthesis first (n = 7) or unpowered prosthesis first (n = 5) and ten completed the full study. There were no differences in metabolic costs (p = 0.585), daily step count (p = 0.995), walking speed in-lab (p = 0.145) and in daily life (p = 0.226), or perception of mobility between prostheses (p ≥ 0.058). Changes varied across participants, however. There were several medium-sized effects for device comparisons. With the powered prosthesis, participants had increased self-reported ambulation (g = 0.682) and decreased frustration (g = 0.506). Conclusions There were no universal benefits of the powered prosthesis on function in the lab or home environment. However, the effects were subject-specific, with some reporting preference for power and improved mobility, and some increasing their activity and decreasing their metabolic effort. Additionally, self-reported preferences did not often correlate with objective measures of function. This highlights the need for future clinical research to include both perception and objective measures to better inform prosthetic prescription. Trial registration: https://clinicaltrials.gov, #NCT02828982. Registered 12 July 2016, https://clinicaltrials.gov/ct2/show/NCT02828982

Free-Living User Perspectives on Musculoskeletal Pain and Patient-Reported Mobility With Passive and Powered Prosthetic Ankle-Foot Components: A Pragmatic, Exploratory Cross-Sectional Study

“…The present pragmatic, exploratory study aimed at determining whether anecdotal reports of individuals with TTA on reduced musculoskeletal pain when using a PwrAF reflect a common experience among users or just isolated occurrences. As the identification of subjects who are likely to benefit from a PwrAF has been a clinical challenge (9)(10)(11), it was decided to survey a bigger sample of individuals who had been fitted such foot in the past to obtain real-world, long-term use experiences with the PwrAF and passive prosthetic feet. Though recall of ratings for previous interventions has limitations and challenges, this pragmatic approach is very similar to clinical practice where patients are usually asked to compare their current symptoms to those they recall for time points in the past.…”

“…Studies have shown that a commercially available powered prosthetic ankle-foot component (PwrAF) generates speeddependent push-off power that may be comparable with that of the natural ankle (6)(7)(8). However, the results on its impact on function, such as self-selected walking speed (7,(9)(10)(11)(12)(13), metabolic energy expenditure on level ground (7,(9)(10)(11) and inclines (8,10), patient-reported prosthetic function (12), and other aspects of prosthetic mobility have been inconclusive or conflicting.…”

“…This biomechanical evidence makes anecdotal reports from users of PwrAF on improved sound knee pain and pain-free walking distance noteworthy. Several studies with a PwrAF that did not find significant group benefits published the individual results of their subjects (9)(10)(11)18). A thorough review of these subject-specific results revealed that, varying across the outcomes assessed, 35-50% of these individuals had experienced clinically meaningful benefits of the PwrAF during the studies.…”

Understanding patient preference in prosthetic ankle stiffness

“…We did not observe a significant effect of prosthetic ankle stiffness on metabolic expenditure, even when we normalized stiffness by each subject's preference. While it is known that metabolic cost is not highly sensitive to prosthesis mechanics during level walking [41,[60][61][62][63][64][65][66], these previous studies have assessed metabolic cost either as a function of weight-normalized prosthetic joint stiffness, or of categorical stiffness [64]. Given that we have consistently shown that there is no clear linear relationship between weight and preferred stiffness, it is possible that weight-normalization may have obscured any underlying effects, by not adequately aligning the minima of individual subjects' energy landscapes [40].…”

“…In addition, preference is inherently specific to the population from which it is measured, which increases its applicability as an efficacy criterion across pathologies, and drives device development toward solutions that meet patient needs. In light of these benefits, preference has emerged in the research setting as a potential indicator of device efficacy [39][40][41], and has recently been used in combination with humanin-the-loop optimization to tune the behavior of complex wearable mechatronic systems [42,43].…”