Abstract
IntroductionStudies with a powered prosthetic ankle-foot (PwrAF) found a reduction in sound knee loading compared to passive feet. Therefore, the aim of the present study was to determine whether anecdotal reports on reduced musculoskeletal pain and improved patient-reported mobility were isolated occurrences or reflect a common experience in PwrAF users.MethodsTwo hundred and fifty individuals with transtibial amputation (TTA) who had been fitted a PwrAF in the past were invited to an online survey on average sound knee, amputated side knee, and low-back pain assessed with numerical pain rating scales (NPRS), the PROMIS Pain Interference scale, and the PLUS-M for patient-reported mobility in the free-living environment. Subjects rated their current foot and recalled the ratings for their previous foot. Recalled scores were adjusted for recall bias by clinically meaningful amounts following published recommendations. Statistical comparisons were performed using Wilcoxon's signed rank test.ResultsForty-six subjects, all male, with unilateral TTA provided data suitable for analysis. Eighteen individuals (39%) were current PwrAF users, whereas 28 subjects (61%) had reverted to a passive foot. After adjustment for recall bias, current PwrAF users reported significantly less sound knee pain than they recalled for use of a passive foot (−0.5 NPRS, p = 0.036). Current PwrAF users who recalled sound knee pain ≥4 NPRS with a passive foot reported significant and clinically meaningful improvements in sound knee pain (−2.5 NPRS, p = 0.038) and amputated side knee pain (−3 NPRS, p = 0.042). Current PwrAF users also reported significant and clinically meaningful improvements in patient-reported mobility (+4.6 points PLUS-M, p = 0.016). Individuals who had abandoned the PwrAF did not recall any differences between the feet.DiscussionCurrent PwrAF users reported significant and clinically meaningful improvements in patient-reported prosthetic mobility as well as sound knee and amputated side knee pain compared to recalled mobility and pain with passive feet used previously. However, a substantial proportion of individuals who had been fitted such a foot in the past did not recall improvements and had reverted to passive feet. The identification of individuals with unilateral TTA who are likely to benefit from a PwrAF remains a clinical challenge and requires further research.
Highlights
Studies with a powered prosthetic ankle-foot (PwrAF) found a reduction in sound knee loading compared to passive feet
The aim of the present study was to determine whether unsolicited anecdotal reports on reduced sound knee pain, amputated side knee pain, and low-back pain and as well as improved patient-reported prosthetic mobility were isolated occurrences or reflect a common experience in users of PwrAF
There were no significant differences between the groups of current PwrAF and current passive foot (PAS) users
Summary
Studies with a powered prosthetic ankle-foot (PwrAF) found a reduction in sound knee loading compared to passive feet. In individuals with transtibial amputations (TTA), such compensations include slower walking speeds [1], about 25% higher energy expenditure for walking than able-bodied persons [2, 3], decreased sound limb step length [4], and reduced power generation in the residual knee [5]. One important reason for these compensatory mechanisms is that passive prosthetic feet provide only up to 55% of the push-off power of the natural ankle-foot complex [6]. 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]. 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
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