Survey of transfemoral amputee experience and priorities for the user-centered design of powered robotic transfemoral prostheses

Abstract

Background: Transfemoral amputees experience a complex host of physical, psychological, and social challenges, compounded by the functional limitations of current transfemoral prostheses. However, the specific relationships between human factors and prosthesis design and performance characteristics have not yet been adequately investigated. The present study aims to address this knowledge gap.

Methods: A comprehensive single-cohort survey of 114 unilateral transfemoral amputees addressed a broad range of demographic and clinical characteristics, functional autonomy, satisfaction and attitudes towards their current prostheses, and design priorities for an ideal transfemoral prosthesis, including the possibility of active assistance from a robotic knee unit. The survey was custom-developed based on several standard questionnaires used to assess motor abilities and autonomy in activities of daily living, prosthesis satisfaction, and quality of life in lower-limb amputees. Survey data were analyzed to compare the experience (including autonomy and satisfaction) and design priorities of users of transfemoral prostheses with versus without microprocessor-controlled knee units (MPKs and NMPKs, respectively), with a subsequent analyses of cross-category correlation, principal component analysis (PCA), cost-sensitivity segmentation, and unsupervised K-means clustering applied within the most cost-sensitive participants, to identify functional groupings of users with respect to their design priorities.

Results: The cohort featured predominantly younger (< 50 years) traumatic male amputees with respect to the general transfemoral amputee population, with pronounced differences in age distribution and amputation etiology (traumatic vs. non-traumatic) between MPK and NMPK groups. These differences were further reflected in user experience, with MPK users reporting significantly greater overall functional autonomy, satisfaction, and sense of prosthesis ownership than those with NMPKs, in conjunction with a decreased incidence of instability and falls. Across all participants, the leading functional priorities for an ideal transfemoral prosthesis were overall stability, adaptability to variable walking velocity, and lifestyle-related functionality, while the highest-prioritized general characteristics were reliability, comfort, and weight, with highly variable prioritization of cost according to reimbursement status. PCA and user clustering analyses revealed the possibility for functionally relevant groupings of prosthesis features and users, based on their differential prioritization of these features-with implications towards prosthesis design tradeoffs.

Conclusions: This study's findings support the understanding that when appropriately prescribed according to patient characteristics and needs in the context of a proactive rehabilitation program, advanced transfemoral prostheses promote patient mobility, autonomy, and overall health. Survey data indicate overall stability, modularity, and versatility as key design priorities for the continued development of transfemoral prosthesis technology. Finally, observed associations between prosthesis type, user experience, and attitudes concerning prosthesis ownership suggest both that prosthesis characteristics influence device acceptance and functional outcomes, and that psychosocial factors should be specifically and proactively addressed during the rehabilitation process.

Keywords: Human factors; Lower-limb prostheses; Powered prosthesis; Rehabilitation; Transfemoral amputation; User-centered design.

Fig. 1

Autonomy in Activities of Daily Living (ADL): Distribution of Likert scale responses, ranging from “completely autonomous” (5) to “completely non-autonomous [fully dependent]” (1) for each task in a) MPK and b) NMPK users. Significance (p) and common language effect size (f) reported for Mann–Whitney U Test (α = 0.05). *: Aggregate autonomy computed as the median (IQR) of each subject’s median autonomy across all constituent ADL

Fig. 2

Satisfaction with Prosthesis Functionality in ADL in A) all MPK and B) all NMPK users (traumatic + non-traumatic). Likert scale responses range from “completely satisfied” (6) to “completely dissatisfied” (1). Corresponding summary data reported in Table 8

Fig. 3

Design Priorities for an ideal transfemoral prosthesis (TFP) for the categories of general characteristics (Pr-GC), mobility-related functionality (Pr-Fn*), active assistance (Pr-AA), and socket (Pr-S)). Significance (p) assessed using Mann–Whitney U tests, with common language effect size (f) on all valid response data, omitting missing responses. *: An initial survey version without the questions of lifestyle functionality, functioning speed, or stair descent was issued was issued to a total of 50 participants (15 NMPK, 35 MPK), accounting for the outsized number of missing responses to these items

Fig. 4

Distribution of user priorities in principal component (PC) space, segmented by cost sensitivity

Fig. 5

Significantly different user priorities (Pr-GC) across cost-sensitivity tiers. Significance determined by Kruskal Wallis tests across all 3 tiers. Pair-wise significant differences from post-hoc Mann-Whitney U test denoted by horizontal bars. Red lines denote medians, boxes denote inter-quartile ranges, tick marks absolute ranges, with outliers noted as red crosses. NB: Higher priorities denoted by lower priority rankings

Fig. 6

Sub-segmentation of cost-sensitive subjects via K-means clustering (visualized in PC space)