Robotic Emulation of Candidate Prosthetic Foot Designs May Enable Efficient, Evidence-Based, and Individualized Prescriptions

Abstract

Introduction The design and selection of lower-limb prosthetic devices is currently hampered by a shortage of evidence to drive the choice of prosthetic foot parameters. We propose a new approach wherein prostheses could be designed, specified, and provided based on individualized measurements of the benefits provided by candidate feet. In this manuscript, we present a pilot test of this evidence-based and personalized process. Methods We previously developed a “prosthetic foot emulator,” a wearable robotic system that provides users with the physical sensation of trying on different prosthetic feet before definitive fitting. Here we detail preliminary demonstrations of two possible approaches to personalizing foot design: 1) an emulation and test-drive strategy of representative commercial foot models, and 2) a prosthetist-driven tuning procedure to optimize foot parameters. Results The first experiment demonstrated large and sometimes surprising differences in optimal prosthetic foot parameters across a variety of subjects, walking conditions, and outcome measures. The second experiment demonstrated a quick and effective simple manual tuning procedure for identifying preferred prosthetic foot parameters. Conclusions Emulator-based approaches could improve individualization of prosthetic foot prescription. The present results motivate future clinical studies of the validity, efficacy, and economics of the approach across larger and more diverse subject populations. Clinical Relevance Today, emulator technology is being used to accelerate research and development of novel prosthetic and orthotic devices. In the future, after further refinement and validation, this technology could benefit clinical practice by providing a means for rapid test-driving and optimal selection of clinically available prosthetic feet.

Design, Control, and Evaluation of a Robotic Ankle-Foot Prosthesis Emulator

“…This is partly due to the experimental setup for our benchtop tests. It is common to lock the ankle joint during bandwidth tests [19], [31], [34], [35], but this method would likely overestimate our controller's ability to develop torque during walking because it does not account for series elasticity between the ankle, ground, and user. Both the footplate and the interface between the socket and residual limb contribute to additional series elasticity.…”

“…Placing actuation and control hardware off-board greatly simplifies the design of wearable end-effectors, with the trade-off of limiting experiments to treadmill walking. Prosthesis emulators can be programmed to mimic passive prostheses in order to understand and improve the clinical prescription process, emulate the mechanical behavior of proposed devices, and evaluate novel control strategies for robotic ankles [31]- [33].…”

A patient-centered ‘test-drive’ strategy for ankle-foot orthosis prescription: Protocol for a randomized participant-blinded trial

“…A robotic exoskeleton emulator (AFO emulator), capable of mimicking certain mechanical characteristics of AFOs, could facilitate a more efficient approach to AFO prescription that would enable incorporating user feedback. Recent work using a prosthetic foot emulator allowed participants to ‘test-drive’ prosthetic feet [ 24 , 25 ]. The current AFO study incorporates a similar ‘test-drive’ strategy for AFO prescription, using a customizable AFO emulator (Caplex system, Humotech, Pittsburgh, PA, USA) that is worn around the foot and lower leg.…”

A Novel Framework to Facilitate User Preferred Tuning for a Robotic Knee Prosthesis

“…Studies showed that the lack of user input during the device selection, fitting time frame, and changing user needs are among the main reasons for the prosthesis abandonment [18], [19]. In addition, prosthetists make prosthesis control tuning decisions based on not only the observational gait analysis but also the user's preference and feedback in clinics [20], [21]. These insights signify the importance of prosthesis user's preference consideration in regard to prosthetic behavior.…”