Emulating the Effective Ankle Stiffness of Commercial Prosthetic Feet Using a Robotic Prosthetic Foot Emulator

Abstract

Prosthetic foot selection for individuals with lower limb amputation relies primarily on clinician judgment. The prosthesis user rarely has an opportunity to provide experiential input into the decision by trying different feet. A prosthetic foot emulator (PFE) is a robotic prosthetic foot that could facilitate prosthesis users' ability to trial feet with different mechanical characteristics. Here, we introduce a procedure by which a robotic PFE is configured to emulate the sagittal plane effective ankle stiffness of a range of commercial prosthetic forefeet. Mechanical testing was used to collect data on five types of commercial prosthetic feet across a range of foot sizes and intended user body weights. Emulated forefoot profiles were parameterized using Bezier curve fitting on ankle torque-angle data. Mechanical testing was repeated with the PFE, across a subset of emulated foot conditions, to assess the accuracy of the emulation. Linear mixed-effects regression and Bland-Altman Limits of Agreement analyses were used to compare emulated and commercial ankle torque-angle data. Effective ankle stiffness of the emulated feet was significantly associated with the corresponding commercial prosthetic feet (p<.001). On average, the emulated forefeet reproduced the effective ankle stiffness of corresponding commercial feet within 1%. Furthermore, differences were independent of prosthetic foot type, foot size, or user body weight. These findings suggest a PFE could be an effective tool for emulating commercial prosthetic feet, enabling prosthesis users to quickly trial different feet and provide experiential input as part of a prosthetic foot prescription.

Robotic Technology in Foot and Ankle Surgery: A Comprehensive Review

“…Robotic prosthetic foot emulators have recently been developed and are modifiable to mimic existing commercially available prostheses. Through utilization of prosthetic foot emulators, patients and clinicians can accurately trial various commercial models and modify biomechanical variables [ 68 ]. Through their utilization, robotic prosthetic foot emulators could provide the opportunity for prosthetists and patients to find a more individualized fit prior to a potentially costly prosthesis prescription.…”

The development of rating scales to evaluate experiential prosthetic foot preference for people with lower limb amputation

“…[3][4][5][6] Enabling users to trial prosthetic feet could provide the opportunity to incorporate their experience with and preference for a specific foot into the selection process, potentially increasing the likelihood of satisfaction with their prosthesis. As trialing prosthetic feet is sometimes used in certain clinical settings and has more recently been explored in research studies, [7][8][9] there is increasingly a need for a standardized means of evaluating user preference for prosthetic feet after a brief period of within-clinic or within-laboratory use.…”