Informing ankle-foot prosthesis prescription through haptic emulation of candidate devices

Abstract

Robotic prostheses can improve walking performance for amputees, but prescription of these devices has been hindered by their high cost and uncertainty about the degree to which individuals will benefit. The typical prescription process cannot well predict how an individual will respond to a device they have never used because it bases decisions on subjective assessment of an individual’s current activity level. We propose a new approach in which individuals ‘test drive’ candidate devices using a prosthesis emulator while their walking performance is quantitatively assessed and results are distilled to inform prescription. In this system, prosthesis behavior is controlled by software rather than mechanical implementation, so users can quickly experience a broad range of devices. To test the viability of the approach, we developed a prototype emulator and assessment protocol, leveraging hardware and methods we previously developed for basic science experiments. We demonstrated emulations across the spectrum of commercially available prostheses, including traditional (e.g. SACH), dynamic-elastic (e.g. FlexFoot), and powered robotic (e.g. BiOM® T2) prostheses. Emulations exhibited low error with respect to reference data and provided subjectively convincing representations of each device. We demonstrated an assessment protocol that differentiated device classes for each individual based on quantitative performance metrics, providing feedback that could be used to make objective, personalized device prescriptions.

Step-to-Step Ankle Inversion/Eversion Torque Modulation Can Reduce Effort Associated with Balance

“…During all conditions, some amount of ankle inversion torque was applied during stance. The value of this default ankle inversion torque was limited to the range of −5 to 5 N·m (Equation 1, τ nom ) and was determined for each participant by hand tuning and user feedback (Caputo, 2015 ). Values for plantarflexion stiffness and work were set in the same manner.…”

Stiffness and energy storage characteristics of energy storage and return prosthetic feet

“…5,6 As a result, prosthetists often prescribe a small selection of prosthetic feet, 6 which may not be optimal for the patient. Previous research has sought to better inform prescriptions by developing a prosthetic foot emulator that allows patients to try more prosthetic feet 7 or by examining how different prosthetic foot properties affect walking performance. 8–12 However, additional quantitative information on the mechanical properties of prosthetic feet over a broader range of conditions is needed to develop criteria that could help clinicians make more informed prescription decisions.…”

Sensitivity of biomechanical outcomes to independent variations of hindfoot and forefoot stiffness in foot prostheses

“…A recent double-blinded study reported stiffness in three broad categories, alongside prosthetic socket moment data and subjective user preferences (Raschke et al, 2015). And, another recent effort used a robotic prosthesis to test the effects of different emulated prosthesis properties on gait in individual amputees (Caputo, Adamczyk, & Collins, 2015; Caputo, Collins, & Adamczyk, 2014). These efforts appear to be converging on a common goal of understanding the influence of each parameter on biomechanical gait outcomes in amputees.…”