Expanding access to knowledge of prosthetic and orthotic mechanical function: Development and evaluation of a plug-and-play test system

About This Grant

In the United States nearly 91% of prosthetics patient encounters are related to the lower limb, thereby representing the vast majority of delivered device interventions. The Department of Veterans Affairs (VA) is one of the leading providers of prosthetic clinical care in the United States, servicing 380,000 patients with impairments annually across 100 facilities with the aim of restoring function and independence to Veterans. As such, lower limb prostheses are prescribed and custom designed to support the functional mobility and independence of Veterans with limb loss. In accordance with clinical practice, the designs of these devices are personalized to each patient according to individual anatomical characteristics, functional impairments, needs, and goals. These factors are considered when carefully designing and tuning the mechanical function of passive- elastic prosthetic devices to support long-term rehabilitation success, and so a definitive device inherently possesses unique load-bearing mechanical properties (stiffness, damping, and rollover geometry) specific to each Veteran user. There is strong evidence linking these stance-phase mechanical properties to specific rehabilitation outcomes, including limb loading, comfort, and walking economy. While the rigorous component selection and tuning process to personalize each device is responsible for the success of these interventions, clinicians perform this process based on their subjective intuition and skills but without knowledge of the how their design choices influence device mechanical properties. These properties are unknown because: 1) mechanical properties are either not disclosed by manufacturers or are not measured from customized devices; 2) there is no standard, profession-accepted method to measure and communicate these properties; and 3) there is no test system that is accessible in settings with limited resources and expertise, such as clinics. Expanding knowledge of passive-elastic properties of prosthetic devices will help provide objective information on how a device functions for appropriate prescription, identify need for device repair due to degradation, and allow clinical research to correlate device function with Veteran user outcomes to develop our evidence base. The central aim of this project is to develop and evaluate an accessible ‘plug-and-play’ test system that measures mechanical properties of passive-elastic transtibial prostheses (i.e., ankle-feet and pylons) through a user- centered, stage-gate design approach. We will first obtain stakeholder feedback to establish user needs through a focus group involving prosthetics clinicians and researchers/designers. We will seek input on desired functionality, output, and system operation to guide the design of our first-generation prototype. We will develop that prototype with our industry partner, Humotech LLC, who shares the intellectual property with the VA. That prototype will be evaluated for functionality, concurrent validity against measurements from a universal materials test system, and inter-rater reliability by comparing prototype measurements between two stakeholder users (research engineer and prosthetist-orthotist). Feedback from these assessments will be used to design and fabricate the second-generation prototype, which will again be subjected to an evaluation on functionality, validity, and reliability to establish future design improvements. Additionally, data from the second assessment will be entered into our innovative data-driven algorithm to model the non-linear mechanical behavior of these components to establish a novel classification method that can be integrated into a VA data repository on prosthesis characteristics, such as the existing Prosthetics Compendium. The outcome from this project is a mechanical test system that enables VA clinicians and researchers to readily access device mechanical function to help guide clinical decision making on device designs to support user needs and generate accurate, reliable measurements of device mechanical function for communicating these clinically relevant properties.