A passive dorsiflexing ankle prosthesis to increase minimum foot clearance during swing

Area of Science:

• Biomechanics
• Prosthetics and Orthotics
• Rehabilitation Engineering

Background:

• Biological ankles dorsiflex during swing phase for foot clearance.
• Conventional energy storage and return (ESR) prosthetic feet lack this dorsiflexion, increasing trip and toe scuffing risks.
• Existing powered or hydraulic solutions for swing dorsiflexion have limitations.

Purpose of the Study:

• To develop and evaluate a novel passive prosthetic ankle designed to increase minimum foot clearance (MFC) during the swing phase.
• To reduce the risk of falls in transtibial prosthesis users by mimicking biological ankle function.

Main Methods:

• A spring-loaded linkage prosthetic ankle was designed and fabricated.
• The device was tested on a unilateral transtibial prosthesis user during level ground walking.
• Performance was assessed across three conditions: operational ankle, locked ankle, and the user's daily ESR prosthesis.

Main Results:

• The operational prosthetic ankle increased MFC by 13 mm compared to the locked configuration and 15 mm compared to the daily use prosthesis.
• Stance phase energy return was not significantly affected by the operational ankle.
• The passive dorsiflexing ankle demonstrated improved swing phase foot clearance.

Conclusions:

• The novel passive prosthetic ankle effectively increases MFC during swing phase without compromising stance phase energy return.
• This increased foot clearance may be sufficient to reduce the incidence of falls in real-world scenarios for prosthesis users.
• The passive design offers a potentially simpler and more robust solution for enhancing prosthetic ankle function.