Optimal Powered Ankle-Foot Prosthesis Torque Profiles to Improve Walking Performance for Individuals With a...

Area of Science:

• Biomechanics
• Rehabilitation Engineering
• Prosthetics

Background:

• Passive prosthetic ankle-foot devices limit walking performance in individuals with unilateral transtibial amputation (TTA).
• Active powered prostheses offer potential but require optimal tuning for improved outcomes.
• Current challenges include increased metabolic cost, knee loading, and balance asymmetry in TTA users.

Purpose of the Study:

• To identify the optimal ankle torque profile for a powered ankle-foot prosthesis to enhance walking performance in individuals with TTA.
• To investigate how different optimization goals (metabolic cost, knee loading, balance symmetry) influence prosthetic torque profiles.

Main Methods:

• Utilized a musculoskeletal simulation-based optimization framework.
• Emulated group-averaged kinematics and ground reaction forces for able-bodied and TTA walking data.
• Compared simulated conditions: passive prosthesis, powered prosthesis matching able-bodied data, and powered prostheses optimized for specific performance metrics.

Main Results:

• Distinct optimal torque profiles emerged when minimizing metabolic cost, knee joint loading, and dynamic balance asymmetry separately.
• No clear trend was observed in positive prosthetic work, indicating increased work alone is insufficient for performance improvement.
• Prosthetic torque timing throughout the gait cycle is crucial for enhancing walking performance metrics.

Conclusions:

• Optimal prosthetic torque profiles are specific to the targeted performance improvement (metabolic cost, knee loading, balance).
• Proper timing of prosthetic torque application is more critical than simply increasing prosthetic work.
• This study provides a framework for developing customized controllers for powered prostheses to improve TTA walking performance.