A biarticular prosthetic foot to modulate gait biomechanics and improve walking economy

Area of Science:

• Biomechanics
• Prosthetics
• Robotics

Background:

• Powered prosthetic feet with monoarticular actuation restore ankle biomechanics but lead to gait asymmetries and increased effort in transtibial amputees.
• This is hypothesized to stem from the absence of mechanical coupling between the prosthetic foot and thigh, normally provided by the biarticular gastrocnemius (GAS) muscle.

Purpose of the Study:

• To investigate the effects of a powered prosthetic foot incorporating both monoarticular and biarticular GAS actuators on gait biomechanics.
• To determine if modulating the torque contribution of the biarticular GAS actuator influences metabolic cost and gait symmetry.

Main Methods:

• Nine non-impaired subjects walked on a treadmill with a powered prosthetic foot featuring a monoarticular foot and a biarticular GAS actuator.
• The torque contribution ratio (κ) of the GAS actuator was modulated while maintaining total ankle torque.
• Kinematics, kinetics, and metabolic cost were recorded.

Main Results:

• A maximum average reduction in metabolic cost of 8.8%±4.4% was observed at a κ of 0.36±0.09.
• This reduction was attributed to decreased biological hip work, improved inter-leg symmetry in work and step length, and enhanced center of mass movement efficiency.

Conclusions:

• The addition of a biarticular actuator to powered prosthetic feet offers an extra degree of freedom for modulating human gait.
• This technology has the potential to improve walking efficiency and reduce metabolic cost for individuals with transtibial amputations.