A passive wrist with switchable stiffness for a body-powered hydraulically actuated hand prosthesis

Area of Science:

• Biomedical Engineering
• Prosthetics and Orthotics
• Rehabilitation Engineering

Background:

• Current upper limb prostheses often lack sufficient degrees of freedom (DoF), leading to compensatory movements and potential articulation injuries.
• Existing passive prosthetic wrists (stiff or compliant) present limitations, causing exaggerated movements or impracticality in handling heavy objects.

Purpose of the Study:

• To develop and present a novel articulated passive wrist for upper limb prostheses that combines the advantages of both stiff and compliant wrist designs.
• To address the limitations of current prosthetic wrists by offering automatically switchable passive compliance levels.

Main Methods:

• Integration of a prototype wrist with two switchable passive compliance levels into a body-powered hydraulic hand prosthesis.
• Actuation of the wrist using the same hydraulic circuit powering the prosthetic hand.
• Detailed analysis of parameters influencing wrist compliance, critical load capacity, and overall prosthesis performance.

Main Results:

• The developed wrist successfully integrates switchable passive compliance, offering a dual-mode functionality.
• The prototype was successfully actuated via the existing hydraulic circuit of a body-powered hand prosthesis.
• Comprehensive analysis of compliance-affecting parameters, critical load, and performance metrics was conducted.

Conclusions:

• The novel articulated passive wrist offers a promising solution to enhance the functionality of upper limb prostheses.
• This design has the potential to reduce compensatory movements, prevent articulation injuries, and improve the practical usability of prosthetic devices.