Evaluating Reachable Workspace and User Control Over Prehensor Aperture for a Body-Powered Prosthesis

Area of Science:

• Biomedical Engineering
• Rehabilitation Science
• Prosthetics and Orthotics

Background:

• Body-powered upper limb prostheses utilize a harness and control cable for prehensor operation.
• Cable routing often compromises the relationship between shoulder movement and prehensor control, creating a trade-off between reach and control.
• Existing research lacks quantification of the impact of harness systems on the user's reachable workspace and prehensor functionality.

Purpose of the Study:

• To develop and present a methodology for quantifying the reduction in reachable workspace caused by prosthetic harnesses.
• To assess the range-of-motion of the prehensor at various points within the user's reachable workspace.
• To evaluate the impact of harness configuration on functional control of a body-powered prosthesis.

Main Methods:

• Utilized a body-powered prosthesis simulator with ten anatomically intact participants.
• Employed a 3D motion capture system to record arm kinematics and workspace volume.
• Used an electronic goniometer to measure prehensor range-of-motion across different arm postures.

Main Results:

• The harnessed reachable workspace was reduced to 38-85% of the unharnessed volume.
• Participants experienced significant difficulty reaching across the body and overhead.
• Full prehensor range-of-motion was achieved in only 9% of assessed arm postures.

Conclusions:

• Prosthetic harness designs significantly restrict the functional reachable workspace for users.
• The presented methodology can quantitatively assess the impact of harness design on prosthesis usability.
• Findings provide a basis for improving the design of body-powered and myoelectric prostheses to enhance user function.