High Cable Forces Deteriorate Pinch Force Control in Voluntary-Closing Body-Powered Prostheses

Area of Science:

• Biomedical Engineering
• Rehabilitation Technology
• Human-Computer Interaction

Background:

• Effective upper-limb prostheses require sensory feedback for control.
• Body-powered prostheses (BPPs) offer proprioceptive feedback but can have high cable forces.
• High cable forces complicate precise control of terminal devices.

Purpose of the Study:

• To quantify the impact of high cable forces on object manipulation.
• To assess the effect of cable force on voluntary-closing prostheses.

Main Methods:

• Able-bodied subjects used a bypass-prosthesis with low and high cable force settings.
• Participants grasped and transferred a collapsible object with varying fragility.
• Performance was evaluated based on successful manipulation, dropping, or breaking the object.

Main Results:

• Significantly more successful manipulations occurred with lower cable forces (33% more for low, 50% more for high breaking force objects).
• Task completion time did not differ significantly between cable force settings during successful trials.

Conclusions:

• Elevated cable forces in BPPs diminish pinch force control during object manipulation.
• Low cable operation forces are essential for designing effective voluntary-closing BPPs.