Modeling and preliminary testing socket-residual limb interface stiffness of above-elbow prostheses

Area of Science:

• Biomechanics
• Prosthetics Engineering

Background:

• The socket-residual limb (S-RL) interface significantly impacts prosthesis performance.
• Understanding S-RL rotational stiffness is crucial for designing advanced prostheses and evaluating socket technologies.
• No prior studies have quantified S-RL interface rotational stiffness.

Purpose of the Study:

• To develop and validate methods for measuring S-RL interface rotational stiffness.
• To compare mathematical and finite element models with empirical data for S-RL rotational stiffness.
• To investigate factors influencing S-RL interface rotational stiffness.

Main Methods:

• Developed a mathematical model and finite element analysis for S-RL rotational stiffness.
• Utilized fluoroscopic imaging to capture bone-socket movement.
• Recorded force data simultaneously with imaging to calculate empirical rotational stiffness.
• Compared model predictions with empirical measurements.

Main Results:

• Models showed agreement with empirical S-RL rotational stiffness measurements.
• Subjects could modulate S-RL rotational stiffness by nearly one order of magnitude.
• Socket length and co-contraction levels significantly influenced stiffness range.
• Residual limb and bone diameters did not significantly affect stiffness.

Conclusions:

• Mathematical and computational models can accurately predict S-RL rotational stiffness.
• S-RL interface rotational stiffness is a dynamic property influenced by user control and prosthesis design.
• Findings provide valuable data for optimizing prosthetic socket design and control systems.