Ideal operating conditions for a variable stiffness transverse plane adapter for individuals with lower-limb...

Area of Science:

• Biomechanics
• Prosthetics
• Rehabilitation Engineering

Background:

• Transverse plane shear stress at the prosthetic socket-residual limb interface causes discomfort and soft tissue breakdown in lower-limb amputees.
• Understanding the impact of shank stiffness on residual limb loading is crucial for improving prosthetic design and user comfort.

Purpose of the Study:

• To evaluate the effects of a second-generation variable stiffness torsion adapter (VSTA II) on residual limb loading and biomechanical parameters in individuals with transtibial amputation.
• To assess user stiffness preference across different walking speeds and activities (straight walking, turning).

Main Methods:

• Ten individuals with transtibial amputation tested the VSTA II at three stiffness levels (0.25, 0.75, 1.25 Nm/°).
• Measurements included peak transverse plane moments, VSTA II deflection, whole body angular momentum (WBAM), ground reaction impulse, and joint work.
• Testing occurred during straight-line walking and turning at self-selected, fast, and slow speeds.

Main Results:

• Reduced VSTA II stiffness decreased residual limb loading and increased VSTA II displacement.
• Increased walking speed elevated both residual limb loading and VSTA II displacement.
• Ground reaction impulse and joint work remained unaffected by stiffness or speed.
• Decreased stiffness increased the range of WBAM, suggesting a potential increased fall risk.
• User preference showed trends towards lower stiffness for turning/self-selected speeds and higher stiffness for straight/faster walking.

Conclusions:

• The VSTA II demonstrates potential for reducing residual limb loading during walking and turning in lower-limb amputees.
• Optimal VSTA II use is influenced by walking speed, activity type, and individual user preference.
• Further research is needed to optimize stiffness settings and mitigate potential fall risks associated with lower stiffness configurations.