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Oscillation and Reaction Board Techniques for Estimating Inertial Properties of a Below-knee Prosthesis
Published on: May 8, 2014
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Does Decreasing Below-Knee Prosthesis Pylon Longitudinal Stiffness Increase Prosthetic Limb Collision and Push-Off
Matthew J Major1,2, José Luis Zavaleta1, Steven A Gard1,2
11 Northwestern University Department of Physical Medicine and Rehabilitation, Chicago, IL.
Journal of Applied Biomechanics
|May 30, 2019
Summary
Adjusting prosthetic pylon stiffness minimally impacts limb work and mechanical economy in below-knee prosthesis users. Residual limb mechanics may significantly influence overall energy demands during walking.
Area of Science:
- Biomechanics
- Prosthetics Engineering
- Rehabilitation Science
Background:
- Optimizing leg prosthesis design is crucial for enhancing mobility in users.
- Previous research focused on prosthetic foot properties, neglecting the impact of longitudinal stiffness from shock-absorbing pylons.
- The linear spring behavior of pylons may influence the work done on the body's center-of-mass during ambulation.
Purpose of the Study:
- To investigate the effects of varying pylon stiffness on individual limb work in unilateral below-knee prosthesis users.
- To analyze these effects at both customary and fast walking speeds.
- To assess the potential for improved mechanical economy through stiffness modification.
Main Methods:
- Participants: Unilateral below-knee prosthesis users.
- Procedure: Walking at customary and fast speeds with prostheses featuring different levels of longitudinal stiffness.
- Analysis: Measurement of individual limb work, including collision and push-off work, and estimation of residuum and pylon stiffness effects using a series spring model.
Main Results:
- Reductions in longitudinal stiffness led to minor increases in prosthetic limb collision and push-off work, with inconsistent effects on the sound limb.
- Observed changes in limb work did not indicate improved mechanical economy with decreased stiffness.
- Fast walking significantly increased overall center-of-mass work demands across all stiffness conditions.
- Significant limb work asymmetry was noted, with the prosthetic limb performing substantially less collision and push-off work than the sound limb.
Conclusions:
- Modifying pylon stiffness has limited impact on limb work and mechanical economy in below-knee prosthesis users.
- The residual limb's mechanical properties appear to be a dominant factor in the system's response, overshadowing pylon stiffness effects.
- Limb work asymmetry is a key characteristic in prosthesis users, irrespective of pylon stiffness adjustments.
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