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Variable stiffness foot design and validation.

Christophe Lecomte1, Anna Lára Ármannsdóttir2, Felix Starker3

  • 1Össur hf., Grjótháls 5, 110, Reykjavik, Iceland; Faculty of Industrial Engineering, Mechanical Engineering and Computer Science, School of Engineering and Natural Sciences, University of Iceland, Reykjavík, Iceland.

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PubMed
Summary

This study introduces a novel prosthetic foot with adjustable stiffness. This variable stiffness ankle (VSA) unit allows adaptation to user needs, potentially improving satisfaction and prosthetic fitting.

Keywords:
BiomechanicsProsthetic designProsthetic footTrans-tibial amputeeVariable stiffness

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Area of Science:

  • Biomedical Engineering
  • Prosthetics and Orthotics
  • Biomechanics

Background:

  • Energy storing and returning prosthetic feet offer advantages but lack adaptable stiffness.
  • Current prosthetic feet have fixed sagittal plane stiffness, limiting adaptation to diverse walking tasks and user preferences.

Purpose of the Study:

  • To propose and characterize a novel prosthetic foot design with adjustable sagittal plane stiffness.
  • To evaluate the functionality of the Variable Stiffness Ankle (VSA) unit in a prosthetic foot.

Main Methods:

  • A Variable Stiffness Ankle (VSA) unit was integrated with a commercial prosthetic foot, controlled wirelessly by a servo motor.
  • Ankle stiffness modulation was achieved by adjusting support points on a glass fiber leaf spring.
  • Mechanical testing used a six degree of freedom load cell, and biomechanical data was collected from a transtibial amputee walking on an instrumented treadmill.

Main Results:

  • The VSA prosthetic foot demonstrated adjustable ankle stiffness in mechanical testing.
  • Biomechanical analysis confirmed changes in ankle stiffness during level ground walking.
  • The novel design successfully modulated stiffness as intended.

Conclusions:

  • The developed VSA prosthetic foot successfully modulates ankle stiffness in the sagittal plane.
  • This technology has the potential to enhance user satisfaction and aid prosthetists in fine-tuning prosthetic fittings.
  • Further research with additional subjects is warranted to validate findings.