Estimates of stiffness for ankle-foot orthoses are sensitive to loading conditions

Kota Z. Takahashi, Steven J. Stanhope

Research output: Contribution to journalArticlepeer-review

10 Scopus citations

Abstract

Ankle-foot orthoses (AFOs) can act like rotational springs to enhance gait function in individuals with motor impairments. The performance of an AFO during use is primarily a function of its mechanical stiffness properties. Hence, an objective analysis of AFO stiffness is crucial for future prescription and for understanding the contributions of AFO kinetics to gait performance. Valid stiffness estimates can be obtained if the loads applied to an AFO during stiffness testing replicate the loading conditions applied during gait. However, the sensitivity of AFO stiffness estimates to changes in loading conditions (location and directions of all applied forces) is unknown. This study explored the sensitivity of AFO stiffness estimates to the direction (angle) of applied loads by systematically altering the direction (angle) of applied loads to a prototype AFO during a stiffness testing procedure. The results indicate that AFO stiffness estimates are influenced by the angle of force application. Stiffness estimates for the prototype AFO changed 1% for each degree change in the angle of force application. This study highlights the importance of achieving congruent loading conditions during experimental stiffness testing and conditions during use when the goals are to prescribe and evaluate the kinetics associated with AFO performance.

Original languageEnglish (US)
Pages (from-to)211-219
Number of pages9
JournalJournal of Prosthetics and Orthotics
Volume22
Issue number4
DOIs
StatePublished - Oct 2010
Externally publishedYes

Keywords

  • ankle-foot orthoses
  • gait
  • stiffness

ASJC Scopus subject areas

  • Biomedical Engineering
  • Orthopedics and Sports Medicine
  • Rehabilitation

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