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Published on: April 18, 2011
Entropy analysis of tri-axial leg acceleration signal waveforms for measurement of decrease of physiological
Yuki Tochigi1, Neil A Segal, Tanawat Vaseenon
1Department of Orthopaedics and Rehabilitation, University of Iowa, Iowa City, Iowa 52242-1100, USA. yuki-tochigi@uiowa.edu
Summary
Reduced physiological variability, measured by leg motion entropy, may indicate aging and knee osteoarthritis. Lower Sample Entropy (SampEn) in gait suggests functional limitations in knee osteoarthritis patients.
Area of Science:
- Biomedical Engineering
- Biomechanics
- Physiological Measurement
Background:
- Decreased physiological variability in biological time-series data is increasingly recognized as a potential biomarker.
- Measuring variability in periodic motion, like walking, could quantify functional limitations in musculoskeletal disorders.
Purpose of the Study:
- To investigate if cycle-to-cycle variability in leg motion patterns, using tri-axial acceleration signal entropy, is lower in individuals with greater age or knee osteoarthritis symptoms.
- To explore the potential of Sample Entropy (SampEn) as an objective measure of gait function limitations.
Main Methods:
- Assessed leg motion patterns during level walking in 52 adults with symptomatic knee osteoarthritis (OA) and 57 asymptomatic controls (aged 20-79 years).
- Utilized portable inertial monitors attached to ankles to collect tri-axial acceleration data.
- Analyzed data using Sample Entropy (SampEn), a nonlinear variability measurement tool.
Main Results:
- Asymptomatic subjects showed a significant negative correlation between SampEn and age (r = -0.287, p = 0.0306).
- Knee OA subjects exhibited significantly lower SampEn values (p = 0.0002) compared to age-matched asymptomatic controls at equivalent walking velocities.
Conclusions:
- Lower leg motion variability, quantified by SampEn, is associated with increased age and symptomatic knee osteoarthritis.
- This approach offers a promising basis for valid, inexpensive, and convenient objective evaluation of gait function limitations.
