Inter-leg Distance Measurement as a Tool for Accurate Step Counting in Patients with Multiple Sclerosis.

Area of Science:

• Biomedical Engineering
• Gait Analysis
• Rehabilitation Technology

Background:

• Traditional step detection methods using wearable inertial devices struggle with accuracy in slow walkers and abnormal gait patterns.
• Feature extraction from sensor signals can be unreliable for individuals with neurological conditions affecting gait.

Purpose of the Study:

• To test and validate an innovative step counter method (DiSC) based on direct inter-leg distance measurement.
• To assess the accuracy of the DiSC method in individuals with multiple sclerosis (MS) during a six-minute walking test.

Main Methods:

• An innovative wearable system integrating a magneto-inertial unit and distance sensors (DSs) attached to the shank was developed.
• The DiSC method was validated on thirteen people with MS (EDSS 0-6.5) using video recordings as the gold standard.
• Two distance sensor ranges (DS200: 0-200 mm; DS400: 0-400 mm) were evaluated.

Main Results:

• The DiSC method demonstrated good accuracy, with significantly lower errors on the instrumented side compared to the non-instrumented side (e.g., 2.4% vs 4.8% MAPE for DS200).
• Averaging errors across patients compensated for over/underestimations, achieving very high accuracy (E% < 1.2% for DS200, E% < 0.7% for DS400).
• The DS400 configuration is recommended for patients with a wider base of support.

Conclusions:

• The DiSC method offers a promising, accurate approach for step detection, particularly for individuals with gait abnormalities like those seen in MS.
• Direct inter-leg distance measurement provides a robust alternative to feature extraction for step counting in challenging populations.
• The validated wearable system enables reliable step detection using a single device, facilitating gait monitoring and rehabilitation.