A Novel Method for Measuring In-Shoe Navicular Drop during Gait

Simon L Kappel,Peter Ahrendt,Michael S Rathleff,Dan Hermann,Henrik Karstoft,Ole Simonsen

doi:10.3390/s120911697

Simon L Kappel, Peter Ahrendt + Show 4 more

Open Access

https://doi.org/10.3390/s120911697

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Abstract

Analysis of foot movement is essential in the treatment and prevention of foot-related disorders. Measuring the in-shoe foot movement during everyday activities, such as sports, has the potential to become an important diagnostic tool in clinical practice. The current paper describes the development of a thin, flexible and robust capacitive strain sensor for the in-shoe measurement of the navicular drop. The navicular drop is a well-recognized measure of foot movement. The position of the strain sensor on the foot was analyzed to determine the optimal points of attachment. The sensor was evaluated against a state-of-the-art video-based system that tracks reflective markers on the bare foot. Preliminary experimental results show that the developed strain sensor is able to measure navicular drop on the bare foot with an accuracy on par with the video-based system and with a high reproducibility. Temporal comparison of video-based, barefoot and in-shoe measurements indicate that the developed sensor measures the navicular drop accurately in shoes and can be used without any discomfort for the user.

Highlights

The human foot comprises a lightweight complex system combining passive and active elements which act in conjunction allowing for weight transfer, maintenance of balance and generation of propulsive forces during gait
The PolyPower based sensor (PBS) was strained in maximal intervals of 0.5 mm with a strain of up to 20 mm, which corresponded to a strain of 50%
In the current paper we have described the development of a strain sensor to measure navicular drop, which is a frequently used measure of foot movement

Summary

Introduction

The human foot comprises a lightweight complex system combining passive and active elements which act in conjunction allowing for weight transfer, maintenance of balance and generation of propulsive forces during gait. The two most commonly used methods include 3D motion capture using optical systems [1,2] or the use of inertial sensors [3,4] Both methods require the foot to be visible to the cameras or require cutting a hole in the shoe or using sandals so that the inertial sensors can be attached directly to the foot. Current methods to measure in-shoe foot movement rely on specially designed shoes [5,6], radiostereometric analysis (RSA) [7,8] and dynamic MRI [9,10]. All these methods are expensive, time consuming, and not suitable for routine clinical use

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