Fiber Bragg Grating Sensors for Clinical Measurement of the First Metatarsophalangeal Joint Quasi-Stiffness

Pui Wah Kong,Chi Chiu Chan,Daniel T P Fong,Marabelle Liwen Heng,Yimin Liu,Yixuan Leow

doi:10.1109/jsen.2019.2946880

Abstract

Assessing the mobility of the first metatarsophalangeal joint (MTPJ) of a human foot is useful in clinical practice, but there are no standard methods of measurement. The present study developed a new instrumentation using Fiber Bragg grating (FBG) sensor and load cell to quantify the first MTPJ quasi-stiffness in a clinical setting. This system is portable, lightweight, and allows quantification of quasi-stiffness over different ranges of motion in both loading and unloading directions. The laboratory setting validation results showed that FBG sensors could measure MTPJ angular displacement with reasonably good accuracy. The proposed system was successfully trialed in a hospital setting operated by a clinician on eight human subjects. Non-linear torque-angular displacement relationship was observed in both loading and unloading phases, with varying MTPJ quasi-stiffness in the early [loading 6.30 (2.62) Nmm/° unloading 8.46 (2.29) Nmm/°], middle [loading 7.13 (2.17) Nmm/°, unloading 11.11 (2.94) Nmm/°], and late [loading 24.54 (7.14) Nmm/°, unloading 14.50 (4.77) Nmm/°] ranges of motion. The new method for measuring the first MTPJ quasi-stiffness established in the present study serves as a reference and opens up opportunities for future clinical investigations.

Highlights

Common practices adopted by clinicians include subjectively “feeling” how the metatarsophalangeal joint (MTPJ) moves though its range of motion, visually estimating or measuring MTJP range of motion using goniometric devices [1,3,4]
We propose a system to simultaneously measure MTPJ range of motion using fiber Bragg grating (FBG) technology and the force applied by a clinician using a load cell (Sensorcraft Technology (S), Pte Ltd, Singapore, Fig. 1)
This study developed new clinical system for measuring the first MTPJ quasi-stiffness using Fiber Bragg grating (FBG) sensor coupled with a load cell

Summary

Introduction

Fong is with the National Centre for Sport and Exercise Medicine, School of Sport, Exercise and Health Sciences, Loughborough University, I. Common practices adopted by clinicians include subjectively “feeling” how the MTPJ moves though its range of motion, visually estimating or measuring MTJP range of motion using goniometric devices [1,3,4]. These traditional methods are not sufficiently reliable regardless of the experience of the testers [5] and clinicians have yet to come to a consensus on how foot joint mobility should be assessed

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