Fiber Bragg grating sensors for clinical measurement of the first metatarsophalangeal joint quasi-stiffness

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/o unloading 8.46 (2.29) Nmm/ o], middle [loading 7.13 (2.17) Nmm/ o, unloading 11.11 (2.94) Nmm/ o], and late [loading 24.54 (7.14) Nmm/ o, unloading 14.50 (4.77) Nmm/ o] 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

Validity of a FBG-based smart sock system for measuring toe grip function in human foot

This study developed a smart sock system using optical fiber technology to measure the toe grip function of individual toes. The system comprised Fiber Bragg grating (FBG) sensors incorporated into a sock garment for measuring maximum toe flexion displacements. Calibration equation of each FBG sensor was determined from 3D motion capture system on 10 female subjects. The validity of the smart sock system was checked by comparing maximum toe flexion displacement against the gold standard of 3D motion capture. The root mean squared error was 0.95 (0.57) cm across 10 toes. The magnitude of toe displacement and error were similar between the left and right foot. In conclusion, the FBG-based smart sock system can successfully measure maximum toe flexion displacements of individual toes simultaneously. This system can be developed to support the evaluation of toe grip function in clinical and field settings.</div

Within-day and between-day reliability of a FBG-based smart sock system for measuring active toe flexion displacement of the hallux

This study examined the test-retest reliability of hallux flexion displacement measured using a smart sock system with embedded fiber Bragg grating (FBG) sensors. Thirty female participants consisted of 15 hallux valgus (HV) patients and 15 control participants were recruited. Maximum active hallux flexion displacement was measured twice on each participant in the first visit; the same procedures were repeated 7 days later. Intraclass correlation coefficients (ICC2,1) and standard error of measurement (SEM) were applied to test within-day and between-day reliability. Paired-samples T-test was performed to compare the displacements between trials. Results showed almost perfect within-day reliability for both HV and control groups (ICC = .984 and .977, respectively) with small SEM (both 0.5 cm). However, fair to moderate between-day reliability was found (.323 and .438, respectively). Significant differences were found between repeated measurements taken on the same day (mean difference = 0.3 cm, p = .023) and on different days (mean difference = 1.6 cm, p = .027), though the effect size was small. The poorer between-day reliability is likely due to the inconsistency in fitting the sock onto the foot. Future optimization of the prototype design is called for to improve the fitting consistency of wearable sensors onto patients