Smart insole-based analysis of gait biomechanics for insoles in patients with flatfoot

Background: Assessing the effect of insoles on gait biomechanics and foot comfort remains challenging. Our novel in-insole-type wearable sensor device (smart insole) enables accurate quantitative evaluation of gait parameters without affecting the subject's foot comfort. Research question: What are the effects of insoles on gait biomechanics and foot comfort in patients with flatfoot, as evaluated using a novel smart insole? Methods: Thirty-three subjects with 61 flatfeet were recruited. Three different types of prefabricated insoles were tested: a control insole as an experimental control, a flat insole with only cushion pads for the shock absorbing function, and an arch support insole with both cushioning pads and arch support functions. Gait parameters and visual analog scale (VAS) scores for foot comfort were measured during 30 m of straight walking with each insole incorporating the wearable sensor device. The differences in gait parameters and foot comfort between the flat and arch support insoles relative to the control insole were analyzed. Additionally, the correlations between gait parameters and foot comfort were evaluated. Results: Maximum plantarflexion angle significantly decreased (p = 0.03) and the toe-out angle significantly increased (p < 0.01) with arch support insoles compared to flat insoles. Significantly better foot comfort was demonstrated when walking with arch support insoles than with flat insoles (p < 0.01). The only gait parameter correlated with foot comfort was foot lift height while walking with an arch support insole (r = -0.45, p < 0.01). Significance: A novel smart insole revealed that foot lift height was a key gait parameter for determining foot comfort while walking with an arch support insole. Our findings provide important evidence for selecting a comfortable flatfoot insole based on gait data measured using a smart insole.