An active insole to reduce plantar pressure loading: using predictive finite element driven soft hydraulic actuators to minimise plantar pressure and the pressure time integral for diabetic foot ulceration risk management.

Abstract

Objective: This paper aims to design, manufacture and evaluate an active insole to reduce plantar tissue loading to minimise the risk of diabetic foot ulceration for people living with diabetes.

Methods: A prototype hydraulic soft robotic actuating insole was produced. It was controlled by an approximate finite element model of the participants' foot with a cost function to minimise plantar pressure loading and the pressure time integral. The system was evaluated during treadmill walking activity for 3 people (two people with diabetes and one healthy participant), measuring normal plantar stress in shoe both before and after shape changes.

Results: The results from the participants demonstrate a reduction in average peak plantar pressure and pressure time integral by 35% [range from 9% - 52%] and 31% [range from 6% - 44%], respectively, at the high-risk region, whilst minimising edge effect and maintaining gait symmetry, regularity and cadence. The finite element driven controller was implemented when participants rested between walking periods, and it took less than six minutes to run.

Conclusion: This study demonstrates, for the first time on diabetic participants, the feasibility of an active insole system using predictive finite element driven soft hydraulic actuators to reduce plantar loading in people with diabetes.

Significance: Diabetic foot ulceration risk could be reduced using active insole technology and approximate predictive algorithms could play an important role to outwork this in real world activity.