The effect of structural reinforcement in the solid ankle foot orthosis: a finite element analysis

Abstract

Background: Solid Ankle Foot Orthosis (SAFO) has the ability to hold the plantarflexion and dorsiflexion. It helps improve foot clearance which can stop foot drop. During gait, it usually possesses a specific area with high pressure due to gait that leads to cracks in that particular area. Structural reinforcement can be introduced to tackle this problem. This study aims to observe the effect of structural reinforcements on SAFO’s stiffness against the force generated during the stance phase and to find out which parameter combination gives the best results.
Methods: The SAFO was designed into 3 models, SAFO variation I without reinforcement, SAFO variation II with reinforcement of 260 mm, and SAFO variation III with reinforcement of 130 mm. Carbon fiber (CF) and polypropylene (PP) were used as materials in the simulation. The SAFO models were analyzed by the Finite Element Method in the gait cycle and cuff loading simulation.
Results: The simulation showed that the SAFO toughness and stiffness increased as the increase in length of the reinforcement was applied. CF material provided better toughness and stiffness than PP. CF AFO variation II had the highest toughness during the gait cycle simulation. During cuff loading simulation, CF AFO variation II had the highest level of stiffness with a rotational stiffness ratio of 246.52 Nm/°.
Conclusions: The presence of structural reinforcement in SAFO affects the toughness and stiffness of SAFO.