A Computational Biomechanical Analysis of Composite Ankle Foot Orthosis for Pediatric Cerebral Palsy Patient

Abstract

Children with cerebral palsy often suffer from gait abnormalities that limit mobility and increase the risk of chronic joint deformities. Ankle-foot orthoses (AFOs) are commonly prescribed to enhance ankle stability and improve gait patterns. However, conventional orthotic materials may exhibit limitations, such as excessive stiffness or insufficient deformation behavior, which can potentially cause discomfort or restrict natural gait motion. This study investigates the mechanical performance of Orthocryl composites reinforced with carbon nanotubes (CNTs) and polylactic acid (PLA) for pediatric AFO applications. Finite element analysis (FEA) was performed in ANSYS software to evaluate structural behavior and assess the materials' orthopedic suitability. A 3D model of the orthosis was generated using 3D scanning to match the patient's anatomy, then imported into ANSYS for simulation. Four material configurations were analyzed: pure Orthocryl, Orthocryl with CNTs, and two CNT-reinforced composites with varying PLA content. Simulations were conducted under dynamic gait loading, using ground reaction force data to represent heel strike, midstance, and toe-off phases. Results showed that maximum stress occurred during toe-off across all materials, corresponding to peak gait loading. CNT and PLA additions preserved the uniform stress distribution of pure Orthocryl without creating localized concentrations. Deformation analysis revealed minimal deflection in pure Orthocryl, indicating rigidity, while PLA enhanced flexibility, allowing greater deformation in midstance and toe-off. CNTs enhanced structural stability, and the hybrid composites balanced flexibility and support. Safety factors remained within acceptable limits throughout the gait cycle. Overall, CNT/PLA-reinforced composites demonstrated enhanced mechanical adaptability under dynamic gait conditions compared to pure Orthocryl.