Personalised orthotic therapy using 3D printing in children with Charcot-Marie-Tooth disease

Abstract

Children with Charcot-Marie-Tooth disease (CMT), are often prescribed custom-made ankle-foot orthoses (AFO) to manage walking difficulty. These externally worn assistive devices are usually handmade using a plaster cast of the patient's lower limb followed by thermoplastic vacuum forming. This traditional approach is labour-intensive and provides limited design options, resulting in AFOs which are cumbersome and associated with low acceptability, discomfort and suboptimal biomechanical function. The aim of this PhD Thesis was to develop, redesign and evaluate 3D printed AFOs compared to traditional handmade AFOs for children with CMT. A systematic literature review revealed that 3D printing AFOs has many potential benefits over traditional methods, including the development of novel designs that optimise stiffness and energy dissipation, improve gait, comfort and fit. The relationship between functional ability in 60 children with CMT and associated gait deviations using 3D gait analysis was assessed. The results showed that not all children with CMT have the typically described foot drop, push-off deficit and ‘steppage gait’ pattern. Instead, three distinct gait patterns exist at the ankle, indicating patient-specific orthotic design pathways. In 12 children with CMT, traditional handmade AFOs, replicated and iteratively redesigned 3D printed AFOs were compared to a shoe only condition using 3D gait analysis, in-shoe pedobarography and a patient satisfaction scale. Replicated 3D printed AFOs were comparable to traditional AFOs for all gait outcomes and patient satisfaction scores. Iteratively redesigned 3D printed AFOs reduced mass by, on average, 35% and improved ankle plantarflexion angle during the push-off phase of gait by up to 7°. The design, gait and acceptability of traditionally handmade AFOs can be replicated and redesigned with 3D printing in children with CMT.