A computational modeling framework to assess the influence of carbon fiber orthosis use on ankle function and contact mechanics: A pilot study

BACKGROUND: Articular fractures of the distal tibia often lead to post-traumatic osteoarthritis. Precisely restoring the joint surface to lower contact stress is a proven tenet of treatment, but incongruity often persists after operative fracture reduction. Custom dynamic orthoses may offer a non-invasive means to decrease plantarflexor muscle force and in turn contact stress to preferentially offload the ankle. The objective of this study was to develop and pilot a new computational framework to assess the influence of carbon fiber orthosis stiffness on ankle function and contact mechanics. METHODS: A concurrent simulation framework was driven by whole-body gait kinematics and ground reaction kinetics to investigate how custom dynamic orthosis stiffness influence plantarflexor muscle force, joint contact force, and tibiotalar contact stress during stance. Two healthy adults (height: 1.74 m, 1.89 m; mass: 74.5 kg, 92.5 kg) completed gait trials, and weight bearing CT was used to integrate subject-specific ankle joint models into a musculoskeletal gait simulation. Four orthosis walking conditions were simulated, and results were compared to previous findings to verify performance of the framework. FINDINGS: Simulations successfully estimated physiologically reasonable secondary kinematics, muscle forces, and cartilage contact stresses concurrently with low marker error (< 20 mm RMS) and small residual forces and moments, indicating strong dynamic consistency. INTERPRETATION: Suitably validated, this framework enables the systematic examination of the effect of orthosis design on joint and articular contact forces, to inform future interventional trials to mitigate the effects of traumatic fracture.