Multi-Sensor Ankle Foot Orthosis for Continuous Real-World Gait Monitoring for Children with Cerebral Palsy: Preliminary Technical Findings

Introduction: Improving gait in children with cerebral palsy (CP) is a clinical priority, yet clinical decisions often rely on a snapshot of short in-laboratory walking, which may overestimate everyday function and miss meaningful variability. Ankle foot orthoses (AFOs) are used in 51% of children with CP. Worn daily, AFOs provide a clinical interface for sensor integration. Our project combines multiple sensors into a standard AFO to enable real-world continuous gait monitoring outside the lab.

This abstract presents early work, quantifying stride timing error and sensor response patterns for sensor functionality assessment and technical AFO development.

Methods: We developed a multi-sensor AFO with 5 plantar pressure sensors embedded in the insole and an inertial measurement unit (IMU) above the heel. Self-testing of the AFO against laboratory reference systems was conducted with the device worn by a researcher. During 3 minutes of treadmill walking at 4 km/h, AFO stride time (heel strike to heel strike) was compared with a synchronised Qualisys motion capture system across 139 strides. Next, alternating sitting, standing and walking activities were measured by the AFO and visually verified using video recordings.

Results: Mean stride time differed by 2 ms between the AFO and reference system (1.173 s AFO, 1.175 s Qualisys), with RMSE 12.3 ms and MAPE 0.82%. During activity intervals, AFO data showed distinct patterns: standing was characterised by sustained loading, sitting by sustained unloading, and walking by repeated cycles of loading and unloading.

Conclusions: Stride timing showed close agreement with Qualisys, while midfoot plantar pressure responses differed clearly across standing, sitting and walking. These preliminary findings support the technical feasibility of the multi-sensor AFO as an early step toward continuous real-world gait and activity monitoring. Further validation is required in healthy participants before evaluating the system in children with cerebral palsy.