HYDRAULIC ANKLE FOOT ORTHOSIS EMULATOR FOR CHILDREN WITH CEREBRAL PALSY

Area of Science:

• Biomedical Engineering
• Rehabilitation Engineering
• Orthotics and Prosthetics

Background:

• Ankle-foot orthoses (AFOs) are crucial for managing gait impairments in children with cerebral palsy (CP).
• Current AFO prescription relies on practitioner experience rather than objective data.
• Developing technology-based solutions for AFO prescription is a long-term research goal.

Purpose of the Study:

• To design and bench-test a first-generation wearable hydraulic ankle exoskeleton.
• To evaluate if a hydraulic exoskeleton programmed to match conventional AFO stiffness yields similar gait outcomes.
• To assess the feasibility of using hydraulic systems to emulate AFO properties.

Main Methods:

• A wearable hydraulic ankle exoskeleton was developed, tethered to a control cart.
• The system used a novel double-ended cylinder to emulate rotary spring behavior.
• A feasibility clinical trial involved five children with CP walking in conventional and matched hydraulic AFOs, with gait analysis.

Main Results:

• The hydraulic exoskeleton weighed 1.5 kg, exceeding the design goal.
• The system successfully emulated rotary stiffness within the range of conventional AFOs (1-4.6 Nm/deg).
• Gait metrics were comparable between the hydraulic exoskeleton and conventional AFOs.

Conclusions:

• Small-scale hydraulics are effective for creating wearable exoskeletons that mimic passive AFOs.
• Despite increased weight, the hydraulic system did not significantly alter gait.
• Current gait evaluation metrics may not be sensitive enough to detect subtle differences between hydraulic and conventional AFOs.