Low-Profile, Shoe-Type Ankle-Foot Orthosis with Active Variable Ankle Stiffness via Wire-Fabric Compression Mechanism

Area of Science:

• Biomechanics
• Rehabilitation Engineering
• Orthotics

Background:

• Acute ankle sprains often result in chronic ankle instability and muscle atrophy due to immobilization.
• Current ankle-foot orthoses (AFOs) lack dynamic stiffness modulation, potentially worsening muscle atrophy.

Purpose of the Study:

• To introduce Active Variable Compression Shoes (AVC-Shoes) for real-time ankle stiffness modulation.
• To evaluate the variable stiffness capabilities and effects on muscle activity of AVC-Shoes.

Main Methods:

• Development of AVC-Shoes utilizing a wire-fabric compression mechanism inspired by "heel-lock taping."
• Experimental measurement of ankle stiffness in all directions (dorsiflexion, plantarflexion).
• Preliminary human testing with three healthy participants to assess gastrocnemius muscle activity.

Main Results:

• AVC-Shoes demonstrated variable ankle stiffness across all directions.
• Achieved dorsiflexion and plantarflexion stiffness ranges of up to 8.3 and 5.9 Nm/rad, respectively.
• Gastrocnemius muscle activity during push-off increased by 19% in active compression mode compared to brace mode.

Conclusions:

• AVC-Shoes provide selective ankle joint stiffening at critical gait cycle points, particularly heel strikes.
• This technology represents a promising advancement for next-generation AFOs, stabilizing the ankle while mitigating muscle atrophy.