Ankle-joint power and AFO deflection: implications for physiologically relevant fatigue testing conditions

Area of Science:

• Biomechanics
• Orthotics and Prosthetics
• Rehabilitation Engineering

Background:

• Ankle-foot orthoses (AFOs) are crucial for gait improvement in individuals with neuromuscular and musculoskeletal impairments.
• Standardized protocols for characterizing AFO mechanical properties, particularly fatigue life, are lacking.
• Understanding in vivo AFO deformation is essential for developing physiologically relevant testing conditions.

Purpose of the Study:

• To characterize AFO angular deflection and ankle-joint power during various activities.
• To investigate how user-device interactions influence orthotic deformation.
• To inform the development of standardized fatigue testing protocols for AFOs.

Main Methods:

• Nine healthy adults participated in walking, sit-to-stand, stand-to-sit, and stair-ascent tasks with a 3D-printed AFO.
• Kinematic and kinetic data were collected to compute ankle-joint power and AFO angular deflection.
• Relationships between power and deflection events were analyzed across different activities.

Main Results:

• Walking produced the greatest plantarflexion deformation in AFOs.
• Peak plantarflexion deformation occurred during the loading response phase, not at toe-off.
• Peak push-off power generation correlated with increased plantarflexion deflection at toe-off.

Conclusions:

• AFO deformation is significantly influenced by early-stance impact during walking.
• Subject-specific, gait-derived deformation profiles are recommended for fatigue testing of rigid AFOs.
• This approach enhances the physiological relevance of mechanical testing for AFOs.