Passive Rotation Angle Motion Validation for an Ankle-Foot Orthosis Multi-Jointed Surrogate Lower Limb Design

Area of Science:

• Biomechanics and Biomedical Engineering
• Orthotics and Prosthetics

Background:

• Ankle-foot orthoses (AFOs) are crucial for assisting lower limb motion.
• Accurate mechanical testing of AFOs requires simulating in-vivo conditions, which is challenging for cyclic or load-to-failure analyses.
• Current testing methods may not fully capture the functional dependency of AFOs on intimate leg contact.

Purpose of the Study:

• To design and validate a novel surrogate lower limb (SLL) for mechanical testing of ankle-foot orthoses (AFOs).
• To create a testing apparatus that provides anthropometric 3D movement under standard test loads.
• To ensure the SLL's joint kinematics replicate human anatomical ranges of motion.

Main Methods:

• A novel four-joint SLL was designed, inspired by the Rizzoli foot model's five-section lower limb segmentation.
• SLL joint prototypes were 3D printed.
• Prototype joint rotation angles were measured and compared against typical anatomical ranges of motion for validation.

Main Results:

• The developed SLL successfully provides anthropometric 3D movement suitable for AFO testing.
• Validation confirmed that the 3D printed SLL joint prototypes exhibited rotation angles within acceptable variability of human joint movement.
• The SLL is deemed appropriate for use in final AFO testing applications.

Conclusions:

• The novel four-joint SLL is a validated and effective tool for the mechanical testing of ankle-foot orthoses (AFOs).
• This surrogate model accurately replicates human joint movement, enabling more realistic and reliable AFO performance assessments.
• The SLL facilitates advanced testing protocols like cyclic loading and load-to-failure analysis for AFOs.