Ankle-foot orthosis mechanical testing: a scoping review

Ankle-foot orthoses (AFOs) are assistive devices that support the ankle during gait. AFO mechanical properties, such as rotational stiffness about the ankle, influence the level of support these devices provide. Interest in quantifying AFO mechanical properties is on the rise but is limited by the lack of standardized measurement and assessment techniques. This scoping review discusses existing techniques for the measurement of AFO mechanical properties and introduces a taxonomy for organizing and describing these methods.

A scoping review was conducted using a snowballing approach starting from two previously published literature reviews and a database search using PubMed, Engineering Village (Compendex), and Web of Science. Articles with methods that experimentally measured the mechanical properties of AFOs were eligible for inclusion. Data extracted from the selected articles included operation specifications, planes/joints tested, and presence of a biological or surrogate limb during AFO testing.

The majority of methods utilize benchtop AFO testing, with a few in-situ methods that involve a biological limb. We highlight key design challenges related to replicating biological gait, including bending axis location and design, motion in single versus multiple planes, and limited testing speeds and range of motion.

We introduced a taxonomy for describing AFO testing methods to facilitate cross-device comparisons and inform future development. Future work should include developing standardized, biomimetic methods and validation techniques for testing a variety of AFO designs. This would enable more accurate AFO measurement and enable cross-study comparisons, ultimately leading to optimized AFO properties and improved user performance outcomes.