Advances on mechanical designs for assistive ankle-foot orthoses

Abstract

Assistive ankle-foot orthoses (AAFOs) are powerful solutions to assist or rehabilitate gait on humans. Existing AAFO technologies include passive, quasi-passive, and active principles to provide assistance to the users, and their mechanical configuration and control depend on the eventual support they aim for within the gait pattern. In this research we analyze the state-of-the-art of AAFO and classify the different approaches into clusters, describing their basis and working principles. Additionally, we reviewed the purpose and experimental validation of the devices, providing the reader with a better view of the technology readiness level. Finally, the reviewed designs, limitations, and future steps in the field are summarized and discussed.

A usability study on the inGAIT-VSO: effects of a variable-stiffness ankle-foot orthosis on the walking performance of children with cerebral palsy

“…While traditional AFOs have provided many benefits, they are typically rigid and uncomfortable, lacking in mimicking the dynamics, energy cycling, or impedance of the human ankle joint [6][7][8][9][10][11]. Instead, these traditional solutions lock the ankle in place to maintain ground clearance during leg swing, and ensure that each stride begins with a heel strike instead of flat-footed.…”

“…New passive and powered assistive AFOs have been developed to address some of the shortcomings of traditional of the commercially available assistive AFOs are passive, such as the Neuro Swing (Fior&Gentz, Holly Springs, NC, USA), Nexgear Tango (Ottobock, Duderstadt, Germany), and Ultraflex AFO Joint (Ultraflex Systems, Pottstown, PA, USA). There are also several research prototypes, normally intended for adults, that strive to assist the user through passive mechanisms [8,[15][16][17]. Unfortunately, the majority of these research/commercial systems are too heavy for pediatric patients (>1 kg) or cannot customize the shape of the torque-angle relationship to specific user's needs and capabilities, which in CP change with age and stage of rehabilitation [7,8,[15][16][17].…”

“…There are also several research prototypes, normally intended for adults, that strive to assist the user through passive mechanisms [8,[15][16][17]. Unfortunately, the majority of these research/commercial systems are too heavy for pediatric patients (>1 kg) or cannot customize the shape of the torque-angle relationship to specific user's needs and capabilities, which in CP change with age and stage of rehabilitation [7,8,[15][16][17].…”

Comparación de dos principios de diseño de órtesis de tobillo no actuadas para asistir en la fase de propulsión: un estudio de caso

“…Para que las AFO sean prácticas en la vida diaria, es importante que sean ligeras y fáciles de usar y que, al mismo tiempo, proporcionen la asistencia necesaria al usuario (Bayón, 2023). En este sentido, se han producido avances en las AFO no actuadas, entendidas como dispositivos que se basan en elementos pasivos para almacenar y liberar energía durante la marcha (Lora-Millan et al, 2023).…”

“…Una clasificación relevante de las AFOs sin actuación puede hacerse en función de su principio de funcionamiento y de la configuración mecánica utilizada para proporcionar la asistencia (Lora-Millan et al, 2023). En este sentido, cabe destacar dos grandes grupos: (i) las que utilizan un resorte lineal intercambiable que trabaja en paralelo al tendón de Aquiles (e.j., (Collins et al, 2015;Yandell et al, 2019;Wang et al, 2020)), y (ii) las que utilizan una transmisión de resorte-leva para personalizar el par del tobillo en función del ángulo de la articulación (e.j., (Sekiguchi et al, 2020;Yamamoto et al, 2005;Rodriguez et al, 2018)).…”