A literature review conducted to investigate the impact of AFO stiffness on walking mechanics found that AFO stiffness affected ankle and knee kinematics, but not hip kinematics or kinetics. The review, conducted using Pubmed, Engineering Village, and Web of Science databases, found that there was insufficient data to identify the AFO stiffness ranges that affect gait.
After applying exclusion criteria, 25 of 287 potential articles were included. The included papers tested stiffnesses of 0.02 to 8.17 Nm/deg, a variety of populations (e.g., healthy, post-stroke, cerebral palsy), and various gait outcome measures. Ankle kinematics were the most frequently reported measures and the most consistently affected by stiffness variations. Greater stiffnesses generally resulted in reduced peak ankle plantarflexion, dorsiflexion, and total range of motion, as well as increased dorsiflexion at initial contact, according to the review’s authors. At the knee, a few studies reported increased flexion at initial contact, and decreased peak extension and increased peak flexion during stance when stiffness was increased. Stiffness did not affect hip kinetics and there was low evidence for its effects on hip or pelvis kinematics, ankle and knee kinetics, muscle activity, metabolic cost, ground reaction forces, and spatiotemporal parameters. There were no generalizable trends for the impact of stiffness on user preference.
The authors of the literature review suggest that clear reporting standards for AFO design parameters and additional high-quality research is needed with larger sample sizes and different clinical populations to determine the effect of stiffness on gait.
The review was published January 15 in Gait and Posture.
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