Design and effect of ankle-foot orthoses proposed to influence muscle tone: A review

Ankle-foot orthoses (AFOs) designed and proposed to influence muscle tone are generally called as "tone-reducing" AFOs, "tone- inhibiting" AFOs, or "dynamic" AFOs. These orthoses were originally evolved from the use of plaster casts to influence the positive support reflex or tonic reflex, which were either triggered by pressing reflexogenous areas on the plantar surface of the foot or suppressed by offloading them. The effects of wearing AFOs to influence muscle tone have mainly been studied in patients with cerebral palsy, stroke, or head injury. Although different AFO designs exist, it seems that there is a lack of evidence to demonstrate that these AFOs can actually reduce or inhibit spastic muscle tone. This article specifically reviews the classification of patient groups recruited in previous studies, the design characteristics of AFOs, and the clinical and biomechanical effects reported. The results of this review suggested that the level of evidence for AFOs being able to influence muscle tone was very low. Therefore, further research with randomized controlled trials is required to investigate their clinical effects.