Effects of Rigid and Dynamic Ankle-Foot Orthoses on Normal Gait

Abstract

As shown through posturographic data, wearing an ankle-foot orthosis (AFO) causes a backward shift in healthy subjects of the mean position of the center of pressure under the limb wearing it, and difficulty in controlling these displacements. This study evaluated whether this particular positioning influenced gait independent of a neurological disorder. Two AFO models, with different mechanical concepts (a rigid-AFO (R-AFO) and dynamic-AFO (D-AFO)), were worn by 11 healthy subjects required to walk on a 12-m electronic mat. Velocity, step time and step length were assessed for each of the five conditions where subjects walked barefoot, and wearing R-AFO or D-AFO (without and with slight and greater stiffness at the elastic band). Spatial and temporal characteristics of each support were also analyzed. Although wearing R-AFO disturbed velocity, step length and time with an asymmetry between sides, wearing the D-AFO only affected a support characteristic (midline length: length between the pivot points of the two dimensional sensor structure of heel and toe area). No effect was seen when modifying the stiffness of the D-AFO model. Even though the posturographic data might partly explain this behavior, wearing an orthosis caused different effects on normal gait parameters. These features should be useful when prescribing an ankle-foot orthosis by differentiating what alterations are due to the orthosis and which are due to the gait disorder.