Functional Comparison of Conventional AFOs with the Dynamic Response AFO

Ankle foot orthoses (AFOs) are commonly prescribed to provide stability and foot clearance for patients with weakened or injured musculature. The Dynamic Response AFO (DRAFO) was designed to improve proprioception at heel strike. The design includes a rigid outer shell with a cut out heel and a soft inner lining; it is typically aligned in plantarflexion and may incorporate external heel wedges. The objective of this study was to investigate the effects of the DRAFO design features and contrast its biomechanical function with that of conventional locked and articulating AFOs. The research hypotheses were: 1) DRAFO-assisted gait parameters (e.g. ankle plantarflexion during early stance, cross-over times of the shank and thigh vertical angles during stance, step width, dorsi activity duration during stance, and center of pressure progression during loading response) will approximate the no AFO condition and 2) DRAFO-assisted gait parameters (e.g. ankle and knee kinematics, cross-over times of the shank and thigh vertical angles during stance, peak foot progression angle, step width, stance phase dorsiflexion activity duration, and mediolateral motion of the center of pressure) will differ from the locked and articulating AFOs. Ten young healthy subjects were recruited for gait analyses during level treadmill walking; four AFO conditions were contrasted. After five minutes of AFO and treadmill acclimation, each subject walked for two minutes at the self-selected walking speed on a level treadmill. Acquired data included lower extremity joint and segment kinematics, dorsiflexion and plantarflexion muscle activity, and treadmill kinetic data. Ambulation in the DRAFO demonstrated significantly greater knee flexion and ankle plantarflexion than with conventional AFOs, the foot progression angle was reduced in the DRAFO relative to the no AFO condition, the center of pressure progression for the DRAFO was more medial than that observed during the no and articulating AFO conditions, and the time to transition from an inclined to a reclined shank during swing was delayed. These findings suggest that the plantarflexed alignment, external heel wedges, and perhaps the soft heel features of the DRAFO design affect lower limb joint and segment kinematics, while the rigid structure provides stability to the ankle and subtalar joints