Plastic ankle-foot orthoses: evaluation of function.

Plastic ankle-foot orthoses (PAFOs) are worn by persons with hemiplegia to correct gait abnormalities such as foot drop during swing and insufficient pushoff during stance. A PAFO should resist plantarflexion sufficiently to provide toe clearance during the swing phase of gait without excessively increasing the knee bending moment during heelstrike. It should resist dorsiflexion during late stance to raise the heel to simulate gastrocnemiussoleus muscle group function. Five PAFOs were evaluated as to the amount of plantarflexion-dorsiflexion resistance that was provided when worn by hemiplegic and able-bodied subjects. A self-aligning goniometer measured ankle angle as the subject walked, and a gait event marker system recorded occurrences of gait events. The Seattle design polypropylene orthosis which enclosed the malleoli was the least flexible; it provided the greatest plantarflexion resistance to ensure against toe drag during swing for patients with severe plantarflexion spasticity. It offered the greatest dorsiflexion resistance to provide a good substitute for the gastrocnemiussoleus during the latter part of stance as required by patients with flaccid plantarflexors and full ankle range of motion. Progressive trimming of the Seattle design polypropylene orthosis made it more flexible and comparable in function to the commercially available Engen and Teufel orthoses. The latter 2 orthoses did not provide a pushoff substitute as well as the Seattle design orthosis which enclosed the malleoli, but they did provide an adequate amount of toe clearance during swing. The more flexible orthoses would be appropriate for subjects with mild to moderate plantarflexor spasticity.