Immediate and long-term effects of ankle-foot orthosis on muscle activity during walking: a randomized study of patients with unilateral foot drop.

Abstract

To determine (1) whether use of an ankle-foot orthosis (AFO) by patients with ankle dorsiflexor paresis leads to decreased muscle activity, immediately or 6 weeks after AFO use, and (2) whether this decrease (if present) differs between healthy and paretic subjects. Cross-sectional and longitudinal randomized case-control study. Rehabilitation research center in the Netherlands. Fourteen healthy persons and 29 patients with foot drop. Muscle activity was measured by surface electromyography. Electromyographic reproducibility was tested in 14 healthy volunteers walking with and without AFO. Acute changes in muscle activity from AFO use were compared between the 14 healthy persons and the 29 patients with foot drop. Adaptation effects of AFO use after 6 weeks were studied in 29 patients, randomly chosen 16 of whom had started using an AFO at the first measurement. Amount of change in mean rectified electromyographic activity (delta value) between walking with and without AFO. Follow-up measurements were conducted after 3 and 6 weeks. Correlation coefficients, reflecting within-subject reproducibility, varied between.68 and.96 (mean,.86). In patients and healthy subjects, tibialis anterior muscle activity decreased by 7% and 20% (P = .01, P = .04), respectively, when using an AFO. In patients, this decrease was measured in the overall activity during the gait cycle; in healthy subjects, it was measured in the first 15% of the gait cycle. Overall electromyographic activity did not change during 6 weeks; delta values per muscle did not change during follow-up in the AFO group. AFO use immediately reduced muscle activity of the ankle dorsiflexors. However, using an AFO for 6 weeks did not lead to a generally lower electromyographic activity level nor did the amount of activity reduction accumulate in comparison with patients who did not use an AFO. It is, therefore, safe to use an AFO, even with recently paretic patients.