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Immediate and long-term effects of ankle-foot orthosis on muscle activity during walking: A randomized study of patients with unilateral foot drop☆1,☆2,☆3,☆4,☆5,☆6,☆7,☆8,☆9

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Abstract

Geboers JF, Drost MR, Spaans F, Kuipers H, Seelen HA. Immediate and long-term effects of ankle-orthosis on muscle activity during walking: a randomized study of patients with unilateral foot drop. Arch Phys Med Rehabil 2002;83:240-5. Objectives: 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. Design: Cross-sectional and longitudinal randomized case-control study. Setting: Rehabilitation research center in the Netherlands. Participants: Fourteen healthy persons and 29 patients with foot drop. Interventions: 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. Main Outcome Measures: Amount of change in mean rectified electromyographic activity (δ value) between walking with and without AFO. Follow-up measurements were conducted after 3 and 6 weeks. Results: 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; δ values per muscle did not change during follow-up in the AFO group. Conclusion: 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. © 2002 by the American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation

Section snippets

Subjects

Fourteen healthy volunteers (8 women, 6 men; mean age ± standard deviation [SD], 33.2 ± 10.2y) recruited from staff and students at our research institute and 29 patients (21 men, 8 women) with a recent unilateral peripheral paresis of the ankle dorsiflexors participated in all studies. Patients were recruited from regional hospitals. Because no exact SDs were available, sample size was not based on power analysis but on practical considerations (ie, availability of patients). Each subject met

Reproducibility

The differences in mean electromyographic production between the first and second measurement sessions were calculated for each muscle with and without AFO use. Electromyographic activity between T0 and T2 was not significantly different (table 3).

. Differences in mean electromyographic activity of 14 healthy subjects at 2 measurement sessions for walking with and without AFO

Empty CellTA (%)EDL (%)SOL (%)GAS (%)PL (%)
Without AFO0 (±13)−9 (±23)2 (±14)−17 (±53)−6 (±23)
With AFO2 (±27)−13 (±31)−0 (±16)4 (±39)

Discussion

In clinical practice, the question often arises whether an orthosis diminishes muscle activity, thereby worsening an existing paresis. In a case of foot drop, an AFO is often prescribed to restore a more normal and safe walking pattern. In this study, we evaluated the effect of AFO use on electromyographic activity of 5 lower leg muscles in healthy and recent paretic subjects. We found a significant decrease of 7% and 20%, respectively, in paretic and healthy subjects in tibialis anterior

Conclusion

Although AFO use significantly reduces electromyographic activity of the tibialis anterior in healthy subjects (20% during the first 15% of the step cycle), and in paretic subjects (7% calculated over the step cycle as a whole), the reduction does not accumulate over time. This decrease in electromyographic activity during AFO use is easily compensated for by an increase in total walking activity facilitated by AFO use. Therefore, even in recent paretic subjects, no contraindication exists for

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    ☆1

    Supported by the Rehabilitation Foundation Limburg, Hoensbroek, and the Foundation De Drie Lichten, the Netherlands.

    ☆2

    No commercial party having a direct financial interest in the results of the research supporting this article has or will confer a benefit upon the authors or upon any organization with which the authors are associated.

    ☆3

    Reprint requests to Johanna F. Geboers, MD, iRv, Institute for Rehabilitation Research, PO Box 192, 6430 AD Hoensbroek, the Netherlands, e-mail: [email protected].

    ☆4

    Suppliers

    ☆5

    a. K-Lab Kinesiology, Lorentzkade 34 2014 CA Haarlem, Amsterdam.

    ☆6

    b. Medi-Trace®; The Ludlow Co LP, a Tyco Healthcare Co, 2 Ludlow Park Dr, Chicopee, MA 01022.

    ☆7

    c. Otto-Bock Orthopedic Industry GmbH & Co, Max Näderstr 15, 37115 Duderstadt, Germany.

    ☆8

    d. The Math Works Inc, 24 Prime Park Way, Natick, MA 01760.

    ☆9

    e. SPPS Inc, 233 S Wacker Dr, 11th Fl, Chicago, IL 60606.

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