Mechanical adaptations in walking using carbon fiber ankle foot orthoses for patients with peripheral artery disease

Abstract

Background: The effectiveness of community-based walking programs for patients with peripheral artery disease (PAD) can be limited by calf claudication during exercise. Recent evidence finds adding carbon fiber ankle foot orthoses (AFO) to a walking program can result in improvements in patient mobility and delay claudication onset when walking.

Research question: How may carbon fiber AFO alter ankle walking mechanics and corresponding triceps surae muscle recruitment in a manner that could improve patient mobility?

Methods: In this repeated measures cohort study, fifteen patients with PAD were fit with bilateral AFO before completing self-paced gait analysis including electromyography. Patients were then given standard advice to walk at home using the devices for 12 weeks. Twelve patients completed follow-up testing.

Results: There were no significant interactions between main effects for any variable of interest (p ≥ 0.189). Further, there were no within-subjects main effects for testing time for self-selected gait speed or any of the kinetic or kinematic variables (p ≥ 0.435). There were significant main effects for AFO use with reductions in dorsi flexion (p < 0.001), plantar flexion at toe off (p < 0.001), ankle plantar flexor moment (p = 0.037), and ankle plantar flexor power (p < 0.001). Triceps surae recruitment did not change between AFO conditions (p > 0.05).

Significance: Adding carbon fiber AFO limits peak ankle motion and joint power during self-paced walking for people with PAD while maintaining their walking speed. These gait adaptions were maintained over our 12 weeks of walking practice time. A resulting decrease in plantar flexor power while maintaining gait speed may provide the mechanism by which AFO can delay claudication onset which are major barrier to PAD walking programs. Calf muscle recruitment was maintained when adding the AFO which suggests sufficient muscle exertion could exist to maintain muscle integrity with sustained AFO use.

Keywords: Claudication; EMG; Exercise therapy; Vascular disease; Walking mobility.