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

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.

Efficacy of ankle-foot orthoses on walking ability in peripheral artery disease.

Calf claudication is a significant cause of walking limitation for patients with peripheral artery disease (PAD). Ankle-foot orthoses (AFO) are leg devices that can reduce the physical demands on the calf muscles during ambulation. The purpose of this study was to determine the efficacy of AFO on walking ability in patients with PAD. This was an open-label, interventional trial including 15 patients with calf claudication who were fit with AFO. Patients completed graded treadmill testing, followed by 12 weeks of unstructured community-based walking using the AFO ad libitum. Comparison of peak walking time (PWT) at baseline versus 12 weeks was the primary outcome. A secondary outcome was claudication onset time (COT) assessed during graded treadmill tests. Change in walking ability of AFO group patients was also compared to outcomes from a historical PAD control group (n = 10) who received upfront advice to walk at home. Patients in the AFO group significantly improved their walking ability from baseline to 12 weeks (mean ± SD) (PWT: 7.8 ± 5.1 to 9.3 ± 5.4 min, p = 0.049; COT: 3.0 ± 2.3 to 4.8 ± 2.7 min, p = 0.01). Change in PWT for AFO group patients when tested without using the devices was not significantly greater compared to historical controls (+1.4 ± 2.4 vs +0.1 ± 2.6 min, p = 0.16) but it was for COT (+1.8 ± 2.5 vs -0.6 ± 2.2 min, p = 0.02). This study found that AFO used during community-based walking improved the primary outcome of PWT in patients with PAD. Further, using AFO delayed claudication onset, indicating patients may be able to increase their walking activity. Large-scale, randomized controlled trials are needed to further explore the use of AFO for PAD. ClinicalTrials.gov identifier: NCT02280200.