The Effect of Two Different Ankle Foot Orthoses on Reactive Stepping in Young, Healthy Adults

Date of Award

2021

Degree Name

M.S. in Mechanical and Aerospace Engineering

Department

Department of Mechanical and Aerospace Engineering

Advisor/Chair

Kimberly Bigelow

Abstract

In populations where ankle foot orthoses (AFOs) are prescribed, the risk of falling is seen to be high, due to underlying conditions such as muscle weakness, and minimized limb control. These groups include stroke patients, those with Parkinson's disease, and Multiple Sclerosis patients. The AFOs are designed to help prevent foot drop, promote heel strike and create a more normalized gait. While the AFOs have been seen to be beneficial, little information is out on how the AFO may impact a user if they were to fall while wearing the AFO. Additionally, there are many different styles of AFOs ranging in rigidity and material makeup. A previous study in our lab examined how a polypropylene AFO impacted recovery stepping through a lean and release perturbation system. The aim of this study is to expand on that research and see if there is a difference in recovery strategy when using two common types of AFOs, an OPTEC USA Prefabricated Polypropylene AFO (pAFO) and an Allard Toe-Off® carbon composite AFO (cAFO).15 healthy, young adults completed 35 reactive stepping trials in a lean and release system. This included 5 initial practice steps and then 10 steps with the pAFO, 10 with the cAFO, and 10 with no AFO, which were randomized in groups of 2. The forward lean angle was set to around 11° and about 15% of body weight. 31 retroreflective markers were placed on participants back, hips, thighs, shanks and feet. The trials were recorded with VICON Nexus and processed in Visual 3D to extract kinematic and temporal variables. These variables were run through SPSS for one-way ANOVA analysis with Tukey post-hoc in order to determine any differences between the 3 conditions (cAFO, pAFO and no AFO) on the stepping limb. It was seen that reaction time was significantly slower (p = 0.000) when no AFO is present as compared to when either the pAFO or the cAFO are present. While step length was not seen to change significantly between conditions, step duration when wearing the pAFO was seen to be significantly longer as compared to both cAFO (p = 0.024) and no AFO (p = 0.001), resulting in the step velocity for pAFO to be the slowest. As was predicted, the cAFO resulted in a significantly higher maximum knee flexion as compared to no AFO (p = 0.005) and pAFO (p = 0.000).These results indicate that there are significant changes in reactive stepping when wearing the different AFOs. In this study, it was discovered that the cAFO promotes the best recovery step because of increased step velocity, decreased reaction time, and greater step height and knee flexion. For future work, it is important that a population that uses AFOs are utilized to better understand how any impairments may compound on the changes seen in the healthy population.

Keywords

Mechanical Engineering, Biomechanics, Ankle Foot Orthosis, Falls, Balance, Lean and Release, Compensatory Stepping

Rights Statement

Copyright © 2021, author

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