Gait changes associated with the reduced push-off from solid ankle foot orthoses
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Ankle foot orthoses (AFOs) are used to improve walking in some lower extremity conditions but AFOs restrict ankle motion resulting in a trade-off in ankle and hip mechanics. While the use of AFOs have been well documented, there still remain gaps in the literature. The first study compared the differences in sagittal plane ankle and hip kinematics and kinetics across three conditions at two speeds in healthy individuals while the second study compared frontal plane kinetics at the hip and knee and vertical ground reaction forces between two conditions at two speeds in healthy individuals. This was studied by collecting and analyzing three-dimensional joint kinematics and ground reaction forces from twelve healthy adults. Participants walked in three conditions (shod; i.e. athletic shoes only and two reduced push-off conditions using solid ankle foot orthoses (SAFOs); i.e. unilateral brace and bilateral brace conditions) and at two speeds (1.25m/s and 1.5m/s). In the first study, generalized linear models with general estimating equations were used to compare ankle and hip angles, moments and power for the braced and unbraced sides separately in all three conditions. In the second study, frontal plane kinetics and vertical ground reaction forces in the unbraced limb in the unilateral brace condition were compared to the same side during shod walking using paired sample t-tests. From our first study we found that the reduced push-off from the use of SAFOs results in decreased peak plantarflexion angles and power generation at the ankle and increased peak flexion angles, and first and second peak power generation at the hip in the braced limbs in both unilateral (p≤0.05) and bilateral (p≤0.05) brace conditions at both speeds. On the unbraced side in the unilateral brace condition, there were decreased peak power generation at the ankle at 1.25m/s and increased peak extension moments, first and second peak power generation at the hip compared to the shod condition (p<0.05) at both speeds. In the comparison between the unilateral and bilateral brace conditions, the changes in ankle and hip mechanics were similar to the changes between the shod condition and the bilateral brace condition on the unbraced side; in addition, participants also had higher peak extension moments in the unilateral brace condition compared to the bilateral brace condition (p<0.05). On the braced side, participants had lower peak plantarflexion moments at the ankle and lower peak flexion angles at the hip when walking with bilateral SAFOs, compared to walking with unilateral SAFOs (p<0.05). In the second study, we found that peak internal knee and hip abduction moments were 3% and 4% higher, respectively, in the unbraced limb in the unilateral brace condition at 1.25m/s (p≤0.041) compared to the same side in the shod condition. Peak vertical ground reaction force was 3% higher in the unbraced limb in the unilateral brace condition at both speeds (p=0.002). Findings indicate that walking with unilateral ankle foot orthoses presents an increased risk of developing secondary conditions.