Reduction in energy cost of walking is associated with improved ankle plantarflexion moment during mid-stance following ankle-foot orthosis treatment in polio survivors with calf muscle weakness.

PURPOSE: This retrospective study evaluated the associations between change in energy cost of walking and changes in ankle and knee kinematics and kinetics when wearing a dorsiflexion-restricting ankle-foot orthosis compared with shoes alone in polio survivors with calf muscle weakness.

METHODS

All polio survivors with unilateral calf muscle weakness who were provided with a custom-made dorsiflexion-restricting ankle-foot orthosis and who had undergone a walking energy cost test and gait analysis test between April 2006 and January 2020 were included in the analysis (n = 26). Associations between change in energy cost (obtained during a 6-minute walking test with gas-exchange assessment) and changes in ankle and knee biomechanical parameters (obtained with three-dimensional gait analysis) from shoes alone to walking with the orthosis were tested using Pearson's correlations.

RESULTS

Reduced energy cost of walking was significantly correlated with increased maximum internal ankle plantarflexion moment (r=-0.453, 95%CI [-0.695;-0.041], p = 0.023) and increased forward center of pressure progression (r=-0.416, 95%CI [-0.723;0.009], p = 0.034) during mid-stance.

CONCLUSION

In polio survivors with unilateral calf muscle weakness, the reduction in energy cost of walking while wearing an ankle-foot orthosis appears to depend on its ability to improve the ankle plantarflexion moment and forward progression of the center of pressure during mid-stance.