Energy expenditure of diplegic ambulation using flexible plastic ankle foot orthoses

In order to determine whether flexible plastic ankle foot orthoses (AFOs) really have functional advantage for children with spastic diplegia (CP children). Six CP children (13.2 +/- 1.9 years) who showed moderate spasticity walked on a treadmill at relative speeds that ranged from slow to fast for three minutes at each speed. While walking with and without flexible plastic AFOs, oxygen uptake (VO2) was measured. Then an energy expenditure index (EEI) was calculated by taking the VO2 value divided by walking speed. A curve EEI-walking speed relationship was approximated to a parabolic curve. Then, the lowest value of EEI, as an economical EEI, was derived from the curve. In four of the six CP children, the EEI while walking with flexible plastic AFOs were larger than without flexible plastic AFOs. The economical EEI while walking with and without flexible plastic AFOs was 0.56 +/- 0.26 ml/kg/m and 0.42 +/- 0.14 ml/kg/m, respectively. The ambulation with flexible plastic AFOs required more energy than without flexible plastic AFOs (p < 0.05). From these results, flexible plastic AFOs do not seem to provide a functional advantage for CP children.