Effect of ankle-foot orthoses on walking efficiency and gait in children with cerebral palsy

Objective: To determine the effect of ankle-foot orthoses on walking efficiency and gait in a heterogeneous group of children with cerebral palsy, using barefoot walking as the control condition. Design: A retrospective study. Methods: Barefoot and ankle-foot orthosis data for 172 children with spastic cerebral palsy (mean age 9 years; hemiplegia: 21, diplegia: 97, and quadriplegia: 54) were compared. These data consisted of non-dimensional speed, net nondimensional energy cost of walking (NN-cost), and NN-cost as a percentage of speed-matched controls (NN-cost_pct). For 80 of these children the Gillette Gait Index and data for 3D gait kinematics and kinetics were also analyzed. Results: Speed was 9% faster (p<0.001), NN-cost was 6% lower (p=0.007), and NN-cost_pct was 9% lower (p=0.022) when walking with an ankle-foot orthosis. The Gillette Gait Index remained unchanged (p=0.607). Secondary subgroup analysis for involvement pattern showed a significant improvement in NN-cost_pct only for quadriplegics (20%, p=0.004), whereas it remained unchanged for patients with hemiplegia and diplegia. Changes in the minimum knee flexion angle instance phase and in terminal swing were found to be significantly related to the change in NN-cost_pct (p = 0.013 and p = 0.022, respectively). Conclusion: The use of an ankle-foot orthosis resulted in a significant decrease in the energy cost of walking of quadriplegic children with cerebral palsy, compared with barefoot walking, whereas it remained unchanged in hemiplegic and diplegic children with cerebral palsy. Energy cost reduction was related to both a faster and more efficient walking pattern. The improvements in efficiency were reflected in changes of stance and swing phase knee motion, i.e. those children whose knee flexion angle improved toward the typical normal range demonstrated a decrease in energy cost of walking, and vice versa.