Predictors of the Biomechanical Effects of Customized Foot Orthoses in Adults With Flat-Arched Feet.

Objective: To determine the potential presence and characteristics of biomechanical responders to customized toot orthoses during walking in adults with flat-arched feet. Design: Experimental, repeated-measures. Setting: University clinic and laboratory. Participants: Eighteen symptom-free adults with flat-arched feet. Interventions: Customized foot orthoses. Main Outcome Measures: In-shoe foot biomechanics were measured during walking with and without customized foot orthoses using 3D analysis. Selected kinematic and kinetic variables during baseline walking were compared between subgroups who displayed reductions in calcaneal eversion with foot orthoses to those with no change or increases. Results: Biomechanical responders displayed significantly greater peak calcaneal eversion (+2.2 degrees, P = 0.009). Time to peak calcaneal eversion (-11 P = 0.006), peak dorsiflexion of the hallux (-6 degrees, P = 0.001), and medial-lateral excursion of the center of pressure during loading response were all reduced in the responder subgroup (-2 mm, P <= 0.001). Variables significantly different between subgroups were moderately associated with the response to foot orthoses (canonical correlation = 0.687, effect size = 0.47, P = 0.063). Conclusions: Individuals with increased dynamic foot pronation were more likely to show a favorable biomechanical response to customized foot orthoses, providing preliminary evidence to support the stratified use of foot orthoses to optimize their effectiveness.