Static Response of Maximally Pronated and Nonmaximally Pronated Feet to Frontal Plane Wedging of Foot Orthoses

Background: Research on foot orthoses has shown that their effect on the kinematics of the rearfoot is variable, with no consistent patterns of changes being demonstrated. It has also been hypothesized that the mechanical effect of foot orthoses could be subject specific. The purpose of our study was to determine if maximally pronated feet have a different response to frontal plane wedging of foot orthoses than do nonmaximally pronated feet during static stance. Methods: One hundred six feet of 53 healthy asymptomatic subjects were divided into two groups (maximally pronated and nonmaximally pronated) on the basis of their subtalar joint rotational position during relaxed bipedal stance. Functional foot orthoses were constructed for each subject and the relaxed calcaneal stance position was measured while standing on five separate frontal plane orthosis wedging conditions, 10° valgus, 5° valgus, no wedging, 5° varus, and 10° varus, to assess changes in calcaneal position. Results: Relative to the no-wedging condition, there were statistically significant differences (P < .05) in calcaneal position between the maximally pronated and the nonmaximally pronated feet with the 10° valgus and the 10° varus wedging conditions. No significant differences in calcaneal position were found with the 5° varus and the 5° valgus wedging conditions. Conclusions: Our study shows that the response to foot orthoses is variable between individuals. Maximally pronated subjects do not exhibit the same response to frontal plane wedging of foot orthoses as do nonmaximally pronated with 10° wedging. Intrinsic biomechanical factors such as subtalar joint position may influence the response to foot orthoses.