Investigating the effect of foot orthotics on dynamic stability in females with pes planus foot posture

Foot orthotics, a device which can modify the mechanical interaction between foot and the external environment, are commonly prescribed for individuals with pes planus foot postures. The purpose of this study was to investigate the role of foot orthotics on controlling dynamic stability when females with pes planus foot posture experience a modified foot placement orientation during walking.

Can foot orthotics control dynamic stability when females with pes planus foot posture experience a modified foot placement orientation during walking?

Kinematic data were collected from eighteen healthy young females (21.8 ± 3.2years) walking in prefabricated foot orthotics under three different stepping orientations (level, inversion, eversion). Outcome measures included gait parameters (step length, width, velocity) and dynamic stability (center of mass-base of support (COM-BOS), medio-lateral center of pressure (ML-COP) and antero-posterior COP (AP-COP)). Results were statistically evaluated with a repeated-measures ANOVA by within-subject factors of foot orthotic and step orientation. The relationship between foot posture index and dynamic stability was evaluated with spearman correlations.

Results suggest that changing the orientation of the foot significantly challenges the balance control system, as evidenced by a reduction in step length, increased step width, and increased AP-COP maximums. In orthotics, inverting the foot significantly reduced the COM-BOS range (27.9 mm ± 17.8 mm) and AP COM-COP maximum (265.3 mm ± 26.7 mm), whereas everting the foot increased the AP COM-COP maximum (277.0 mm ± 27.3 mm).

As the foot becomes more flexible (higher FPI score), the reduction in COM-BOS range suggests an increased balance control resolution when walking in foot orthotics.