Spatial postural control alterations with chronic ankle instability.

Postural control deficits have been identified among individuals with chronic ankle instability (CAI) compared to healthy controls. Although deficits in static balance have previously been reported using center of pressure (COP) and, more recently, time to boundary (TTB) measures, the underlying mechanism behind these deficits warrants further investigation. It is unclear if there are differences in the spatial distribution of COP and TTB minima data points under the foot. Our purpose was to determine if there are differences in the location of the distribution of the COP and the TTB minima data points between groups with and without CAI. Fifty healthy and 61 CAI subjects participated in this case-control study. The subjects performed three successful 10-s trials of quiet single limb stance on a force plate with eyes-open and -closed conditions. Results showed that during eyes-open trials, the CAI group exhibited more COP and TTB minima data points on the anterolateral aspect of the foot compared to controls. With eyes-closed single limb balance, the CAI group demonstrated significantly more COP and TTB minima data points anterior to the horizontal midline of the foot compared to controls. Overall, the CAI group showed a greater anterior displacement of COP and TTB minima during single limb static stance compared to controls. This alteration may result from the CAI subjects adopting a more dorsiflexed position in an effort to keep the ankle in a more stable, closed pack position and limiting the available degrees of freedom in the distal lower extremity.