Prediction of postural sway velocity by foot posture index, foot size and plantar pressure values in unilateral stance.

OBJECTIVES This study aims to assess whether the plantar pressure, the foot posture index (FPI) and foot size can predict the postural sway velocity in terms of postural stability in unilateral stance. PATIENTS AND METHODS A total of 236 feet of 118 participants (62 males, 56 females; mean age 22.1±3.1 years; range 18 to 36 years) were enrolled. The feet were classified as prone, normal and supine based on the FPI. Postural sway velocity during unilateral stance with eye open (US-EO) and eye closed (US-EC) condition was measured using the Balance Master. Plantar pressure for each foot was measured from 10 different areas using EMED-M pedobarography. The force-time-area (FTA) integral was calculated based on the plantar pressure values, while standardized foot size (SFS) was calculated dividing foot width by foot length. The one-way ANOVA was used to determine differences in postural sway velocity between the groups. Multiple linear regression analysis was used to evaluate the predictability of the postural sway velocity. RESULTS The postural sway velocities in US-EO condition were similar among three groups (p>0.05). In the US-EC condition, the highest postural sway velocity in the prone feet and lowest postural sway velocity in the supine feet were measured (p<0.05). There was a significant relationship between the postural sway velocity which was measured in the US-EC condition and SFS (β= 0.141, p<0.05), FTA integral under the hindfoot (β= -0.127, p<0.05) and FPI values (β= 0.246, p<0.05). CONCLUSION The predictive value of FTA integral and SFS parameters for postural sway velocity is lower in unilateral stance. The postural sway velocity is rather associated with FPI and increases by pronation of the foot.