Evaluation of postural instability in stroke patient during quiet standing.

This study was designed to investigate the postural instability in stroke survivals during quiet standing. Eleven stroke patients and 11 healthy volunteers (gender- and age-matched) were recruited for this experiment. The center of pressure (COP) signals from both planta in anterior-posterior (AP) and medial-lateral (ML) directions were recorded using a three-dimensional motion capture system (BTS Bioengineering Corp, Italy) when subjects stood on the two adjacent force platforms quietly with their eyes open (EO) for 30 s and with their eyes close (EC) for another 30 s. The standard deviation (SD) for the two limbs and the inter-limb cross correlation-coefficient (CC) of COP series were calculated under EO and EC conditions, respectively. Patients showed significant differences in SD of AP-COP between two sides under EO (p <; 0.05) and EC (p <; 0.001) conditions. The SD of the ML-COP on non-paretic limb of patients was higher than that of controls under EC (p <; 0.05). Lower CC values of AP-COP was found in patients versus controls under two vision conditions (p <; 0.05), and the values in two groups increased significantly after removal of vision information (p <; 0.05). Stroke led to an increased postural sway and decreased inter-limb coordination during quiet standing. This study may facilitate the evaluation of the standing instability in stroke survivors and may improve the strategies for rehabilitation.