Evaluation of postural stability in the elderly with stroke

OBJECTIVE: To compare clinical and biomechanical measures of balance in elderly stroke patients with those of healthy elderly people. DESIGN: Two-group comparison design. SETTING: Laboratory environment. PARTICIPANTS: Fifteen poststroke patients and 15 healthy age-matched older adults (N=30). INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: The biomechanical variable COP-COM, which represents the distance between the center of pressure (COP) and the center of mass (COM) in terms of root mean square. The mean of 4 trials of the COP-COM variable for each test condition was used for statistical analysis. Furthermore, the different systems (sensory, motor, central processor) related to postural stability were evaluated. RESULTS: Statistical significance of the COP-COM variable was larger in the stroke group than in healthy subjects, in both the anteroposterior (AP) and mediolateral (ML) directions. Furthermore, statistically, stroke subjects showed amplitudes of the COP-COM variable that were significantly larger in the eyes-closed condition. The significant negative correlation demonstrated between COP-COM amplitude and the balance scales (Berg, Tinetti) indicated that the patients with larger COP-COM amplitudes had lower clinical balance score. Furthermore, correlation coefficient scores between COP-COM variables in both AP and ML directions and motor performance using Fugl-Meyer Assessment (rho=-.53, rho=-.51, respectively) and reaction time (rho=-.53, rho=-.44, respectively) were significant. Vibration (rho=.41) and touch-pressure (rho=.42) perception thresholds correlated significantly only in the AP direction. CONCLUSIONS: Evaluating postural stability with COP-COM variable provided an accurate measure of postural stability in poststroke elderly people. Furthermore, postural stability in quiet stance, as measured by COP-COM amplitude, was related to functional measures of balance as well as physiologic factors relating to balance, such as visual conditions, lower-extremity peripheral sensibility, motor recovery, and simple reaction time.