Between-day reliability of centre of pressure measures for balance assessment in hemiplegic stroke patients

Abstract

BackgroundStroke patients have impaired postural balance that increases the risk of falls and impairs their mobility. Assessment of postural balance is commonly carried out by recording centre of pressure (CoP) displacements, but the lack of data concerning reliability of these measures compromises their interpretation. The purpose of this study was to investigate the between-day reliability of six CoP-based variables, in order to provide i) reliability data for monitoring postural sway and weight-bearing asymmetry of stroke patients in clinical practice and ii) consistent assessment method of measurement error for applications in physical medicine and rehabilitation.MethodsPostural balance of 20 stroke patients was assessed in quiet standing on a force platform, in two sessions, 7 days apart. Six CoP-based variables were collected in eyes open and eyes closed conditions: postural sway was assessed with mean and standart deviation of CoP-velocity, CoP-velocity along the mediolateral and anteroposterior axes, and confidence ellipse area (CEAREA); weight-bearing asymmetry was assessed with mean CoP position along the mediolateral axis (CoPML). The intraclass correlation coefficient (ICC) was used to determine the level of agreement between test-retest. Small real difference (SRD), corresponding to the smallest change that indicates a real improvement for a single individual, was used to determine the extent of measurement error.ResultsICCs were satisfactory (>0.9) for all CoP-based variables, except for CEAREA in eyes open condition and CoPML (<0.8). The SRDs (eyes open/closed conditions) were: 6.1/9.5 mm.s-1 for mean velocity; 12.3/12.2 mm.s-1 for standard deviation of CoP-velocity; 3.6/5.5 mm.s-1 and 4.9/7.3 mm.s-1 for CoP-velocity in mediolateral and anteroposterior axes, respectively; 17.4/21.4 mm for CoPML. Because CEAREA showed heteroscedasticity of measurement error distribution, SRD (eyes open/closed conditions) was expressed as a percentage (121/75%) and a ratio (3.68/2.16) obtained after log-antilog procedure.ConclusionsIn clinical practice, the CoP-based velocity variables should be prefer to CEAREA to assess and monitor postural sway over time in hemiplegic stroke patients. The poor reliability of CoPML compromises its use to assess weight-bearing asymmetry. The procedure we used could be applied in reliability studies concerning other CoP-based variables or other biological variables in the field of physical medicine and rehabilitation.

Body balance in standing position in people after cerebral stroke on the basis of posturographic examinations

“…Balance problems adversely affect the quality of gait and are closely related to an increased risk of falling [13]. The studies have demonstrated a negative impact of stroke on body balance.…”

“…Problem z utrzymywaniem równowagi ciała niekorzystnie wpływa na jakość chodu i jest ściśle związa-ny z podwyższonym ryzykiem upadków [13]. Na podstawie przeprowadzonych badań stwierdzono negatywne oddziały-wanie udaru na równowagę ciała.…”

Feasibility and Effectiveness of Virtual Reality Training on Balance and Gait Recovery Early after Stroke: A Pilot Study

“…CoP velocity measurements are commonly used in studies focussing on balance in the stroke population [34][35][36]. Participants were asked to stand on the treadmill in most stable standing position with their head straight.…”

Uso del Centro de Masa Personalizado para la Evaluaci´on del Equilibrio

“…Es decir, su CoP estará contenido dentro de unárea menor [4]. Buscando medir el balanceo de los pacientes se han examinado métricas basadas tanto en el CoM como en el CoP tratando de relacionarlo con el riesgo de caída y las evaluaciones BBS y TUG [3,[5][6][7]. Algunas de estas pruebas requieren el uso de plataformas de fuerza de alto costo [5], de acceleróme-tros [3,6] o de cámaras [7,8].…”

“…Buscando medir el balanceo de los pacientes se han examinado métricas basadas tanto en el CoM como en el CoP tratando de relacionarlo con el riesgo de caída y las evaluaciones BBS y TUG [3,[5][6][7]. Algunas de estas pruebas requieren el uso de plataformas de fuerza de alto costo [5], de acceleróme-tros [3,6] o de cámaras [7,8]. Estosúltimos implementan sistemas de captura de movimiento, sin marcadores, y modelan al cuerpo como un péndulo invertido con la finalidad de realizar pruebas posturográficas basadas en el movimiento del CoM [7,8].…”