Stabilometry is a predictor of gait performance in chronic hemiparetic stroke patients Antonio Nardone a,b , Marco Godi a, *, Margherita Grasso a , Simone Guglielmetti a , Marco Schieppati c,d a Fondazione Salvatore Maugeri (IRCCS), Scientific Institute of Veruno (NO), Posture and Movement Laboratory, 28010 Veruno (No), Italy b Department of Clinical and Experimental Medicine, University of Eastern Piedmont, 28100 Novara, Italy c Fondazione Salvatore Maugeri (IRCCS), Scientific Institute of Pavia, Human Movement Laboratory (CSAM), 27100 Pavia, Italy d Department of Experimental Medicine, University of Pavia, 27100 Pavia, Italy 1. Introduction Stability during stance implies that the centre of mass (CoM) of the body is projected onto the base of support [1] close to the sagittal plane of the body [2]. Even small deviations from the set position are regulated by postural adjustments relying on both feedback and feedforward control mechanisms [3,4]. This regulation is obtained through appropriate torques produced by the feet on the base of support [5]. The point of application of the resultant forces, measured through a force platform, is the centre of pressure (CoP). During gait, CoM shifts alternately from one side to the other describing a sinusoidal path along the line of progression [6]. The horizontal accelerations needed for lateral shifts and forward progression are provided by the difference between CoP and CoM position [1]. In normal subjects, no asymmetries of the spatial– temporal variables of gait (step length, duration of stance and swing phases) between left and right limb are observed [7]. In standing patients with hemiparesis, CoM and CoP are generally shifted toward the unaffected limb [2,8,9] so that it is not easy to transfer body weight from one to the other limb [10]. It is not known if the extent of the lateral CoP shift during quiet stance affects the variables of gait in stroke patients [11]. Since the association between postural stability during stance [2] and gait performance also remains to be established [12], we aimed to investigate the relationship between CoP position and sway and changes in gait variables in stroke patients. 2. Materials and methods 2.1. Subjects and patients The study was designed to have a desired minimum power for the statistical tests of 0.80 for detecting an effect size larger than 1.20 at the one-sided, 0.01 level of significance [13]. From previous research, such an effect size was expected for stabilometry [2] and pedobarography [7]. Fifteen patients with spastic hemiparesis (10 right, RH, and 5 left hemiparesis, LH), 10 men and 5 women, aged 68.1 years Æ 7.6 (standard deviation, S.D.) and 17 normal subjects, 7 men and 10 women, aged 66.1 years Æ 5.7, were recruited. Gender difference within each group was not significant (chi- squared test, P < 0.47 and P < 0.27, respectively, for normals and patients). Duration of disease ranged from 7 months to 19 years. Patients had been just readmitted for evaluation and physical treatment to our Department of Physical Therapy and Rehabilitation. They were tested before commencement of the rehabilitation program. Inclusion criteria were: supratentorial ischemic stroke; time-interval after stroke longer than 6 months; spasticity greater than 1 in at least one muscle group of the lower limb Gait & Posture 30 (2009) 5–10 ARTICLE INFO Article history: Received 9 August 2008 Received in revised form 11 February 2009 Accepted 14 February 2009 Keywords: Hemiparesis Gait Stabilometry Posture CoP ABSTRACT In patients with spastic hemiparesis, centre of foot pressure (CoP) is shifted toward the unaffected limb during quiet stance. We hypothesised that abnormal gait features would correlate with the degree of asymmetry during stance. In 15 patients and 17 normals we recorded CoP and body sway by a force platform and measured spatial–temporal variables of gait with pedobarography. In patients CoP was shifted toward the unaffected limb and sway was larger than in normals. CoP position was associated with the decrease in strength of the affected lower-limb muscles. Spatio-temporal variables of gait were also affected by the disease. Cadence and velocity were decreased, duration of single support on the unaffected limb and of double support were increased with respect to normals. The degree of impairment of gait variables correlated with CoP. We found a negative relationship between velocity or cadence and CoP, and a positive relationship between duration of single support and CoP in the unaffected but not in the affected limb. Duration of double support correlated positively with CoP. CoP asymmetry during both standing and walking suggests that postural and gait problems share some common neural origin in hemiparetic patients. This asymmetry affects gait performance by increasing the time and effort needed to shift body weight toward the affected limb. The degree of postural asymmetry measured by stabilometry is associated with the level of impairment of gait variables. ß 2009 Elsevier B.V. All rights reserved. * Corresponding author. Tel.: +39 0322884900; fax: +39 0322884904. E-mail address: marco.godi@fsm.it (M. Godi). Contents lists available at ScienceDirect Gait & Posture journal homepage: www.elsevier.com/locate/gaitpost 0966-6362/$ – see front matter ß 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.gaitpost.2009.02.006