Neurorehabilitation and Neural Repair. When might a cane be necessary for walking following a stroke?

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1 Neurorehabilitation and Neural Repair When might a cane be necessary for walking following a stroke? Journal: Neurorehabilitation and Neural Repair Manuscript ID: NNR-0-0.R Manuscript Type: Brief Date Submitted by the Author: -Mar-0 Complete List of Authors: Guillebastre, Bastien; University of Savoie, CISM - STAPS Rougier, Patrice; University of Savoie, CISM - STAPS Sibille, Brice; Clinique de Médecine Physique et Réadaptation, Institut de Rééducation, Hôpital Sud-CHU Chrispin, Anne; Clinique de Médecine Physique et Réadaptation, Institut de Rééducation, Hôpital Sud-CHU Perennou, Dominic; Clinique de Médecine Physique et Réadaptation, Hôpital Sud CHU Grenoble, Institut de Rééducation et Laboratoire TIMC-IMAG-CNRS Keyword: Gait, Stroke, Body weight asymmetry, Rehabilitation, Cane

2 Page of Neurorehabilitation and Neural Repair Title When might a cane be necessary for walking following a stroke? Authors information Bastien Guillebastre (MS) Laboratoire de Physiologie de l Exercice, Université de Savoie, Domaine Universitaire du Bourget-du-Lac, F- Le Bourget-du-Lac cedex; France. bastien.guillebastre@univsavoie.fr Patrice R. Rougier (PhD) Laboratoire de Physiologie de l Exercice, Université de Savoie, Domaine Universitaire du Bourget-du-Lac, Le Bourget-du-Lac cedex; France. patrice.rougier@univ-savoie.fr Brice Sibille (PT) Clinique de Médecine Physique et Réadaptation, Institut de Rééducation Hôpital Sud-CHU, Grenoble BP ; France. BSibille@chu-grenoble.fr Anne Chrispin (MD) Clinique de Médecine Physique et Réadaptation, Institut de Rééducation Hôpital Sud CHU, Grenoble BP ; France. AChrispin@chu-grenoble.fr Dominic Pérennou (MD, PhD) (Guarantor and Corresponding author) Clinique de Médecine Physique et de Réadaptation, Laboratoire TIMC-IMAG CNRS, Hôpital Sud CHU, Grenoble BP ; France. Tel: + (0) 0 ; Fax: + (0) 0. DPerennou@chu-grenoble.fr

3 Neurorehabilitation and Neural Repair Page of Abstract BACKGROUND: For individuals with lateral postural imbalance such as post-stroke patients, the decision to adopt a cane for walking remains difficult because no objective argument supports this decision. OBJECTIVE: The present study was conducted to investigate the explanatory values of two posturographic criteria of lateral postural imbalance on the walking abilities of post-stroke subjects. METHODS: Indices of postural asymmetry (% of body weight on the less loaded lower limb) and instability (medio-lateral variance of centre-of-pressure displacements) were measured in 0 healthy individuals required to stand still on a double force-platform. Cut-off values (mean + standard-deviations) were calculated to determine whether the posturographic data of poststroke subjects tested in similar conditions. days after a first hemisphere stroke were normal. Predictive values of both postural indices on walking abilities with or without a cane were then analysed in patients. RESULTS: Of the patients tested,.% were classified as unstable along medio-lateral axis (variance >mm²), and.% were classified as asymmetrical (% body weight <0%); 0% needed a technical aid and % walked without a cane. For a given patient, the probability of being able to walk without a cane was less than % if the paretic lower limb was not loaded over 0%. The postural instability index was less informative. CONCLUSIONS: This study suggests that for patients who do not spontaneously load more than 0% of their body weight on their paretic lower limb, the use of a cane for walking may be recommended. Key-words Gait / Stroke / Body weight asymmetry / Rehabilitation / Cane

4 Page of Neurorehabilitation and Neural Repair Introduction A stable standing posture is a prerequisite for recovering an autonomous gait after a stroke, and therefore is a major goal of rehabilitation. Changes in balance capacities, assessed by ordinal scales, is one of the best factors explaining walking recovery after a stroke. Bodyweight loading-unloading mechanisms are indeed involved in the control of both gait and upright standing along the medio-lateral axis. This explains why postural asymmetry and lateral instability, two major determinants of impaired postural capacities in post-stroke subjects, very often induces gait limitation. Postural asymmetry, with more weight on the nonparetic lower limb, and the patient s inability to compensate for it by loading the paretic lower limb, is due to many factors - such as lower limb muscular strength, can be compensated, at least temporarily, by the use of a cane. This postural asymmetry has repercussions on gait performance. The use of a standard cane has recently been shown to improve gait symmetry, velocity and walking distance. 0 The decision of when to adopt or discontinue the cane is often difficult to make. Discontinuing the use of the cane too soon might expose the patient to a risk of falling, a major problem in stroke rehabilitation. Keeping the cane too long might slow down the recovery of an efficient gait. The value of the cane is twofold: () stabilizing, i.e. reducing postural movements and () unloading the paretic limb during the single support of gait to facilitate the step. The purpose of the present investigation was to evaluate the relevance of posturography, which quantifies both postural asymmetry and instability,, in explaining the walking ability of post-stroke subjects, and to analyze posturographic indices which could better guide their rehabilitation. Methods Subjects

5 Neurorehabilitation and Neural Repair Page of After giving informed consent, subjects having recently experienced their first hemispheric stroke (Table ) were consecutively admitted to a stroke rehabilitation unit, as were 0 healthy individuals, age-matched and not significantly different in sex ratio (age, 0. ±. years; gender, M, F). They all participated in the study approved by our institutional ethics committee. Patients with significant orthopaedic disease were excluded from this study. Written informed consent was obtained from all participants. Posture and gait assessment The stability of standing posture was assessed by posturography using a double-force platform (PF0, Equi+, France). Subjects were asked to stand still, barefoot, in a standardised position with their feet placed on marks (heels cm apart, toes pointing out at 0 ), arms hanging freely, eyes open, for four trials lasting s separated by - to -min periods where the subject was seated. Postural instability and asymmetry were quantified respectively by the variance of the center-of-pressure (CP) movements along the medio-lateral axis (Var-CP-ML, mm ), and the percentage of body weight (BW) over the paretic (or less loaded in controls) foot (BW uf, %). Among various parameters aimed at evaluating postural instability, the variance of the CP movements is known to be one of the least sensitive to data recording conditions, with a high test-retest reliability. In post-stroke subjects, gait ability was assessed through direct observation by a clinician who did not know their posturographic data, using a seven-point walking score (Table ) which differentiated the subjects unable to walk without cane (score <), from those who could walk without cane (score ). Prediction analysis As the distribution of both posturographic indices is Gaussian in the control group, a range of mean + standard-deviations was used to diagnose a postural abnormality (instability,

6 Page of Neurorehabilitation and Neural Repair asymmetry) for determining the inability to walk from an abnormal posturographic score. The clinimetric properties of posturographic criteria to explain the ability to walk without or with a cane was analyzed according to its sensitivity and specificity values. The sensitivity of a posturographic criterion was the probability of it being abnormal (i.e. below BW uf cut-off and/or above Var-CP-ML cut-off) in patients unable to walk without a cane. The specificity of a posturographic criterion was the probability of it being normal in patients able to walk without cane. In addition, the Youden index (sensitivity+specificity-), as a validity coefficient informing about test efficiency, was calculated, with being the strongest possible value. Finally, the positive predictive values (PPV) were the probabilities of the gait score being less than when posturographic indices were abnormal (i.e. below the BW uf cut-off and/or above the Var-CP-ML cut-off). The negative predictive values (NPV) were the probabilities of gait being equal to or higher than when posturographic indices were normal. Statistical analysis Since the distribution of the posturographic data of post-stroke subjects was not Gaussian (assessment using Kolmogorov-Smirnov tests), the groups were compared using Mann-Whitney tests. The data were expressed as the mean ± standard-deviation when distributions were normal and as the mean [ th percentile] when they were not. Results Posturographic data Instability was diagnosed when variance was greater than mm along the ML axis and BW uf was less than 0%. Compared to controls, post-stroke subjects were more unstable along the ML axis (.[.] mm vs..[.] mm (mean[ th percentile]); P<0.000) and more asymmetric (.[.]% vs..[.]%; P=0.00). Among patients,.% and.% were classified as unstable and asymmetrical, respectively.

7 Neurorehabilitation and Neural Repair Page of Explaining the ability to walk without a cane The tables present predictive values for patients ability to walk with or without a cane according to postural instability (Table ) and asymmetry (Table ). Table shows poor predictive validity of instability, especially in terms of Youden s index (0.). The Youden index was twice as high for the asymmetry criteria (0.; Table) as for the instability criteria, meaning that postural asymmetry explained much better the need to use a cane than postural instability, with satisfactory sensitivity (.%) and great specificity (.%). Almost all patients who walked without cane behaved symmetrically on the force platform (Specificity=.%; see table ). The PPV of postural asymmetry reached.% for the inability to walk without any aid, meaning that less than % of patients who spontaneously loaded their paretic lower limb with less than 0% of BW could walk without any aid. However, among patients in whom normal weight-bearing symmetry was observed, only.% (NPV) could walk without aid. In other words, for a given patient, the probability of walking without any aid was.% if they spontaneously loaded their paretic lower limb over 0% of their total BW. Discussion To our knowledge, this study is the first to be based on a predictive analysis of gait ability from posturographic data. Our approach was cross-sectional, with posture and gait assessments carried out within a short time span. Our study confirms that posturography can be a determinant of gait ability and yields novel findings for determining when patients need a cane. In an undisturbed stance, lateral body movements, resulting from loading-unloading mechanisms, are similar to what occurs during gait where BW is alternatively supported by each lower limb. Postural parameters along the ML axis (% of BW on paretic limb and ML

8 Page of Neurorehabilitation and Neural Repair instability) therefore appear thus relevant for explaining gait capacities in patients with lateral imbalance. Our study reveals that the usefulness of a cane for walking is much better determined using postural asymmetry data than instability data. The probability for a given patient of being able to walk without a cane is less than % if they do not spontaneously load their paretic lower limb with over 0% of their BW, as normal gait requires loading each lower limb sufficiently to master the single support phase of the stride. Insufficient loading may be compensated for by additional support. Reducing postural asymmetry is a major goal in stroke rehabilitation. Our study suggests that any asymmetry corresponding to less than 0% of BW on the paretic lower limb would be a fair target. However, loading 0% of the BW on the paretic limb must not be considered a sufficient condition to begin walking without a cane: other factors are involved in gait impairment, such as postural instability, or verticality perception. Could the variability of the delay of the stroke onset be a limitation of this study? Indeed, a great variability in delays is shown in table. The fact that patients who needed help to walk were investigated later than those who walked without help may be explained by the fact that all were required to maintain balance without aid for the posturography tests. Posturography was therefore performed later for the most impaired patients. Overall, this variability did not impact the explanation of the ability to walk by the capacity to stand for any given patient. Although our findings are sufficiently interesting to be completed by a longitudinal prediction study involving more patients, we are aware that several technical points could be improved. A first limitation comes from the fact that our study involves a real dynamic task, in which single stance duration does not exceed s, and a postural static task lasting several tens of seconds. A second one is that the posturographic parameters used in this study are measured during a nonimposed, comfortable, standing posture, hence possibly hiding the ability of subjects to increase the load on their paretic lower limbs. Lastly, the cross-sectional design of this study does not

9 Neurorehabilitation and Neural Repair Page of provide any information regarding the assistance needed by post-stroke patients during gait recovery. Conclusion BW asymmetry better explains than postural instability the need to use a cane in post-stroke subjects. This parameter may be easily obtained, even from a single force platform, or from bathroom scales. -0 In stroke rehabilitation, the question of when to continue or discontinue cane use is very often raised as patients recover. So far no objective argument has been available to help decision making. Our study shows that cane use may be recommended to any patient who does not load more that 0% of their body weight on their paretic lower limb. Acknowledgments The authors are grateful to Noélie Buisson-Descombes for the proofreading in English language. References. Kollen B, van de Port I, Lindeman E, Twisk J, Kwakkel G. Predicting improvement in gait after stroke: a longitudinal prospective study. Stroke 00;:-0.. Rougier PR, Genthon N. Dynamical assessment of weight-bearing asymmetry during upright quiet stance in humans. Gait Posture 00;:-.. Nardone A, Godi M, Grasso M, Guglielmetti S, Schieppati M. Stabilometry is a predictor of gait performance in chronic hemiparetic stroke patients. Gait Posture 00;0:-0.

10 Page of Neurorehabilitation and Neural Repair Genthon N, Rougier P, Gissot AS, Froger J, Pélissier J, Pérennou D. Contribution of each lower limb to upright standing in stroke patients. Stroke 00;:-.. Barra J, Oujamaa L, Chauvineau V, Rougier P, Pérennou D. Asymmetric standing posture after stroke is related to a biased egocentric coordinate system. Neurology 00;:-.. Pérennou D. Weight bearing asymmetry in standing hemiparetic patients. J Neurol Neurosurg Psychiatry 00;:.. Bohannon RW. Relationship among paretic knee extension strength, maximum weightbearing, and gait speed in patients with stroke. J Stroke Cerebrovasc Dis ;:-.. Tyson SF, Rogerson L. Assistive walking devices in nonambulant patients undergoing rehabilitation after stroke: the effects on functional mobility, walking impairments, and patients opinion. Arch Phys Med Rehabil 00;0:-.. Beauchamp MK, Skrela M, Southmayd D, et al. Immediate effects of cane use on gait symmetry in individuals with subacute stroke. Physiother Can 00;: Allet L, Leemann B, Guyen E, et al. Effect of different walking aids on walking capacity of patients with poststroke hemiparesis. Arch Phys Med Rehabil 00;0:0-.. Nyberg L, Gustafson Y. Patient falls in stroke rehabilitation. A challenge to rehabilitation strategies. Stroke ;:-.

11 Neurorehabilitation and Neural Repair Page 0 of de Haart M, Geurts AC, Huidekoper SC, Fasotti L, van Limbeek J. Recovery of standing balance in postacute stroke patients: a rehabilitation cohort study. Arch Phys Med Rehabil 00;:-.. Pinsault N, Vuillerme N. Test-retest reliability of centre of pressure measures to assess postural control during unperturbed stance. Med Eng Phys 00;:-.. Lindmark B, Hamrin E. Evaluation of functional capacity after stroke as a basis for active intervention. Presentation of a modified chart for motor capacity assessment and its reliability. Scand J Rehabil Med ;0:0-0.. Rougier PR. Relative contribution of the pressure variations under the feet and body weight distribution over both legs in the control of upright stance. J Biomech 00;0:-.. Pérennou DA, Mazibrada G, Chauvineau V, et al. Lateropulsion, pushing and verticality perception in hemisphere stroke: a causal relationship? Brain 00;:0-.. Goldie P, Matyas T, Evans O, Galea M, Bach T. Maximum voluntary weight-bearing by the affected and unaffected legs in standing following stroke. Clin Biomech ;:-.. Genthon N, Gissot AS, Froger J, Rougier P, Pérennou D. Posturography in patients with stroke: estimating the percentage of body weight on each foot from a single force platform. Stroke 00;:-. 0

12 Page of Neurorehabilitation and Neural Repair Bohannon RW, Larkin PA. Lower extremity weight bearing under various standing conditions in independently ambulatory patients with hemiparesis. Phys Ther ;:-. 0. Caldwell C, MacDonald D, MacNeil K, et al. Symmetry of weight distribution in normal and stroke patients using digital weigh scales. Physiother Pract ;:0-.

13 Neurorehabilitation and Neural Repair Page of Table : Patients demographic characteristics and walking score distribution. Needs a human or technical aid Walk without a technical aid Lindmark & Hamrin walking scale Score Meaning n Sex Age (years) 0 cannot walk can take a few steps with the help of two persons can take a few steps with the help of one person can walk with a roller, crutches or quadripods can walk with one stick or one crutch can walk without a walking aid, but walks slowly or limps can walk at a normal speed for his or her age Demographic characteristics Hemisphere stroke side Days from onset M; 0 F. ± 0. Left; Right 0. ± 0. M; F. ±. Left; Right. ±. Total M; F. ±. 0 Left; Right. ±.

14 Page of Neurorehabilitation and Neural Repair Table : Distribution of post-stroke subjects according to gait capacities and CP movement variance along ML axis. Results of predictive validity (sensitivity, specificity and Youden s index) and predictive analysis with Positive and Negative Predictive Values (PPV and NPV, respectively) for patients ability to walk with or without walking aid. ML instability (mm²) Walking without aid Unable Able (gait score <) (gait score ) > PPV:.% < NPV:.% Sensitivity Specificity.%.% Youden's index 0.

15 Neurorehabilitation and Neural Repair Page of Table : Distribution of post-stroke subjects according to gait capacities and percentage of BW on paretic-unloaded foot (BW uf ). Results of predictive validity (sensitivity, specificity and Youden s index) and predictive analysis with Positive and Negative Predictive Values (PPV and NPV, respectively) for patients ability to walk with or without a walking aid. BWuf (%) Walking without aid Unable Able (gait score <) (gait score ) <0 PPV:.% >0 NPV:.% Sensitivity Specificity.%.% Youden's index 0.

16 Page of Neurorehabilitation and Neural Repair Table Needs a human or technical aid Walk without a technical aid Lindmark & Hamrin walking scale Score Meaning n Sex Age (years) 0 cannot walk can take a few steps with the help of two persons can take a few steps with the help of one person can walk with a roller, crutches or quadripods can walk with one stick or one crutch can walk without a walking aid, but walks slowly or limps can walk at a normal speed for his or her age Demographic characteristics Hemisphere stroke side Days from onset M; 0 F. ± 0. Left; Right 0. ± 0. M; F. ±. Left; Right. ±. Total M; F. ±. 0 Left; Right. ±.

17 Neurorehabilitation and Neural Repair Page of Table ML instability (mm²) Walking without aid Unable Able (gait score <) (gait score ) > PPV:.% < NPV:.% Sensitivity Specificity.%.% Youden's index 0.

18 Page of Neurorehabilitation and Neural Repair Table BWuf (%) Walking without aid Unable Able (gait score <) (gait score ) <0 PPV:.% >0 NPV:.% Sensitivity Specificity.%.% Youden's index 0.