533614
research-article2014
NNRXXX10.1177/1545968314533614Neurorehabilitation and Neural RepairPatterson et al
Clinical Research Article
Longitudinal Changes in Poststroke Spatiotemporal Gait Asymmetry Over Inpatient Rehabilitation
Neurorehabilitation and Neural Repair 2015, Vol. 29(2) 153–162 © The Author(s) 2014 Reprints and permissions: sagepub.com/journalsPermissions.nav DOI: 10.1177/1545968314533614 nnr.sagepub.com
Kara K. Patterson, PhD1,2,3, Avril Mansfield, PhD1,2,3, Louis Biasin2, Karen Brunton1,2, Elizabeth L. Inness1,2, and William E. McIlroy, PhD2,3,4
Abstract Background. Little information exists about longitudinal changes in spatiotemporal gait asymmetry during rehabilitation, despite it being a common goal. Objectives. To describe longitudinal changes in spatiotemporal gait asymmetry over rehabilitation and examine relationships with changes in other poststroke impairments. Methods. Retrospective chart reviews were conducted for 71 stroke rehabilitation inpatients. Admission and discharge measures of spatiotemporal symmetry, velocity, motor impairment, mobility and balance were extracted and change scores were calculated. Relationships between changes in spatiotemporal symmetry and other change scores were investigated with Spearman correlations. Individuals were divided into four groups (worse, no change-symmetric, no change-asymmetric, improved) based on (1) symmetry/asymmetry at admission and (2) symmetry change scores >minimal detectable change. Differences in change scores between groups were investigated with analyses of covariance using the admission value as a covariate. Results. At admission, 59% and 49% of individuals were asymmetric in swing time and step length, respectively. Of these individuals, 21% and 14% improved swing symmetry or step symmetry, respectively. In contrast, 30% improved gait velocity, 62% improved functional balance and 73% improved functional mobility. Associations between change in swing symmetry and change in paretic limb weight bearing in standing and change in step symmetry and change in velocity were significant. There were no significant differences in change scores between the symmetry groups. Conclusions. The majority of asymmetric stroke patients did not improve spatiotemporal asymmetry during rehabilitation despite the fact that velocity, balance and functional mobility improved. Future work should investigate other factors associated with improved spatiotemporal symmetry and interventions to specifically improve it. Keywords stroke, gait, rehabilitation, symmetry, longitudinal change
Introduction Stroke-induced gait impairments can limit independence, quality of life, and participation, and improved walking function is the top rehabilitation goal poststroke.1,2 Two common poststroke gait impairments are temporal and spatial asymmetry, exhibited by 55.5% and 33.3% of individuals with chronic stroke, respectively.3 Reducing this asymmetry is commonly addressed by physiotherapists.4 This emphasis is likely because of the potential negative consequences associated with persisting spatiotemporal gait asymmetry, which include (1) challenges to balance control, (2) gait inefficiencies, (3) cumulative musculoskeletal injury to the nonparetic lower limb, (4) loss of bone mineral density in the paretic lower limb, and (5) reduced activity which may occur in response to any one or a combination of the preceding consequences3,5,6
Spatiotemporal gait asymmetry has been described as resistant to intervention.7 This resistance may be due in part to lack of training specificity; interventions that focus on ameliorating spatiotemporal gait asymmetry8 have had more success than interventions to improve velocity or 1
University of Toronto, Toronto, Ontario, Canada Toronto Rehab, University Health Network, Toronto, Ontario, Canada 3 Heart and Stroke Foundation Canadian Partnership for Stroke Recovery, Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada 4 University of Waterloo, Waterloo, Ontario, Canada 2
Corresponding Author: Kara K. Patterson, Department of Physical Therapy, University of Toronto, 500 University Avenue, Room 160, Toronto, Ontario, M5G 1V7, Canada. Email: [email protected]
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cardiovascular fitness.7,9 New spatiotemporal gait symmetry interventions will be guided by information about changes in asymmetry with current rehabilitation practice. Furthermore, information about factors associated with changes in spatiotemporal gait asymmetry may facilitate tailoring interventions to specific patient deficits. Despite the clinical importance of spatiotemporal gait symmetry, there is little information about longitudinal changes. It appears that spatiotemporal gait asymmetry may worsen in the chronic stage of stroke.10,11 However, no studies have examined changes in spatiotemporal gait asymmetry over inpatient rehabilitation when it is likely to be a target for intervention. Thus, the purpose of this study was to describe longitudinal changes in spatial and temporal gait asymmetry over inpatient rehabilitation. A secondary objective was to examine longitudinal changes during inpatient rehabilitation in other related dimensions that may be associated with changes in either spatial or temporal gait asymmetry, including lower limb motor impairment, gait function, quiet standing balance and reactive balance.
Methods Data were obtained through retrospective chart reviews of individuals admitted to stroke rehabilitation from October 2009 to September 2011. Inclusion criteria were the ability to (1) stand independently for 30 seconds without a mobility aid and (2) walk 10 m without an aid and without physical assistance. Exclusion criteria were (1) previous lower limb orthopedic surgeries, prosthetics, or ankle-foot orthotics; (2) history of other neurological conditions that would influence gait; (3) bilateral strokes or bilateral sensorimotor impairment; and (4) greater than 10 days between tests at admission or discharge. Seventy-one individuals met these criteria and were included. The review was approved by the institution’s research ethics board with a waiver of patient consent.
Standardized Gait and Balance Assessment The assessment was carried out in a novel on-site clinic that integrates technology (eg, force plates, pressure-sensitive mat) with clinical measures of gait and balance.12,13 This standardized assessment is considered routine care and is completed on admission and discharge from inpatient stroke rehabilitation. Measures of spatiotemporal overground gait parameters, quiet standing balance control, and reactive balance control are obtained and the results are entered as part of the patient care record. Assessments were administered by a trained physiotherapist. The assessment methods are described in detail elsewhere14,15 but will also be described briefly here. Overground Gait Assessment. Spatiotemporal parameters of gait were measured using a pressure-sensitive mat (GaitRite,
CIR Systems, Clifton, NJ) that measures 4.6 m × 0.9 m and records the timing and location of each foot fall during walking. Data were stored in a personal computer that calculated spatial and temporal parameters using application software. Participants walked at their preferred speed across a level 10-m walkway which included the pressure sensitive mat in the middle. Participants walked without any gait aids but were permitted to wear any customary braces or orthotics (eg, ankle-foot orthosis). Walking trials were performed until 18 footfalls were collected (typically 2-3 trials; up to 5 trials were completed for those with long stride lengths). Quiet Standing Balance Assessment. Quiet standing balance was measured using 2 force plates. Individuals stood with 1 foot on each force plate in a standardized position (heels 17 cm apart, 14° between the long axes of the feet.16 Weightbearing on the paretic limb was recorded under 2 conditions: (1) standing quietly with eyes open for 30 seconds, which is an estimate of an individual’s natural tendency to bear weight on their paretic limb (stand condition) and (2) standing while bearing as much weight as possible on the paretic limb for up to 20 seconds, which is an estimate of an individual’s capacity to bear weight on the paretic limb (load condition). The shorter duration for the latter condition is because of decreased tolerance individuals with stroke have for this condition compared to the quiet stance condition. Reactive Balance Assessment. Compensatory stepping reactions were evaluated in a videotaped session, using a leanand-release postural perturbation system.17 Patients stood in the standardized foot position16 with 1 foot on each of the 2 force plates and leaned forward with approximately 10% of their body weight supported by a cable attached to the wall. A load cell attached in series with the cable measured forces placed on the cable prior to the perturbation. This output was monitored to ensure consistency of the lean prior to the perturbation. A perturbation was created by releasing the cable at an unexpected time, which caused the individual to fall forward. This type of perturbation consistently evokes compensatory stepping reactions in young healthy individuals.17 There were no instructions or constraints placed on reactions. Individuals wore a safety harness attached to an overhead frame to prevent a fall where there was a failure to recover balance. A physiotherapist also provided standby assistance for every trial and provided hands-on assistance if individuals were unable to regain stability alone. The load cell output was used to detect perturbation onset time (ie, time when force recorded was minimal detectable change (MDC; 0.26 for swing symmetry, 0.19 for step symmetry22) were classified as either “improved” or “worse” depending on whether the discharge symmetry ratio was closer to or further away from 1.0, respectively. All others were classified as “no change.” Finally, the “no change” group was divided again into those who were symmetric and those who were asymmetric on admission. This process divided the study sample into four groups with respect to changes in swing and step symmetry: improved, no change and asymmetric on admission (no change-a), no change and symmetric on admission (no change-s), and worse. Individuals in the improved and worse groups were also classified by the change in direction of the swing and step asymmetry from admission to discharge. Individuals were classified as “no change” (NC) if the direction of asymmetry (ie. larger paretic or nonparetic swing time/step length value) was the same at admission and discharge. Individuals who exhibited a change in symmetry direction were classified as either (1) change from a larger paretic value at admission to a larger nonparetic value at discharge (PtoNP) or (2) change from a larger nonparetic value at admission to a larger paretic value at discharge (NPtoP). Classification of Participants According to Velocity, Functional Balance, and Functional Mobility. Participants were classified as either improved, worse, or no change in those measures for which change could be compared to an objective
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Neurorehabilitation and Neural Repair 29(2)
level accounting for either (1) error and variability in the measurement (MDC) or (2) the amount of change that has significance for the patient (minimal clinically important difference MCID) depending on what was available in the literature. Thus the following values were used: velocity (MDC = 0.30m/s),23 BBS (MDC = 6),24 and COVS (MCID = 5).25 Participants were classified as “improved” or “worse” if the change score >MDC or MCID and if the discharge score was greater or less than the admission score, respectively. All others were classified as “no change.” Statistical Analyses. All data were tested for normal distribution using the Shaprio–Wilk test. Variables that were not normally distributed were rank transformed and the ranked values were used in the subsequent analysis of variance (ANOVA) and analysis of covariance (ANCOVA) analyses. The three symmetry change groups (improved, no change-a, no change-s) were compared for differences in age, length of stay, and time poststroke at admission to rehabilitation with 1-way ANOVAs. To investigate within-subject changes from admission to discharge in functional outcomes and balance measures Wilcoxon signed rank tests were performed on velocity, %BWPstand, %BWPload, RMS-COP, PERT-freq, CMSA leg and foot scores, COVS, and BBS. Multiple comparisons were corrected with the Holm method26 and the initial adjusted level of significance was set to P = .006. Spearman correlations were used to investigate relationships between changes in swing and step symmetry and changes in velocity, COVS, BBS, CMSA leg and foot scores, %BWPstand, %BWPload, RMS-COP, PERT-freq, and PERT-swing. Multiple comparisons were corrected with the Holm method26 and the initial adjusted level of significance was set to P = .005. To investigate differences across the symmetry change groups for swing and step symmetry, ANCOVAs were computed on the change scores for velocity, CMSA leg and foot scores, BBS, COVS, %BWPstand, %BWPload, RMS-COP, PERT-swing, and PERT-freq. The admission value for each respective variable was used as a covariate. Ordinal data were rank transformed prior to analysis (eg, CMSA, BBS, and COVS) and the Holm26 method was used to correct for multiple comparisons. The initial adjusted level of significance was .005.26 The no change-s group was included in the analysis so as not to misrepresent our entire study sample as more impaired or having lower gait and balance function.
Results The mean (standard deviation [SD]) age for the group was 67.4 (11.8) years, 43 individuals in the group were men and 43 exhibited right-sided hemiparesis. The mean (SD) time
poststroke on admission was 19.7 (18.5) days and mean length of stay was 30.1 (9.0) days. On average, the entire group exhibited asymmetric gait on admission with mean swing symmetry and step symmetry ratios of 1.21 (0.35) and 1.14 (0.21), respectively. The mean swing and step symmetry magnitude and the direction of asymmetry for each of the symmetry change groups are summarized in Table 1.
Change in Spatiotemporal Gait Symmetry At admission, 59% (42/71) and 49% (35/71) of individuals were classified as asymmetric in swing time and step length asymmetry respectively. The majority of these individuals did not exhibit a change in symmetry over inpatient rehabilitation that exceeded the MDC; 79 % (33/42) did not change swing symmetry and 86% (30/35) did not change step symmetry. The number of individuals categorized as improved, no change-a, no change-s, or worse, in terms of the magnitude of the asymmetry, is summarized in Table 1. The number of individuals (within the worse and improved groups) categorized as no change, PtoNP or NPtoP, in terms of the direction of asymmetry is also summarized in Table 1.
Change in Functional Outcomes, Balance, and Motor Impairment Mean admission and discharge values are summarized in Table 2. Table 2 also summarizes the number of individuals classified as worse, improved and no change for velocity, BBS and COVS. Some admission and discharge values were missing; thus the number of individuals included in each analysis is also reported. On average, there was a significant improvement from admission and discharge for velocity, CMSA leg and foot scores, BBS, COVS, and PERT-freq. Table 3 contains a summary of the classification of individuals based on PERT-swing compared to the 95% CI for healthy individuals at admission and discharge. Of the 31 individuals who met the inclusion criteria for extracting the PERT-swing values (ie, completed 5 trials of external perturbations), 61% (19/31) did not exhibit a change in compensatory step swing time with the nonparetic limb.
Relationships Between Changes in Spatiotemporal Gait Symmetry and Changes in Measures of Functional Balance and Mobility and Motor Impairment There was a significant positive association between change in swing symmetry and change in %BWstand (rs =0.36, P = .002; Figure 1). There was a significant negative association between change in step symmetry and change in velocity
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Patterson et al Table 1. Summary of Swing and Step Symmetry Change Groups.a Worse
No Change—Asymmetric
No Change—Symmetric
Admission
Discharge
Admission
Discharge
Admission
2 33 1.21 (0.01) 1.73 (0.10) 1.21 (0.18) 1.13 (0.17)
1.0 (0.02)
29 1.05 (0.06)
1.99 (0.63)
1.45 (0.39)
7/0
7/0
Admission
Swing symmetry Number in group Swing symmetry magnitude (ratio) Swing symmetry direction (paretic/ nonparetic) Change in direction (PtoNP/NC/NPtoP) Step symmetry Number in group Step symmetry magnitude (ratio) Step symmetry direction (paretic/ nonparetic) Change in direction (PtoNP/NC/NPtoP)
Discharge
1/1
1/1
24/9
0/2/0
22/11 —
1
14/15
Discharge 7
15/14
—
0/7/0
30
1.04
2.44
1.18 (0.12)
1.13 (0.13)
1.03 (0.02)
1/0
0/1
11/19
11/19
15/20
1/0/0
Improved
35 1.05 (0.03)
5 1.59 (0.54)
1.15 (0.12)
4/1
3/2
18/17
—
—
1/4/0
a Symmetry magnitude is the ratio of right and left values with the larger value in the numerator irrespective of paretic side. The number of individuals who were classified as worse, no change—asymmetric, no change—symmetric, or improved from admission to discharge, based on the magnitude of swing and step length symmetry, are listed along with the mean symmetry magnitude values at admission and discharge for each group. Symmetry direction is determined with respect to the limb that exhibited the larger swing time/step length value; paretic or nonparetic and is represented in the table as the number of individuals exhibiting asymmetry in the paretic/nonparetic direction. Finally, the number of individuals who exhibited no change (NC) in the direction of asymmetry (ie, larger paretic vs nonparetic value), a change from the larger value on the paretic to the nonparetic limb (PtoNP), or a change from the larger value on the nonparetic to the paretic limb (NPtoP) is also listed for the worse and improved groups.
Table 2. Group Mean Values for Balance, Gait, and Motor Impairment on Admission and Discharge for the Entire Study Group.a
Velocity (m/s) CMSA leg (score) CMSA foot (score) COVS (score) BBS (score) %BWPstand %BWPload RMS-COP PERT-freq
Admission
Discharge
P Value, (n)
Adjusted Level of Significance24
Worse
No Change
Improved
0.65 (0.34) 4.7 (1.0)
0.84 (0.33)* 5.2 (1.0)*
research-article2014
NNRXXX10.1177/1545968314533614Neurorehabilitation and Neural RepairPatterson et al
Clinical Research Article
Longitudinal Changes in Poststroke Spatiotemporal Gait Asymmetry Over Inpatient Rehabilitation
Neurorehabilitation and Neural Repair 2015, Vol. 29(2) 153–162 © The Author(s) 2014 Reprints and permissions: sagepub.com/journalsPermissions.nav DOI: 10.1177/1545968314533614 nnr.sagepub.com
Kara K. Patterson, PhD1,2,3, Avril Mansfield, PhD1,2,3, Louis Biasin2, Karen Brunton1,2, Elizabeth L. Inness1,2, and William E. McIlroy, PhD2,3,4
Abstract Background. Little information exists about longitudinal changes in spatiotemporal gait asymmetry during rehabilitation, despite it being a common goal. Objectives. To describe longitudinal changes in spatiotemporal gait asymmetry over rehabilitation and examine relationships with changes in other poststroke impairments. Methods. Retrospective chart reviews were conducted for 71 stroke rehabilitation inpatients. Admission and discharge measures of spatiotemporal symmetry, velocity, motor impairment, mobility and balance were extracted and change scores were calculated. Relationships between changes in spatiotemporal symmetry and other change scores were investigated with Spearman correlations. Individuals were divided into four groups (worse, no change-symmetric, no change-asymmetric, improved) based on (1) symmetry/asymmetry at admission and (2) symmetry change scores >minimal detectable change. Differences in change scores between groups were investigated with analyses of covariance using the admission value as a covariate. Results. At admission, 59% and 49% of individuals were asymmetric in swing time and step length, respectively. Of these individuals, 21% and 14% improved swing symmetry or step symmetry, respectively. In contrast, 30% improved gait velocity, 62% improved functional balance and 73% improved functional mobility. Associations between change in swing symmetry and change in paretic limb weight bearing in standing and change in step symmetry and change in velocity were significant. There were no significant differences in change scores between the symmetry groups. Conclusions. The majority of asymmetric stroke patients did not improve spatiotemporal asymmetry during rehabilitation despite the fact that velocity, balance and functional mobility improved. Future work should investigate other factors associated with improved spatiotemporal symmetry and interventions to specifically improve it. Keywords stroke, gait, rehabilitation, symmetry, longitudinal change
Introduction Stroke-induced gait impairments can limit independence, quality of life, and participation, and improved walking function is the top rehabilitation goal poststroke.1,2 Two common poststroke gait impairments are temporal and spatial asymmetry, exhibited by 55.5% and 33.3% of individuals with chronic stroke, respectively.3 Reducing this asymmetry is commonly addressed by physiotherapists.4 This emphasis is likely because of the potential negative consequences associated with persisting spatiotemporal gait asymmetry, which include (1) challenges to balance control, (2) gait inefficiencies, (3) cumulative musculoskeletal injury to the nonparetic lower limb, (4) loss of bone mineral density in the paretic lower limb, and (5) reduced activity which may occur in response to any one or a combination of the preceding consequences3,5,6
Spatiotemporal gait asymmetry has been described as resistant to intervention.7 This resistance may be due in part to lack of training specificity; interventions that focus on ameliorating spatiotemporal gait asymmetry8 have had more success than interventions to improve velocity or 1
University of Toronto, Toronto, Ontario, Canada Toronto Rehab, University Health Network, Toronto, Ontario, Canada 3 Heart and Stroke Foundation Canadian Partnership for Stroke Recovery, Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada 4 University of Waterloo, Waterloo, Ontario, Canada 2
Corresponding Author: Kara K. Patterson, Department of Physical Therapy, University of Toronto, 500 University Avenue, Room 160, Toronto, Ontario, M5G 1V7, Canada. Email: [email protected]
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Neurorehabilitation and Neural Repair 29(2)
cardiovascular fitness.7,9 New spatiotemporal gait symmetry interventions will be guided by information about changes in asymmetry with current rehabilitation practice. Furthermore, information about factors associated with changes in spatiotemporal gait asymmetry may facilitate tailoring interventions to specific patient deficits. Despite the clinical importance of spatiotemporal gait symmetry, there is little information about longitudinal changes. It appears that spatiotemporal gait asymmetry may worsen in the chronic stage of stroke.10,11 However, no studies have examined changes in spatiotemporal gait asymmetry over inpatient rehabilitation when it is likely to be a target for intervention. Thus, the purpose of this study was to describe longitudinal changes in spatial and temporal gait asymmetry over inpatient rehabilitation. A secondary objective was to examine longitudinal changes during inpatient rehabilitation in other related dimensions that may be associated with changes in either spatial or temporal gait asymmetry, including lower limb motor impairment, gait function, quiet standing balance and reactive balance.
Methods Data were obtained through retrospective chart reviews of individuals admitted to stroke rehabilitation from October 2009 to September 2011. Inclusion criteria were the ability to (1) stand independently for 30 seconds without a mobility aid and (2) walk 10 m without an aid and without physical assistance. Exclusion criteria were (1) previous lower limb orthopedic surgeries, prosthetics, or ankle-foot orthotics; (2) history of other neurological conditions that would influence gait; (3) bilateral strokes or bilateral sensorimotor impairment; and (4) greater than 10 days between tests at admission or discharge. Seventy-one individuals met these criteria and were included. The review was approved by the institution’s research ethics board with a waiver of patient consent.
Standardized Gait and Balance Assessment The assessment was carried out in a novel on-site clinic that integrates technology (eg, force plates, pressure-sensitive mat) with clinical measures of gait and balance.12,13 This standardized assessment is considered routine care and is completed on admission and discharge from inpatient stroke rehabilitation. Measures of spatiotemporal overground gait parameters, quiet standing balance control, and reactive balance control are obtained and the results are entered as part of the patient care record. Assessments were administered by a trained physiotherapist. The assessment methods are described in detail elsewhere14,15 but will also be described briefly here. Overground Gait Assessment. Spatiotemporal parameters of gait were measured using a pressure-sensitive mat (GaitRite,
CIR Systems, Clifton, NJ) that measures 4.6 m × 0.9 m and records the timing and location of each foot fall during walking. Data were stored in a personal computer that calculated spatial and temporal parameters using application software. Participants walked at their preferred speed across a level 10-m walkway which included the pressure sensitive mat in the middle. Participants walked without any gait aids but were permitted to wear any customary braces or orthotics (eg, ankle-foot orthosis). Walking trials were performed until 18 footfalls were collected (typically 2-3 trials; up to 5 trials were completed for those with long stride lengths). Quiet Standing Balance Assessment. Quiet standing balance was measured using 2 force plates. Individuals stood with 1 foot on each force plate in a standardized position (heels 17 cm apart, 14° between the long axes of the feet.16 Weightbearing on the paretic limb was recorded under 2 conditions: (1) standing quietly with eyes open for 30 seconds, which is an estimate of an individual’s natural tendency to bear weight on their paretic limb (stand condition) and (2) standing while bearing as much weight as possible on the paretic limb for up to 20 seconds, which is an estimate of an individual’s capacity to bear weight on the paretic limb (load condition). The shorter duration for the latter condition is because of decreased tolerance individuals with stroke have for this condition compared to the quiet stance condition. Reactive Balance Assessment. Compensatory stepping reactions were evaluated in a videotaped session, using a leanand-release postural perturbation system.17 Patients stood in the standardized foot position16 with 1 foot on each of the 2 force plates and leaned forward with approximately 10% of their body weight supported by a cable attached to the wall. A load cell attached in series with the cable measured forces placed on the cable prior to the perturbation. This output was monitored to ensure consistency of the lean prior to the perturbation. A perturbation was created by releasing the cable at an unexpected time, which caused the individual to fall forward. This type of perturbation consistently evokes compensatory stepping reactions in young healthy individuals.17 There were no instructions or constraints placed on reactions. Individuals wore a safety harness attached to an overhead frame to prevent a fall where there was a failure to recover balance. A physiotherapist also provided standby assistance for every trial and provided hands-on assistance if individuals were unable to regain stability alone. The load cell output was used to detect perturbation onset time (ie, time when force recorded was minimal detectable change (MDC; 0.26 for swing symmetry, 0.19 for step symmetry22) were classified as either “improved” or “worse” depending on whether the discharge symmetry ratio was closer to or further away from 1.0, respectively. All others were classified as “no change.” Finally, the “no change” group was divided again into those who were symmetric and those who were asymmetric on admission. This process divided the study sample into four groups with respect to changes in swing and step symmetry: improved, no change and asymmetric on admission (no change-a), no change and symmetric on admission (no change-s), and worse. Individuals in the improved and worse groups were also classified by the change in direction of the swing and step asymmetry from admission to discharge. Individuals were classified as “no change” (NC) if the direction of asymmetry (ie. larger paretic or nonparetic swing time/step length value) was the same at admission and discharge. Individuals who exhibited a change in symmetry direction were classified as either (1) change from a larger paretic value at admission to a larger nonparetic value at discharge (PtoNP) or (2) change from a larger nonparetic value at admission to a larger paretic value at discharge (NPtoP). Classification of Participants According to Velocity, Functional Balance, and Functional Mobility. Participants were classified as either improved, worse, or no change in those measures for which change could be compared to an objective
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level accounting for either (1) error and variability in the measurement (MDC) or (2) the amount of change that has significance for the patient (minimal clinically important difference MCID) depending on what was available in the literature. Thus the following values were used: velocity (MDC = 0.30m/s),23 BBS (MDC = 6),24 and COVS (MCID = 5).25 Participants were classified as “improved” or “worse” if the change score >MDC or MCID and if the discharge score was greater or less than the admission score, respectively. All others were classified as “no change.” Statistical Analyses. All data were tested for normal distribution using the Shaprio–Wilk test. Variables that were not normally distributed were rank transformed and the ranked values were used in the subsequent analysis of variance (ANOVA) and analysis of covariance (ANCOVA) analyses. The three symmetry change groups (improved, no change-a, no change-s) were compared for differences in age, length of stay, and time poststroke at admission to rehabilitation with 1-way ANOVAs. To investigate within-subject changes from admission to discharge in functional outcomes and balance measures Wilcoxon signed rank tests were performed on velocity, %BWPstand, %BWPload, RMS-COP, PERT-freq, CMSA leg and foot scores, COVS, and BBS. Multiple comparisons were corrected with the Holm method26 and the initial adjusted level of significance was set to P = .006. Spearman correlations were used to investigate relationships between changes in swing and step symmetry and changes in velocity, COVS, BBS, CMSA leg and foot scores, %BWPstand, %BWPload, RMS-COP, PERT-freq, and PERT-swing. Multiple comparisons were corrected with the Holm method26 and the initial adjusted level of significance was set to P = .005. To investigate differences across the symmetry change groups for swing and step symmetry, ANCOVAs were computed on the change scores for velocity, CMSA leg and foot scores, BBS, COVS, %BWPstand, %BWPload, RMS-COP, PERT-swing, and PERT-freq. The admission value for each respective variable was used as a covariate. Ordinal data were rank transformed prior to analysis (eg, CMSA, BBS, and COVS) and the Holm26 method was used to correct for multiple comparisons. The initial adjusted level of significance was .005.26 The no change-s group was included in the analysis so as not to misrepresent our entire study sample as more impaired or having lower gait and balance function.
Results The mean (standard deviation [SD]) age for the group was 67.4 (11.8) years, 43 individuals in the group were men and 43 exhibited right-sided hemiparesis. The mean (SD) time
poststroke on admission was 19.7 (18.5) days and mean length of stay was 30.1 (9.0) days. On average, the entire group exhibited asymmetric gait on admission with mean swing symmetry and step symmetry ratios of 1.21 (0.35) and 1.14 (0.21), respectively. The mean swing and step symmetry magnitude and the direction of asymmetry for each of the symmetry change groups are summarized in Table 1.
Change in Spatiotemporal Gait Symmetry At admission, 59% (42/71) and 49% (35/71) of individuals were classified as asymmetric in swing time and step length asymmetry respectively. The majority of these individuals did not exhibit a change in symmetry over inpatient rehabilitation that exceeded the MDC; 79 % (33/42) did not change swing symmetry and 86% (30/35) did not change step symmetry. The number of individuals categorized as improved, no change-a, no change-s, or worse, in terms of the magnitude of the asymmetry, is summarized in Table 1. The number of individuals (within the worse and improved groups) categorized as no change, PtoNP or NPtoP, in terms of the direction of asymmetry is also summarized in Table 1.
Change in Functional Outcomes, Balance, and Motor Impairment Mean admission and discharge values are summarized in Table 2. Table 2 also summarizes the number of individuals classified as worse, improved and no change for velocity, BBS and COVS. Some admission and discharge values were missing; thus the number of individuals included in each analysis is also reported. On average, there was a significant improvement from admission and discharge for velocity, CMSA leg and foot scores, BBS, COVS, and PERT-freq. Table 3 contains a summary of the classification of individuals based on PERT-swing compared to the 95% CI for healthy individuals at admission and discharge. Of the 31 individuals who met the inclusion criteria for extracting the PERT-swing values (ie, completed 5 trials of external perturbations), 61% (19/31) did not exhibit a change in compensatory step swing time with the nonparetic limb.
Relationships Between Changes in Spatiotemporal Gait Symmetry and Changes in Measures of Functional Balance and Mobility and Motor Impairment There was a significant positive association between change in swing symmetry and change in %BWstand (rs =0.36, P = .002; Figure 1). There was a significant negative association between change in step symmetry and change in velocity
Downloaded from nnr.sagepub.com at UNIV OF GEORGIA LIBRARIES on June 7, 2015
157
Patterson et al Table 1. Summary of Swing and Step Symmetry Change Groups.a Worse
No Change—Asymmetric
No Change—Symmetric
Admission
Discharge
Admission
Discharge
Admission
2 33 1.21 (0.01) 1.73 (0.10) 1.21 (0.18) 1.13 (0.17)
1.0 (0.02)
29 1.05 (0.06)
1.99 (0.63)
1.45 (0.39)
7/0
7/0
Admission
Swing symmetry Number in group Swing symmetry magnitude (ratio) Swing symmetry direction (paretic/ nonparetic) Change in direction (PtoNP/NC/NPtoP) Step symmetry Number in group Step symmetry magnitude (ratio) Step symmetry direction (paretic/ nonparetic) Change in direction (PtoNP/NC/NPtoP)
Discharge
1/1
1/1
24/9
0/2/0
22/11 —
1
14/15
Discharge 7
15/14
—
0/7/0
30
1.04
2.44
1.18 (0.12)
1.13 (0.13)
1.03 (0.02)
1/0
0/1
11/19
11/19
15/20
1/0/0
Improved
35 1.05 (0.03)
5 1.59 (0.54)
1.15 (0.12)
4/1
3/2
18/17
—
—
1/4/0
a Symmetry magnitude is the ratio of right and left values with the larger value in the numerator irrespective of paretic side. The number of individuals who were classified as worse, no change—asymmetric, no change—symmetric, or improved from admission to discharge, based on the magnitude of swing and step length symmetry, are listed along with the mean symmetry magnitude values at admission and discharge for each group. Symmetry direction is determined with respect to the limb that exhibited the larger swing time/step length value; paretic or nonparetic and is represented in the table as the number of individuals exhibiting asymmetry in the paretic/nonparetic direction. Finally, the number of individuals who exhibited no change (NC) in the direction of asymmetry (ie, larger paretic vs nonparetic value), a change from the larger value on the paretic to the nonparetic limb (PtoNP), or a change from the larger value on the nonparetic to the paretic limb (NPtoP) is also listed for the worse and improved groups.
Table 2. Group Mean Values for Balance, Gait, and Motor Impairment on Admission and Discharge for the Entire Study Group.a
Velocity (m/s) CMSA leg (score) CMSA foot (score) COVS (score) BBS (score) %BWPstand %BWPload RMS-COP PERT-freq
Admission
Discharge
P Value, (n)
Adjusted Level of Significance24
Worse
No Change
Improved
0.65 (0.34) 4.7 (1.0)
0.84 (0.33)* 5.2 (1.0)*
