gait symmetry in subjects with multiple sclerosis
DESCRIPTION
Gait Symmetry in Subjects with Multiple Sclerosis. Stephanie Crenshaw, James Richards, Caralynne Miller Department of Health, Nutrition, and Exercise Sciences University of Delaware American College of Medicine 53 rd Annual Meeting May 31-June 3, 2006 Denver, Colorado. Purposes. - PowerPoint PPT PresentationTRANSCRIPT
Gait Symmetry in Subjects with Multiple Sclerosis
Stephanie Crenshaw, James Richards, Caralynne MillerDepartment of Health, Nutrition, and Exercise SciencesUniversity of DelawareAmerican College of Medicine 53rd Annual MeetingMay 31-June 3, 2006 Denver, Colorado
Purposes
1. To explain newly developed Symmetry Analysis Method
2. To apply Symmetry Analysis Method to Clinical Population of Subjects with Multiple Sclerosis
MULTIPLE SCLEROSIS
Disease of the CNS Characterized by
demyelinated areas/axon damage in brain and spinal cord
Damage interferes with nerve signals that control muscle coordination, strength, sensation, and vision
Signs and Symptoms
Vision disturbances Numbness/weakness Tingling/pain Dizziness Unsteady Gait Fatigue
Measure of Disease SeverityExpanded Disability Status Scale
The EDSS is based upon Neurological testing of Functional Systems (CNS areas regulating body functions): Pyramidal (Walking Ability) Cerebellar (Coordination) BrainStem (Speech and Swallowing) Sensory (Touch and Pain) Bowel and Bladder Visual Mental Other (includes any other Neurological
findings due to MS)
EDSS Steps 1.0-4.5 patients are fully
ambulatory Precise step number determined by FS score
Steps 5.0-9.5 defined by impairment to ambulation
Steps 6.0-7.0 need assistive device
Steps 7.5-9.5 Wheelchair-bound/bedridden
MS Gait Compared to healthy controls:
Decreased velocity, stride length, range of motion
As disease severity increases: Variability of 25 FTW, Stance phase percentage
increase Gait Speed, Stride Length, Stride Rate decrease
With increased fatigue, no change in
balance performance (Frzovic, 2000) gait speed (Morris, 2002) stride length (Morris, 2002) double limb support duration (Morris, 2002)
Velocity, Peak Knee Flexion, Ankle Power Generation Decreased (Crenshaw, in press)
Symmetry Symmetry measures often
used to assess populations with unilateral injuries/disabilities
MS lesions develop in a random pattern in
CNS are distributed unequally
between right and left hemispheres of the brain
MS subjects Unequal stance duration Unequal step length
http://mccoy.lib.siu.edu/projects/mgrey/pathology/brain/multiple_selerosis/
Symmetry
Definition: Both limbs are behaving identically
Measures of Symmetry Symmetry Index Symmetry Ratio Statistical Methods
Symmetry Index
SI when it = 0, the gait is symmetricalDifferences are reported against their average value. If a large asymmetry is present, the average value does not correctly reflect the performance of either limbRobinson RO, Herzog W, Nigg BM. Use of force platform variables to quantify the effects of chiropractic manipulation on gait symmetry. J Manipulative Physiol Ther 1987;10(4):172–6.
%100*)(5.0
)(
LR
LR
XX
XXSI
Symmetry Ratio
Limitations: relatively small asymmetry and a failure to provide info regarding location of asymmetry
Low sensitivity
Seliktar R, Mizrahi J. Some gait characteristics of below-knee amputees and their reflection on the ground reaction forces. Eng Med 1986;15(1):27–34.
%100*L
R
X
XSR
Statistical Measures of Symmetry Correlation Coefficients Principal Component Analysis Analysis of Variance
•Use single points or limited set of points•Do not analyze the entire waveform
Sadeghi H, et al. Symmetry and limb dominance in able-bodied gait: areview. Gait Posture 2000;12(1):34–45.Sadeghi H, Allard P, Duhaime M. Functional gait asymmetry in ablebodied subjects. Hum Movement Sci 1997;16:243–58.
New Method - Eigenvector Analysis The method proposed utilizes eigenvector
analysis to compare time-normalized right leg gait cycles to time-normalized left leg gait cycles.
Paired data points from the right and left waveforms are entered into an m row x n column matrix, where each pair of points is one of the m number of rows. Singular Value Decomposition (SVD) is then performed on this matrix to determine the principal and secondary eigenvectors.
Eigenvector Analysis
Use eigenvector analysis to determine Waveform Trend Similarity
Trend Similarity is defined as the ratio of the variance about the principle eigenvector to the variance along the principle eigenvector
Additional Symmetry Measures Range ratio quantifies the difference in
range of motion of each limb, and is calculated by dividing the range of motion of the right limb from that of the left limb.
Range offset, a measure of the differences in operating range of each limb, is calculated by subtracting the average of the right side waveform from the average of the left side waveform.
Trend Symmetry
Expressed as ratio of the variance about eigenvector to the variance along the eigenvectorTrend Symmetry: 5.17% Range Amplitude Ratio: 0.79, Range Offset:0
Range Amplitude Ratio
Expressed as a ratio of the range of motion of the left limb to that of the right limbRange Amplitude Ratio: 2.0 Trend Symmetry: 0.0, Range Offset: 19.45
Range Offset
Calculated by subtracting the average of the right side waveform from the average of the left side waveformRange Offset: 10.0 Trend Symmetry: 0.0, Range Amplitude Ratio: 1.0
Final Adjustments A second measure of symmetry examines the
phase relationship between waveforms. To do this, we calculated the trend similarity for the sagittal plane joint angle between the normalized right and left limb waveforms. Then, one waveform was phase-shifted in 1-percent increments (e.g. sample 100 becomes sample 1, sample 1 becomes sample 2…) and the trend similarity was recalculated for each shift. The phase shift was then determined by identifying the index at which the smallest value for trend similarity occurred. The minimum trend similarity values are also reported.
Methods - Subjects
13 with MS Age 44.4±10.6
years Height 167.0±8.7
cm Mass 79.1±20.1
kg EDSS average 3.5 (range 2.5-4.5)
8 Healthy Controls Age 40.9±9.6
years Height
167.4±14.6 cm Mass 72.6±14.2
kg
Methods – Data Collection
Data Collection: 8 Motion-Analysis Cameras
60 Hz 2 AMTI Force Plates
960 Hz 2 Gait Analysis Conditions
Fresh Fatigued
Methods – Data Analysis
Created Ensemble averages of 15 gait cycles sagittal plane kinematics for fresh and
fatigued conditions Calculated Symmetry values
Affected/Unaffected – MS subjects Left/Right – HC subjects
Hip, Knee, and Ankle values were summed to determine composite symmetry measures
Methods – Data Analysis (HC)
HIP KNEE ANKLE SUM Trend Symmetry 0.01 0.36 0.73 1.01 Range Amplitude Ratio 0.94 0.93 0.88 2.75 Range Offset -0.72 0.02 0.49 0.2
Methods – Data Analysis (MS Fresh)
HIP KNEE ANKLE SUM Trend Symmetry 0.23 2.55 6.93 9.71 Range Amplitude Ratio 1.31 1.14 0.65 3.1 Range Offset -4.48 1.49 1.34 -1.65
Methods – Data Analysis (MS Fatigued)
HIP KNEE ANKLE SUM Trend Symmetry 0.79 5.86 3.52 10.17 Range Amplitude Ratio 1.55 1.07 0.75 3.37 Range Offset -6.08 -0.39 1.39 -5.08
Methods – Statistics
One-tailed independent samples t-test Changes between fresh conditions of MS and
control subjects
One-tailed dependent samples t-test Changes between fresh and fatigued
conditions for MS subjects
Correlation EDSS and differences between fresh and
fatigued conditions
Results – MS vs. Control example
HC
MS
Results – MS and Controls
MS subjects generally more asymmetrical than controls
p<0.05
MS HC Trend Symmetry * 3.6 ± 2.6 1.1 ± 0.5 Range Amplitude Ratio 3.1 ± 0.3 3.0 ± 0.2 Range Offset -1.1 ± 5.7 -1.6 ± 4.9 Phase Shift * 2.7 ± 1.6 1.3 ± 0.5 Adjusted Trend Symmetry * 2.6 ± 2.2 0.8 ± 0.5
Results – Fresh vs. Fatigued example
Fresh
Fatigued
Results – MS Fresh and Fatigued MS subjects generally become more
asymmetrical when fatigued
* p<.10
FRESH FATIGUED Trend Symmetry * 3.6 ± 2.6 4.6 ± 3.3 Range Amplitude Ratio * 3.1 ± 0.3 3.2 ± 0.3 Range Offset -1.1 ± 5.7 -0.8 ± 6.4 Phase Shift * 2.7 ± 1.6 3.5 ± 2.7 Adjusted Trend Symmetry 2.6 ± 2.2 3.0 ± 2.4
Results – Symmetry and EDSS
No significant correlations between disease severity and changes in symmetry from fresh to fatigued conditions
-6.0
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Conclusions
MS subjects are less symmetrical than healthy control subjects
MS subjects generally become less symmetrical when fatigued
There was no significant correlation between disease severity and changes in symmetry measures from fresh to fatigued conditions.
Ankle Joint
Trend Symmetry
Phase Shift (% Cycle
Min Trend Symmetry
Range Amplitude
Range Offset
95% CI 0 – 6.30 -2.2 – 2.6 0 – 4.94 0.70 - 1.27
-6.8 – 6.2
Unbraced 0.94 1 1.37 0.89 3.8
Braced 29.01 -3 24.76 1.72 -5.6
Amputee 17.56 0 17.56 1.30 -3.7
Symmetry Example…Ankle Joint