1) Gait analysis provides quantitative measures of walking ability, but the measures need to accurately detect meaningful changes for clinical use. 2) The Gait Profile Score (GPS) summarizes overall gait deviation and has a Minimal Clinically Important Difference (MCID) of 1.6 degrees, meaning changes less than this are not noticeable. 3) An analysis of children who underwent surgery found that 66% improved over the MCID, 32% saw no meaningful change, and 2% deteriorated, showing the ability of GPS to evaluate the effects of interventions.

1. Outcome evaluation
Richard Baker
Professor of Clinical Gait Analysis
Blog: wwRichard.net
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2. WHO International Classification of
Functioning, Disabilities and Handicaps
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Temporal spatial parameters

3. Temporal spatial parameters
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4. Walking speed
• Best measured independently of gait
analysis.
• Walk tests as far as possible in a given
time
– 6 minute walk test (6MWT)
– 2 minute walk test (2MWT)
– 1 minute walk test (1MWT)
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ATS statement: guidelines for the six-minute walk test.
Am J Respir Crit Care Med, 2002. 166(1): p. 111-7.

5. 6 minute walk test
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ATS statement: guidelines for the six-minute walk test.
Am J Respir Crit Care Med, 2002. 166(1): p. 111-7.

6. 1 minute walk test
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McDowell, B.C., et al., Validity of a 1 minute walk test for children with cerebral palsy.
Developmental Medicine and Child Neurology, 2005. 47(11): p. 744-8.

7. 1 minute walk test
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McDowell, B.C., et al., Test-retest reliability of a 1-min walk test in children with bilateral
spastic cerebral palsy (BSCP). Gait and Posture, 2009. 29(2): p. 267-9.
No equivalent data for self-selected walking speed?
(After practice walk)

8. Walking speed
is a consequence of
stride length
and
cadence
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9. Non-dimensional normalisation
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Hof A.
Scaling gait data to body size.
Gait Posture. 1996;4:222-3.

10. Should really be tested
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Schwartz MH, Koop SE, Bourke JL, Baker R.
A nondimensional normalization scheme for oxygen utilization data.
Gait Posture. 2006; 4(1):14-22.
“Raw” “By mass” “Non-dimensional”

11. Non-dimensional normalisation
Results do not have units.
Not familiar (particularly to referring clinicians).
Report as % of normative reference values.
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12. Gait indices
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13. Gait indices
Single number to reflect the quality of gait.
• Gillette Gait Index (GGI, normalcy index)
• Gait deviation index (GDI)
• Gait profile score (GPS)
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14. Gillette Gait Index
• Originally called “Normalcy” index
• Doesn’t feel right!
– Small number of parameters
– Mixes temporal-spatial and kinematics
– Black box
– No significance to values
– Forgot to take the square root!
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15. GPS an GDI
The same measure scaled in two different ways.
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An New Method for Computing the Gait Deviation Index and Motion Analysis Profile
Schwartz, Rozumalski and Baker, GCMAS 2013
𝐆𝐃𝐈 ≈ 𝟏𝟎𝟎 − 𝟏𝟎 ×
𝐥𝐧 𝑮𝑷𝑺 − 𝑨
𝑩
𝐆𝐏𝐒 ≈ 𝐞𝐱𝐩
𝐁(𝟏𝟎𝟎 − 𝐆𝐃𝐈)
𝟏𝟎
+ 𝑨
A = mean ln RMS , and B = sd ln RMS
Absolutely no point calculating both
– they tell you the same thing!

16. GPS and GDI
• GPS simple score (how many degrees
different from normal)
– About 6º is normal
• GDI –
– 100 = normal
– 10 points = one standard deviation
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17. 17
Baker, R., et al., The gait profile score and movement analysis profile.
Gait Posture 2009;30(3):265-9.
GPS and GDI

18. 18
Baker, R., et al., The gait profile score and movement analysis profile.
Gait Posture 2009;30(3):265-9.
GPS and GDI

19. GPS and MAP
GPS = 16.2° (normal = 6 °)
GPS = 9.1° (normal = 6 °)

20. Gait profile score vs GMFCS
Baker R, McGinley JL, Schwartz MH, Beynon S, Rozumalski A, Graham HK, et al.
The gait profile score and movement analysis profile.
Gait Posture. 2009; 30(3):265-9.

21. Gait profile score vs FAQ
Baker R, McGinley JL, Schwartz MH, Beynon S, Rozumalski A, Graham HK, et al.
The gait profile score and movement analysis profile.
Gait Posture. 2009; 30(3):265-9.

22. Gait profile score vs speed
Baker et al. Gait and Posture 2009

23. Gait profile score vs clinical opinion
Beynon S, McGinley JL, Dobson F, Baker R.
Correlations of the Gait Profile Score and the Movement Analysis Profile relative to clinical judgments.
Gait Posture. 201;32(1):129-32.

24. MAP vs clinical opinion
Beynon S, McGinley JL, Dobson F, Baker R.
Correlations of the Gait Profile Score and the Movement Analysis Profile relative to clinical judgments.
Gait Posture. 201;32(1):129-32.

25. Minimal clinically important difference
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Baker R, McGinley JL, Schwartz M, Thomason P, Rodda J, Graham HK. The minimal clinically
important difference for the Gait Profile Score. Gait Posture. 2012;35(4):612-5.
MCID = 1.6°

26. Assessing efficacy of
interventions
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27. Change in GPS following SEMLS
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y = 0.16x + 8.10
R² = 0.07
y = 0.12x + 10.77
R² = 0.04
0°
5°
10°
15°
20°
25°
30°
0° 5° 10° 15° 20° 25° 30°
PostoperativeGPS
PreoperativeGPS
GMFCS II
GMFCS III
95% normal range
90%
80%
50%

28. Change in GPS following SEMLS
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y = 0.84x - 8.10
R² = 0.68
y = 0.88x - 10.77
R² = 0.68
-10°
-5°
0°
5°
10°
15°
20°
0° 5° 10° 15° 20° 25° 30°
Improvement(decrease)inGPS
Pre-operative GPS
GMFCS II
GMFCS III
95% normal range
90%
80%
50%
+MCID
-MCID

29. Change in GPS following SEMLS
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If we analyse all these children as a group
then we might conclude that surgery
improves gait quality for all children.
If we look at the underlying data we realise
that it only really benefits the more severely
affected children.

30. MCID
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y = 0.84x - 8.10
R² = 0.68
y = 0.88x - 10.77
R² = 0.68
-10°
-5°
0°
5°
10°
15°
20°
0° 5° 10° 15° 20° 25° 30°
Improvement(decrease)inGPS
Pre-operative GPS
GMFCS II
GMFCS III
95% normal range
90%
80%
50%
+MCID
-MCID
66% of children had a change
of greater than MCID.
Improved

31. MCID
31
y = 0.84x - 8.10
R² = 0.68
y = 0.88x - 10.77
R² = 0.68
-10°
-5°
0°
5°
10°
15°
20°
0° 5° 10° 15° 20° 25° 30°
Improvement(decrease)inGPS
Pre-operative GPS
GMFCS II
GMFCS III
95% normal range
90%
80%
50%
+MCID
-MCID
66% of children had a change
of greater than MCID.
Improved
32% of children had a change a
change of less than MCID either way.
No change

32. MCID
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y = 0.84x - 8.10
R² = 0.68
y = 0.88x - 10.77
R² = 0.68
-10°
-5°
0°
5°
10°
15°
20°
0° 5° 10° 15° 20° 25° 30°
Improvement(decrease)inGPS
Pre-operative GPS
GMFCS II
GMFCS III
95% normal range
90%
80%
50%
+MCID
-MCID
66% of children had a change
of greater than MCID.
Improved
32% of children had a change a
change of less than MCID either way.
No change
2% of children deteriorated by more
than MCID
Deteriorated

33. Statistically significant
change
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34. Detecting change
Statistically importance
To have 95% confidence that 2 measures
are different the change needs to be 3 times
the standard error of measurement (SEM)
• Need to know the SEM.
• Can be quite large for many clinical
measures.
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35. Detecting change
Statistically importance
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McGinley JL, Baker R, Wolfe R, Morris ME.
The reliability of three-dimensional kinematic gait measurements: a systematic review.
Gait Posture. 2009 Apr;29(3):360-9.
x3!

36. Detecting change
Statistically important change
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McDowell BC, Hewitt V, Nurse A, Weston T, Baker R.
The variability of goniometric measurements in ambulatory children with spastic cerebral palsy.
Gait Posture. 2000 Oct;12(2):114-21.
x3!

37. Need more reliable measures
for clinical use than we do for
research
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38. Thanks for listening
Richard Baker
Professor of Clinical Gait Analysis
Blog: wwRichard.net
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