Outcome evaluation
Richard Baker
Professor of Clinical Gait Analysis
Blog: wwRichard.net
1
WHO International Classification of
Functioning, Disabilities and Handicaps
2
Temporal spatial parameters
Temporal spatial parameters
3
Walking speed
• Best measured independently of gait
analysis.
• Walk tests as far as possible in a given
time
– 6 minute w...
6 minute walk test
5
ATS statement: guidelines for the six-minute walk test.
Am J Respir Crit Care Med, 2002. 166(1): p. 1...
1 minute walk test
6
McDowell, B.C., et al., Validity of a 1 minute walk test for children with cerebral palsy.
Developmen...
1 minute walk test
7
McDowell, B.C., et al., Test-retest reliability of a 1-min walk test in children with bilateral
spast...
Walking speed
is a consequence of
stride length
and
cadence
8
Non-dimensional normalisation
9
Hof A.
Scaling gait data to body size.
Gait Posture. 1996;4:222-3.
Should really be tested
10
Schwartz MH, Koop SE, Bourke JL, Baker R.
A nondimensional normalization scheme for oxygen util...
Non-dimensional normalisation
Results do not have units.
Not familiar (particularly to referring clinicians).
Report as % ...
Gait indices
12
Gait indices
Single number to reflect the quality of gait.
• Gillette Gait Index (GGI, normalcy index)
• Gait deviation in...
Gillette Gait Index
• Originally called “Normalcy” index
• Doesn’t feel right!
– Small number of parameters
– Mixes tempor...
GPS an GDI
The same measure scaled in two different ways.
15
An New Method for Computing the Gait Deviation Index and Moti...
GPS and GDI
• GPS simple score (how many degrees
different from normal)
– About 6º is normal
• GDI –
– 100 = normal
– 10 p...
17
Baker, R., et al., The gait profile score and movement analysis profile.
Gait Posture 2009;30(3):265-9.
GPS and GDI
18
Baker, R., et al., The gait profile score and movement analysis profile.
Gait Posture 2009;30(3):265-9.
GPS and GDI
GPS and MAP
GPS = 16.2° (normal = 6 °)
GPS = 9.1° (normal = 6 °)
Gait profile score vs GMFCS
Baker R, McGinley JL, Schwartz MH, Beynon S, Rozumalski A, Graham HK, et al.
The gait profile ...
Gait profile score vs FAQ
Baker R, McGinley JL, Schwartz MH, Beynon S, Rozumalski A, Graham HK, et al.
The gait profile sc...
Gait profile score vs speed
Baker et al. Gait and Posture 2009
Gait profile score vs clinical opinion
Beynon S, McGinley JL, Dobson F, Baker R.
Correlations of the Gait Profile Score an...
MAP vs clinical opinion
Beynon S, McGinley JL, Dobson F, Baker R.
Correlations of the Gait Profile Score and the Movement ...
Minimal clinically important difference
25
Baker R, McGinley JL, Schwartz M, Thomason P, Rodda J, Graham HK. The minimal c...
Assessing efficacy of
interventions
26
Change in GPS following SEMLS
27
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...
Change in GPS following SEMLS
28
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° 1...
Change in GPS following SEMLS
29
If we analyse all these children as a group
then we might conclude that surgery
improves ...
MCID
30
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°
Improv...
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°
Improv...
MCID
32
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°
Improv...
Statistically significant
change
33
Detecting change
Statistically importance
To have 95% confidence that 2 measures
are different the change needs to be 3 ti...
Detecting change
Statistically importance
35
McGinley JL, Baker R, Wolfe R, Morris ME.
The reliability of three-dimensiona...
Detecting change
Statistically important change
36
McDowell BC, Hewitt V, Nurse A, Weston T, Baker R.
The variability of g...
Need more reliable measures
for clinical use than we do for
research
37
Thanks for listening
Richard Baker
Professor of Clinical Gait Analysis
Blog: wwRichard.net
38
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Evaluating outcomes (2014)

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Evaluating outcomes (2014)

  1. 1. Outcome evaluation Richard Baker Professor of Clinical Gait Analysis Blog: wwRichard.net 1
  2. 2. WHO International Classification of Functioning, Disabilities and Handicaps 2 Temporal spatial parameters
  3. 3. Temporal spatial parameters 3
  4. 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) 4 ATS statement: guidelines for the six-minute walk test. Am J Respir Crit Care Med, 2002. 166(1): p. 111-7.
  5. 5. 6 minute walk test 5 ATS statement: guidelines for the six-minute walk test. Am J Respir Crit Care Med, 2002. 166(1): p. 111-7.
  6. 6. 1 minute walk test 6 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. 7. 1 minute walk test 7 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. 8. Walking speed is a consequence of stride length and cadence 8
  9. 9. Non-dimensional normalisation 9 Hof A. Scaling gait data to body size. Gait Posture. 1996;4:222-3.
  10. 10. Should really be tested 10 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. 11. Non-dimensional normalisation Results do not have units. Not familiar (particularly to referring clinicians). Report as % of normative reference values. 11
  12. 12. Gait indices 12
  13. 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) 13
  14. 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! 14
  15. 15. GPS an GDI The same measure scaled in two different ways. 15 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. 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 16
  17. 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. 18 Baker, R., et al., The gait profile score and movement analysis profile. Gait Posture 2009;30(3):265-9. GPS and GDI
  19. 19. GPS and MAP GPS = 16.2° (normal = 6 °) GPS = 9.1° (normal = 6 °)
  20. 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. 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. 22. Gait profile score vs speed Baker et al. Gait and Posture 2009
  23. 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. 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. 25. Minimal clinically important difference 25 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. 26. Assessing efficacy of interventions 26
  27. 27. Change in GPS following SEMLS 27 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. 28. Change in GPS following SEMLS 28 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. 29. Change in GPS following SEMLS 29 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. 30. MCID 30 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. 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. 32. MCID 32 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. 33. Statistically significant change 33
  34. 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. 34
  35. 35. Detecting change Statistically importance 35 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. 36. Detecting change Statistically important change 36 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. 37. Need more reliable measures for clinical use than we do for research 37
  38. 38. Thanks for listening Richard Baker Professor of Clinical Gait Analysis Blog: wwRichard.net 38

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