Observational Gait Analysis

1. Observational Gait Analysis Nerrolyn Ford PhD

2. Issues for discussion • The observational gait analysis process • Reliability/Validity • What is done in practice? • Visual search strategies • Decision making strategies

3. Selection of Cues to observe Evaluation of Cues Interpretation of findings The Observational Gait Analysis process

4. Selection of Cues to observe Evaluation of Cues Interpretation of findings Plane: Coronal Sagittal Parameter Temporal Spatial Kinematic Region: Feet KneesHipsTrunkShoulderArmsHandsHead

5. Selection of Cues to observe Evaluation of Cues Interpretation of findings Theoretical/biomechanical knowledge Working environment/ Interaction with colleagues Internalizedmodel of “normal walking” Experience/exposure to similar cases

6. Selection of Cues to observe Evaluation of Cues Interpretation of findings Decision not to intervene Normal Decision to intervene Decision about success of treatment Abnormal Decision to attend to different cues

7. Observational gait analysis reliability

8. Research Aims • Investigate and describe the current practice of observational gait analysis from an information processing and visual search perspective • Develop and test an observational gait analysis training program

9. Decision making in OGA • Examine specific methods and cognitive processes used by clinicians performing observational gait analysis. • Identify sources of error and bias that may compromise OGA reliability and validity

10. Method (subjects) • 17 clinicians represent different professional groups • Prosthetics, orthotics, physiotherapy, medicine • Clinicians evaluated in their own clinical environment while performing a gait related consultation • Video assisted recall

11. Method • Prior to performing a clinical consultation clinicians were fitted with a lightweight head mounted video camera

12. Recall session • Immediately after performing the consultation clinicians participated in a recall session • View video and attempt to verbalise thoughts, feeling and decisions they remember having had at the time of the consultation • Recall sessions dubbed over a copy of the original tape and transcribed verbatim for coding and analysis

13. Transcript coding • Decision type • treatment or diagnostic • Decision strategy • Hypothetico-deductive, pattern recognition, exhaustive, multiple branching • Observational variables • kinematic upper limb • kinematic lower limb • temporospatial

14. Results (decision strategy)

15. Results (observational variables)

16. % of OGA spent viewing coronal versus sagittal plane

17. All clinicians tend to use a pattern recognition decision strategy Clinicians differ in the types of decisions made Clinicians differ in the observational variables they consider Major findings

18. If clinicians differ in the information they consider, do they differ in the information they visually attend to?

19. Study aims • Compare the visual search strategies of expert clinicians, novice clinicians and lay subjects

20. Testing sessions • Video taped footage of 10 gait affected and 2 non affected subjects (split screen) • Identify “major” walking problems • Eye movements tracked using video based eye tracking system (DBA systems inc.)

21. Participants 16 expert clinicians Prosthetists, orthotists, physiotherapists, medical specialist 13 novice clinicians 2nd year prosthetics and orthotics students 5 lay subjects No prior experience in gait assessment

22. Recording of eye movements using video based tracking system

24. Data analysis procedure • x-y coordinates of eye position (eye tracker) • x-y coordinates of major joints, head & trunk (PEAK) • visual fixation occurs when eye remains within designated region for 0.24 seconds

25. Data analysis Visual fixations Location Plane (coronal or sagittal) Body region (feet, knees, hips, trunk, shoulders, elbows, hands, head) Sequencing

26. Location of visual fixations (expert/novice/lay)

27. Location of visual fixations (expert/novice/lay)

28. Sequencing of visual fixations Lay subjects Novice subjects Expert subjects

29. Important findings • Coronal plane viewing bias (expert/novice and lay subjects) • expert clinicians allocate significantly greater proportion of fixations to the trunk and upper body • eye movement transitions most likely to occur from superior to an inferior body region • Novice clinicians more likely to make eye movement transitions between anatomically distant body regions

30. Can visual search strategies be taught to novice clinicians?

31. Traditional model of teaching observational gait analysis • Knowledge/cue based learning • Specific body regions (Segment by segment) • Theoretical training rather than experience based training

32. Perceptual training • Novice task performers will eventually gravitate towards pattern recognition decision strategies • Training more efficient if it complements pattern recognition strategies from the outset • (Kirlik et al., 1996)

33. Perceptual training • Reduces cognitive load • Less sensitive to situations of high stress, time pressures • More likely to be retained over a period of time (Rogers et al., 1997)

34. Aim Investigate effects of perceptual training on visual search strategies of novice clinicians

35. Method Testing sessions 1 - pre-training 2 - post training 3 - five months post training

36. Results - Coronal versus sagittal plane viewing * * * *

37. Distribution of fixations pre v/s post training

38. Distribution of fixations pre v/s 5-months post training

39. Sequencing of visual fixationsPathology-based learning group Pre-training Post-training 5 months post

40. Sequencing of visual fixationsCue-based learning group Pre-training Post-training 5 months post

41. Discussion • Both training groups significantly increased the proportion of fixations directed at the upper body • Cue groups were less rapid to respond to training, did not adopt the search strategy emphasised throughout training.

42. How can we improve our OGA skills • Recognize errors and biases • Observer training • Optimize viewing conditions • Collect appropriate patient information (narrow the search) • Identify visual cues that can be observed in a valid and reliable manner • Nature and number of visual cues that must be observed in order to make a valid and reliable decision