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2 introduction to the conventional gait model
This document provides an introduction to the conventional gait model used in clinical gait analysis. It discusses the key aspects of the model including the anatomical segment definitions for the pelvis, femur, tibia, and foot. Marker placement for each segment is described, highlighting the importance of placing markers over bony landmarks to define segment axes and reference points according to the model. Challenges of applying the model to individuals with anatomical variations are also addressed.
In this document
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Introduction to the Conventional Gait Model; it is widely used and well-validated in clinical gait analysis.
Definition of a model; triangles define planes; importance of anatomical segments and marker placement.
Definitions of anatomical segments including femur, tibia, pelvis, and foot, helping define movement.
Theory of marker placement, emphasizing the use of landmarks and accuracy for an ideal person.
Principal axis, reference points, and measurements concerning the femur; calculations involving ASIS.
Focus on the tibia's principal axis, reference points, and how measurements are obtained.
Foot’s principal axis and how to accurately place markers for analyzing foot movement.
Considerations for placing markers on less ideal subjects to maintain accuracy and symmetry.
Concluding remarks and thanks from Richard Baker, emphasizing expertise in Clinical Gait Analysis.
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2 introduction to the conventional gait model
- 1. Introduction to the Conventional Gait Model Richard Baker Professor of Clinical Gait Analysis Blog: wwRichard.net 1
- 2. Conventional Gait Model Newington, Davis,Gage Helen Hayes, Kadaba Vicon Clinical Manager (VCM), Plugin Gait Conventional gait model (Visual 3d) 2
- 3. Conventional Gait Model By far the most widely used and best understood model in clinical gait analysis. Widely used in more general applications. Better validated than any other model. Better standardised than any other model. 3
- 4. What is amodel 4
- 5. Triangles 5 Triangle= Line + point
- 6. Triangles 6 Definesa plane
- 7. Understanding the model 7 Where are the lines and points that define the triangles?
- 8. Understanding the model • Anatomical segment definition • Theory of marker placement • Placing markers on the ideal person • Placing markers on less ideal people. 8
- 9.
- 10. Femur 10 Principalaxis From hip joint centre to knee joint centre Reference point Lateral epicondyle
- 11. Tibia 11 Principalaxis From knee joint centre to ankle joint centre Reference point Lateral malleolus
- 12. Pelvis 12 Principalaxis From one ASIS to the other Reference point Mid point of PSIS
- 13. Foot 13 Principalaxis Along long axis of foot
- 14. Foot 14 Principalaxis Along long axis of foot
- 15. Theory of markerplacement (Ideal person) 15
- 16. Marker placement •The system only sees the middle of the marker (not the baseplate) • Use landmarks as a guide and try and visualise the lines and planes • Always place markers on skin 16
- 17.
- 18. Pelvis 18 Principalaxis From one ASIS to the other Reference point Mid point of PSIS Right ASIS (Anterior superior iliac spine) Left ASIS
- 19. Pelvis 19 Principalaxis From one ASIS to the other Reference point Mid point of PSIS Left PSIS (Posterior superior iliac spine) Right PSIS
- 20. Pelvis 20 Principalaxis From one ASIS to the other Reference point Mid point of PSIS Marker centres are a marker radius in front of ASIS Need to tell software what the marker diameter is
- 21. Femur 21 Principalaxis From hip joint centre to knee joint centre Reference point Lateral epicondyle Lateral epicondyle
- 22. Femur 22 Femoralhead (femur) and cetnre of acetabulum (pelvis) are in same place.
- 23. Femur 23 Medio-lateraldistance is a proportion of ASIS width If InterASISDistance is measured and entered PiG will use this. If not PiG will take measured distance between ASIS
- 24. Femur 24 Anterior-posteriodistance If AsisTrocDist is entered then PiG will calculate a distance based on this and leg length. If not the distance is calculated as a function of leg length only
- 25. AsisTrocDist 25 Distancein anterior-posterior direction (not measured round body)
- 26. Femur 26 Proximal-distaldistance If AsisTrocDist is entered then PiG will calculate a distance based on this and leg length. If not the distance is calculated as a function of leg length only
- 27. Femur 27 Thighwand determines the coronal plane of the femur
- 28. Femur 28 50%to 70% of distance from hip to knee
- 29. AsisTrocDist 29 Distancein anterior-posterior direction (not measured round body)
- 30. AsisTrocDist 30 Distancein anterior-posterior direction (not measured round body)
- 31. Tibia 31 Principalaxis From knee joint centre to ankle joint centre Reference point Lateral malleolus Lateral malleolus
- 32. Tibia 32 Kneejoint centre assumed fixed in both femur and tibia
- 33. Tibia 33 Kneejoint centre is half knee width in from lateral epicondyle
- 34. Tibia 34 50%to 70% of distance from knee to ankle Shank wand determines the coronal plane of the tibia
- 35. Foot 35 Principalaxis Along long axis of foot
- 36.
- 37. Foot 37 Kneejoint centre is half knee width in from lateral epicondyle
- 38. Foot 38 Onsecond ray at level of “bump” on 1st cuneiform-metatarsal joint A more distal marker may give erroneous dorsiflexion if foot deforms
- 39. Foot 39 Foot rotation offset Plantarflexion offset Need to define green line in static test
- 40. Foot 40 Foot rotation offset Plantarflexion offset Line from heel to forefoot markers defines long axis of foot in horixontal plane
- 41. Foot 41 Foot rotation offset Plantarflexion offset Line from heel to forefoot markers defines long axis of in sagittal plane (or check foot flat box)
- 42. Foot 42 Plantarflexion offset If foot not flat on the ground heel marker must be same distance from plantar surface as forefoot marker
- 43. Placing markers onless ideal people 43
- 44. Pelvis 44 Mustenter AsisTrocDist Must still palpate landmarks
- 45. Pelvis 45 Keepmarkers symmetrical
- 46. Pelvis 46 Ifyou move markers out and forwards you must enter interAsis distance
- 47. Thanks for listening Richard Baker Professor of Clinical Gait Analysis Blog: wwRichard.net 47