Introduction to Computerized Gait Analysis

History of gait analysis

• If a man were to walk on the ground alongside a wall with a reed dipped in ink attached to his head, the line traced by the reed would not be straight but zigzag, because it goes lower when he bends and higher when he stands upright

• Leonardo da Vinci (1452-1519)
• Giovanni Borelli (1608-79)
• Weber brothers (1836)
• du Bois-Raymond (1849): Electromyography
• Duchenne (1855)

• Eadweard Muybridge  
• Leland Stanford, Governor of California, asked him to photograph his famous horse, Occident, to find out whether a trotting horse ever had all four feet off the ground (Sacramento 1872) ground at any one point in time
• 20,000 photographs of men, women, children, animals & birds in motion (Palo Alto, 1878-1879)
• "Attitudes of Animals in Motion" (1881)Animated by Charl Lucasson
• Animal Locomotion (1887)
• The Human Figure in Motion" (1901)
• Gave rise to the invention of cinema
• Braune & Fischer (1895): classic scientific study of human gait: body & joint forces calculated
• Bernstein (1935): studies in Russia
• Elftmann (1938): mechanical force platforms
• Murray (1964): Walking patterns of normal men
• Paul (1966):  Hip joint forces in normal walking
• Winter (1978): TV system, Joint powers

Why do we need to do computerised motion analysis?

• eye is too slow (flicker-fusion rate about 12 Hz)
• motion leaves no record
• to analyse internal forces and moments (torques)

Uses

• diagnosis
• monitoring (before/after treatment) 

• documentation 
• research

Types of measurement systems

• electro-goniometers (e.g. Penny & Giles)
• electro-magnetic (e.g. Polhemus Flock of Birds, Ascension Motion Tracker)
• cine film
• video
• visual light (e.g. Peak) 
• infra-red
• passive markers (e.g. Vicon, Motion Analysis Corp., Elite)
• active markers (e.g. CODA, Optotrak, Selspot)

Video systems

• charge-coupled device cameras
• fast shutter-speed (1/500 s or less)
• retro-reflective markers
• one camera for 2D, several (e.g. 6) for 3D

Force Platforms 

• Joint reaction forces and  moments can be calculated from kinematics (Inverse Dynamics)
• During stance phase, foot is in contact with ground, so need to measure ground reaction
• Force platform measures 6 components (3 forces, 3 moments) of the vector:
• Problems in hitting platform
• targetting
• short step-length

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Interpretation: Five common abnormalities

Normal pattern

• Loss of loading responseknee pain orweak quads
• Loss of plantarflexor-knee extensor couple (crouch-gait)
• Poor pelvic stabilisation (Trendelenberg) 

• Inadequate push-off & step-length
• weak
• spastic

• Incomplete extension in terminal swing and stiff knee

Electromyography

• Surface electrodes - fine wire for peroneii
• Filtering
• Problems of noise, interpretation

Laboratory 

• Capture normal gait with Vicon 370 motion analysis system
• Analyse with Vicon Clinical Manager

The Vicon Clinical Manager Marker Set

•                                                13 markers

• Hip-joint centre estimated by anthropometry

• Knee-joint axis estimated clinically (femoral condyle)
• antero-posterior errors result in flexion-offset
• rotational errors result in knee varus/valgus artifact 
• Ankle-joint axis assumed to be at lateral malleolus

• Thigh and shank wands need to be in a straight line

Normal Curves

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