Gait Analysis: Technology and Clinical Applications دکترامیر هوشنگ واحدی متخصص طب فیزیکی و توانبخشی قسمت 1

The goal of this chapter is to introduce and familiarize the clinician with the terminology, the biomechanics, and the complex interaction that exists between the body and the physical factors that impact human gait the clinician must be able to produce a hypothesis and then attempt to understand what the problem is where and when it is present why it occurs

Humans are the only animals who characteristically have upright walking. The fundamental goal of ambulation is to move from one place to another

locomotion the act or power of moving the body from place to place by means of one's own mechanisms or power ambulation one type of locomotion which is characterized by moving the body on the level surface

Types of Locomotion Types Examples on feet · walking (ambulation, level walking) · race walking . ascending or descending ramp · running · ascending or descending stairs · jumping on wheels · bicycling · roller skating · ice skating · wheelchair propelling on hands · walking on hands · crutch walking · stunts on hands and knees · creeping · crawling on hands and feet · bear walking · ropewalking rotary locomotion · cartwheels · handsprings · rolls

Top-Down Approach

cortex: cerebellum Brain stem basal ganglia Spinal cord peripheral nerves NMJ muscle

The sequence of events that must take place for walking to occur may be summarized as follows: 1. Registration and activation of the gait command in the central nervous system 2. Transmission of the gait signals to the peripheral nervous system 3. Contraction of muscles that develop tension 4. Generation of forces at, and moments across, synovial joints 5. Regulation of the joint forces and moments by the rigid skeletal segments based on their anthropometry 6. Displacement (i.e., movement) of the segments in a manner that is recognized as functional gait 7. Generation of ground reaction forces

Clinical Usefulness of the Top-Down Approach understand pathology determine methods of treatment decide on which methods we should use to study patients gait. For example, a patient.s lesion could be central nervous system (as in cerebral palsy) peripheral nervous system (as in Charcot- Marie-Tooth disease) the muscular level (as in muscular dystrophy) the synovial joint (as in rheumatoid arthritis).

Gait analysis surgical planning therapeutic interventions planning :botulinum toxin injection in the management of spasticity optimization of lower extremity orthotic and prosthetic devices sport movement analysis analysis of musculoskeletal conditions, and outcomes measurement quantitative assessment tool for movement generally and walking specifically. (the most important)

Normal Gait Series of rhythmical , alternating movements of the trunk & limbs which result in the forward progression of the center of gravity Intermittant : Propulsion movements & Restraining movements

Normal Gait

Gait Cycle A single sequence of functions of one limb is called a gait cycle. It is essentially the functional unit of gait. Gait Cycle:There are two basic phases in the full cycle of a step Stance phase : the weightbearing period Swing phase: the non weightbearing period

This analogy of a wheel can be applied to human gait.

Support: Double-limb support : period during which both feet are in contact with the floor. 2) Single- limb support: period starts when the opposite foot is lifted for the swing phase

Gait parameters Distance parameters Time parameters Speed parameters

step width (Walking Base) Spatial (Distance) parameters Step Length Distance between corresponding successive points of heel contact of the opposite feet Rt step length = Lt step length (in normal gait) Stride Length Distance between successive points of heel contact of the same foot Double the step length (in normal gait) 144 cm in healthy adults step width (Walking Base) lateral distance between both heel centers of 2 consecutive foot contacts 7-9 cm in healthy adults foot angle angle (degree of toe-out) between the line of progression of the body and the longitudinal axis of the foot 7º in healthy adults

Time parameters stride time step time stance time single support time Definition Significance stride time the duration for the completion of a full gait cycle slightly > 1 sec step time the duration for the completion of a right or left step = the reciprocal of cadence for a symmetric gait stance time the duration when the foot is on the ground during one gait cycle 60% of one gait cycle single support time the duration when only one foot is on the ground during one gait cycle double support time the duration when both feet are in contact with the ground simultaneously during one gait cycle ~20% of one gait cycle as walking speed á in the elderly in patients with balanced disorders swing time the duration when the foot is in the air during one gait cycle 40% of one gait cycle as walking speed

Time Frame: A. Stance vs. Swing: Stance phase = 60% of gait cycle Swing phase = 40% B. Single vs. Double support: Single support = 80% of gait cycle Double support = 20%

1.Initial contact (0%) 2. Loading response (0-15%) 3. Midstance (15-40%) 4. Terminal stance (40-50%) 5. Preswing (50-60%) 6. Initial Swing (60-70%) 7. Midswing (70-85%) 8. Terminal swing (85-100%)

Speed parameters Parameter Definition Significance cadence (step rate) number of steps per minute comfortable speed： 80-110 steps/min slow speed： <70 steps/min fast speed： >120 steps/min walking speed distance per unit of time Speed in duration of all the component phases, especially double support phase as cadence, stride length, or both as angle of toe out or limb length

Cadence Number of steps per unit time Normal: 100 – 115 steps/min _Cultural/social variations Comfortable Walking Speed (CWS) Least energy consumption per unit distance Average= 80 m/min (~ 5 km/h)

Velocity Distance covered by the body in unit time Usually measured in m/s Instantaneous velocity varies during the gait cycle Average velocity (m/min) = step length (m) x cadence (steps/min) Velocity = stride length x cadence 120  

With increasing walking speeds: Stance phase: decreases Swing phase: increases Double support: decreases Running: walking without double support Ratio stance/swing reverses Double support disappears. ‘Double swing’ develops

Line of gravity The line of gravity through the center of mass of the body Note center of mass (COM): the weighed average of the center of mass of each body segments center of gravity (COG): the vertical projection of the COM to the ground

The Center of Gravity (COG) COG located at S1 - S2 During preferred rate walking the COG approximates a sinusoidal curve from the: Center of gravity (COG)—located 5 cm anterior to second sacral vertebra. The COG is displaced 5 cm (< 2 in.) horizontally and 5 cm vertically during an average adult male step

Path of the COG Vertical plane Horizontal plane

Path of Center of Gravity A-Vertical displacement: Rhythmic up & down movement Highest point: midstance Lowest point: double support Average displacement: 5cm Path: extremely smooth sinusoidal curve

Path of Center of Gravity B-Lateral displacement: Rhythmic side-to-side movement Lateral limit: midstance Average displacement: 5cm Path: extremely smooth sinusoidal curve

Path of Center of Gravity c- Overall displacement: Sum of vertical & horizontal displacement Figure ‘8’ movement of COG as seen from AP view

Elements of the Normal Pattern of Gait Alignment Gross Movements Fine Movements

Alignment Head is erect. Shoulders are level. Trunk is vertical.

Gross Movements Arms swing reciprocally and with equal amplitude at normal walking speed. Steps are of the same length and timing is synchronized. Body vertical oscillations