Dynamic Posturography

Sensory Organization

Motor Control Testing

Posture Evoked Response

Computerized Dynamic Posturography

• Sensory Organization Test—measurement of sway energy under various visual and support conditions.

• Motor Control Test—measurement of sway in response to tilt or translation in the support surface.

• Posture Evoked Responses—EMG recordings during the Motor Control Test.

Measuring Sway Energy

• Pt stands on force plates (pressure transducers)

• pick up vertical forces– weight distribution

• front-back

• left-right

• Pick up horizontal sheer forces

LIMITS OFLIMITS OF STABILITYSTABILITYLIMITS OFLIMITS OF STABILITYSTABILITYThe furthest distance in any direction a

person can lean away from midline (vertical) without altering the original base-of-support (by stepping, reaching, or falling)

Dynamic EquilibriumDynamic Equilibrium

Sensory Organization Motor Coordination

Choice ofBody Movement

EnvironmentalInteraction

VisualSystem

VestibularSystem

Somato-Sensation

Compare, Select& Combine Senses

Determinationof Body Position

Select & AdjustMuscle Contractile Patterns

AnkleMuscles

Generation ofBody Movement

TrunkMuscles

ThighMuscles

Equilibrium Score

• Maximum sway compared to calculated limits of stability

• 1 – (Max sway/LOS)

• 100 % = No Sway

• 0% = Sway reaches LOS

• Normed for age and height

F

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Sw

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Su

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NormalNormalVisionVision

EyesEyesClosedClosed

Sway-ReferencedSway-Referenced VisionVision

SO

T

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Sen

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Org

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Test

Sen

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11 22 33

44 55 66

Equilibrium Scores

• For each of the 6 conditions

• Composite of all 6

• Derived Sensory Analysis

Ratio Conds. Functional Relevance

Somatosensory (SOM)

2/1 Pt’s ability to use input from the somatosensory system to maintain balance.

Visual (VIS) 4/1 Pt’s ability to use input from the visual system to maintain balance.

Vestibular (VEST)

5/1 Pt’s ability to use input to the vestibular system to maintain balance.

Preference (PREF)

3+6/2+5 The degree to which pt relies on visual info to maintain balance, even when the info is incorrect.

Sensory Analysis

Strategy Analysis

• Hip vs. Ankle Dominant

• Hip–high frequency, greater effect in horizontal shearing force

• Ankle–low frequency, greater effect in vertical forces.

COG Alignment• Average weight distribution

• Displayed for each conditions

• Offsets may reflect:– peripheral sensory– neurogenic– musculoskeletal– adaptation

Motor Control Test

• Support Surface Translations– Forward– Backward

• Sway amplitude

• Latency

• Weight symmetry

• Amplitudes- Threshold/Small- Mid-range/Medium- Saturating/Large

• Directions- Forward- Backward

• Measures- Latency- Strength- Symmetry

Motor ControlTest (MCT)

• Latencies Slightly Shorter For Large vs Medium Displacements

• Latencies Symmetrical Between Left & Right Sides

MCT: Normal LatenciesMCT: Normal LatenciesMCT: Normal LatenciesMCT: Normal Latencies

MCT: Latencies ProlongedMCT: Latencies ProlongedMCT: Latencies ProlongedMCT: Latencies Prolonged

• Possible Deficits:- Extremity/Spinal Orthopedic Injury- Output Pathways

• Problem Conditions:- Minor If Isolated- Major If Combined

• Possible Treatments:- Rehabilitation?- Lifestyle

Un

ilate

rally

Un

ilate

rally

Bilate

rally

Bilate

rally

Possible Deficits:- Neuropathy- Multiple Sclerosis- Spinal Orthopedic- Brainstem/Cortical

Problem Conditions:- Minor If Isolated- Major If Combined

Possible Treatments:- Lifestyle

MCT: Latencies ProlongedMCT: Latencies ProlongedMCT: Latencies ProlongedMCT: Latencies Prolonged

Adaptation Test (ADT)

•Slow Toes Up (Down) Rotations- 8 degrees/sec

•Sequences of 5 Trials measure response time

• Sway Energy Scores Higher During Initial Trials

Sway Energy Decreases Progressively With Repeated Rotations

Norm

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Norm

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ADT: Adaptation TestADT: Adaptation TestADT: Adaptation TestADT: Adaptation Test

Failu

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Possible Deficits- Mal Adaptation- Ankle Weakness

- ROM impairments

Problem Conditions- Irregular Surfaces

Possible Treatments- Rehabilitation

ADT: Adaptation TestADT: Adaptation TestADT: Adaptation TestADT: Adaptation Test

Elderly Fallers: Fail Toes-Up AdaptationElderly Fallers: Fail Toes-Up AdaptationWhipple & Wolfson, Balance, 1990Whipple & Wolfson, Balance, 1990

• Age-Matched Age-Matched Groups of Fallers & Groups of Fallers & Non-Fallers Non-Fallers ComparedCompared

• Toes-Up Adaptation Toes-Up Adaptation Failure Significantly Failure Significantly Higher in Faller Higher in Faller GroupGroup

Posture Evoked Responses

• EMG from:

Gastrocnemius Tibialis anterior

PERs

Short Latency approx 30 msMonosynaptic stretch reflex

Mid Latency approx 73 msPolysynaptic segmental reflex

Long Latency approx 104 msPostural response – possibly automatic?