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 OF STABILITY
The 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 Equilibrium
Sensory Organization
Motor Coordination
Determination
of Body Position
Choice of
Body Movement
Compare, Select
& Combine Senses
Select & Adjust
Muscle Contractile Patterns
Visual
System
Vestibular
System
Environmental
Interaction
SomatoSensation
Ankle
Muscles
Thigh
Muscles
Trunk
Muscles
Generation of
Body Movement
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
Sway-Referenced
Surface
Eyes
Closed
Sway-Referenced
Vision
1
2
3
4
5
6
SOT
Sensory Organization Test
Fixed
Surface
Normal
Vision
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 3+6/2+5 The degree to which pt relies on
visual info to maintain balance, even
(PREF)
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
Motor ControlTest (MCT)
• Amplitudes
- Threshold/Small
- Mid-range/Medium
- Saturating/Large
• Directions
- Forward
- Backward
• Measures
- Latency
- Strength
- Symmetry
MCT: Normal Latencies
• Latencies Slightly Shorter For
Large vs Medium Displacements
• Latencies Symmetrical Between
Left & Right Sides
• Possible Deficits:
- Extremity/Spinal
Orthopedic Injury
- Output Pathways
• Problem Conditions:
- Minor If Isolated
- Major If Combined
• Possible Treatments:
- Rehabilitation?
- Lifestyle
Unilaterally
MCT: Latencies Prolonged



Possible Deficits:
- Neuropathy
- Multiple Sclerosis
- Spinal Orthopedic
- Brainstem/Cortical
Problem Conditions:
- Minor If Isolated
- Major If Combined
Possible Treatments:
- Lifestyle
Bilaterally
MCT: Latencies Prolonged
Adaptation
Test (ADT)
•Slow Toes Up (Down) Rotations
- 8 degrees/sec
•Sequences of 5 Trials measure response time
ADT: Adaptation Test
•
Sway Energy Scores
Higher During Initial Trials

Sway Energy Decreases
Progressively With
Repeated Rotations
ADT: Adaptation Test



Possible Deficits
- Mal Adaptation
- Ankle Weakness
- ROM impairments
Problem Conditions
- Irregular Surfaces
Possible Treatments
- Rehabilitation
Elderly Fallers: Fail Toes-Up Adaptation
Whipple & Wolfson, Balance, 1990
Falls On Toes-Up Adaptation
• Toes-Up Adaptation
Failure Significantly
Higher in Faller
Group
80
70
Non-Fallers
60
Fallers
Percentage
• Age-Matched
Groups of Fallers &
Non-Fallers
Compared
50
40
30
20
10
0
Trial 1
Trial 5
Posture Evoked Responses
• EMG from:
Gastrocnemius
Tibialis anterior
PERs
Short Latency approx 30 ms
Monosynaptic stretch reflex
Mid Latency approx 73 ms
Polysynaptic segmental reflex
Long Latency approx 104 ms
Postural response – possibly automatic?