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Dynamic Posturography

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.

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Dynamic Posturography

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  1. Dynamic Posturography Sensory Organization Motor Control Testing Posture Evoked Response

  2. 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.

  3. 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

  4. LIMITS OFSTABILITY The furthestdistancein any directiona person can leanaway frommidline(vertical) without alteringthe originalbase-of-support(by stepping, reaching, or falling)

  5. Dynamic Equilibrium Sensory Organization Motor Coordination Choice of Body Movement Determination of BodyPosition Compare, Select & Combine Senses Select & Adjust Muscle Contractile Patterns Ankle Muscles Thigh Muscles Trunk Muscles Visual System Vestibular System Somato- Sensation Generation of Body Movement Environmental Interaction

  6. 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

  7. Normal Vision Eyes Closed Sway-Referenced Vision Fixed Surface SOT Sensory Organization Test 3 1 2 Sway-Referenced Surface 4 5 6

  8. Equilibrium Scores • For each of the 6 conditions • Composite of all 6 • Derived Sensory Analysis

  9. Sensory Analysis

  10. Strategy Analysis • Hip vs. Ankle Dominant • Hip–high frequency, greater effect in horizontal shearing force • Ankle–low frequency, greater effect in vertical forces.

  11. COG Alignment • Average weight distribution • Displayed for each conditions • Offsets may reflect: • peripheral sensory • neurogenic • musculoskeletal • adaptation

  12. Motor Control Test • Support Surface Translations • Forward • Backward • Sway amplitude • Latency • Weight symmetry

  13. Motor ControlTest (MCT) • Amplitudes- Threshold/Small- Mid-range/Medium- Saturating/Large • Directions- Forward- Backward • Measures- Latency- Strength- Symmetry

  14. MCT: Normal Latencies • Latencies Slightly Shorter For Large vs Medium Displacements • Latencies Symmetrical Between Left & Right Sides

  15. MCT: Latencies Prolonged • Possible Deficits:- Extremity/Spinal Orthopedic Injury- Output Pathways • Problem Conditions:- Minor If Isolated- Major If Combined • Possible Treatments:- Rehabilitation?- Lifestyle Unilaterally

  16. MCT: Latencies Prolonged • Possible Deficits:- Neuropathy- Multiple Sclerosis- Spinal Orthopedic- Brainstem/Cortical • Problem Conditions:- Minor If Isolated- Major If Combined • Possible Treatments:- Lifestyle Bilaterally

  17. Adaptation Test (ADT) • Slow Toes Up (Down) Rotations- 8 degrees/sec • Sequences of 5 Trials measure response time

  18. ADT: Adaptation Test • Sway Energy Scores Higher During Initial Trials • Sway Energy Decreases Progressively With Repeated Rotations Normal Adaptation

  19. ADT: Adaptation Test • Possible Deficits- Mal Adaptation- Ankle Weakness - ROM impairments • Problem Conditions- Irregular Surfaces • Possible Treatments- Rehabilitation Failure to Adapt

  20. Elderly Fallers: Fail Toes-Up AdaptationWhipple & Wolfson, Balance, 1990 • Age-Matched Groups of Fallers & Non-Fallers Compared • Toes-Up Adaptation Failure Significantly Higher in Faller Group

  21. Posture Evoked Responses • EMG from: Gastrocnemius Tibialis anterior

  22. 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?

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