Posturography Presented by: Mike Darnell
Objectives • What is Posturography? • Force Platforms • Stabilographic analysis • Computerized Dynamic Posturography • Sensory Organization Test (SOT) • Motor control Test (MCT) • Adaptation Test (ADT)
Posturography • Posturography - A term covering all of the techniques used to quantify postural control in upright stance, in either static or dynamic conditions. • Static Posturography (stabilometry) - Places the subject in a standing posture on a force plate connected to force and movement transducers, which are able to detect the tiny oscillations of the body. • Dynamic Posturography (CDP) – Disturbs the subject’s posture by means of a special apparatus with a movable platform.
Force Platforms / Plates • Measure the ground reaction forces generated by a body standing on or moving across the platform. • Used to quantify balance, gait, and other parameters of biomechanics. • Forces in three perpendicular directions are usually plotted against time • Vertical (Fz) • Horizontal –antero-posterior (Fy) • Lateral –medio-lateral (Fx)
Stabilographic analysis:Terminology • Postural Sway – A measure of the movement of the center of gravity within the base of support. • Postural Stability – Measured on the basis of the horizontal difference in sway motion between center of gravity and center of pressure.
Stabilographic Analysis • Measures stability of stance or posturalequilibrium. • Highlights poor posture, instability and asymmetry. • Variables that can be altered • Base of support (feet together/separated, standing on one foot, etc) • Surface (hard or foam) • Vision (opened v. closed)
Sample Graphs - Stabilometry
Computerized Dynamic Posturography • Most common method of measuring postural sway. • Is balance getting better or worse? • Three types of tests: • Sensory Organization Test (SOT) • Motor Control Test (MCT) • Adaptation Test (ADT)
Sensory Organization Test (SOT) • Identifiesproblems with the patient's ability to effectively use visual, vestibular, and proprioceptive information. • Sensory information is eliminated through calibrated "sway referencing" of the support surface and/or visual surround. • Patients may display an inability to make effective use of individual sensory systems.
SOT: six sensory condition • Eyes open, fixed surface and visual surround. • Eyes closed, fixed surface. • Eyes open, fixed surface, sway referenced visual surround. • Eyes open, sway referenced surface, fixed visual surround. • Eyes closed, sway referenced surface. • Eyes open, sway referenced surface and visual surround.
Scenario – before • 35-year-old female with a chief complaint of dizziness. • Patient history, physical exam, and other diagnostic tests are inconclusive. • Data from CDP indicate vestibular impairment.
Scenario – after • As a result of CDP data, the patient was referred to physical therapy • After several PT sessions supplemented by an individualized home exercise program, the patient was re-evaluated with CDP.
Motor Control Test (MCT) • Assesses the patient's ability to quickly and automatically recover from unexpected external provocations. • Measurements include onset timing, strength and lateral symmetry of responses.
Sample Graph - MCT
Adaptation Test (ADT) • Assesses the patient's ability to modify motor reactions and minimize sway when the support moves unpredictably in the toes-up or toes-down direction. • This adaptive test simulates daily life conditions such as irregular support surfaces.
Sample Graph - ADT
Points to Remember • Static v. Dynamic Posturography • Relationship of Newton’s laws to force plate analyses • How to differentiate between the various tests • What the individual tests are used to determine
References: • Allum, J.H., Shepard, N.T., (1999). An overview of the clinical use of dynamic posturography in the differential diagnosis of balance disorders. Journal of Vestibular Research, 9, 223-252. • Jones, R., (2008). The relationship between postural stability and virtual environment adaptation. Neuroscience Letters, 435(3), 204-209. • Parker, K., (2001). Use of force platforms in physics and sport. Physics Education, 36, 18-22. • Riley, M.A., Clark, S., (2003), Recurrence analysis of human postural sway during the sensory organization test. Neuroscience letters, 342, 45-48. • http://resourcesonbalance.com/neurocom/protocols/motorI mpairment/index.aspx
