Spasticity Evaluation System

Published: October 3, 2003  |  Source: depts.washington.edu
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The Spasticity Evaluation System is based on an electromechanical method of eliciting and measuring spasticity at the ankle. The system has been used to evaluate spasticity and Contracture in SCI, TBI and CP patients. Other medical conditions with abnormal elastic and viscous ankle joint stiffness can also be evaluated.

The evaluation is performed by measuring ankle stiffness in response to applied ankle movements of various frequencies. Concomitant surface EMG measurements of tibial and gastrocnemius muscles provide visualization of the Reflex responses and feedback to the examiner to ensure the subject is otherwise relaxed. Elastic and viscous stiffness components vs. applied movement frequency permit the quantification of ankle spasticity.

To perform the test, a subject is positioned Prone and the ankle is positioned at maximum dorsiflexion in a foot binding. The foot is rotated over a 5-degree range at frequencies of 3 to 12 Hz via a computer-controlled actuator. Ankle torque and displacement are measured via a computer over the course of thirty randomly applied 20-second trials (3 trials at each of 10 frequencies). Inertial and parasitic drag torques are computed and deducted from the total torque resulting in computation of net passive and spasticity-induced elastic (position dependent) and viscous (velocity dependent) ankle stiffness. Variation of stiffness over the applied frequencies forms the basis for quantifying spasticity via a total and an elastic path length parameter. Values are compared to normative data to assess the degree of ankle spasticity. Changes of total and elastic path length over time and across treatments permit tracking changes in spasticity. The magnitude of, and variations in, net passive stiffness may be used to assess contracture as well.

For more information contact:
Robert Price, M.S.M.E.
Research Scientist
UW Dept. of Rehabilitation Medicine
206-543-3720
pricer@u.washington.edu