Cybex II isokinetic dynamometer for the documentation of spasticity. Suggestion from the field.

Recent studies involving patients with CNS lesions have clearly demonstrated that agonist paresis rather than antagonist spasticity is the primary factor limiting torque production. The presence of spasticity can, nonetheless, be important because of its effect on the quality of movement and because of the propensity of spastic muscles toward contracture. Therefore, methods for more precisely documenting spasticity remain of value to those clinicians who include among their therapeutic goals the reduction of spasticity. Among the methods proposed for measuring spasticity (resistance to passive movement) are the Ashworth test and the goniometric pendulum test. Alfieri reported that the Ashworth test can provide an indication of therapeutic efficacy but is of limited objectivity because it uses an ordinal scale. The pendulum test, on the other hand, provides a more objective measurement on a continuous ratio scale. The instruments required for the pendulum test are an electrogoniometer and recording system. The Cybex® II isokinetic dynamometer,* which is available to some clinicians, can be used to perform a pendulum test because it incorporates an electrogoniometer and recorder. The purpose of this article is to describe how the Cybex® II isokinetic dynamometer can be used to document objectively spasticity in patients with CNS lesions and to discuss some limitations of the procedure. To perform a pendulum test with the Cybex® II isokinetic dynamometer, we take the following steps: 1. The patient is positioned in either a sitting or supine position on the Cybex® exertest table. 2. The patient is stabilized to the table with thigh, pelvis, and trunk straps. 3. The dynamometer input shaft is positioned laterally over the knee's axis of rotation, and the skin pad of the dynamometer lever arm is strapped just proximal to the malleoli. 4. The speed of the isokinetic dynamometer is adjusted to 300°/sec. 5. The patient is instructed to relax completely. 6. The stylus of the position angle (electrogoniometer) channel is adjusted to assure that angular recordings of knee position will fall within the range of the scale. 7. The knee is flexed by the examiner and the lower leg pushed back until the heel contacts the padded tableleg clamp. 8. A short strip of chart paper is run at 5 mm/sec to mark this position. 9. The lower leg is then raised by the examiner until the knee is fully extended. 10. Paper speed is set at 5 mm/sec. 11. The patient is reminded to relax his leg, which is then dropped by the examiner. 12. Steps 4 through 11 are performed two more times.