The effects of time after stroke and selected therapeutic techniques on quadriceps muscle tone in stroke patients

Ankle stiffness and tissue compliance in stroke survivors: A validation of Myotonometer measurements11No commercial party having a direct financial interest in the results of the research supporting this article has or will confer a benefit upon the author(s) or upon any organization with which the author(s) is/are associated

OBJECTIVE

To determine the construct validity of Myotonometer measurements of tissue compliance as being reflective of ankle plantarflexor tone.

DESIGN

Cross sectional.

SETTING

Motor performance research laboratory.

PARTICIPANTS

Twenty-three stroke survivors (67.5+/-10.9y) and 24 control subjects (71.2+/-9.0y) recruited from the community.

INTERVENTIONS

Not applicable. Main outcome measures Plantarflexor tone was measured using the Modified Ashworth Scale (MAS), ankle stiffness (total, passive, intrinsic and reflex components) was quantified using a torque motor, and tissue compliance during relaxation and activation of the plantarflexors was measured with the Myotonometer.

RESULTS

MAS scores in the stroke group ranged from 1 to 4, whereas all control subjects had normal tone. Mean total ankle stiffness was higher in the stroke group than in the control group (P<.02), mainly due to elevated passive stiffness (P<.03). Compliance did not change as a function of muscle activation in stroke, but it decreased when control subjects contracted their plantarflexors (P<.04). The difference in Myotonometer measurements acquired during active and relaxed states was associated with total ankle stiffness and, specifically, intrinsic stiffness. The relationships were strongest when only stroke data were considered.

CONCLUSIONS

Stiffness and compliance measures distinguished between control subjects and persons with hypertonia secondary to stroke. Compliance differences in the relaxed and active gastrocnemius muscle reflected intrinsic stiffness associated with the contractile elements of the plantarflexor group of muscles as a whole.

A video-based version of the pendulum test: technique and normal response

The pendulum test, where the leg is dropped and the knee allowed to swing passively in the manner of a pendulum, has been recognized as a reliable and potentially valuable measure of hypertonia. In this study the traditional form of the test, where a goniometer is attached to the leg, has been replaced by a procedure involving computerized video motion analysis. Using 77 control subjects, a battery of 10 amplitude and time-based measures were obtained for purposes of investigating reliable and valid indicators of the damped, unsustained, oscillatory motion that characterizes this test. The results from the control subjects were congruous with those obtained by other workers using the goniometric version of the test. The measures of the response considered in this study showed evidence of increasing resistance to pendular passive joint motion with advancing age. Retest reliability of pendulum test responses in 14 subjects examined on average 26.8 days apart, produced Intraclass Correlation (2,1) values for the entire pendulum test response of an average of 0.84. It is concluded that the video-based pendulum test is a simple reliable source of measures with considerable potential for the clinical and physiological investigation of neurological and nonneurological features of normal and abnormal passive joint motion, and as a standard against which the effects of therapeutic intervention, such as medication, may be evaluated.