USE OF A HAND-HELD DYNAMOMETER AND A KIN-COM(R) DYNAMOMETER FOR EVALUATING SPASTIC HYPERTONIA IN CHILDREN - A RELIABILITY STUDY

Background and Purpose. Studies in subjects with spastic hypertonia in dicate that the higher resistance to stretch in the spastic muscles is not only due to hyperactive stretch reflexes but also to changes in t he muscle-tendon unit (nonreflex components). The aim of this study wa s to compare the test-retest reliability of two methods: hand-held dyn amometry and isokinetic dynamometry for the evaluation of nonreflex an d reflex-mediated resistive force in the plantarflexors of young child ren with spastic cerebral palsy (CP). Subjects. Ten children 2 to 7 ye ars of age with a diagnosis of spastic CP (either diplegia [n = 7] or hemiplegia [n = 3]) participated in the study. Methods. The resistive force recorded at 0 degrees of dorsiflexion during passive ankle dorsi flexions executed at low and high velocities was evaluated twice at a I-month interval with a Penny and Giles myometer (a hand-held dynamome ter) and a Kin-Com(R) dynamometer. The electromyographic activity of t he soleus and tibialis anterior muscles was recorded during Kin-Com(R) testing to detect unwanted activity during low-velocity tests and to identify trials with a reflex response during high-velocity tests. Res ults. High intraclass correlation coefficients (ICCs) for the resistiv e force values recorded at the test and retest were computed for both the myometer (ICCs = .79 and .90) and the Kin-Com(R) (ICCs = .84 and . 84) at low and high velocities, respectively. Coefficients of variatio n for force values measured at a 1-month interval at low and high velo cities were 13.9% and 13.2% with the myometer and 11.8% and 12.8% with the Kin-Com(R). Conclusion and Discussion The results suggest that th e myometer can provide a measure of spastic hypertonia with a reproduc ibility and a variation in the measures that compare to those of a com puter-controlled dynamometer. From a clinical point of view the myomet er is simpler and cheaper to use given the lower cost and the little t ime required for testing and data analysis. Care must be taken to sele ct a velocity that is low enough not to evoke a stretch reflex (to iso late no nonreflex components) and another that is high enough to elici t a reflex response, so that it becomes possible to differentiate the reflex and nonreflex components involved in spasticity. Such a distinc tion is important for the choice of treatment procedures.