Use of a hand-held dynamometer and a Kin-Com dynamometer for evaluating spastic hypertonia in children: a reliability study.

BACKGROUND AND PURPOSE Studies in subjects with spastic hypertonia indicate that the higher resistance to stretch in the spastic muscles is not only due to hyperactive stretch reflexes but also to changes in the muscle-tendon unit (nonreflex components). The aim of this study was to compare the test-retest reliability of two methods: hand-held dynamometry and isokinetic dynamometry for the evaluation of nonreflex and reflex-mediated resistive force in the plantar flexors of young children with spastic cerebral palsy (CP). SUBJECTS Ten children 2 to 7 years 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 dorsiflexions executed at low and high velocities was evaluated twice at a 1-month interval with a Penny and Giles myometer (a hand-held dynamometer) and a Kin-Com dynamometer. The electromyographic activity of the soleus and tibialis anterior muscles was recorded during Kin-Com testing to detect unwanted activity during low-velocity tests and to identify trials with a reflex response during high-velocity tests. RESULTS High intraclass correlation coefficients (ICCs) for the resistive force values recorded at the test and retest were computed for both the myometer (ICCs = .79 and .90) and the Kin-Com (ICCs = .84 and .84) at low and high velocities, respectively. Coefficients of variation for force values measured at a 1-month interval at low and high velocities were 13.9% and 13.2% with the myometer and 11.8% and 12.8% with the Kin-Com. CONCLUSION AND DISCUSSION The results suggest that the myometer can provide a measure of spastic hypertonia with a reproducibility and a variation in the measures that compare to those of a computer-controlled dynamometer. From a clinical point of view, the myometer is simpler and cheaper to use given the lower cost and the little time required for testing and data analysis. Care must be taken to select a velocity that is low enough not to evoke a stretch reflex (to isolate nonreflex components) and another that is high enough to elicit a reflex response, so that it becomes possible to differentiate the reflex and non-reflex components involved in spasticity. Such a distinction is important for the choice of treatment procedures.