Assessing the spastic condition of individuals with upper motoneuron involvement: Validity of the myotonometer

Objectives: To examine the validity of a newly developed tissue compliance device to measure muscle tone and to quantify the level of severity of the spastic condition. Design: Validity study. Setting: Research laboratory. Participants: Twenty subjects, 10 with upper motoneuron (UMN) disorders (spastic-type cerebral palsy or adult-onset cerebrovascular accident) who comprised the experimental group; and 10 nondisabled, age-equivalent subjects, who served as controls. Interventions: Not applicable. Main Outcome Measures: Muscle tone of the biceps brachii muscle was assessed with the Myotonometer(TM) and Modified Ashworth Scale (MAS). The Myotonometer was used to quantify the muscle's resistance to stretch in a relaxed state and during maximal voluntary isometric contractions. Analyses of variance determined differences among subjects. Correlations between Myotonometer measurements and MAS scores were calculated. Results: Significant differences (p < .05) were observed between experimental and control groups and between the involved and uninvolved extremities of the experimental group with Myotonometer measurements. Correlations between MAS scores and Myotonometer measurements ranged from .64 to .81. Conclusion: The Myotonometer effectively identified differences in the spastic condition of the biceps brachii muscle in subjects with UMN involvement, Correlations with the MAS were moderate to high.