Biomechanical and electromyographic assessment of spastic hypertonus in motor complete traumatic spinal cord-injured individuals.

ABSTRACT

STUDY DESIGN: Between-groups design with repeated measures. OBJECTIVE: To quantify spastic hypertonia in spinal cord-injured (SCI) individuals. SETTING: Rehabilitative Center, Italy. SUBJECTS: 29 individuals with a motor complete SCI (American Spinal Injury Association impairment scale grade A or B) and 22 controls. METHODS: According to the modified Ashworth scale (MAS), patients were subgrouped as SCI-1 (MAS=1, 1+) and SCI-2 (MAS=2, 3). Passive flexo-extensions of the knee were applied using an isokinetic device (LIDO Active) at 30°, 60°, 90° and 120° s(-1). We measured the peak torque, mean torque (MT) and work. Simultaneous electromyography (EMG) was recorded from leg muscles. RESULTS: At the speed of 120° s(-1) all SCI-2 patients presented EMG reflex activities in the hamstring muscle. All biomechanical parameter values increased significantly according to speed, but analysis of variance revealed a significant interaction between the angular velocity and group (F(d.f. 6, 138) = 8.89, P < 0.0001); post hoc analysis showed significantly greater torque parameter values in the SCI-2 group compared with the SCI-1 group and the control group at 90° and 120° s(-1). Receiver operating characteristic curves showed that using peak torque values the probability of correctly classifying a patient into SCI-1 and SCI-2 was 95%, compared with 70% for MT and 68% for work. CONCLUSIONS: The isokinetic device is useful for distinguishing individuals with a high level of spastic hypertonus. Examination of EMG activity may help ascertain whether increased muscle tone is caused by reflex hyper excitability and to determine whether muscle spasm is present. Peak torque and simultaneous EMG assessment should be considered for the evaluation of individuals with SCI in the rehabilitative context, that is, in measuring therapeutic interventions.