Biomechanic characteristics of patients with spastic and dystonic hypertonia in cerebral palsy

Lebiedowska MK, Gaebler-Spira D, Burns RS, Fisk JR. Biomechanic characteristics of patients with spastic and dystonic hypertonia in cerebral palsy. Arch Phys Med Rehabil 2004;85:875-80. Objective To determine what biomechanic characteristics of knee joint motion and walking show potential to quantitatively differentiate spasticity and dystonia in cerebral palsy (CP). Design Descriptive measurement study. Setting University hospital. Participants Seventeen pediatric and adult patients with CP. Interventions Not applicable. Main outcome measures We measured the resistance of the knee joint at different velocities and positions, maximum muscle activation during external motion, amplitude of knee tendon reflexes, maximum isometric flexion and extension torques, velocity of walking, and knee kinematics during the gait cycle. Patients were classified into 2 groups (dystonia or spasticity) if at least 2 of 3 physicians agreed that a prominent component of dystonia was present. Results Patients with dystonia had a greater degree of cocontraction and an increased resistance to external motion at slow velocities. The tendon reflexes were almost normal in patients with dystonia, whereas they were increased in patients with spasticity. Muscle strength was more impaired in patients with dystonia, probably as a result of greater muscle cocontraction. They also walked slower, with smaller knee ranges of motion, during the stance phase of walking. Conclusions The measurement of resistance and of muscle activation during passive motion and tendon reflexes shows potential to differentiate dystonia from spasticity in CP patients with a mixed form of hypertonia. More studies are needed to confirm these results.