Spastic velocity threshold constrains functional performance in cerebral palsy

Objectives: To evaluate a quantitative, velocity-based assessment of spasticity in the quadriceps and hamstrings muscles of children with cerebral palsy (CP) and to show the effects of spasticity in constraining knee velocities during fast gait. Design: A quantitative comparison of neuromuscular and biomechanical performance in patients with CP and controls without CP. Setting: Movement analysis laboratory within a university clinical referral center. Participants: A convenience sample of 18 ambulatory patients with CP and 11 control subjects without CP. Interventions: Not applicable. Main Outcome Measures: Spastic threshold velocity recorded from electromyographic response during passive isovelocity knee movement was compared with knee angular velocity during fast walking, Gross Motor Function Measure (GMFM) scores. and Ashworth Scale score. Results: Patients with measurable spasticity showed slower peak knee angular velocity during walking than patients without spasticity (P<.005). A significant correlation existed between spastic threshold velocity and peak knee angular velocity during fast walking (r=.85, P<.001). Spastic threshold velocity correlated significantly with GMFM (r=.58, P<.05) but not with Ashworth score. Conclusions: The velocity dependency of spasticity can be measured by electromyograph and dynamometer to determine spastic threshold velocity. Spastic threshold velocity correlated with limitations in joint angular velocity during walking and functional performance.