Signs of spasticity during walking in children with spastic cerebral palsy
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Introduction: Spasticity is one of the most common neurological impairment that can lead to gait problems in cerebral palsy (CP). It limits function by reducing normal muscle lengthening and voluntary activation during gait. Assessments of spasticity is usually done in a clinical setting by passively stretching the muscle and classifying the resistance felt, but its relation to spasticity during gait is not clear. During the mid-stance phase in the gait cycle the calf muscles are stretched, possibly resulting in a spastic contraction. Aim: The aim of the study is to see if there is a relation between muscle activity during walking and a passive test for spasticity, in children with spastic cerebral palsy. Method: Twelve children with CP, 7-16 years and 7 typically developing (TD) children 6-15 years conducted a 3D gait analysis with surface EMG from m. soleus (SOL) and m. gastrocnemius medialis (GM). Subjects were instructed to walk at self-selected walking speed. The EMG signals were band-pass filtered (20-400 Hz) and the root mean square amplitude was calculated in ten 10 % periods during stance and normalized to its maximal. The degree of spasticity was evaluated with the clinical Tardieu Test with the knee flexed in 90 degrees. Both limbs in bilateral CP, most affected limb in unilateral CP and left limb in TD were used. The limbs from the CP participants were classified upon clinical score from Modified Tardieu Scale: 1) no catch, 2) catch. Results: Legs of children with CP with and without catch had significantly more activation in GM and SOL during 10-20 % of stance compared to TD (p<0.05). CP with catch had statistically non-significant more GM and SOL activation in that period than CP without catch (p=0.335, p=0.338). Both CP groups had higher ankle angular velocities during 10-20 % than TD children (p<0.05). Conclusion: While the GM and SOL of TD are hardly active during 10-20 % of stance, those muscles and especially the SOL were more active in children with CP. Although not statistically significant, this seems to be more present in children with a clinically detected catch. This indicates that it is possible to observe signs of spasticity in stance phase during walking. Ankle angular velocities were higher during the Tardieu Test than during stance. This may point to a discrepancy between gait and the Tardieu Test, in relation to how a spastic reflex is elicited during the passive test, and in normal walking.