A modified surface EMG biomarker for gait assessment in spastic cerebral palsy.

Abstract

Muscle clinical metrics are crucial for spastic cocontraction management in children with Cerebral Palsy (CP). We investigated whether the ankle plantar flexors cocontraction index (CCI) normalized with respect to the bipedal heel rise (BHR) approach provides more robust spastic cocontraction estimates during gait than those obtained through the widely accepted standard maximal isometric plantar flexion (IPF). Ten control and 10 CP children with equinus gait pattern performed the BHR and IPF testing and walked barefoot 10-m distance. We compared agonist medial gastrocnemius EMG during both testing and CCIs obtained as the ratios of antagonist EMG during swing phase of gait and either BHR or IPF agonist EMG. Agonist EMG values from the BHR were: (i) internally reliable (Cronbach's α=0.993), (ii) ~50±0.4% larger than IPF, (iii) and positively correlated. Derived CCIs were significantly smaller (p<0.05) in both populations. The bipedal heel rise approach may be accurate enough to reveal greater agonist activity of plantar flexors than the maximal isometric plantar flexion and seems to be more appropriate to obtain cocontraction estimates during swing of gait. This modified biomarker may represent a step forward towards improved accuracy of spastic gait management in pediatric.