Short communicationO 021 – Does including EMG data in the estimation of muscle forces alter the evaluation of the effect of botulinum toxin injections?
Introduction
Children with cerebral palsy (CP) present altered electromyography (EMG) activity [1]. Botulinum Toxin Injections (BTI) are used to reduce the spasticity of specific muscles. Muscle forces can be calculated with musculoskeletal models by either a static optimization (SO), which does not take EMG activity into account, or an EMG-constrained optimization. Considering children with CP have distinct EMG deviations, an EMG-constrained approach seems more appropriate.
Section snippets
Research question
Does including EMG data in the estimation of muscle forces alter the evaluation of the effect of BTI on muscle force distribution?
Methods
Fourteen children with spastic diplegic CP (7.25 ± 1.15 years) and ten typically developing (TD) children (8.00 ± 1.60 years) were included. All CP children received multilevel BTI in the hamstrings and psoas and 12 children also in the gastrocnemius. All children joined a gait analysis session, the CP children prior and six weeks after BTI. Three representative strides of the right and left limb were selected. Marker trajectories (Vicon, Oxford Metrics, UK) and ground reaction forces (AMTI,
Results
Muscle forces were significantly increased (p < 0.05) when using EMGcon compared to SO for both TD and CP children for all phases of the gait cycle (Fig. 1), expect for the gastrocnemius in SS. Significantly decreased muscle forces were found in IDS post BTI in the medial hamstrings and gastrocnemius when using both EMGcon and SO. For the gastrocnemius, a significantly higher muscle force in TDS was only observed when using SO.
Discussion
Compared to SO, EMGcon led to higher muscle forces in TD and CP children, as increased co-contraction was included. The use of SO, without accounting for increased co-activation, affects the observed muscle force distribution and therefore can alter the observed treatment effect at a muscle level.
References (1)
Electromyogr. Clin. Neurophysiol.
(1996)