Fabien Leboeuf

Impact of muscle activation on ranges of motion during active elbow movement in children with spastic hemiplegic cerebral palsy

BACKGROUNDnChildren with spastic hemiplegic cerebral palsy are restricted in their daily activities due to limited active ranges of motion of their involved upper limb, specifically at the elbow. Their impaired muscles are frequently targeted by anti-spastic treatments that reduce muscle tone. But these treatments do not necessarily improve the limb function. There is a lack of comprehensive knowledge of the quantitative relations between muscle activation and joint active ranges of motion. Consequently, the objective of this study is to quantify the impact of muscle activation on the elbow active ranges of motion.nnnMETHODSnDuring voluntary elbow pronation/supination and extension/flexion movements, kinematic and electromyographic measurements were collected from the involved upper limb of 15 children with spastic hemiplegic cerebral palsy (mean age=8.7 years, standard deviation=2.2) and the dominant upper limb of 15 age-matched children who are typically developing. Representative indicators of the muscle activation, such as the muscle co-activation, were extracted from the electromyographic measurements.nnnFINDINGSnMuscle co-activation in the involved upper limb accounted for 78% and 59% of the explained variance of the supination and extension limited active ranges of motion respectively. The agonist and antagonist muscle activations were both longer in the involved upper limb.nnnINTERPRETATIONSnThis study succeeded in quantifying the impact of longer antagonist muscle activation on decreased elbow active ranges of motion in children with spastic hemiplegic cerebral palsy. Longer agonist muscle activation suggests that strengthening agonist muscles could increase the extension and supination ranges of motion, which constitutes a perspective of future clinical studies.

Pathological and physiological muscle co-activation during active elbow extension in children with unilateral cerebral palsy

OBJECTIVEnTo address the roles and mechanisms of co-activation in two flexor/extensor pairs during elbow extension in children with cerebral palsy (CP).nnnMETHODSn13 Typically Developing (TD) and 13 children with unilateral spastic CP performed elbow extension/flexion at different speeds. Elbow angle and velocity were recorded using a 3D motion analysis system. The acceleration and deceleration phases of extension were analyzed. Co-activation of the brachioradialis/triceps and biceps/triceps pairs was computed for each phase from surface electromyographic signals. Statistical analysis involved linear mixed effects models and Spearman rank correlations.nnnRESULTSnDuring the acceleration phase, there was strong co-activation in both muscle pairs in the children with CP, which increased with speed. Co-activation was weak in the TD children and it was not speed-dependent. During the deceleration phase, co-activation was strong and increased with speed in both groups; co-activation of brachioradialis/triceps was stronger in children with CP, and was negatively correlated with extension range and positively correlated with flexor spasticity.nnnCONCLUSIONSnAbnormal patterns of co-activation in children with CP were found throughout the entire movement. Co-activation was specific to the movement phase and to each flexor muscle.nnnSIGNIFICANCEnCo-activation in children with CP is both physiological and pathological.

Neurotomy of the rectus femoris nerve: Short-term effectiveness for spastic stiff knee gait: Clinical assessment and quantitative gait analysis

BACKGROUNDnStiff knee gait is a troublesome gait disturbance related to spastic paresis, frequently associated with overactivity of the rectus femoris muscle in the swing phase of gait.nnnOBJECTIVEnThe aim of this study was to assess the short-term effects of rectus femoris neurotomy for the treatment of spastic stiff-knee gait in patients with hemiparesis.nnnPATIENTS AND METHODSnAn Intervention study (before-after trial) with an observational design was carried out in a university hospital. Seven ambulatory patients with hemiparesis of spinal or cerebral origin and spastic stiff-knee gait, which had previously been improved by botulinum toxin injections, were proposed a selective neurotomy of the rectus femoris muscle. A functional evaluation (Functional Ambulation Classification and maximal walking distance), clinical evaluation (spasticity - Ashworth scale and Duncan-Ely test, muscle strength - Medical Research Council scale), and quantitative gait analysis (spatiotemporal parameters, stiff knee gait-related kinematic and kinetic parameters, and dynamic electromyography of rectus femoris) were performed as outcome measures, before and 3 months after rectus femoris neurotomy.nnnRESULTSnCompared with preoperative values, there was a significant increase in maximal walking distance, gait speed, and stride length at 3 months. All kinematic parameters improved, and the average early swing phase knee extension moment decreased. The duration of the rectus femoris burst decreased post-op.nnnCONCLUSIONnThis study is the first to show that rectus femoris neurotomy helps to normalise muscle activity during gait, and results in improvements in kinetic, kinematic, and functional parameters in patients with spastic stiff knee gait.

Modulation of lower limb muscle activity induced by curved walking in typically developing children.

• Muscle activity during curved walking was investigated in typically developing children.

O 111 - accuracy of the conventional gait model: preliminary results

The Conventional Gait Model (CGM), distributed as Vicon Plugin gait (Vicon PiG) became a standard in the field of 3D Clinical Gait Analysis. Its reliability is assessed thought repeatability tests. On the other hand, accuracy of the CGM in terms of underlying bone motion has never been quantified. It’s all the more important CGM outputs might orientate a patient towards bone surgery. Thanks to a consensus, data from invasive approaches are available in open-access. They can serve as basis for model validation. This communication proposes to assess the knee kinematic accuracy of the CGM with fluoroscopic data during a gait cycle.

P 120 - CGM2 : Proposal of an evolved conventional gait model

Developed during the 1990s, the Conventional Gait Model (CGM), distributed as Vicon Plugin gait (Vicon PiG), has formed the basis of gait analysis in many clinical gait analysis services. However, it is also associated with several shortcomings and producing data which is inadequate for musculoskeletal simulation. Our communication aims to propose an evolved gait model.

Estimation of muscle activation during different walking speeds with two mathematical approaches compared to surface EMG

BACKGROUNDnMuscle force estimation could improve clinical gait analysis by enhancing insight into causes of impairments and informing targeted treatments. However, it is not currently standard practice to use muscle force models to augment clinical gait analysis, partly, because robust validations of estimated muscle activations, underpinning force modelling processes, against recorded electromyography (EMG) are lacking.nnnRESEARCH QUESTIONnTherefore, in order to facilitate future clinical use, this study sought to validate estimated lower limb muscle activation using two mathematical models (static optimisation SO, computed muscle control CMC) against recorded muscle activations of ten healthy participants.nnnMETHODSnParticipants walked at five speeds. Visual agreement in activation onset and offset as well as linear correlation (r) and mean absolute error (MAE) between models and EMG were evaluated.nnnRESULTSnMAE between measured and recorded activations were variable across speeds (SO vs EMG 15-68%, CMC vs EMG 13-69%). Slower speeds resulted in smaller deviations (mean MAEu202f<u202f30%) than faster speeds. Correlation was high (r > 0.5) for only 11/40 (CMC) and 6/40 (SO) conditions (muscles X speeds) compared to EMG.nnnSIGNIFICANCEnModelling approaches do not yet show sufficient consistency of agreement between estimated and recorded muscle activation to support recommending immediate clinical adoption of muscle force modelling. This may be because assumptions underlying muscle activation estimations (e.g. muscles anatomy and maximum voluntary contraction) are not yet sufficiently individualizable. Future research needs to find timely and cost efficient ways to scale musculoskeletal models for better individualisation to facilitate future clinical implementation.

Évaluation de l’effet de la pente sur l’activation musculaire et la cinématique du genou de l’enfant crouch gait : quelle pistes pour la rééducation ?

Introduction Les reeducateurs manquent de preuves concernant leurs interventions aupres des enfants paralyses cerebraux (PC), notamment sur l’utilisation du plan incline pour ameliorer la marche en situation ecologique. Nous nous proposons d’evaluer l’interet de la pente en reeducation sur la cinematique du genou et les activations musculaires de l’enfant diplegique ayant une marche de type crouch gait . Materiel et methodes Cinq enfants diplegiques et six enfants a developpement typique ont participe a cette etude. Nous avons mesure les parametres spatiotemporels, cinematiques et musculaires de 8xa0muscles des membres inferieurs lors d’une marche sur sol plan, puis sur tapis roulant pour trois conditions de pentes et a l’issue d’un entrainement de 6xa0min a 7°. Resultats La course articulaire du genou augmente avec la pente pendant le cycle de marche. Les enfants des deux groupes maintiennent leur extension en phase d’appui et augmentent leur flexion au contact initial et en fin de phase oscillante. Avec la pente, ils ont tendance a augmenter l’activation de tous les muscles etudies. La strategie de propulsion est cependant differente entre les deux groupes. Aucune difference significative n’a ete trouvee a l’issue de l’entrainement de 6xa0min a 7°. Discussion–conclusion Le but de la reeducation est d’ameliorer l’extension de genou et la force musculaire chez l’enfant PC avec marche en crouch . La marche sur tapis roulant ascendant y contribue. L’entrainement de 6xa0min propose dans ce protocole ne suffisait pas a mettre en evidence un post-effet sur la marche a 0°. Les perspectives sont d’evaluer les effets d’une reeducation sur plan incline de plusieurs semaines. D’autres populations comme les enfants hemiplegiques et ceux ayant une marche genou raide pourront etre egalement inclus.