B. Perrouin-Verbe

The influence of gait speed on co-activation in unilateral spastic cerebral palsy children☆

BACKGROUND Physiological co-activation of antagonistic muscles during gait allows stability of loaded joints. Excessive co-activation restrains motion and increases energy expenditure. Co-activation is increased by gait speed and in the case of upper motor neuron lesions. This study aimed to assess the pathological component of co-activation in children with unilateral cerebral palsy. METHODS 10 children with unilateral cerebral palsy and 10 typically developing children walked at spontaneous, slow and fast speeds. The spatio-temporal parameters and electromyographic activity of the rectus femoris, vastus medialis, semi-tendinosus, tibialis anterior and soleus of both lower limbs were recorded. A co-activation index was computed from the EMG envelopes. A mixed linear model was used to assess the effect of walking speed on the index of the antagonistic muscle couples (rectus femoris/semi-tendinosus, vastus medialis/semi-tendinosus and tibialis anterior/soleus) in the different limbs. FINDINGS A greater effect of walking speed on co-activation was found in the involved limbs of children with cerebral palsy for all muscle couples, compared with their uninvolved limbs and the limbs of typically developing children. In typically developing children, but not in children with cerebral palsy, the effect of gait speed on the co-activation index was lower in the rectus femoris/semi-tendinosus than in the other agonist/antagonist muscle couples. INTERPRETATIONS In children with cerebral palsy, a pathological component of muscle activation might be responsible for the greater increase in co-activation with gait speed in the involved limb. Altered motor control could explain why the co-activation in the rectus femoris/semi-tendinosus couple becomes more sensitive to speed.

Unstable gait due to spasticity of the rectus femoris: gait analysis and motor nerve block.

We present the case of a 54 year-old man presenting with a right Brown-Séquard plus syndrome (BSPS) after a traumatic cervical spinal cord injury. After being operated on with selective tibial neurotomy and triceps surae lengthening because of a right spastic equinus foot, he developed a gait disorder at high speed. The patient complained about an instability of the right knee. Observational gait analysis exhibited an oscillating, flexion/extension motion of the right knee during stance, which was confirmed by gait analysis. Dynamic electromyographic recordings exhibited a clonus of the right rectus femoris (RF) during stance. The spastic activity of the RF and the abnormal knee motion totally reversed after a motor nerve block of the RF, as well as after botulinum toxin type A injection into the RF. We emphasize that complex, spastic gait disorders can benefit from a comprehensive assessment including gait analysis and nerve blocks.

Does muscle coactivation influence joint excursions during gait in children with and without hemiplegic cerebral palsy? Relationship between muscle coactivation and joint kinematics☆

BACKGROUND The theoretical role of muscle coactivation is to stiffen joints. The aim of this study was to assess the relationship between muscle coactivation and joint excursions during gait in children with and without hemiplegic cerebral palsy. METHODS Twelve children with hemiplegic cerebral palsy and twelve typically developing children underwent gait analysis at three different gait speeds. Sagittal hip, knee, and ankle kinematics were divided into their main components corresponding to joint excursions. A coactivation index was calculated for each excursion from the electromyographic envelopes of the rectus femoris/semitendinosus, vastus medialis/semitendinosus, or tibialis anterior/soleus muscles. Mixed linear analyses of covariance modeled joint excursions as a function of the coactivation index and limb. FINDINGS In typically developing children, increased coactivation was associated with reduced joint excursion for 8 of the 14 linear models (hip flexion, knee loading, knee extension in stance, knee flexion in swing, ankle plantarflexion from initial contact to foot-flat, ankle dorsiflexion in stance and in swing). Conversely, ankle plantarflexion excursion at push-off increased with increasing tibialis anterior/soleus coactivation. In the involved limbs of the children with cerebral palsy, knee loading, ankle plantarflexion at push off, and ankle dorsiflexion in swing decreased, while hip extension increased, with increasing muscle coactivation. INTERPRETATION The relationships between muscle coactivation and joint excursion were not equally distributed in both groups, and predominant in typically developing children. The results suggest that excessive muscle coactivation is not a cause of stiff-knee gait in children with hemiplegic cerebral palsy, but appears to be related to spastic drop foot.

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

OBJECTIVE To address the roles and mechanisms of co-activation in two flexor/extensor pairs during elbow extension in children with cerebral palsy (CP). METHODS 13 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. RESULTS During 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. CONCLUSIONS Abnormal 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. SIGNIFICANCE Co-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

BACKGROUND Stiff 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. OBJECTIVE The 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. PATIENTS AND METHODS An 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. RESULTS Compared 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. CONCLUSION This 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.

Spinal cord injury associated with cervical spinal canal stenosis: Outcomes and prognostic factors

OBJECTIVES To specify outcomes and identify prognostic factors of neurologic and functional recovery in patients with an acute traumatic spinal cord injury (SCI) associated with cervical spinal canal stenosis (SCS), without spinal instability. METHODS A retrospective study was conducted using data from a Regional Department for SCI rehabilitation in France. A description of the population characteristics, clinical data and neurological and functional outcomes of all patients treated for acute SCI due to cervical trauma associated with SCS was performed. A statistical analysis provided insights into the prognostic factors associated with the outcomes. RESULTS Sixty-three patients (mean age 60.1 years) were hospitalized for traumatic SCI with SCS and without instability between January 2000 and December 2012. Falls were the most frequent cause of trauma (77.8%). At admission, most patients had an American Spinal Injury Association Impairment Scale (AIS) grade of C (43.3%) or D (41.7%) and the most frequent neurological levels of injury were C4 (35.7%) and C5 (28.6%). Clinical syndromes were frequently identified (78.6%), with the most frequent being the Brown-Sequard plus syndrome (BSPS) (30.9%), followed by central cord syndrome (CCS, 23.8%). Almost 80% of survivors returned to the community, 60% were able to walk and 75% recovered complete voluntary control of bladder function. Identified prognostic factors of favourable functional outcomes were higher AIS at admission, age under 60 years and presence of BSPS or CCS. CONCLUSION Traumatic SCI, associated with SCS results mostly in incomplete injuries, can cause various syndromes and is associated with favourable functional outcomes.