The Non-Affected Muscle Volume Compensates for the Partial Loss of Strength after Injection of Botulinum Toxin A.

Local botulinum toxin (BTX-A, Botox®) injection in overactive muscles is a standard treatment in patients with cerebral palsy. The effect is markedly reduced in children above the age of 6 to 7. One possible reason for this is the muscle volume affected by the drug. Nine patients (aged 11.5; 8.7-14.5 years) with cerebral palsy GMFCS I were treated with BTX-A for equinus gait at the gastrocnemii and soleus muscles. BTX-A was administered at one or two injection sites per muscle belly and with a maximum of 50 U per injection site. Physical examination, instrumented gait analysis, and musculoskeletal modelling were used to assess standard muscle parameters, kinematics, and kinetics during gait. Magnetic resonance imaging (MRI) was used to detect the affected muscle volume. All the measurements were carried out pre-, 6 weeks post-, and 12 weeks post-BTX-A. Between 9 and 15% of the muscle volume was affected by BTX-A. There was no effect on gait kinematics and kinetics after BTX-A injection, indicating that the overall kinetic demand placed on the plantar flexor muscles remained unchanged. BTX-A is an effective drug for inducing muscle weakness. However, in our patient cohort, the volume of the affected muscle section was limited, and the remaining non-affected parts were able to compensate for the weakened part of the muscle by taking over the kinetic demands associated with gait, thus not enabling a net functional effect in older children. We recommend distributing the drug over the whole muscle belly through multiple injection sites.

Quantification and Monitoring of the Effect of Botulinum Toxin A on Paretic Calf Muscles of Children With Cerebral Palsy With MRI: A Preliminary Study.

Background: Muscles from patients with cerebral palsy (CP) are often spastic and form contractures that limit the range of motion. Injections of botulinum toxin A (BTX) into the calf muscles are an important treatment for functional equinus; however, improvement in gait function is not always achieved. BTX is also used to test muscle weakening for risk evaluation of muscle lengthening surgery. Our aim was to assess the effect of BTX over time on calf muscle properties in pediatric CP patients with MRI. Material and Methods: Six toe-walking CP patients (mean age 11.6 years) with indication for lengthening surgery were prospectively enrolled and received BTX injections into the gastrocnemius and soleus muscles. MRI scans at 3T of the lower legs and clinical examinations were performed pre-BTX, 6 weeks (6w), and 12 weeks (12w) post-BTX. A fat-suppressed 2D multi-spin-echo sequence was used to acquire T2 maps and for segmentation. Fat fraction maps were calculated from 3D multi-echo Dixon images. Diffusion tensor imaging (DTI) with a 2D echo-planar imaging (EPI) sequence yielded maps of the mean apparent diffusion coefficient (ADC) and of the fractional anisotropy (FA). Hyperintense regions of interest (ROIs) on the T2-weighted (T2w) images at 6w were segmented in treated muscles. Mean values of T2, fat fraction, ADC, and FA were calculated in hyperintense ROIs and in reference ROIs in non-treated muscles. Results: Hyperintensity on T2w scans and increased T2 (group mean ± standard deviation: 35 ± 1 ms pre-BTX, 45 ± 2 ms at 6w, and 44 ± 2 ms at 12w) were observed in all patients at the injection sites. The T2 increase was spatially limited to parts of the injected muscles. FA increased (0.30 ± 0.03 pre-BTX, 0.34 ± 0.02 at 6w, and 0.36 ± 0.03 at 12w) while ADC did not change in hyperintense ROIs, indicating a BTX-induced increase in extracellular space and a simultaneous decrease of muscle fiber diameter. Fat fraction showed a trend for increase at 12w. Mean values in reference ROIs remained unchanged. Conclusion: MRI showed limited spatial distribution of the BTX-induced effects in pediatric CP patients. It could be a promising non-invasive tool for future studies to test BTX treatment protocols.

Walking on uneven ground: How do patients with unilateral cerebral palsy adapt?

BACKGROUND: Children with cerebral palsy experience movement disorders that influence gait stability. It is likely that gait stability further decreases when walking on uneven compared to even ground. Therefore, the aim of this study was to investigate gait on uneven ground in children with unilateral cerebral palsy. METHODS: Twenty children with unilateral cerebral palsy and twenty typically developing children performed a three-dimensional gait analysis when walking on even and uneven ground. Spatio-temporal parameters, full-body joint kinematics and centre of mass displacements were compared. FINDINGS: On uneven versus even ground, both groups showed decreased cadence, increased stance phase and double support time, increased toe clearance height, and increased knee and hip flexion during swing phase. Whereas only the typically developing children walked slower and had increased dorsiflexion and external foot progression during stance phase, only the patients showed increased stride width, increased elbow flexion (affected and non-affected side), and kept the centre of mass more medial when standing on the affected leg. INTERPRETATION: Patients and healthy children use similar adaptation mechanisms when walking on uneven ground. Both groups increased the toe clearance height by increasing knee and hip flexion during swing. However, whereas patients enlarge their base of support by increasing stride width, healthy children do so by increasing their external foot progression angle. Furthermore, patients seem to feel more insecure and hold their arms in a position to prepare for falls on uneven ground. They also do not compensate with their non-affected side for their affected side on uneven ground.

Visual targeting one step before force plates has no effect on gait parameters in orthopaedic patients during level walking.

In clinical gait analysis, it is challenging to acquire usable force plate data for a patient in a limited amount of time. The aim of this study was to compare three measurement protocols, to investigate if any one of them was more time-efficient than the others at collecting kinetic data. Three conditions were compared for 15 orthopaedic patients: 1) approaching the force plate with four steps, 2) approaching the force plate with six steps, and 3) approaching the force plate with four steps while stepping on a target one step before the first force plate. Then, the following characteristics were analysed: the rate of usable force plate steps, the spatio-temporal parameters, the full-body gait kinematics, and the lower body kinetics. For the condition with four steps and targeting, the rate of usable force plate steps was highest: 84% (6.8 usable trials out of 8.1 trials on average per patient). Left hip adduction and rotation, right shoulder flexion, and total left hip power were the gait parameters with statistically significant differences between the four and six step approach. Left cadence, right step time, left thorax lateroflexion, left shoulder abduction, total right knee power, hip rotation, thorax tilt, and head tilt on both sides were statistically different between the four step approach with targeting and without targeting. None of the differences in gait parameters (except for head tilt) were of clinical relevance. Therefore, approaching the force plate with four steps and stepping on a foot-sized target one step prior to stepping on the force plate increases the rate of usable kinetic data.

The effects of walking speed on upper body kinematics during gait in healthy subjects.

Patients undergoing a clinical gait analysis often walk slower than healthy people. However, data on how speed affects upper body movements, especially of the arms and shoulders, are scarce. Therefore, in this descriptive study, we examined how changes in walking speed affect upper-body kinematics and aspects of intersegmental coordination between upper and lower body during overground walking in a group of healthy adult subjects. Three-dimensional gait data were collected on 20 healthy subjects (aged between 22 and 31 years) walking at six speeds ranging from extremely slow to very fast. Our results showed significant speed-related changes of upper body kinematic movement curves in three aspects, namely in amplitude (curves for shoulder flexion and abduction, elbow flexion, pelvic obliquity and rotation), timing (curves for shoulder extension and abduction, elbow extension, pelvic rotation) and curve pattern (curves for shoulder and elbow flexion, shoulder rotation, pelvic tilt). The intersegmental coordination between the thorax and pelvis and arm and leg was also affected by a change of walking speed. Our data supplement the already available data in the literature examining the effects of walking speed on lower extremity motion. Furthermore, the data can be used as a reference for both basic biomechanical and clinical gait studies. The results will help in clinical practice to differentiate between effects caused by walking speed and underlying pathology.