Guy Molenaers

Safety and efficacy of botulinum toxin type A following long-term use

Botulinum toxin serotype A (BoNT‐A) has long heritage of use leading to confidence in its safety and efficacy. The application of BoNT‐A does not lead to persistent histological changes in the nerve terminal or the target muscle. Clinical trials defined the safety and tolerability profile of BoNT‐A across common therapeutic indications and showed an incidence of adverse events of approximately 25% in the BoNT‐A‐treated group compared with 15% in the control group. Focal weakness was the only adverse event to occur more often following BoNT‐A treatment. Long‐term BoNT‐A administration has been assessed in various treatment settings, with the level and duration of BoNT‐A efficacy response being maintained over repeated rounds of injection with no major safety concerns. The treatment of children with cerebral palsy often require long‐term, repeated, multimuscle BoNT‐A injections that lead to the administration of comparably higher toxin doses. Despite the high total body doses used, their distribution over multiple muscles and injection sites means that systemic side effects are rare. Recent formulation changes have reduced the incidence of antibody development following treatment with BOTOX®. These findings show long‐term BoNT‐A treatment to be both safe and efficacious for a wide variety of indications.

Kinematic and kinetic asymmetry in patients with leg-length discrepancy

The symmetry index (SI), as one of methods to evaluate gait pattern in patients with leg-length discrepancy (LLD), helps to estimate the acceptable range of inequality and to determine symmetry in the kinematic and kinetic data before and after a heel lift, although this parameter has a large standard deviation that undermines its accuracy. Thirty patients with LLD were studied by a motion-analysis system and a force plate. Joint motion of the lower extremity in the sagittal plane, back movement in the coronal plane, and three-dimensional ground-reaction forces (GRFs) were registered. From a linear-regression analysis, a mean value of inequality of 2.33 cm (range, 2.12-2.54) was found to correspond to an acceptable gait symmetry. After a heel lift, the SI of the pelvic tilt at midstance and of the vertical GRF at initial contact increases significantly, but the SI of the medial GRF at terminal stance decreases. Patients with an inequality of a mean value of 0.51 cm determined by palpating bilaterally the top of the iliac crest (the TIC1 subgroup) showed a lesser value of the SI of the center of pressure in the forward direction during stance compared with the group with a mean value of inequality of 1.39 cm (the TIC2 subgroup). As a result of our findings, we conclude that the effect of the amount of correction by a heel lift on gait symmetry is unpredictable.

A multilevel approach to botulinum toxin type A treatment of the (ilio)psoas in spasticity in cerebral palsy

In spasticity, flexion deformity of the hip is frequently associated with contracture or hyper‐reflexia of the psoas muscle. Botulinum toxin type A (BTX‐A) has been used for some considerable time in the management of paediatric gait disorders. We have been using a multilevel approach to manage spasticity in cerebral palsy for several years, the combination of gait analysis and clinical evaluation being important for the selection of target muscles for BTX‐A injections. Twenty cerebral palsy children (12 female) with spasticity were treated with BTX‐A injections (BOTOX® mean dose, 2 U/kg body weight) into the psoas muscle. Patients were monitored using range of motion measurements of maximal hip extension, clinical estimates of hypertonia in the hip flexors, gait analysis (three‐dimensional kinematics and kinetics) and surface electromyography of major lower limb muscles. Full gait analysis was carried out on 12 of the patients. Significant clinical improvements were observed following 15 of the 21 psoas treatments. Furthermore, the kinematics results of gait analysis showed improvement in one or more parameters in nine of the 12 patients. In conclusion, we have demonstrated the value of a multilevel approach to BTX‐A treatment in the management of spasticity in children with cerebral palsy.

O 053 - Femoral deformities affect gait performance more than hip muscle weakness

Four hundred models were created with varying FA, NSA and muscle weakness, for one healthy child (9 years), based on marker trajectories (Vicon, Oxford Metrics, UK) and ground reaction forces (AMTI, Watertown, MA) measured during gait and starting from a scaled generic musculoskeletal model (SIMM, Motion Analysis Corp., Santa Rosa, CA). In each of the models, the FA and NSA were increased, in steps of 10° from 20° to 60° and from 120° to 160°, respectively. In all created models, the maximal isometric muscle force of the rectus femoris, gluteus maximus, gluteus medius, psoas or biceps femoris was decreased by 0% to 75% in steps of 25%. A reference gait pattern was calculated for the original scaled model based on the measured marker trajectories in Opensim 3.3, which was imposed to all models. Next, muscle forces were calculated using static optimization. If muscle forces were unable to restore the moment balance, reserve actuators were activated. These indicate the capability gap, i.e. the gap between the required hip joint torques for normal gait and the maximal joint torque the muscles could produce. A regression analysis related the FA, NSA and hip muscle weakness to the maximal absolute capability gap for the hip.