Kaat Desloovere

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.

O 107 – Impact of subject-specific musculoskeletal geometry on estimated joint kinematics, joint kinetics and muscle forces in typically developing children

1.. Introduction: Gait analysis together with musculoskeletal modeling can be used to calculate muscle forces and assess pathological gait [1]. No generic, pediatric musculoskeletal models are available and, therefore, linear scaling methods are commonly used to personalize a generic, adult musculoskeletal model to the child’s anthropometry. 2. Research: How different are joint kinematics, joint kinetics and muscle force estimates of generic scaled models compared to medical-imaging based models in typically developing (TD) children? 3. Methods: 3D motion capture data and magnetic resonance images (MRI) of a TD boy (age: 8 years; height: 1.23 m; weight: 20.4 kg) were collected. Two musculoskeletal OpenSim models were created: (1) a scaled generic model (M_gen), and (2) a MRI-based model, which included subject-specific musculoskeletal geometry (M_mri) [2]. Joint kinematics, joint kinetics and muscle forces were calculated for each model using OpenSim 3.3 [3]. Joint kinematics, joint kinetics, muscle force waveforms, as well as femoral anteversion angle, neck-shaft angle and hip joint centre location were compared between both models. 4. Results: Joint kinematics and joint kinetics were surprisingly similar between the M_gen and M_mri with root-mean-square-differences below 2.8° and 0.05Nm/kg for joint angles and moments, respectively (Fig. 1, Fig. 2). Depending on the analyzed muscle, differences in muscle forces varied substantially (up to 230% difference) between the M_gen and M_mri (Fig. 3). Femoral anteversion and neck-shaft angles differed between M_gen and M_mri by 12 and 5 degrees, respectively. The hip joint centre position differed between both models by 5, 15 and 6 mm in the anterior/posterior, superior/inferior and medial/lateral direction, respectively.