Gastrocnemius medialis Muscle-tendon unit Properties do not differ between Children with unilateral and bilateral spastic Cerebral Palsy

Most of the studies investigating lower limb muscle-tendon properties in individuals with spastic cerebral palsy (SCP) often include both unilaterally and bilaterally affected individuals. Although known distinctions exist between groups (e.g., type of deformities, severity of SCP), there is yet no information about possible differences in the muscle-tendon units. Such information would help to answer the question whether both groups should be separately investigated in future studies due to existent heterogeneity, and particularly treated differently due to specific muscle-tendon characteristics. Therefore, the main aim of this retrospective study was to determine whether differences in ankle joint function and gastrocnemius medialis (GM) muscle-tendon properties exist between children and adolescents with unilateral and bilateral SCP. Are there any differences in ankle joint function and GM muscle-tendon properties at rest between children and adolescents with unilateral and bilateral SCP? Datasets of 14 children and adolescents with unilateral (10.0 ± 2.4 years) and 18 with bilateral SCP (10.8 ± 2.5 years) were analyzed in this retrospective study. Ankle joint range of motion, maximum dorsiflexion angle, isometric muscle strength, and muscle-tendon properties of the GM muscle-tendon unit (e.g., muscle belly and tendon lengths, fascicle lengths, muscle thickness and volume, tissue length changes) of the (more) affected leg were determined by use of isokinetic dynamometry [1] and 3D freehand ultrasound [2], respectively. Statistical analyses (α = 0.05) were performed with independent t-tests or Mann-Whitney tests depending on (non-) normal distribution of the variables. Furthermore, effect sizes (Cohen’s d) were calculated [3]. Anthropometric characteristics did not differ between groups (Table 1). Furthermore, our preliminary results show no significant differences in any assessed parameter (Table 1) between the individuals with unilateral and bilateral SCP (p > 0.05), whereby small to medium effect sizes were observed (i.e., d > 0.6 for muscle thickness, as well as lengthening of the muscle-tendon unit and fascicles). Table 1. Ankle joint function and gastrocnemius medialis (GM) muscle-tendon unit (MTU), muscle belly, and Achilles tendon (AT) properties at rest (0 Nm externally applied torque) in children with unilateral and bilateral spastic cerebral palsy (SCP). Cohen’s d = effect size: small effect: = 0.2; medium effect: = 0.5; large effect: = 0.8; normalized: Values are normalized to lower leg length.Download : Download high-res image (186KB)Download : Download full-size image Our preliminary results indicate that the GM muscle-tendon unit seems to be similarly developed in children and adolescents with unilateral and bilateral SCP, who are ambulatory and well-functioning. However, to gain a holistic view and to come to a conclusion, our investigations, which further involve comparisons of gait parameters and the related tissue behavior (e.g., muscle-tendon lengthening behavior during gait, muscle forces, joint contact forces), are currently ongoing. Acknowledgements: We acknowledge the financial support of the Austrian Academy of Sciences for Andreas Habersack, who is a recipient of a DOC Fellowship (25940) at the Department of Orthopaedics and Trauma, Medical University of Graz, and the Institute of Human Movement Science, Sport and Health, University of Graz.