Exploring gastrocnemius medialis behavior during gait in children with cerebral palsy across different gait patterns

Background: Children with spastic cerebral palsy show varied gait patterns and muscle morphological alterations. We explored gastrocnemius medialis behavior during gait in typically developing children and children with cerebral palsy across different gait patterns.

Methods: Eighteen children with spasticity of the leg muscles (female: 8, age: 11.1 ± 3.3 y) with a diagnosis of cerebral palsy (n = 17) or hereditary spastic paraplegia (n = 1) and 16 typically developing children (female: 11, age: 11.2 ± 3.2 y) walked on an instrumented treadmill. Three distinct gait patterns were determined in children with cerebral palsy. Muscle-tendon unit, fascicle, belly, and tendon behavior were assessed with dynamic ultrasound imaging. Unpaired statistical non-parametric mapping (SnPM) t-tests and Mann-Whitney U tests assessed differences between children with cerebral palsy and typically developing children. One-way ANOVA SnPM tests and Kruskall-Wallis tests assessed differences across gait patterns.

Findings: Tendon lengthening in the first half of stance was higher in children with cerebral palsy compared to typically developing children (Δ6.6 mm), yet total tendon lengthening in stance (Δ5.3 mm) and fascicle shortening during push-off were decreased (Δ6.2 mm). Children with cerebral palsy displaying a mildly affected kinematic gait pattern showed pathological muscle belly lengthening in stance (Δ5.7 mm), while children with equinus (Δ6.4 mm) or crouch gait (Δ6.0 mm) showed reduced tendon lengthening.

Interpretation: Efficient gastrocnemius medialis behavior is compromised in children with spastic cerebral palsy. Children with mildly affected gait show the most deviation in muscular components involved in active force generation, while those with equinus and crouch gait also show deviations in tendinous components. Interventions aimed at improving gait should consider this aberrant behavior.