How are Achilles tendon properties associated with gait performance in cerebral palsy?

Abstract

Achilles tendon (AT) plays a crucial role during walking. In cerebral palsy (CP), altered neuromuscular development appears to affect AT morphology and stiffness, disrupting muscle-tendon interaction and gait. This study quantified differences in static AT morphology and passive mechanical properties in children and young adults with CP and examined whether these properties are related to AT function during walking. Twelve young individuals with CP and 12 typically developing (TD) peers underwent three-dimensional freehand ultrasonography to obtain AT datasets from which cross-sectional area (CSA) and lengths were extracted. Shear wave elastography was used to estimate the shear modulus of the free AT. Three-dimensional gait analysis was synchronized with ultrasound during overground walking, enabling estimation of AT length changes during stance along with lower-limb kinematics and kinetics. Free AT was 86.7 ± 34.6 mm longer in CP than TD (p = 0.015) and remained longer after normalization to tibia length (p = 0.025). No significant differences were observed in medial gastrocnemius AT length and CSA. Within CP, CSA was correlated negatively with walking speed (r = -0.66, p = 0.026) and positively correlated with AT length changes during walking (r = 0.79, p = 0.002). This study shows that the free AT length is longer in CP than in TD peers, with no differences in AT CSA. Only limited structure-function associations were observed, suggesting altered involvement of AT stretch-recoil during walking in CP. These explorative results require further evaluation with larger samples and homogenous CP groups.