Impact of lower muscle stiffness on ankle dorsiflexion restriction in children with cerebral palsy evaluated using ultrasound elastography

Abstract

Background: Plantar flexor muscles always contribute to limiting the range of motion of ankle dorsiflexion in children with spastic cerebral palsy, but the individual contributions of these muscles are not well defined. This study aimed to identify which muscles' stiffness impacts the dorsiflexion range of motion in children with cerebral palsy.

Methods: Twenty-five children with cerebral palsy were included. The maximum passive dorsiflexion range of motion was measured in two positions: hip and knee joints in flexion, and both joints in full extension. Strain ratios indicating muscle stiffness were measured using strain elastography of the lateral and medial gastrocnemius, soleus, flexor hallucis longus, peroneus longus, peroneus brevis, and tibialis posterior muscles. To analyze which muscles impact the limitation of the dorsiflexion range, multiple regression analyses were conducted. The values of muscle stiffness were included as independent valuables, and the values of the dorsiflexion range were included as dependent valuables. A p-value <0.05 was considered statistically significant.

Findings: In the analyses, the soleus and flexor hallucis longus muscle stiffness were significant independent factors for the dorsiflexion range of motion of hip and knee flexion (adjusted R²: 0.50). The lateral gastrocnemius muscle stiffness was a significant independent factor for the dorsiflexion range of motion with both joints in full extension (adjusted R²: 0.61).

Interpretation: Flexor hallucis longus muscle stiffness, in addition to triceps surae muscle stiffness, was shown to impact dorsiflexion range; attention should be paid to muscle stiffness in children with cerebral palsy.

Keywords: Ankle dorsiflexion restriction; Cerebral palsy; Flexor hallucis longus muscle; Muscle stiffness; Ultrasound elastography.