Spastic cerebral palsy in children: dynamic sonoelastographic findings of medial gastrocnemius

To study the elastic properties of the medial gastrocnemius (GCM) in children with spastic cerebral palsy. The study protocol was approved by the Research Ethics Committee of the hospital, and informed consent was obtained from each child's parent. Fifteen children with spastic cerebral palsy (group 1) and 13 children without neurologic and musculoskeletal disabilities (group 2) were included. Because group 1 included three children with hemiplegia, the total number of legs examined was 27. Children in group 2 had both legs examined, for a total of 26 legs studied. The modified Ashworth scale score of the ankle in group 1 was assessed by a physical therapist. A physiatrist performed ultrasonography and dynamic sonoelastography (DS) together, measured the thickness of the GCM, and calculated the GCM ratio in both groups. On color-scaled DS images, the DS score of the GCM was graded from DS 1 (purple to green: soft) to DS 4 (red: stiff), and the color histogram of the GCM was subsequently analyzed. Strain ratio and local shear wave velocity were calculated in the GCM and the soleus muscle by using acoustic radiation force impulse imaging. The GCM ratio in group 1 was significantly smaller than that in group 2. The DS score of GCM in group 1 was significantly higher than that in group 2. The median red pixel values were significantly higher, and the blue pixel values were significantly lower on color histogram in group 1 than those in group 2. The strain ratio in group 1 was significantly lower than that in group 2, and the local shear wave velocity of GCM in group 1 was higher than that in group 2. There were significant correlations between the modified Ashworth scale scores and DS parameters. DS demonstrated a difference in muscle stiffness in the GCM between children with spastic cerebral palsy and those without neurologic and musculoskeletal disabilities.