Normal sonoanatomy of the paediatric entheses including echostructure and vascularisation changes during growth.

Objectives: To describe the sonoanatomy of paediatric lower-limb entheses according to age and gender. We studied sites that most commonly involved entheses in spondyloarthritis.

Methods: We studied 41 consecutive healthy children (20 girls, 21 boys; age 2-15 years) divided into four age groups: 2-4 years (n = 9), 5-7 years (n = 11), 8-12 years (n = 12) and 13-15 years (n = 9). Ultrasound was used to obtain both transverse and longitudinal views of each enthesis. We assessed the echostructural components of the lower limb entheses and the vascularisation of the entheses and cartilage according to the different anatomical sites and age and gender.

Results: At all sites on B-mode, cartilage and tendon thicknesses showed positive or negative correlations with age (P < 0.0001). Side-to-side correlations were good (P < 0.0001 overall) and stronger for cartilage (r, 0.77-0.97) than for tendon thickness (r, 0.58-0.63). Agreement between the two sides for discrete data was very good to excellent (kappa, 0.77-1). Cartilage thickness at the various sites was significantly greater in boys than in girls (P ≤ 0.05). Tendon thickness was not significantly influenced by gender. Blood vessels were seen within the cartilage with differences across age groups.

Conclusions: This study provides the first data on normal entheseal sonoanatomy and vascularisation in children.

Key Points: • The tendons of children exhibit the same fibrillar structure as adults • Tendon thickness at enthesis insertion in children is not influenced by gender • Cartilage thickness in children decreases with advancing age and varies with gender.