Differential pattern of Doppler signals at lower-extremity entheses of healthy children.

Background: Ultrasonography might be an important imaging method for assessing the pediatric enthesis. To diagnose pathology, knowledge of physiological findings is essential but limited.
Objective: To provide a detailed ultrasonographic assessment of four lower-extremity entheses in healthy adolescents as a reference for the correct interpretation of findings in children with rheumatic diseases.
Materials and Methods: The quadriceps tendon, proximal and distal patella tendon, and Achilles enthesis were examined in B-mode, Power and color Doppler in 41 boys and girls ages 11-14 years in neutral position and 30° flexion. We assessed Doppler signals at various distances from the enthesis and analyzed the data using a marginal logistic regression model with generalized estimating equation. We assessed agreement between observers using weighted kappa and we determined agreement on repeat scans using prevalence- and bias-adjusted kappa.
Results: Doppler signals were predominantly in the quadriceps and distal patella tendon with odds ratios of 50.85 and 21.35 (P<0.001) compared to the Achilles tendon. They were within 2 mm or 5 mm of the enthesis (odds ratios [ORs] of 4.58 and 4.24, P<0.001), without significant difference between flexion and neutral position and between the right and the left legs. Agreement between first and second assessment was good, with aggregate kappas from 0.79 to 0.90. The inter-reader agreement was also good, with aggregate kappas ranging from 0.75 to 0.95.
Conclusion: We found a differential Doppler pattern in lower-extremity entheses, with signals present mostly in the quadriceps and distal patella entheses.