Grey-scale ultrasound findings of lower extremity entheses in healthy children

BACKGROUND To describe grey-scale sonographic findings in lower extremity entheses in healthy children. METHODS Healthy patients referred to Orthopedic Surgery or Adolescent Medicine outpatient clinics or their siblings ages 5-18 years were recruited. Grey-scale ultrasound was performed on 3 entheseal sites bilaterally, the proximal patellar ligament insertion (PPL), distal patellar ligament insertion (DPL), and Achilles tendon insertion (AT). Entheseal thickness and quality were recorded. Comparison of thickness between contralateral sites was evaluated to determine within subject site variability. RESULTS 702 entheses were examined in 117 children. Age had a weak positive correlation with thickness with large variability. Weight had the strongest correlation to thickness. Contralateral sites are comparable in thickness; a difference of 28%, 26%, and 18% between bilateral PPL, DPL, and AT, respectively, falls within the 95th percentile of the healthy pediatric population in this study. The patellar ligament contour evolved with age from a curved to linear contour. CONCLUSIONS Weight is the best predictor of entheseal thickness in children although there is a large degree of variability. Contralateral entheses are comparable in thickness. A difference below 28%, 26%, and 18% between bilateral PPL, DPL, and AT, respectively, falls within the 95(th) percentile.