Background/Purpose: The aim of our study is to describe the grey-scale and Power Doppler findings in lower extremity entheses in healthy children ages 5-18 years.   

Methods: Healthy patients, ages 5-18 years, were recruited for the study. Demographics, weight, and BMI were collected.  Grey-scale and Power Doppler 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 presence and intensity of Doppler signal (DS) were recorded.  Differences in entheseal thickness and DS between contra lateral sites in the each subject were evaluated.  Entheseal quality (fibrillar pattern, bony changes, and tendon/ligament contour) was also evaluated. 

Results: 702 entheses were examined in 117 children ages 5-18 years with a mean age of 10.44±3.66 years.  There was large variability in entheseal thickness and DS in children.  Age had a weak positive correlation with thickness (R²=0.13-0.26).  Weight had the strongest correlation to thickness (R²=0.26-0.35).  Using linear regression models with generalized estimating equations techniques, multivariate analysis demonstrated that entheseal thickness at all 3 sites increases by 0.02 mm for every additional kilogram of weight (n=104, 95% CI= 0.02-0.03 mm, p= <0.0001).   Using the same model, multivariate analysis demonstrated that  entheseal thickness  of all 3 entheseal sites is 0.25 mm larger in males than females (n=87, 95% CI= 0.02-0.47, p=0.03), and entheseal thickness in Hispanics is 0.32 mm smaller compared to non-Hispanic Whites (n=87, 95% CI=-0.60- -0.03, p=0.03).  Entheseal thickness in bilateral sites correlated well with each other (Pearson’s correlation coefficient=0.8-0.94) , but there is some degree of variability; a difference below 27.85%, 25.88%, and 17.54% between bilateral PPL, DPL, and AT thickness, respectively, falls within the 95^thpercentile of the healthy pediatric population in this study.  DS was seen in 14% of all entheses in 45.3% of subjects.  DS was most commonly seen in the DPL (31%).  Presence and intensity of DS varied between contra lateral sites of an individual; however, DS is typically seen in the same location of each enthesis.  Entheseal attachment changed with age from a completely cartilaginous to completely bony attachment. The patellar ligament contour evolved with age from a curved contour to a linear contour that is parallel to the skin surface. 

Conclusion: Weight is the best predictor of entheseal thickness; however there is a large degree of variability.  Contra lateral entheseal sites are comparable in thickness, and a difference below 27.85%, 25.88%, and 17.54% between bilateral PPL, DPL, and AT, respectively, falls within the 95^th percentile of the healthy pediatric population in this study.   DS is seen in entheses of healthy children, most commonly in the DPL, and may not be symmetric in presence or intensity in bilateral sites.  Entheses in children have a homogeneous fibrillar pattern of the tendon/ligament without bony changes, and the patellar ligament contour changes with age.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/grey-scale-and-power-doppler-findings-of-lower-extremity-entheses-in-healthy-children/