Background Musculoskeletal Ultrasound (MSUS) is an emerging tool in pediatric rheumatology, particularly in the diagnosis and monitoring of Juvenile Idiopathic Arthritis. Its wide use is still limited by the lack of definitions of normal and pathologic US features in the pediatric population; few studies evaluated US features of healthy joints in children and US definitions for some joint components have only recently been proposed.
Objectives To describe the normal US findings of joints and entheses frequently involved in rheumatic diseases, in a population of healthy children
Methods We enrolled consecutive healthy children (age range 1-14y) reaching a pediatric outpatient clinic for routinary visit between October and November 2014. US exams was performed by an operator expert in adult MSUS and with a two years experience in pediatric MSUS, with a 8-13 MHz linear transducer (Esaote MyLab Alpha). 18 joints (wrists, MCF, hips, knees, ankles) and 8 entheses (knee entheses and Achilles tendon) were evaluated in children older than 3 yo, using a stardardized technique as described for adults; for children younger than 3yo the evaluation was limited to hip and knee joints and entheses of the lower limbs. Grey scale (GS) and power Doppler (PD) US exam was performed to evaluate the presence of joint effusion, synovitis and PD, classified with a dicotomic and a semiquantitative (grade 0-1-2-3) score. PD exam, with dynamic scans of joints and entheses, was also used to identify the presence of vascular flow within the structures suggestive of normal vascularization. Data were collected about children's sport activity
Results We evaluated 788 joints and 416 entheses from 53 children. 42 children (24 girls) were older than 3 yo (744 joints and 328 entheses): in this group we observed a mild effusion (grade 1) in 62 joints (8,3%): 27 knees, 24 ankles, 8 wrists and 3 MCF. In one child we observed a mild synovitis (grade 1) and presence PD signal within the articular fat pad of 3 MCF joints; in this case we supposed a possible correlation with joint overuse in sport activity. PD exam revealed a flow signal in 290 joints (39%) and 133 entheses (40,5%), notably in younger children; the most frequent findings were the presence of nutritive vessels above quadriceps enthesis and through patellar cartilage (82% and 87% of children), and flow signal of wrist (94%) and ankle (79,5%) joints. 11 children <3yo (6 girls) were evaluated (44 joints and 88 entheses): a grade 1 joint effusion was found in 1 knee (2,3%). Flow PD signal was observed within the hip joints capsule in 3 cases and at 13 entheseal sites (11,4%); the most frequent finding was the presence of vessels within patellar cartilage. However, PD evaluation in these subjects was limited by children movements.
Conclusions PD US exam found a mild joint effusion in 8% of healty joints in children and PD abnormalities in a single child among our cohort; a flow PD signal was detected in a large number of joints and entheses, notably in younger children. Our observation, together with other recent acquisitions from the literature, could be very relevant in order to describe normal US features and vascular patterns of growing joints, and to better recognize and interpret abnormal findings in children with inflammatory diseases
Disclosure of Interest None declared