Background/Purpose: Ultrasound (US) has been demonstrated to be a very sensitive and objective tool for evaluating synovitis in children. However sometimes due to the age variability especially in the vascularization of the epiphysis and short bone cartilage, the distinction between physiological and pathological grey-scale (GS) and power Doppler (PD) findings can be difficult. The aim of the study was to test the intra- and inter-observer reliability of US detected age related vascularization and ossification grade in healthy children.

Methods: Following standardized image acquisition and machine setting protocol, 10 international ultrasound experts examined four joints (wrist, 2^ndMCP, knee and ankle) in 12 healthy children (divided in four age groups: 2–4; 5–8; 9–12 and 13–16 years). GS and PD US were used to detect physiological vascularization and ossification grade. Ossification was graded as follow: grade 0 – non-ossified epiphyseal bone, short bones or patella; grade 1 – small ossification centers, dominant cartilage, visible growth plate; grade 2 – large ossification centers, thin cartilage, visible growth plate; grade 3 – completed ossification. PD was defined as any PD signal inside the joint. Kappa statistics were applied for intra- and inter-observer reliability.

Results: According to specific joint and age up to 4 solitary PD signals (mean 1.5/joint) were detected within the joint areas due to the physiological vascularization localized predominantly in some specific anatomic positions: fat pad, epiphysis, the physis and the short bone cartilage. The kappa values for grading ossification were 0.87 (range 0.85-0.91) for intra-observer and 0.58 for inter-observer reliability respectively. Since the prevalence of the PD detected lesions was not uniformly distributed, we used the bias adjusted kappa, which was 0.71 (range 0.44-1) for intra-observer and 0.69 for inter-observer reliability.

Conclusion: Our study showed that the detection of normal findings (i.e. grading of physiological ossification in the skeletal maturation including physiological vessels) can be high reliable by using clear definitions and a standardized acquisition protocol. These data will permit to develop a reliable and standardized US approach for evaluating pediatric joint pathologies.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/international-multi-observer-ultrasound-reliability-study-of-age-related-vascularization-and-ossification-in-healthy-children-the-omeract-pediatric-ultrasound-task-force/