Ultrasound and MRI measurements of joint cartilage in healthy children: a validation study

In juvenile idiopathic arthritis (JIA), proliferative changes in the synovium and synovial fluid accumulation are pathological findings responsible for damage to the cartilaginous tissue and periarticular bone, which are late radiographic findings in conventional radiography. Early detection of these joint changes would allow the clinicians to initiate relevant therapies as is essential for the long-term outcome of JIA. Ultrasonography (US) has shown great potential for this purpose but validation in a pediatric setting is needed. The objective of this study was to validate US measurements of cartilage thickness in target joints in healthy children by comparing them with MRI.

Twenty-five healthy Caucasian children (17 boys/ 8 girls), mean age 11.33 years, were examined with MRI (1.5 T, fat-suppressed T 1-weighted 3D sequences) and US (real-time Hitachi EUB 6500 CFM, B-mode 6 - 14 MHz linear transducer) in the right knee, ankle, wrist, metacarpophalangeal (MCP) and proximal interphalangeal (PIP) joints. US was obtained according to the EULAR standard scans.

All differences in cartilage thickness measurements between MRI and US were less than 0.5 millimeters. The coefficient of variation (CV) was found to be good (16 %) except for in the case of the wrist joint (20 %).

We found a good level of agreement and no significant systematic joint size-related differences in cartilage thickness measurements between MRI and US. US appears to be a feasible method for evaluating cartilage thickness in JIA target joints, especially when age and sex-related references are defined.