Is the frequent sonographic anechoic area distally in metacarpophalangeal joints a sign of arthritis?

In clinical practice, ultrasonography (US) often reveals, in the dorsal scan, a small anechoic area distally in both inflamed and clinically non-inflamed metacarpophalangeal joints. This "distal anechogenicity in the metacarpophalangeal joint'' (DAEM) might thus be scored false positively as arthritis. We aimed to investigate whether the DAEM is a sign of arthritis. We evaluated the prevalence of DAEMs in 24 non-arthritic subjects. We then compared the dimensions of the DAEM in 10 non-arthritic subjects with a DAEM and 7 consecutive rheumatoid arthritis (RA) outpatients, using 2-D and 3-D ultrasound. Furthermore, we dissected two fresh-frozen postmortem hand specimens after US. A DAEM was observed in the metacarpophalangeal 2 (MCP2) joints of 54% of the 24 non-selected non-arthritic individuals; in none of those did the joint exhibit a power Doppler signal. A DAEM was observed in 86% of the 7 RA patients. Dimensions of DAEMs did not statistically significantly differ between these groups. At 3-D imaging and dissection, the DAEM was found to be an extension of the metacarpophalangeal joint capsule. In conclusion, DAEMs occur frequently and are not a sign of arthritis, but are distal joint recesses. This should be taken into account when using current sensitive ultrasonographic scoring systems grading arthritis. (C) 2014 World Federation for Ultrasound in Medicine & Biology.