Ultrasound of synovitis in rheumatoid arthritis: advantages of the dorsal over the palmar approach to finger joints.

OBJECTIVE: To compare the dorsal and palmar ultrasound (US) examination of finger joints in early rheumatoid arthritis (RA) with regard to the concurrence of greyscale (GSUS) and power Doppler (PDUS) positivity, and to correlate both approaches with clinical variables.

METHODS: Patients with newly diagnosed RA were assessed by clinical examination and US. GSUS and PDUS of metacarpophalangeal (MCP) and proximal interphalangeal (PIP) joints were performed using the dorsal and palmar approach. Findings of synovitis in GSUS and PDUS were graded semiquantitatively from 0 to 3. Clinical and sonographic reevaluation was performed after 6 months.

RESULTS: With 44.6% versus 32.2% positive findings, palmar GSUS identified significantly more joints with synovitis than did dorsal GSUS. With 22.1% versus 8.9%, PDUS abnormalities were detected significantly more often from the dorsal side. With 71.2% versus 21.8% for the MCP and 57.5% versus 17.4% for the PIP joints, significantly more GSUS and PDUS double-positive joints were found with the dorsal as opposed to the palmar approach. These differences remained significant at Month 6. Both palmar and dorsal GSUS and PDUS correlated with comparable strength with clinical variables such as the Disease Activity Score 28, Clinical Disease Activity Index, and Simple Disease Activity Index.

CONCLUSION: Although the dorsal approach detected fewer GSUS findings than the palmar approach, PDUS signals were significantly more frequently detected by dorsal US. In addition, the prevalence of double-positive joints with concurrent GSUS and PDUS findings was significantly higher with the dorsal approach. These data argue in favor of the dorsal US approach to finger joints in RA.