To compare ultrasonography (US) with magnetic resonance imaging (MRI), conventional radiography, and clinical examination in the evaluation of bone destruction and signs of inflammation in the metatarsophalangeal (MTP) joints of patients with rheumatoid arthritis (RA).
Two hundred MTP joints of 40 patients with RA and 100 MTP joints of 20 healthy control subjects were assessed with B-mode US, contrast-enhanced MRI, conventional radiography, and clinical examination for signs of bone destruction and joint inflammation.
With MRI considered the reference method, the sensitivity, specificity, and accuracy of US for the detection of bone erosions were 0.79, 0.97, and 0.96, respectively, while the corresponding values for radiography were 0.32, 0.98, and 0.93. The sensitivity, specificity, and accuracy of US for the detection of synovitis were 0.87, 0.74, and 0.79, while for clinical examination, the corresponding values were 0.43, 0.89, and 0.71. Erosive disease was identified in 26 patients by US, compared with 20 patients by MRI and 11 patients by radiography. Evaluation by US indicated signs of inflammation in 36 patients, while MRI and clinical examination revealed signs of inflammation in 31 patients and 20 patients, respectively. US and MRI volume-based gradings of synovitis showed intraclass correlation coefficients of 0.56-0.72 (P < 0.0001). The MRI and radiographic visualizations of US-detected bone changes were closely related to their size-based gradings on US.
US enables detection and grading of destructive and inflammatory changes in the MTP joints of patients with RA. By comparison with MRI, US was found to be markedly more sensitive and accurate than clinical examination and conventional radiography. Considering the early and frequent involvement of the MTP joints, evaluation of these joints by US may be of major clinical importance in RA.