Background Ultrasonography (US) has been recently established as an imaging modality to evaluate inflamed joints of patients with rheumatoid arthritis (RA). It is reported that power doppler ultrasonography (PDUS) is capable of directly visualizing and quantifying synovial inflammation . However, detailed correlation between the PDUS findings and histopathological findings of RA synovial tissues, such as accumulation of various inflammatory cells, neovasculogenesis, and synovial hyperplasia, still remains unclear.
Objectives To assess the significance of PDUS in the evaluation of synovial lesion of the knee joint by comparing the PDUS findings with site-matched histopathological findings.
Methods We studied 23 patients who were undergoing arthroplasty of the knee joint because of RA or osteoarthritis (OA). Predetermined sites of the knee joint were examined with US before arthroplasty. Synovitis was classified semiquantitatively with grey scale (GS) and PDUS findings. PD signal was graded as 0 (normal), 1 (minor), 2 (moderate), and 3 (major) . Synovial tissues were obtained during arthroplasty from the corresponding sites evaluated by the US. Histopathology of the synovial tissue was evaluated by haematoxylin and eosin staining and immunohistochemical staining with factor VIII. The degree of inflammatory cell infiltrates, synovial lining layer thickness and vascularity was graded as 0 (normal), 1 (mild change), 2 (moderate change), and 3 (severe change) .
Results Positive PDUS (grade 2 or 3) was found in 11 of 19 knee joints in patients with RA, but was not observed in all patients with OA. We compared imaging findings of preoperative PDUS with histopathological findings of the synovial specimens. We found that the PDUS findings were mostly correlated with each histopathological grade of synovitis and the vascularity showed the highest correlation with the PDUS findings (r=0.541, P<0.01) as expected. However, the site-matched comparison indicated that the blood vessels, possibly low-velocity blood flow, were not apparently detected by the PDUS. Thus, the sensitivity and specificity of PDUS findings for histopathological vascularity were 91% and 58%, respectively.
Conclusions We showed that positive findings of PDUS were closely associated with histopathological findings of active synovitis. However, our results suggest that PDUS is not sufficiently powerful in evaluating blood vessels with low-velocity blood flow in the synovial tissue.
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Disclosure of Interest None Declared
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