Tuberculous versus pyogenic arthritis: MR imaging evaluation

PURPOSE: To assess magnetic resonance (MR) imaging features in differentiat ing tuberculous arthritis from pyogenic arthritis. MATERIALS AND METHODS: Findings in 29 patients with tuberculous arthritis w ere compared with those of 13 patients with pyogenic arthritis. Bone erosio n, marrow signal intensity, synovial lesion signal intensity, boundaries (s mooth or irregular) for extraarticular extension of infection, and abscess rim enhancement (thin and smooth or thick and irregular) were analyzed. RESULTS: Bone erosion was more common in patients with tuberculous arthriti s (24 [83%] of 29) than in those with pyogenic arthritis (six [46%] of 13) (P =.026), while subchondral marrow signal intensity abnormality was seen m ore frequently in patients with pyogenic arthritis (12 [92%] of 13) than in those with tuberculous arthritis (17 [59%] of 29) (P =.036). On T2-weighte d images, there was no significant difference between the synovial lesion s ignal intensities of tuberculous arthritis and pyogenic arthritis. Lesions in 16 (70%) of 23 patients with tuberculous arthritis and two (17%) of 12 p atients with pyogenic arthritis had smooth extraarticular boundaries, while those in seven (30%) of 23 patients with tuberculous arthritis and 10 (83% ) of 12 patients with pyogenic arthritis had irregular boundaries (P =.005) . Tuberculous abscesses (16 [100%] of 16) had thin and smooth rim enhanceme nt, while most pyogenic abscesses (five [71%] of seven) had thick and irreg ular rims (P =.001). CONCLUSION: MR imaging of bone abnormalities, extraarticular lesions, and a ssociated abscesses provides useful information in the differentiation of t uberculous arthritis and pyogenic arthritis.