Magnetic resonance arthrography of lesser metatarsophalangeal joints in patients with rheumatoid arthritis: relationship to clinical, biomechanical, and radiographic variables.

Objective: Our exploratory study of painful lesser metatarsophalangeal (MTP) joints in patients with rheumatoid arthritis (RA) primarily aimed to compare the clinical, biomechanical, and plain radiography findings with magnetic resonance (MR) arthrography findings. Our secondary aim was to compare standard unenhanced MR with MR arthrography in imaging the lesser MTP joints in RA.

Methods: In 15 patients with RA, the more symptomatic forefoot was imaged using 3T MR imaging. Proton density fat-suppressed images were acquired through the lesser MTP joints prior to arthrography. Under ultrasound guidance, contrast agent was injected into 2 lesser MTP joints. T1-weighted fat-suppressed sequences were subsequently acquired. The MR images were read by 2 musculoskeletal radiologists and consensus was reached. Spearman's correlation coefficient was used to assess the association between abnormalities seen on MR arthrography and the clinical, biomechanical, and plain radiography findings.

Results: MR arthrography demonstrated pathology at 18 of 28 lesser MTP joints (64%) examined in patients with RA. MR arthrography abnormalities were associated with RA disease duration, forefoot deformity, Larsen score, subluxation, and peak plantar pressure. Unenhanced MR had a sensitivity of 78% and specificity of 90% for detecting pathology compared to MR arthrography.

Conclusion: Capsule and plantar plate pathology occurs in the painful forefoot of patients with RA and is associated with features of disease and deformity at the lesser MTP joints. Compared with MR arthrography, standard MR imaging was highly specific and moderately sensitive for diagnosing lesser MTP joint pathology in patients with RA.