Diagnostic value of magnetic resonance imaging of the forefeet in early rheumatoid arthritis when findings on imaging of the metacarpophalangeal joints of the hands remain normal.

OBJECTIVE: To investigate the diagnostic role of magnetic resonance imaging (MRI) of the forefeet in patients with early rheumatoid arthritis (RA) in whom findings on MR images of the hands are normal and conventional radiographs of the hands and feet do not show erosions.

METHODS: The study group comprised 25 patients with early RA (disease duration of <12 months) in whom erosions were not demonstrated on conventional radiographs of the hands and feet. These patients underwent MRI of the clinically dominant hand to detect signs of arthritis. If results of MRI of the hand were normal according to the Outcome Measures in Rheumatology Clinical Trials (OMERACT) RA-MRI scoring system (RAMRIS), MRI of the dominant forefoot was performed. The MRI protocol comprised coronal and sagittal T1-weighted spin-echo (before and after administration of contrast medium), coronal fat-suppressed short tau inversion recovery sequences, coronal and sagittal T2-weighted turbo spin-echo sequences, and axial fat-suppressed T1-weighted spin-echo sequences after administration of contrast medium. MRI of the forefeet was analyzed on the basis of a modified RAMRIS.

RESULTS: MRI revealed pathologic findings in the hands of 15 of 25 patients (edema in 9 patients, synovitis in 12, erosions in 6, defects in 3). In 10 patients with a mean disease duration of 9.4 weeks, hand MRI scans were normal according to RAMRIS. Four of these 10 patients had tenosynovitis of the finger flexor tendons (there was no OMERACT criterion for tenosynovitis). RAMRIS analysis of the corresponding MRI scans of the forefeet of these patients revealed signs of edema in 7 patients, synovitis in all 10 patients (at the third metatarsophalangeal [MTP] joint in 7, at the fourth MTP joint in 6, at the first MTP joint in 4, and at the fifth MTP joint in 2 patients), tenosynovitis of the foot flexor tendons in 2 patients, erosions at the second and third MTP joints in 1 patient, and a single defect at the first MTP joint in 1 patient.

CONCLUSION: RAMRIS analysis of MRI scans of the forefeet detected synovitis and bone edema in patients with early RA in whom MRI of the finger joints was normal. MRI of the forefeet contributes an additional tool aimed at earlier and more accurate diagnosis and thus might allow an earlier decision to start appropriate medication in patients with early RA.