Magnetic resonance imaging in the assessment of synovial inflammation of the hindfoot in patients with rheumatoid arthritis and other polyarthritis.

OBJECTIVES: To describe the localisation of synovitis and tenosynovitis of the hindfoot observed on magnetic resonance imaging (MRI) in patients with chronic polyarthritis, and to correlate the findings of physical examination and MRI.

METHODS: Patients with chronic polyarthritis, and one or two painful hindfoot were included. On physical examination and on MRI, the tibio-talar, talo-calcaneal, and talo-navicular and calcaneo-cuboidal joints were adjudged to have or not synovitis, and the tibialis anterior and posterior, the peroneus longus and brevis, the flector digitorum and hallucis longus tendons to have or not tenosynovitis. Criteria for synovitis and tenosynovitis were a high signal intensity on T2-weighted images, a low signal intensity on T1-weighted images, and enhancement after Gd-DTPA injection, in the joint area, and around the tendon, respectively. The correlation between the findings of physical examination and those of MRI were evaluated using the Kappa statistics.

RESULTS: 12 patients (three men, nine women, mean age of 55.5 years+/-11.4 S.D.) with chronic polyarthritis (rheumatoid arthritis (RA): nine, ankylosing spondylitis: one; psoriatic arthritis: one, unclassified: one) were included. All presented with one (7 patients) or two (5 patients) painful hindfeet (and swelling for 16 out of 17 hindfeet). On physical examination, 25 joints and eight tendons were adjudged to have synovitis and tenosynovitis. MRI showed synovitis in 12 out of 25 of these joints (48%), and tenosynovotis in three out of eight of these tendons (37.5%). Moreover, MRI showed ten and seven clinically unsuspected synovitis and tenosynovitis, respectively. The proportion of agreements between physical examination and MRI were 54.9% (kappa=0.1) and 88.2% (kappa=0.27) for synovitis and tenosynovitis, respectively.

CONCLUSION: A weak correlation was observed between the findings of physical examination and MRI in patients with chronic polyarthritis and a painful hindfoot. MRI might be used to localise synovitis in the area before performing some intra-articular injections. However, other studies are needed to address this question.