Pigmented villonodular synovitis of the foot: MR findings.

PURPOSE: To evaluate the MRI findings in the various forms of pigmented villonodular synovitis (PVNS) of the foot. MATERIALS AND METHODS: Seven hundred and fifty-three MR studies of the foot performed at our institute between June 1994 and April 2000 were retrospectively reviewed for the presence of PVNS. Spin echo (SE) T1W, Gradient echo (GE) T2*W, and fat suppression (Short Time Inversion Recovery: STIR) images were acquired with a 0.5 T superconductive unit (Vectra, GE Medical System, Milwaukee, WI, USA) provided with a dedicated transmitter/receiver coil. The site and type of lesions, the signal intensity patterns, and the presence of associated changes were evaluated. RESULTS: On the basis of the MR images and the above parameters, six patients (3 men, 3 women, age range: 35-48 years) with PVNS were selected. Three out of six PVNS were nodular, whereas the remaining three were diffuse. Of the three nodular forms, one was found in the sub-talar joint and the remaining two antero-medially to the talus. Instead, all of the diffuse lesions were located on the metatarsus. Perilesional oedema was seen in all cases, although more obvious in the nodular forms, whereas bone involvement (osteochondral erosion) was observed only in the diffuse metatarsal PVNS. Intra-articular bloody effusion was never observed. The MRI findings were confirmed by surgery in all cases. DISCUSSION: The high contrast resolution and multiplanar capabilities of MRI allow the complete evaluation of the structures of the foot affected by PVNS, and of the extent of soft tissue (bursae, synovial or nervous structures), bone and articular involvement. Although not specific, the presence of haemosiderin results in characteristic MR findings, due to the shortening of both T1 and T2 relaxation times. GET2* images are particularly well suited to this PURPOSE: Furthermore, in our experience, FIR images added better depiction of associated swelling. CONCLUSIONS: According to our results, MRI is now the most reliable technique for identifying and classifying PVNS, and allows correct treatment planning and effective monitoring.