Low-Field Magnetic Resonance Imaging of the Thumb Base in Severe Symptomatic Osteoarthritis: A Comparison with Radiographs and Clini- cal Symptoms

The objectives of this pilot study were to assess the findings of low-field MRI in symptomatic thumb base osteoarthritis (OA), to identify suitable MRI sequences with or without Gadolinium contrast, and to compare these findings with conventional radiographs scored by the Altman atlas and patient reported pain. Twelve patients with symptomatic thumb base osteoarthritis participated. We used a 0,2T MRI system, before and after i.v. Gadolinium. The MRI images were scored on a 0-3 scale for synovitis (SYN), bone marrow edema (BME), cysts/erosions (CE) and osteophytes (OP). Interreader agreement on MRI scores was best for BME and CE but less for SYN and OP. Difficulties were in determining the soft tissue involvement of the CMC1 joint, especially in demarcating the joint capsule and ligament pathology. The most informative MRI sequences were the High Resolution Gradient Echo, the STIR and the 3D volume.Gadolinium contrast provided little additional information. Cumulative MRI and radiographic scores for the 24 CMC1 joints studied were strongly correlated (Rs 0.81, p<0.001). Both BME in adjacent bones and SYN in the CMC1 joint correlated with rest pain (Rs 0.54, p<0.01 and Rs 0.45, p<0.05) respectively). BME was also associated with pain intensity on a 0-10 scale (R 0.44, p<0.05). Other radiographic and MRI variables showed no association with pain. Low-field MRI reflects CMC1 joint osteoarthritis damage and gives additional information regarding bone marrow edema and synovitis, both of which are strongly related to clinical symptoms. This study encourages further research to identify the most suitable equipment and sequences and to standardize the reading of MRI images.