High-resolution ultrasonography and 3.0 T magnetic resonance imaging in erosive and nodal hand osteoarthritis: high frequency of erosions in nodal osteoarthritis.

Erosive osteoarthritis (EOA) is defined as hand osteoarthritis (OA) with interphalangeal joint erosions on plain radiographs. We sought to find ultrasound (US) and magnetic resonance imaging (MRI) features that could distinguish EOA from nodal hand OA (NOA). Symptomatic consecutive patients with hand OA as defined by the American College of Rheumatology criteria (13 EOA patients as defined by erosion in ≥1 interphalangeal joint and seven nodal OA patients) and five normal individuals were examined by plain radiography, US, and MRI. Patients and controls underwent evaluation of metacarpophalangeal and interphalangeal joints by US, and all fingers from second to fifth digit by MRI. A total of 240 joints in symptomatic patients were examined by both imaging modalities. Synovitis, osteophytes, cartilage loss, and erosions were frequently detected in the joints of patients with EOA and NOA. Six of seven patients with NOA had joint erosions that were seen on MRI or US scan but seen on plain radiographs. The overall concordance between MRI and US findings was substantial for osteophytes (κ = 0.79) and excellent for cysts (κ = 0.85), erosions (κ = 0.84), synovitis (κ = 0.82), and tenosynovitis (κ = 0.83) in both groups. Inflammatory changes, such as effusions and synovitis, and structural changes, such as erosions, were frequently detected by US and MRI in EOA and nodal OA. These findings may support the hypothesis that EOA could not be a separate entity but may represent the severe end of the spectrum of hand OA.