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Open Access Research article

Conventional radiography requires a MRI-estimated bone volume loss of 20% to 30% to allow certain detection of bone erosions in rheumatoid arthritis metacarpophalangeal joints

Bo Jannik Ejbjerg1*, Aage Vestergaard2, Søren Jacobsen3, Henrik Thomsen4 and Mikkel Østergaard5

Author Affiliations

1 Department of Rheumatology, Copenhagen University Hospitals at Hvidovre and Gentofte, Kettegaard Allé30, 2650 Hvidovre, Denmark

2 Department of Radiology, Copenhagen University Hospital at Hvidovre, Kettegaard Allé30, 2650 Hvidovre, Denmark

3 Department of Rheumatology, Copenhagen University Hospitals at Rigshospitalet, Blegdamsvej 9, 2100 Copenhagen, Denmark

4 Department of Diagnostic Radiology, Copenhagen University Hospitals at Herlev, Herlev Ringvej 75, 2730 Herlev, Denmark

5 Department of Rheumatology, Copenhagen University Hospitals at Hvidovre and Herley, Kettegaard Allé30, 2650 Hvidovre, Denmark

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Arthritis Research & Therapy 2006, 8:R59  doi:10.1186/ar1919

Published: 15 March 2006

Abstract

The aim of this study was to demonstrate the ability of conventional radiography to detect bone erosions of different sizes in metacarpophalangeal (MCP) joints of rheumatoid arthritis (RA) patients using magnetic resonance imaging (MRI) as the standard reference. A 0.2 T Esaote dedicated extremity MRI unit was used to obtain axial and coronal T1-weighted gradient echo images of the dominant 2nd to 5th MCP joints of 69 RA patients. MR images were obtained and evaluated for bone erosions according to the OMERACT recommendations. Conventional radiographs of the 2nd to 5th MCP joints were obtained in posterior-anterior projection and evaluated for bone erosions. The MRI and radiography readers were blinded to each other's assessments. Grade 1 MRI erosions (1% to 10% of bone volume eroded) were detected by radiography in 20%, 4%, 7% and 13% in the 2nd, 3rd, 4th and 5th MCP joint, respectively. Corresponding results for grade 2 erosions (11% to 20% of bone volume eroded) were 42%, 10%, 60% and 24%, and for grade 3 erosions (21% to 30% of bone volume eroded) 75%, 67%, 75% and 100%. All grade 4 (and above) erosions were detected on radiographs. Conventional radiography required a MRI-estimated bone erosion volume of 20% to 30% to allow a certain detection, indicating that MRI is a better method for detection and grading of minor erosive changes in RA MCP joints.