Objective: To test the hypothesis that microanatomical differences in joint disease localisation could be exploited using high-resolution MRI to better differentiate among rheumatoid arthritis (RA), spondyloarthritis/psoriatic arthritis (SpA/PsA) and osteoarthritis (OA) in clinical practice.
Methods: Sixty-nine patients with suspected inflammatory joint disease of the hand or feet underwent high-resolution MRI using a small loop coil. Images were scored blinded to the clinical status. Various joint changes like periostitis, osteitis, erosions, enthesitis and synovitis were recorded. The image-based diagnosis was compared with the clinical diagnosis.
Results: In 59.4 % of the patients the clinical diagnosis was confirmed on image analysis. This was high for OA (80 %), moderately good for RA (67 %) but only 50 % for SpA/PsA. The major difficulty was to distinguish OA from SpA/PsA where common imaging findings are evident including periostitis (SpA/PsA 45 %, OA 40 % compared with RA 0 %; P = 0.015). Likewise, osteitis was frequently detected in SpA/PsA (79 %) and OA (80 %) and less frequently in RA (42 %) (P = 0.014).
Conclusion: Characterisation of inflammatory disorders of small joints merely using high-resolution MRI remains challenging especially in the differentiation between OA and PsA. These findings are likely explained by common microanatomical similarities in disease expression rather than limitations of imaging techniques.
Key points: • High-resolution MRI is increasingly used to investigate joint disease. • Osteitis and periostitis occur in psoriatic and osteoarthritis (but not rheumatoid arthritis). • In severely affected patients the amount of synovitis and erosions is similar.