Hand osteoarthritis and MRI: development and first validation step of the proposed Oslo Hand Osteoarthritis MRI score

Objectives MRI scoring systems for hand osteoarthritis (HOA) are currently not available. The present work proposes the Oslo HOA MRI (OHOA-MRI) score and examines the intrareader and inter-reader reliability. Methods Relevant HOA features were included in the initial version of the OHOA-MRI score after literature review and informal group discussions. After a training session and two calibration exercises (with three readers), features with low reliability and/or low prevalence were excluded, and feature definitions/gradings were improved. In the reliability exercise 3 readers independently evaluated MRI scans of distal interphalangeal (DIP) and proximal interphalangeal (PIP) joints in 10 patients with HOA according to the final proposed score. The reading was repeated after 1 week. Intraclass correlation coefficients (ICCs), percentage exact agreement/percentage close agreement (PEA/PCA) and smallest detectable difference were calculated. Results The final proposed OHOA-MRI score includes assessment of synovitis, flexor tenosynovitis, erosions, osteophytes (OPs), joint space narrowing (JSN) and bone marrow lesions (BMLs) on a 0-3 scale, and absence/presence of cysts, malalignment (frontal/sagittal plane), collateral ligaments (CLs) and BMLs at CL insertion sites. Inter-reader reliability was very good for synovitis, erosions, OPs, JSN, malalignment (frontal) and BMLs (ICCs >= 0.83, PCA >= 89%), and good for flexor tenosynovitis (ICC 0.64, PCA 80%) and CL presence (ICC 0.79, PEA 63%). Cysts, malalignment (sagittal) and BMLs at CL insertion sites showed high PEA (>= 85%), but poor to moderate ICCs (0.00-0.59). Intrareader reliability was similar. The reliability was generally highest in PIP joints. Conclusions The proposed OHOA-MRI score could reliably assess HOA features. However, further validation is needed.