Development and reliability of a preliminary Foot Osteoarthritis Magnetic Resonance Imaging Score

Objective. Foot osteoarthritis (OA) is very common but underinvestigated musculoskeletal condition and there is little consensus as to common magnetic resonance imaging (MRI) features. The aim of this study was to develop a preliminary foot OA MRI score (FOAMRIS) and evaluate its reliability. Methods. This preliminary semiquantitative score included the hindfoot, midfoot, and metatarsophalangeal joints. Joints were scored for joint space narrowing (JSN; 0–3), osteophytes (0–3), joint effusion/synovitis, and bone cysts (present/absent). Erosions and bone marrow lesions (BML) were scored (0–3) and BML were evaluated adjacent to entheses and at sub-tendon sites (present/absent). Additionally, tenosynovitis (0–3) and midfoot ligament pathology (present/absent) were scored. Reliability was evaluated in 15 people with foot pain and MRI-detected OA using 3.0T MRI multi-sequence protocols, and assessed using ICC as an overall score and per anatomical site. Results. Intrareader agreement (ICC) was generally good to excellent across the foot in joint features (JSN 0.90, osteophytes 0.90, effusion/synovitis 0.46, cysts 0.87), bone features (BML 0.83, erosion 0.66, BML entheses 0.66, BML sub-tendon 0.60) and soft tissue features (tenosynovitis 0.83, ligaments 0.77). Interreader agreement was lower for joint features (JSN 0.43, osteophytes 0.27, effusion/synovitis 0.02, cysts 0.48), bone features (BML 0.68, erosion 0.00, BML entheses 0.34, BML sub-tendon 0.13), and soft tissue features (tenosynovitis 0.35, ligaments 0.33). Conclusion. This preliminary FOAMRIS demonstrated good intrareader reliability and fair interreader reliability when assessing the total feature scores. Further development is required in cohorts with a range of pathologies and to assess the psychometric measurement properties