Definitions and scaling of features in proposed OMERACT TOMS
| MRI feature | Definition | Scaling | Suggested plane and MRI sequence |
| Synovitis† | Thickened synovium with enhancement after Gd injection. | 0=normal; 1=mild (1%–33%); 2=moderate (34%–66%); 3=severe (67%–100%). Based on thirds of the presumed maximum thickness of enhancing tissue in the synovial compartment. | Coronal and axial. T1w pre-Gd and post-Gd with fs. In the absence of post-Gd images T2w-fs/STIR/PD-fs can be used. |
| Subchondral bone defects†‡ | Subchondral bone loss, including erosions (sharply marginated bone lesions with cortical break), cysts (sharply marginated bone lesions without cortical break) and bone attrition (diffuse loss of bone contour). | 0=no bone defects; 1=mild (≤25% of bone volume or joint surface affected); 2=moderate (26%–50% of bone volume or joint surface affected); 3=severe (>50% of bone volume or joint surface affected). | Coronal and axial. T1w and T2w-fs/STIR/PD-fs. |
| Osteophytes‡ | Abnormal bone protuberance at joint margins or surfaces. | 0=no osteophytes; 1=mild (1–2 small osteophytes); 2=moderate (≥3 small osteophytes and/or≥1 moderate osteophyte(s)); 3=severe (≥1 large osteophyte(s)). | Coronal (and sagittal if available). T1w. |
| Cartilage assessment | Loss of cartilage or loss of cartilage space based on the interbone distance¶. | 0=no loss of cartilage or cartilage space; 1=mild (cartilage loss without complete denuding, or cartilage space loss without bone-to-bone contact); 2=moderate (cartilage loss with denuding ≤50% of joint surface or focal complete cartilage space loss with bone-to-bone contact ≤50% of the articulating area); 3=severe (cartilage loss with denuding >50% of joint surface or complete cartilage space loss over >50% of the articulating area). | Coronal. T1w-fs-3D-GE, otherwise use T1w-fs, T2w-fs or PD-fs. |
| Subluxation§ | Subluxation of the CMC-1 joint in the frontal plane. | 0=MC-1 subluxed 0%–25% of the MC-width; 1=MC-1 subluxed ≥26% of the MC-width. | Coronal. T1w. |
| Bone marrow lesions†‡ | Lesions within the trabecular bone with signal characteristic consistent with increased water content** and with ill-defined margins. | 0=no bone marrow lesions; 1=mild (1%–33% bone volume); 2=moderate (34%–66% bone volume); 3=severe (67%–100% bone volume). | Coronal and axial. T2w-fs/STIR/PD-fs. |
Table was reprinted with permission from Kroon et al. 1 All rights reserved.
†In longitudinal studies, 0.5 increments can be included to indicate within-grade change in synovitis, subchondral bone defects and bone marrow lesions.
‡Proximal and distal parts of joint are scored separately for subchondral bone defects, osteophytes and bone marrow lesions.
§Only the CMC-1 joint is evaluated for this feature.
¶If assessment of cartilage and cartilage space are in conflict, direct visualisation of the cartilage should be prioritised.
**High signal intensity on STIR/T2w-fs images.
CMC-1, first carpometacarpal; fs, fat saturated; Gd, gadolinium-based contrast agent; GE, gradient echo; MC-1, first metacarpal; PD, proton density; OA, osteoarthritis; OMERACT, Outcome Measures in Rheumatology Clinical Trials; STIR, Short T1 Inversion Recovery; STT, scapho-trapezio-trapezoid; TOMS, thumb base OA MRI scoring system; w, weighted.