Figure 1

Different types of fat lesion in the FAt Spondyloarthritis Spine Score. (A) Types of fat lesions in the FAt Spondyloarthritis Spine Score (FASSS) and the scores applied. Scoring method is described in further detail in the text. (B) Corner fat lesions in central sagittal slices. Several focal fat lesions with variable size are located at the anterior corners of the vertebral bodies. The fat lesions at the anterior corner of the upper endplate of T12, L1, L2 and L3 are all small; that is, they do not involve 25% or more of the anterior–posterior diameter of the vertebral endplate and/or of the height of the vertebral body. The fat lesion at the anterior corner of the lower endplate of L2 fulfills the definition of being large (involves ≥25% of the anterior–posterior diameter of the vertebral endplate and/or the height of the vertebral body), and a score of 1 is added. If the fat lesion fulfils the definition of combined corner and noncorner lesion (involves ≥50% of the anterior–posterior diameter of the vertebral endplate), a score of 1 is added if the lesion involves ≥25% of the height of the vertebral body at either the anterior or posterior vertebral cortex. A score of 2 is added if the lesion involves ≥25% of the height of the vertebral body measured at the midpoint of the vertebral endplate. The small corner fat lesions are all scored 1, whereas the large corner lesion is scored 2. The total FASSS for T12–L3 for this single sagittal slice is 6. The score per disco-vertebral unit (DVU) is 1 for T11/T12, T12/L1 and L1/L2, respectively, and is 3 for L2/L3.