A. Definitions of important PsA joint pathologies
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Synovitis: An area in the synovial compartment that shows increased postgadolinium (post-Gd) enhancement* of a thickness greater than the width of the normal synovium.
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Tenosynovitis: Signal characteristics consistent with increased water content* or abnormal post-Gd enhancement** adjacent to a tendon, in an area with a tendon sheath.
* High signal intensity on T2-weighted (T2w) fat-saturated (FS) and short tau inversion recovery (STIR) images, and low signal intensity on T1 w images. **Enhancement is judged by comparison between T1w images obtained before and after IV Gd contrast.
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Periarticular inflammation: Signal characteristics consistent with increased water content* or abnormal post-Gd enhancement** at extraarticular sites including the periosteum (‘periostitis’) and the entheses (‘enthesitis’), but not the tendon sheaths ***
*High signal intensity on T2w FS and STIR images. 1 w images, obtained before and after IV Gd contrast. **Enhancement is judged by comparison between T1w images, obtained before and after IV Gd contrast. ***Defined as tenosynovitis.
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Bone marrow oedema: A lesion* within trabecular bone, with signal characteristics consistent with increased water content** and often with ill-defined margins.
*May occur alone or surrounding an erosion or other bone abnormalities. **High signal intensity on T2w FS and STIR images, and low signal intensity on T1w images.
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Bone erosion: A sharply marginated bone lesion, with typical signal characteristics*, which is visible in two planes with a cortical break seen in at least one plane**.
*On T1w images: loss of normal low signal intensity of cortical bone and loss of normal high signal intensity of marrow fat. **This appearance is nonspecific for focal bone loss. Other lesions such as bone cysts may mimic erosions.
Bone proliferation: Abnormal bone formation in the periarticular region, such as at the entheses (enthesophytes) and across the joint (ankylosis).
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B. Scoring system (OMERACT PsAMRIS) for hands
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Regions to score: Regions are delimited at the midpoint of phalangeal bones. D: Distal interphalangeal (DIP) joint region; P:
Proximal interphalangeal joint (PIP) region; M: Metacarpophalangeal (MCP) joint region. Each region is subdivided into two sub regions (D1, D2, P1, P2, M1 and M2) by a transverse line through the joint space.
Synovitis: To be scored 0—3 per M, P and D region. Grading scale: Score 0: normal; 1: mild; 2: moderate; 3: severe (by thirds of the maximum potential volume of enhancing tissue in the synovial compartment). Flexor tenosynovitis: To be scored 0—3 per M, P and D region. Grading scale: Per maximal thickness of enhancing/bright signal on T1w postcontrast/STIR or T2w FS images, as follows: Grading scale: 0: none; 1: < ½ tendon thickness; 2: ≥ ½ and <1 tendon thickness; 3: ≥ 1 tendon thickness. Periarticular inflammation: To be scored 0—1 in the dorsal part and 0—1 in the palmar part of each M, P and D region. Grading scale: 0: absent; 1: present. Bone oedema: To be scored 0—3 per M1, M2, P1, P2, D1 and D2 regions. Grading scale: The scale is 0—3 based on the proportion of bone with oedema, compared with the ‘assessed bone volume’, judged on all available images: 0: no oedema; 1: 1—33% of bone oedematous; 2: 34—66%; 3: 67—100% Bone erosion: To be scored 0—10 per M1, M2, P1, P2, D1 and D2 regions. Grading scale: The scale is 0—10, based on the proportion of eroded bone compared with the ‘assessed bone volume’, judged on all available images: 0: no erosion; 1: 1—10% of bone eroded, 2; 11—20% etc. The ‘assessed bone volume’ is from the articular surface (or its best estimated position if absent) to a depth of 1 cm. Bone proliferation: To be scored 0—1 in each M, P and D region. Grading scale: 0: absent; 1: present.
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