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Background Dactylitis is a hallmark of psoriatic arthritis (PsA) occurring in around 40% of cases at some point in the disease course. At the micro anatomical level PsA is strongly linked to disease localisation to entheses and other sites of high mechanical stress. Recently high resolution MRI has shown prominent abnormalities at the mini-entheses of the flexor tendon pulleys may be common Objectives . In this study we aimed to understand the changes within the pulleys for patients with PsA, with or without dactylitis to explore the role of the pulley disease in the dactylitis. Methods Consecutive 20 cases of PsA with dactylitis were recruited and had an US scan of the A1, A2 and A4 pulleys of the digit with dactylitis and the contralateral side. A high resolution probe (22 MHZ) was used to explore a) the thickness of the pulleys, b) the presence of Doppler signals. A comparison was made within digits with or without dactylitis Results Half of the A1 pulleys with dactylitic digits had Doppler signals (10/20, 50%), which was less common in A2 (6/20 (30%)) and A4 pulleys (6/20 (30%)) (figure). The digits without dactylitis had Doppler signals less frequently (A1: 1/19 (5%); A2: 1/19 (5%) A4: 1/19 (5%)) A1, A2 and A4 pulleys were significantly thicker in dactylitis fingers compared to fingers without dactylitis, both in longitudinal and transverse planes (table 1). Conclusions This study demonstrates that pulleys contribute to the pathogenesis of dactylitis with increased vascularity and thickening, probably due to the micro-enthesitis at the level where the flexor tendons are exposed to high mechanical stress. This is important to understand the anatomical basis of a complex disease feature in PsA, dactylitis Disclosure of Interest None declared |
