THU0298 Peritenon extensor tendon inflammation, synovitis and enthesopathy in psoriatic arthritis: what is the connexion?

Background Metacarpophalangeal joint (MCPj) swelling in Psoriatic Arthritis (PsA) can be produced both by intra-articular synovitis (IAS) and peritenon extensor tendon inflammation (PTI). This last lesion has been reported as an enthesitis-like lesion. Objectives To evaluate if PTI is a synovitis or enthesitis related lesion using MASEI (Madrid Sonographic Enthesis Index) to analyse the existence of association with IAS and PTI. Methods 27 consecutive non selected PsA patients were included. An expert rheumatologist obtained the US images from the dorsal aspect of 2nd to 5th MCPj of both hands evaluating IAS and PTI, and also performed the MASEI examination. In addition to the PD item of MASEI (defined as signal in bone profile or intratendon or bursa at the enthesis), PD OMERACT was evaluated as present or absent (defined as signal in the enthesis ≤2 mm to the bone profile). We used a MyLab 70 XVG machine, Esaote, Genova, Italy, with a greyscale (GS) 13 MHz probe and 7.1 MHz power Doppler (PD) frequency, PRF 750 Hz and 60 Gain. 3–5 s videos of each MCPj and enthesis were obtained in transverse and longitudinal views for further reliability analysis. Reliability of IAS and PTI was performed by 5 readers (true US result was the consensus of at least three) and MASEI’s reliability was performed by 3 readers (true US result was the consensus of at least two). For reliability analysis, mean Cohen kappa was used for IAS and PTI, and intraclass correlation coefficient (ICC) for MASEI based on a mean-rating three readers, absolute-agreement, two-way mixed effect model. Statistical association between IAS, PTI and MASEI was analysed with T student test. SPSS statistical package version 20 (SPSS Inc, Chicago, IL) was used. Results Eighteen patients had PTI PD (66,7%), same for SIA PD. Inter-reader reliability for PTI and SIA was 0.685 and 0.680 kappa values respectively. Inter-reader reliability for MASEI was excellent ICC 0,922 (IC 95% 0,852–0,962), similar to PD MASEI ICC 0,921 (IC 95% 0,851–0,962) and PD OMERACT ICC 0.895 (IC 95% 0,802–0,949). Association data are shown in table 1. Conclusions In PsA, IAS at MCPj didn’t show any association with enthesitis. However, PTI showed a significant statistically association with active enthesitis (PD MASEI and PD OMERACT). This finding reinforces the idea that PTI at MCPj level is related with the swelling of the functional enthesis related to the retinaculum pulley structure. References [1] Mc Gonagle D, et al. The concept of a synovio-enthesal complex and its implications for understanding joint inflammation and damage in psoriatic arthritis and beyond. AR56(8):2482–91. [2] De Miguel E, et al. Validity of enthesis ultrasound assessment in spondyloarthropathy. ARD2009;68:169–74. Disclosure of Interest None declared