Doppler signal and bone erosions at the enthesis are independently associated with ultrasound joint erosive damage in psoriatic arthritis

Objective: To explore the association of the OMERACT ultrasound (US) entheseal abnormalities with the presence of US joint bone erosions in psoriatic arthritis (PsA). Methods: Consecutive PsA patients were included in this cross-sectional study. Demographic and clinical parameters were collected. A bilateral US assessment was carried out at the following entheses: plantar fascia, quadriceps, patellar (proximal and distal) and Achilles tendons. The following US entheseal abnormalities were registered: hypoechogenicity, thickening, Doppler signal <2mm from the bony cortex, calcification/enthesophyte, bone erosion. The presence of US joint bone erosions was investigated at the 2nd and 5th metacarpophalangeal (MCP) joints, ulnar head and 5th metatarsophalangeal (MTP) joint, bilaterally, as well as at the level of the most inflamed joint on physical examination. Multiple linear regression analysis was performed to identify clinical and/or US variables associated with US-detected joint bone erosions. Results: A total of 104 PsA patients were enrolled. At least one joint bone erosion was found in 47/104 patients (45.2%). Bone erosions were most frequently detected at 5th MTP joint level (42/208 joints, 20.2 %; 32/104 patients, 30.8%). In the multivariate model, only PD signal at the enthesis (P<0.001, standardized β=0.51), bone erosions at the enthesis (P=0.02, standardized β=0.2), PsA disease duration (P=0.04, standardized β=0.17) and greyscale joint synovitis (P=0.03, standardized β=0.42) were associated with US-detected joint bone erosions. Conclusion: PD signal and bone erosions at the enthesis represent sonographic biomarkers of a more severe subset of PsA in terms of US-detected joint erosive damage.