Ankle retinacula abnormalities as features of psoriatic arthritis: An ultrasound study.

OBJECTIVE

To compare the ultrasonography (US) assessment of the retinacula of ankles in patients with rheumatoid arthritis (RA) and psoriatic arthritis (PsA).

METHODS

This cross-sectional study included RA or PsA patients with ankle pain and healthy controls. The following US features were recorded: presence of synovitis, tenosynovitis and abnormalities of two retinacula (the superior peroneal retinaculum [SPR] and the flexor retinaculum [FR] evaluated in mode B and power Doppler).

RESULTS

Among the 80 included patients, 37 (46%) and 23 (29%) had RA and PsA; 20 (25%) patients were healthy controls. The FR was thicker in PsA than RA ankles 0.96±0.39 vs. 0.64±0.15, P<0.001 with no difference between RA patients and HCs. Other FR abnormalities such as hypoechogenicity, PD positivity or periostosis were more frequent in PsA than RA patients, P<0.001. On receiver-operating-characteristic curve analysis, a cut-off of 1mm FR thickness provided a sensitivity of 49% and specificity of 97% for the diagnosis of PsA. Overall, 39 and 3% of PsA and RA ankles exhibited retinaculitis of FR (thickness≥1mm with hypervascularization or hypoechogenicity). The two disease groups did not differ in the evaluation of SPR.

CONCLUSIONS

US abnormalities of FR were more frequent in PsA than RA and appeared to be specific for PsA. US assessment of FR might be useful to distinguish RA and PsA.