Power Doppler enhancement of accessory pulleys confirming disease localization in psoriatic dactylitis

The digital accessory pulleys are highly mechanically stressed mini-entheses that are thickened in patients with a history of PsA-related dactylits. This study explored whether these pulleys are involved in PsA dactylitis as assessed by intra-pulley US power Doppler changes.

Fifty-eight PsA patients with dactylitis had US of the second to fourth digits for pulleys of the dactylitic and contralateral digits. The Leeds Dactylometer was used for thickness measurement. The presence of digital pain, tenderness, and swelling in the dactylitis finger and in the contralateral side was evaluated.

We recruited 34 patients with acute and 24 patients with chronic dactylitis, 45/58 (77%) of which had tenderness on clinical assessment. Intra-pulley power Doppler was more frequently found in the dactylitic digits compared with contralateral sides and linked to A1, A2 and A4 pulleys thickening [power Doppler signals in A1 pulley (51%), A2 (22%) and A4 (12%) in dactylitic digit; compared with 1 A1, A2 and A4 pulleys each in the contralateral side (1.7%)]. Almost all cases had peri-tendinous oedema, and 82.6% of dactylitic digits had flexor tenosynovitis with power Doppler signals in 65.2% of flexor tendons.

Despite their small size and relatively avascular, the accessory pulleys exhibit power Doppler change in active Psoriatic dactylitis, supporting a pivotal role in dactylitis-related tenosynovitis and extra-tendinous disease.