[Ultrasound patterns of rheumatoid and psoriatic arthritis in finger joints]

Rheumatoid and psoriasic arthritis involve proximal joints symmetrically and distal joints asymmetrically, respectively, the differential diagnosis between these two types of arthritis is not easy. Therefore we investigated which US signs could help the diagnosis and/or treatment of these conditions and compared them with radiographic patterns and articular and physical symptoms.

Fifty-one patients, 30 women and 21 men aged 19-42 years were enrolled in this study. Thirty patients had rheumatoid and 21 psoriasic arthritis. US of the skin and joints of the fingers was performed with a GE Sonora Logic 500 MD unit with 7.5 and 10 MHz scanheads. We studied the shape of articular bone heads, the intra-articular space distance and the thickness of extensor tendon and of the dermis and hypodermis covering it. These findings show the extent of damage in articular bone heads and intra-articular space and they indicate cutaneous and articular inflammation. US patterns were also compared with radiographic findings in all patients.

US showed bone and joint and/or inflammatory damage in both types of arthritis. Articular bone heads had a bodkin-like appearance in proximal phalanges in rheumatoid arthritis, versus a hook-like appearance in distal phalanges in psoriasic arthritis. Inflammatory damage was indicated by intra-articular space thinning and by tendon, dermis and hypodermis thickening. These signs, confirmed radiographically, account for finger deformation and functional impairment, swelling and pain.

US signs can help the diagnosis of rheumatoid and psoriasic arthritis. US can show inflammatory damage and the disease evolution.