Analysis of distribution and severity of inflammation in patients with osteoarthitis compared to rheumatoid arthritis by ICG-enhanced fluorescence optical imaging and musculoskeletal ultrasound: a pilot study

BACKGROUND: In rheumatoid arthritis (RA), hand synovitis appears especially in wrist, metacarpophalangeal (MCP) and proximal interphalangeal (PIP) joints. In hand osteoarthritis (OA), potential inflammatory changes are mainly present in PIP and distal interphalangeal (DIP) joints. Joint inflammation can be visualised by fluorescence optical imaging (FOI) and musculoskeletal ultrasound (US). OBJECTIVE: Comparison of the amount and distribution of inflammatory signs in wrist and finger joints of the clinically dominant hand in patients with OA and RA by FOI and gray-scale (GSUS) and power Doppler US (PDUS). METHODS: FOI and GSUS/PDUS were performed in 1.170 joints (wrists, MCP, PIP, DIP) in 90 patients (67 RA, 23 OA). Joint inflammation was graded by a semiquantitative score (0–3) for each imaging method. RESULTS: GSUS/PDUS showed wrist and MCP joints mostly affected in RA. DIP joints were graded higher in OA. In FOI, RA and OA featured inflammatory changes in the respective joint groups depending on the phase of fluorescence dye flooding. CONCLUSIONS: US and FOI detected inflammation in both RA and OA highlighting the inflammatory component in the course of OA. The different inflammatory patterns and various shapes of fluorescence enhancement in FOI may offer opportunities to distinguish and determine the inflammatory status in both diseases.