Ultrasound findings of calcium pyrophosphate deposition disease at metacarpophalangeal joints

Objective: To explore the spectrum of articular and peri-articular ultrasound (US) findings at metacarpophalangeal (MCP) joints in calcium pyrophosphate (CPP) deposition disease (CPPD). Methods: Consecutive CPPD patients (chronic CPP crystal inflammatory arthritis or osteoarthritis (OA) with CPPD), and age- and sex-matched controls with rheumatoid arthritis (RA) were prospectively enrolled. Patients underwent bilateral US examination of MCP joints. CPP deposits, synovial inflammation, osteophytes, cartilage damage, and bone erosions were recorded. Results: Sixty CPPD patients (33, 55.0% with osteoarthritis with CPPD and 27, 45.0% with chronic CPP crystal inflammatory arthritis) and 40 RA patients were enrolled. CPP deposits were detected in 24 (40.0%) CPPD patients and in 3 (7.5%) RA patients (p< 0.01). In CPPD patients, different types of CPP deposits were identified at MCP joints: 17 (28.3%) patients had dorsal capsuloligamentous deposits, 14 (23.3%) intra-cartilaginous deposits, 13 (21.7%) lateral capsuloligamentous deposits, 12 (20.0%) intra-articular deposits, 8 (13.3%) double contour sign, and 5 (8.3%) flexor digitorum tendons' deposits.CPPD patients with chronic CPP crystal inflammatory arthritis showed more US findings indicating synovial inflammation and CPP deposits than those with osteoarthritis with CPPD. Conversely, a higher prevalence of US features indicating structural damage was noted in this latter phenotype.CPP deposits and bone erosions were the US findings with the highest value for diagnosing chronic CPP crystal inflammatory arthritis and RA, respectively. Conclusion: This study provides pictorial evidence of the broad spectrum of US findings indicating CPP deposits at MCP joints in CPPD. Furthermore, we reported different US patterns in different CPPD phenotypes.