Revisiting the metacarpophalangeal joint: comparison of ultrasound tissue patterns with its anatomical, histological, and immunohistochemical features

This study aimed to identify the structures and tissues of the dorsal aspect of the metacarpophalangeal joint (MCPJ) using ultrasound, with gross anatomy as a comparator and learning source. In addition, the composition of several MCPJ tissues was investigated by histology and immunohistochemistry.The study comprised 3 steps. First, 4 rheumatologist ultrasonographers identified on B-mode imaging the tissue patterns of the structures in the dorsal aspect of the MCPJ in fresh-frozen cadaveric hands. In the second step, 2 anatomists performed dissections on fresh-frozen and embalmed cadaveric hands to characterize the components of the dorsal MCPJ, providing anatomy-based feedback to aid ultrasound tissue interpretation. Histological and immunohistochemical analyses were also conducted on selected dorsal MCPJ tissues. In the third step, the anatomy and histology-based knowledge were applied to identify and evaluate these structures in healthy subjects using B-mode and Doppler mode ultrasound.Ultrasound examination of the cadaveric hands identified the key dorsal MCPJ structures, including the extensor tendon, joint capsule, dorsal plate, synovial recesses, and metacarpal head cartilage. Anatomical and histological analyses further characterized these structures, enhancing their identification in healthy subjects. Additionally, new insight into the histological and immunohistological features of these structures is provided.Ultrasound successfully identified the main structures of the dorsal MCPJ. Integrating anatomical and histological features improved ultrasound imaging observations and confidence.