Abstract

The roentgen appearance and pathogenesis of carpal instability are described in an evaluation of patients and cadavers with rheumatoid arthritis and calcium pyrophosphate deposition disease. Dorsiflexion (16%) and palmar flexion (8%) instability occurs in rheumatoid arthritis, particularly in patients with moderate to advanced disease. Navicular-lunate dissociation frequently accompanies dorsiflexion instability and results from involvement of the interosseous ligament between the two bones by rheumatoid pannus. Carpal instability and navicular-lunate dissociation also accompany pyrophosphate arthropathy, resulting from calcific deposition and cystic degeneration of ligamentous structures.