Déstabilisation du carpe après fractures méconnues du scaphoïde

Scaphoid fractures are often pauci-symptomatic and frequently diagnosed late. This allows enough time for carpal instability to develop due to the loss of the lateral bony constraint. The lunate bone is the pivot of the destabilization process. Schematically, in the normal state the opposing forces involve on one hand the flexion constraint of the scaphoid bone and on the other the extension constraint of the triquetrum. After scaphoid fracture, the lunate bone is only exposed to the extension forces of the triquetrum, causing a dorsal pivot and DISI (dorsal intercalated segment instability). This instability modifies the normal joint relations of the first row (radius) and with the second row, leading at mid-term to osteoarthritis. Treatment of carpal instability depends on the status of the cartilage assessed radiographically and on the degree of osteoarthritis. The objective of treating the scaphoid nonunion is to stabilize the carpus and also to restore its height by correcting the fracture flexion. This generally requires a bone graft. Anatomic restitution of the scaphoid is the key to success of treatment of carpal instability after nonunion.