[Scapholunate dissociation].

Scapholunate dissociation is a rotatory subluxation of the scaphoid with widening of the gap between the scaphoid and lunate. It is caused by rupture of the ligaments between radius, scaphoid, lunate and capitate bones. The scaphoid has lost its stabilizing function as a bridge between the proximal and distal carpal row, so that the wrist shows the typical "concertina" deformity of dorsal instability. The scapholunate angle measures about 100 degrees (more than 70 degrees). The subluxation of the scaphoid and lunate with the wide gap between these bones is best treated by primary repair of the ruptured ligaments. However, most cases are seen late and a ligament reconstruction by a free or pedicled tendon graft becomes necessary. The results are often unsatisfactory radiologically, but cause the patient minimal disability. An alternative to the ligament reconstruction is the scapho-trapezio-trapezoid arthrodesis. By this procedure the scaphoid regains its stabilizing function to the "link system" of the carpus.