[Perilunar dislocation of the corpus in a patient with aplasia of the scaphoid]

Congenital aplasia of the scaphoid is a rare abnormality arising when the distal row of carpal bones is dislocated radially and proximally, the capitate replaces the scaphoid, and the lunate is triangular instead of quadrilateral in shape. The scaphoid bone which makes a functional bridge between the proximal and the distal row is a stabilising element under normal anatomical conditions. If it is absent, the carpus structure is disturbed and its radial part is prone to perilunar dislocation, because stability is provided only by the ligaments. However, a perilunar dislocation associated with aplasia of the scaphoid has not been described in the literature yet. In the case reported here, after arthroscopic examination ascertaining that the capsular ligaments are not interposed between the joints, the dislocation was managed by closed reduction and Kirschner wire transfixation for 8 weeks, and the wrist was immobilised with a below-elbow plaster splint for the same period. A 22-month follow-up did not show any signs of wrist instability or restriction in hand function.