Congenital proximal radioulnar synostosis associated with bilateral hypoplasia of the scaphoid bone, bilateral os lunatotriquetrum, and anomalies of the carpometacarpal complex.

We describe a unique case of bilateral os lunatotriquetrum associated with bilateral hypoplasia of the scaphoid bone. On both sides, the medial carpi were in a single row. The capitate bone occupied the lunate position, whereas the lunatotriquetral bone was displaced ulnarly and tilted. The capitate thus articulated with the radius and metacarpal bones, consistent with carpal collapse. In addition, there was congenital proximal radioulnar synostosis on the left side.