Irreducible fracture-dislocation of the distal radioulnar joint secondary to entrapment of the extensor carpi ulnaris tendon.

Entrapment of the extensor carpi ulnaris (ECU) tendon between the ulnar head and the sigmoid notch of the radius occurred in a 12-year-old boy. This led to an irreducible dorsal dislocation of the distal radioulnar joint (DRUJ). Irreducible DRUJ dislocations are uncommon, and the entrapped ECU has not been previously described in a skeletally immature patient. The physical and roentgenographic findings of a dorsally displaced ulna, a widened DRUJ, and the inability to obtain a closed reduction should alert the examiner to the need for exploration. A dorsal exposure is required to free the ECU and reconstruct the triangular fibrocartilage complex.