Coronal shift of distal radius fractures: influence of the distal interosseous membrane on distal radioulnar joint instability

ISTAL RADIUS FRACTURES ARE frequently associated with distal radioulnar joint (DRUJ) injury and a substantial proportion of patients develop symptomatic instability after fracture union. Distal radioulnar joint instability can lead to ulnarsided wrist pain, painful or limited forearm rotation, grip strength weakness, and/or degenerative arthritis. Distal radioulnar joint stability depends on the triangular fibrocartilage complex (TFCC), bony articulation between the ulnar head and sigmoid notch of the radius with its fibrocartilaginous rim, dorsal and palmar radioulnar ligaments, distal interosseous membrane (DIOM), and the musculotendinous units of the extensor carpi ulnaris and pronator quadratus. Cadaveric studies have demonstrated that the primary stabilizer of the DRUJ is the TFCC (specifically the radioulnar ligaments) and that the DIOM is an important secondary stabilizer of the DRUJ. 1,2 In the setting of a distal radius fracture, the usually intact DIOM has a central role in DRUJ stability because the TFCC is frequently injured. The DIOM is an isometric stabilizer of the forearm and its stabilizing effect has been attributed to its resting tension. 1 A recent anatomic study defined the DIOM as originating palmar and proximal on the ulna and inserting distal and dorsal on the radius, thus providing a structural basis for its function in resisting dorsal translation of the radius in supination. 3 In addition, approximately 40% of patients have a distinct ligamentous thickening of the DIOM known