The distal interosseous membrane: current concepts in wrist anatomy and biomechanics.

The distal interosseous membrane (DIOM) of the forearm acts as a secondary stabilizer of the distal radioulnar joint (DRUJ) when the dorsal and palmar radioulnar ligaments of the triangular fibrocartilage complex are cut. Recent anatomical studies revealed that thickness of the DIOM varies widely among specimens and the distal oblique bundle (DOB) exists within the DIOM in 40% of specimens. The DOB originates from the distal one-sixth of the ulnar shaft and runs distally to insert on the inferior rim of the sigmoid notch of the radius. The mean thickness of the DIOM without a DOB was 0.4 mm, which was significantly thinner than 1.2 mm with a DOB. Biomechanical studies have shown that the DOB is an isometric stabilizer of the forearm during pronosupination. The presence of a DOB was shown to have a significant impact on DRUJ stability. Innate DRUJ laxity in the neutral forearm position was greater in the group without a DOB than in the group with a DOB. Ulnar shortening with the osteotomy performed proximal to the attachment of the DIOM had a more favorable effect on stability of the DRUJ compared with the effect of distal osteotomy, especially in the presence of a DOB. The longitudinal resistance to ulnar shortening was significantly greater in proximal shortening than in distal shortening. It also suggested that the DIOM is of great importance in the management of concomitant ulnar-side injuries in distal radius fracture.