Anatomy and Biomechanics of the Forearm Interosseous Membrane

Abstract

To examine the anatomy and function of the forearm interosseous membrane by exploring the anatomical insertions of the central band (CB) on the radius and the ulna and by quantifying the length of the intact ligament and replacement grafts located at the original CB attachment sites and alternative locations. Eight fresh cadaver forearms were supinated and pronated and the wrist was extended and flexed while the motion between the distal radius and ulna were recorded. The length of the CB was computed for the intact CB as well for several alternative graft orientations and positions. The maximum length of the CB did not significantly change among different wrist motions. However, with the wrist in a static neutral position, the CB length was significantly shorter in forearm supination than in neutral. During active forearm rotation when CB replacement grafts were positioned distal or proximal to the original CB site, yet still parallel to it, each had a similar trend to be longer in neutral than in supination. If a graft was more transversely oriented, the computed CB length would be 1.6 mm shorter in supination than in neutral. These results support tensioning a CB graft with the forearm in supination if the goal is to maximize graft tension and to maintain the native 22° angle for a CB graft between the radius and ulna. The results also suggest that the CB graft can probably be located slightly distal or slightly proximal to its original attachment sites. Reconstruction of the interosseous membrane has been hampered by a lack of understanding of its length changes with forearm or wrist motion. These results provide a starting point in helping clinicians understand how to more precisely reconstruct this ligament in an anatomical manner.