Role of the forearm interosseous ligament: is it more than just longitudinal load transfer?

The objective of our study was to measure 3-dimensional force vectors (magnitude and direction) acting in the forearm when load is applied to the hand and to measure the actual force in the interosseous ligament (IOL). Fourteen cadaveric forearms were loaded to 136 N of compression while special load cells measured force vectors in the forearm. Computer forearm models were used to display the 3-dimensional force vector directions. The study results showed that the radius bears most of the load at the wrist but load on the radius at the elbow is reduced because the IOL transfers load to the ulna between the wrist and the elbow. In addition to this role in longitudinal load transfer, our measurement of 3-dimensional forces allowed identification of transverse vectors which suggest that the IOL also functions to keep the radius and ulna from splaying apart. Our results imply that the IOL participates not only in longitudinal load transfer but also in the maintenance of transverse stability of the forearm during compressive load transfer from the hand to the elbow.