Bi-directional mechanical properties of the human forearm interosseous ligament.

Interest in reconstruction of the interosseous ligament (IOL) of the forearm in the setting of longitudinal radio-ulnar dissociation has increased in recent years with hopes of improving clinical outcomes. This increased interest has been accompanied by research on biomechanics of the IOL. However, little is known about stress and strain in the IOL under externally applied forearm loads. This information is needed to help guide reconstruction. Mechanical properties of the IOL are needed to properly model the IOL for analyses such as finite element models. The objective of this study was to document the bi-directional mechanical properties along the fiber direction (longitudinal) and perpendicular to the fiber direction (transverse). Twenty specimens were mounted in a materials testing machine to perform preconditioning and a load to failure tensile test in each direction. Strain markers on the surface of the specimens were tracked with a video system. Data analysis provided stress-strain curves for each specimen. The elastic moduli of longitudinal and transverse specimens were 515+/-277 and 1.82+/-2.93 MPa, respectively. The tensile strength and ultimate strain of longitudinal and transverse specimens were 54.1+/-25.2 and 0.18+/-0.20 and 16+/-5% and 34+/-32%, respectively. The bi-directional mechanical properties of the IOL compared well with those published for the medial collateral ligament of the knee. The mechanical properties in the longitudinal direction were much greater than those in the transverse direction, which is indicative of the IOL's role in resisting longitudinal loading. The results of this study can be used to generate mathematical models of stress and strain in the IOL.