The forearm is a complex structure, with two bones that articulate across six joints. The bones of the forearm are connected centrally by the interosseous ligament (IOL). Compressive loading at the hand is one mode of loading required for many everyday activities and is known to cause forearm injury and long-term clinical problems. Although it has been speculated that the IOL becomes tense when compressive load is applied to the forearm, little is still known about the forces in this structure. Therefore, the objective of this thesis was to provide quantitative data on the forces in the IOL when a compressive load is applied to the hand.

A combined experimental and theoretical approach was undertaken in this thesis. Experience from dissection led to the hypotheses that tension in the IOL changes with forearm rotation, and that fibers of the IOL do not carry load evenly. A forearm loading experiment was developed to apply compressive loads to the hand in pronation, neutral and supination rotation positions. Universal force sensors and 3-D kinematic measurements were used to quantify the force vectors acting on the radius and ulna when load was applied to the hand. Results showed that the radius bears most of the load across the wrist while tension in the IOL acts to transfer load from the radius to the ulna. IOL forces were highest in neutral rotation and lowest in pronation.

To quantify the stress distribution across the fibers of the IOL, a theoretical model was developed. The IOL was modeled as a thin network of collagen fibers that do not interact and can carry force along fiber directions only (1-D model). For comparison, a transversely isotropic finite element model (3-D model) was developed using an academic code, NIKE3D. Material properties, 3-D geometry and displacement boundary conditions were measured from experiments. Results showed that the IOL does not carry load evenly:​ in neutral rotation and pronation stresses were higher in proximal fibers, while in supination, stresses were higher in distal fibers. The 3-D finite element model agreed well with the 1-D model, indicating that neglecting effects in the transverse direction for the 1-D model may be a good approximation.

In this thesis several techniques for measuring and modeling forces carried by the IOL were developed. Quantitative data on the net force in the IOL as well as the stress and strain distribution in the IOL was successfully obtained, and represents a valuable contribution to the field of forearm biomechanics and important information for surgeons. Future work should focus on biomechanics of forearm structural disruption and repair such as IOL injury and reconstruction.