The distal radioulnar ligaments: a biomechanical study.

The mechanical roles of the triangular fibrocartilage have been examined in three experiments. Kinematic analysis by a stereophotogrammetric method revealed that the palmar radioulnar ligament was taut in supination and that the dorsal radioulnar ligament was taut in pronation. In full pronation, the palmar radioulnar ligament decreased to an average of 71% of its length in tension. In full supination, the dorsal radioulnar ligament decreased to an average of 90% of its length. Mechanical testing of the triangular fibrocartilage under axial load disclosed a significant laxity (mean: 10.4 mm), which was decreased in pronation. Transverse loading tests demonstrated that the triangular fibrocartilage is less stiff in neutral forearm rotation. Study of the material properties of the palmar and dorsal parts of the triangular fibrocartilage showed these structures to be strong ligaments with material properties similar to those of the radiocarpal ligaments.