The stabilizing mechanism of the distal radioulnar joint during pronation and supination.

A biomechanical cadaver study was performed to determine the roles of the stabilizing structures of the distal radioulnar joint during pronation and supination. Subluxation and dislocation of the radius with respect to the ulna were evaluated in seven cadaver forearms placed in supination, pronation, and neutral forearm rotation. The amount of subluxation was measured with all structures intact, and after sectioning in various sequences the dorsal and palmar radioulnar ligaments, the distal portion of the interosseous membrane including the pronator quadratus, and the entire interosseous membrane. After sectioning two of any four structures, the distal radioulnar joint remained stable. When the interosseous membrane was disrupted first, the dorsal radioulnar ligament was found to be more important than the palmar radioulnar ligament in stabilizing the distal radioulnar joint in pronation, and conversely the palmar radioulnar ligament was more important than the dorsal radioulnar ligament in supination. Dislocation, and frequently diastasis, occurred only with sectioning of all four structures. This suggests that all four structures contribute to stability of the distal radioulnar joint.