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 prona tion and supination. Subluxation and dislocation of the radius with re spect to the ulna were evaluated in seven cadaver forearms placed in s upination, pronation, and neutral forearm rotation. The amount of subl uxation was measured with all structures intact, and after sectioning in various sequences the dorsal and palmar radioulnar ligaments, the d istal portion of the interosseous membrane including the pronator quad ratus, and the entire interosseous membrane. After sectioning two of a ny four structures, the distal radioulnar joint remained stable. When the interosseous membrane was disrupted first, the dorsal radioulnar l igament was found to be more important than the pal mar radioulnar lig ament in stabilizing the distal radioulnar joint in pronation, and con versely the palmar radioulnar ligament was more important than the dor sal radioulnar ligament in supination. Dislocation, and frequently dia stasis, occurred only with sectioning of all four structures. This sug gests that all four structures contribute to stability of the distal r adioulnar joint.