The treatment of isolated fractures of the distal ulna.

The integrity of the periosteum and the interosseous membrane determine the stability of fractures of the distal ulna; this is indicated by the initial displacement. In fractures displaced by less than 50% the periosteum and interosseous membranes are largely intact; these fractures are stable and require only below-elbow immobilisation for protection and relief of pain. In fractures displaced by more than 50% the membranes are disrupted; these fractures are unstable and require above-elbow immobilisation for stability. As most fractures are displaced by less than 50%, immobilisation of the elbow, which significantly increases morbidity, is usually unnecessary. I report the results of a cadaveric study on the pathomechanics of fractures of the distal ulna, and of a prospective clinical trial in which the type of cast used for immobilisation was determined by the stability of the fracture.