Analysis of mechanical factors affecting fixation of olecranon fractures

Fractures of the most distal part of the olecranon process differ from more proximal fractures because a plane of instability exists between the humerus and the radial head. Thus, the fixation of these fractures must resist the deforming forces of the forearm flexor muscles. The investigators fixed 10 paired cadaver ulnae with either the tension-band wire technique or a one-third tubular plate, and tested the specimens to simulate the effect of the biceps and brachialis muscles. The average maximum fixation stiffness for specimens fixed with the one-third tubular plate was found to be 163 N/mm compared with 53 N/mm for the tension-band wire group. This study indicates that for fractures of the distal part of the olecranon, fixation with screws and a one-third tubular plate affords better resistance to the forces applied by the brachialis and the biceps brachii than the tension-band wire technique.