Mechanism of loosening of the Souter-Strathclyde total elbow replacement evidence from revision surgery.

Nine Souter-Strathclyde humeral and ulnar components retrieved from revision surgery for aseptic loosening were examined macro- and microscopically. The wear patterns were compared and photographed. Humeral components demonstrated no evidence of wear. All ulnar components exhibited similar wear patterns. Six of the nine exhibited macroscopic evidence taking the form of deep linear grooves on either the medial or lateral articulating surfaces. Microscopic examinations revealed wear on all nine, exhibited as disruption of the polyethylene machining lines on the articular surfaces, but almost complete preservation on the central gliding ridge. We believe our observations are explained by 'rocking' of the humeral component on the ulnar as a result of the congruent surfaces of the Souter-Strathclyde prosthesis, which resist rotational and translational movements, characteristic of the normal elbow.