The mechanisms of elbow fractures: an investigation using impact tests in vitro.

Various mechanisms of injury have been hypothesized for each of the common elbow fractures, but few have been proved. This paper describes cadaveric experiments demonstrating some fracture mechanisms. Tests were performed at different angles of flexion, with impacts around the elbow or along the forearm bones. A range of fractures occurred. Radial head and coronoid fractures followed impact along the forearm up to 80 degrees flexion. Olecranon fractures occurred by direct impact around 90 degrees flexion. Distal humeral fractures mostly occurred above 110 degrees flexion. A flexion-extension 'arc of injury' is shown, which relates fracture types to elbow position at the moment of impact. The results confirmed some of the mechanism hypotheses, and cast doubt on others. Knowledge of these mechanisms can give greater understanding of the injury which has occurred, such as the abnormal bone excursions which occur during impact and likely patterns of soft tissue damage.