Flexion-compression injury of the sternum.

Injuries of the sternum are commonly due to either direct violence to the front of the chest or indirect violence from flexion-compression of the spine. Injuries from hyperextension are exceedingly rare and will not be considered further. Nowadays many injuries of the sternum result from road accidents. Crushing injuries are frequently due to the impact of the steering column, and flexion-compression injuries may occur if the vehicle turns over or if passengers are flung out. In order to emphasise the distinctive features of the flexioncompression injury a short description of both kinds of sternal injury will be given. Direct injuries-Direct violence may cause two different types of sternal injury. The first and by far the commoner is due to crushing of the lower part of the front of the chest. The lower mobile part of the sternum receives the impact, but the sternum yields at a variable level above the site of impact. The sternum usually gives way near the junction of the mobile body with the relatively fixed manubrium in the same way that a branch of a tree breaks off near the trunk (Figs. 1 to 3). The second type of direct sternal injury occurs when the blow on the chest is localised and at a higher level (Figs. 4 and 5). The sternum is injured at the site of impact, and one fragment of the sternum may be displaced behind