Volume changes within the true pelvis during disruption of the pelvic ring--where does the haemorrhage go?

Fractures of the pelvis are not only common but are very varied in their complexity. They represent 3% of all fractures (1), they account for 1 in every 1000 surgical admissions and are the third most commonly encountered injury in motor vehicle accident fatalities (2). However, only a small percentage of all pelvic fractures are associated with major disruption of the pelvic ring (3). Life threatening haemorrhage is a frequent complication of major pelvic fractures (1, 4) and haemorrhage is the leading cause of death in these patients (5, 6). It was believed that fracture and subsequent displacement of the ring greatly increased pelvic volume. However, clinical practice seemed to indicate that this might not be true. This study aimed to assess the change in pelvic volume which occurs in severely displaced pelvic fractures. A model of the bony pelvis was designed to permit extreme displacements of the symphyseal and sacroiliac joints. The volume of a polythene balloon placed within the true pelvis was measured as an indication of true pelvic volume. Our finding was that the increase in the volume of the true pelvis which occurs in a fracture with massive diastasis is much smaller than previously assumed.