Pelvis Injury Mechanisms

There are three main types of injuries produced by direct impacts to the pelvis:-

• Isolated fractures of the pelvis ring, which include unilateral fracture of the pubic bones or ilium, which do not require surgical intervention and do not result in long-term disabilities

• Multiple fractures or fracture-dislocation of the pelvis ring which leads to pelvis instability or compression of the pelvis causing urinary tract injuries.  These can either be multiple fracture of the pubis bones produced by a direct lateral impact, common in pedestrian impacts with cars, or dislocations of the pubis symyphsis or sacroiliac joint common in frontal or rear impacts

• Injuries to the sacrum and coccyx caused by vertical impacts while in a sitting position which although are not serious are extremely painful

Indirect load injuries are produced by axial and / or lateral loads via the femur, as shown in Table 33, through the hip joint, acetabulum and into the pelvis which can cause traumatic hip dislocations and fractures.  The type of injury will depend on the direction of the load from the femur: -

• In high lateral loads as shown in Figure 19, the femur head can punch through the thin wall of the acetabulum with the potential for long-term disabilities

• In high axial loads the femur head can fracture the lip of the acetabulum and dislocate. These can be exacerbated if the loading is slightly off line and is often produced in frontal impacts with the occupants legs crossed

Lateral Impact	Axial Impact
Figure 19 Lateral And Axial Impact Areas Of The Pelvis