Abdominal CT: pelvic fractures

Pelvic fractures are common in high velocity trauma, and the pelvis has predictable patterns of injury due to its ring structure. It is helpful to think of pelvic fractures like breaking a pretzel – you cannot break it in just one place.

In this lesson, we will consider three types of pelvic fractures:

• Pubic ramus fractures
• Sacral fractures
• Acetabular fractures

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Pubic ramus fractures

A common fracture pattern is a fracture of the pubic ramus involving both small bones of the pubis, the superior and inferior pubic rami. The pubic rami connect in the midline to form the pubic body

Below is a 3-dimensional (3D) image of the pelvis in a patient who has fractured both the left and right sides of the pelvis. Let’s be sure to remember that this ring will fracture in two places and look for injuries in both superior and inferior pubic rami in the axial images.

Superior pubic ramus injuries

For the superior pubic ramus injuries in this patient, the right side involves part of the pubic body. The left side is higher and involves the anterior acetabulum.

Inferior pubic ramus injuries

For the lower pubic ramus, the right fracture is relatively subtle with a thin cortical defect. But the left fracture is displaced and slightly offset.

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Sacral fractures

In severe trauma with compressive forces, there can be fractures involving the sacrum and sacroiliac joint, often with either widening of the pubic symphysis or fracture of the pubic ring.

Sacral fractures typically follow a vertical orientation along the bone. On CT, sacral fractures look like irregular lines and cortical defects, which means abnormal dark lines through the dense outer bone indicating fracture.

These injuries can also be associated with widening of the sacroiliac joint. In the case below, there is injury to the left sacrum with cortical irregularities and linear defects extending deeper into the trabecular bone. The sacroiliac joint is slightly wider on the left than on the right, but it is a fairly subtle difference in this case.

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Acetabular fractures

Fractures of the acetabulum occur when the femoral head is driven into the pelvis.

Acetabular fractures are best seen on the coronal images, where we can see the familiar appearance of the hip joint. In this example, there is a large displaced cortical defect in the left acetabulum, as well as a fracture of the iliac bone.

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References

• Top 100 CT scan quiz. LITFL

Radiology Library: Abdominal Trauma. Musculoskeletal injuries

• Hartung MP. Abdominal Trauma: rib fractures
• Hartung MP. Abdominal CT: spinal fractures
• Hartung MP. Abdominal CT: body wall injuries
• Hartung MP. Abdominal CT: pelvic fractures
• Hartung MP. Abdominal CT: bladder injuries

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