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A 27-year-old construction worker fell from a 6-feet high scaffolding. He was hemodynamically stable and had no signs of head, chest, or abdominal trauma. His pelvis was stable but tender to compression. There was an obvious fracture of his wrist.

  • Are there any abnormalities on his pelvis radiograph? (see Figure 1)

Because the pelvis has a rigid ring-like structure, a single break in the pelvis, especially if displaced, is nearly always associated with a second break elsewhere in the ring. If not immediately obvious, a second fracture must be carefully sought. The same principle holds true for fractures of the obturator ring (Figure 2). A single break in the obturator ring must be accompanied by another break elsewhere in the ring. For example, a superior pubic ramus fractures is often associated with an inferior pubic ramus fracture.

Figure 2

(A) The pelvic ring.

The pelvis is a nearly rigid osseus ring made up by the sacrum and the two innominate bones.

The innominate bone is formed from the fused ilium, ischium, and pubic bones.

The arcuate line forms the inner circumference of the pelvic ring.

The obturator ring is made up by the superior and inferior pubic rami and the ischial ramus.

(B) Anatomical landmarks of the pelvis.

In Patient 5, there is deformity of the left side of the pubic symphysis (Figure 3A). This is due to a fracture through the body of the left pubic bone. The fracture is better seen on an “outlet” view (Figure 3B). This is an unusual location for a fracture; most obturator ring fractures occur through the superior or inferior pubic rami.

Figure 3

(A) In Patient 5, irregularity of the left pubic bone is due to a fracture (arrowhead). (B) An AP view with cranial angulation of the x-ray beam (an “outlet view,” see Figure 15) shows the pubic bone en-face and clearly demonstrates the pubic fracture (arrowhead).

With a pubic bone fracture, a typical site for the second fracture is the acetabulum. Detection of fractures in this region requires knowledge of radiographic anatomy of the acetabulum. Interpretation of the radiograph is aided by the symmetry of the pelvis, which provides an opposite side for comparison.

The Radiographic Teardrop

There are several radiographic landmarks that are important in identifying acetabular fractures (Figures 4 and 5). The iliopubic line...

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