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
(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
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.
(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.
There are several radiographic landmarks that are important in
identifying acetabular fractures ...