Pelvic fractures and associated injuries are a cause of significant
morbidity and mortality. Most pelvic fractures are secondary to
automobile passenger or pedestrian accidents but are also the result
of minor falls in older persons and from major falls or crush injuries.
The mortality rate from all pelvic fractures is approximately 5%.
However, with complex pelvic fractures, the mortality rate is 22%.1
The major functions of the pelvis are protection, support, and
hematopoiesis. The pelvis consists of the two innominate bones,
which are made up of the ilium, ischium, and pubis; the sacrum;
and the coccyx. The two innominate bones and sacrum form a ring
structure, which is the basis of pelvic stability. This stability
is largely dependent on the strong posterior sacroiliac (SI), sacrotuberous,
and sacrospinous ligaments (Figure 269-1).
A small amount of pelvic stability is also provided by the pubic symphysis. Any
single break in the ring will yield a stable injury without significant
risk of displacement. An injury with two breaks in the ring is unstable
with the risk of displacement.
The major posterior stabilizing structures of the pelvic ring—that
is, the posterior tension band of the pelvis—include the
iliolumbar ligament and the posterior sacroiliac, sacrospinous,
and sacrotuberous ligaments.
The iliopectineal, or arcuate, line divides the pelvis into the
upper, or false, pelvis, which is part of the abdomen, and the lower,
true pelvis (Figure 269-2). In addition,
this line constitutes the major portion of the femorosacral arch,
which, along with the subsidiary tie arch (bodies of pubic bones
and superior rami), supports the body in the erect position. In
the sitting position, the weightbearing forces are transmitted by
the ischiosacral arch augmented by its tie arch, the pubic bones,
inferior pubic rami, and ischial rami. The tie arches fracture first,
especially at the symphysis pubis, pubic rami, and just lateral
to the SI joints. Incorporated in the pelvic structure are five
joints that allow some movement in the bony ring. The lumbosacral,
SI, and sacrococcygeal joints, and the symphysis pubis allow little
movement. The acetabulum is a ball-and-socket joint that is divided
into three portions: the iliac portion, or superior dome, is the
chief weightbearing surface; the inner wall consists of the pubis
and is thin and easily fractured; and the posterior acetabulum is
derived from the thick ischium.
Roentgenographic anatomy of the pelvis and acetabulum.
The pelvis is extremely vascular. The iliac artery and venous
trunks pass near the SI joints bilaterally. The nerve
supply through the pelvis is derived from the lumbar and sacral
plexuses. Injury to the pelvis may produce deficits at any level
from the nerve root to small peripheral branches (Figure
269-3). The lower urinary ...