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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.

Figure 269-1.

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.

Figure 269-2.

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 tract is ...

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