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EPIDEMIOLOGY

Pelvic fractures are most commonly the result of a motor vehicle or motorcycle collision, automobile versus pedestrian collision, fall from a significant height, or a crush injury. Isolated pubic rami fractures can occur in the elderly following a low-energy mechanism of injury, such as falling off of a chair, due to underlying fragility and osteopenia.1 The in-hospital mortality rate from all pelvic fractures is approximately 8% and approaches 20% with complex pelvic fractures.2 Higher mortality rates are found in older patients, men, African Americans, and those living in the northeastern United States.2 The mortality rate is 30% in patients who present in shock.3 Pelvic ring fractures have been found to be an independent risk factor for death.4

ANATOMY AND BIOMECHANICS

The major functions of the bony pelvis are protection of the visceral organs, mechanical support, and hematopoiesis. The bony pelvis consists of the sacrum, coccyx, and bilateral innominate bones: the ischium, ilium, and pubis. Collectively, they provide pelvic stability that is further supported by the strong posterior sacroiliac, sacrotuberous, and sacrospinous ligaments (Figures 272-1 and 272-2). A small amount of pelvic stability is also provided by the pubic symphysis.

FIGURE 272-1.

Bones and joints of the pelvis.

Five joints that allow some movement of the bony ring are incorporated into the pelvic structure. The lumbosacral, sacroiliac, and sacrococcygeal joints, as well as the symphysis pubis, allow limited movement. The acetabulum, a ball-and-socket joint, is divided into three portions: (1) the iliac portion, or superior dome, is the chief weight-bearing surface; (2) the inner wall, which consists of the pubis, is thin and easily fractured; and (3) the posterior acetabulum, which is derived from the thick ischium. Generally, a single break in the ring results in a stable injury without significant risk of displacement, and two breaks in the ring result in an unstable injury.

The pelvis is extremely vascular. The iliac artery and venous trunks pass near the sacroiliac 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 272-3). The lower urinary tract is contained in the pelvis (Figure 272-4). In the adult, the bladder lies behind the symphysis and pubic bones, and the peritoneum covers the dome and base posteriorly. The location of the bladder and the degree of peritoneal reflection are determined by urine volume. Portions of the lower GI tract are housed in the pelvis including a portion of the descending colon, as well as the sigmoid colon, rectum, and anus. In women, the uterus ...

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