Pelvic fractures from blunt force trauma are broadly categorized as either stable or unstable based on the status of the pelvic ring. The pelvis is composed of three bones (the iliopubic bones and the sacrum), which are held together by strong ligaments: the symphysis pubis anteriorly and the anterior and posterior iliosacral ligament posterolaterally. A pelvic fracture is generally considered unstable if the ring is broken in two or more places.
The unstable pelvic fracture is sometimes identified during the secondary survey, when the pelvis is noted to a ‘move’ during either anteroposterior or lateral compression on physical examination. More commonly, today it is detected on plain radiograph or abdominal computed tomography (CT). However an unstable pelvic fracture is identified, once the diagnosis has been made, all further manual manipulation (i.e., rocking the pelvis) must cease. Although it is tempting to use an unstable pelvic exam as a prime teaching point, the unstable pelvis should not be manipulated. Each time the damaged joint is moved, the clot may be disrupted, resulting in additional bleeding from the torn veins and bony surfaces. Consumption coagulopathy may occur as coagulation factors are used for new clot formation.
Unstable pelvic fractures include disruption of the ring anteriorly at the symphysis pubis or through a pubic bone and are broadly categorized into three types: anterior-posterior open book pelvic fracture, lateral compression fracture, and vertical shear malgaigne pelvic fracture.
Anterior-Posterior open book pelvic fracture
Open book pelvic fracture type of injury typically occurs after an anterior-posterior blunt force injury to the pelvis, in which the anterior ring fracture is accompanied by disruption of the anterior iliosacral ligaments. With the stability of the anterior ring lost, the pelvis opens anteriorly and laterally and the iliac bones hinge on the posterior pelvic ligaments, much as a book opens around its spine. Open book pelvic fracture disrupts the iliosacral joint and the veins that lie anterior to the iliosacral joint. This results in a large amount of venous and bony bleeding into the retroperitoneal space. Approximately 10% of patients of open book pelvic fracture have associated arterial bleeding. Initial stabilization should be in the form of external binding of the pelvis with a bed sheet tied tightly around the pelvis or a pelvic binder device.
Lateral Compression Fracture
This type of injury typically occurs after lateral blunt force injury to the pelvis, such as a in a pedestrian struck by a car. The anterior ring fracture is accompanied by disruption of the posterior iliosacral ligaments. The iliac bones hinge on the anterior iliosacral ligaments. Venous and bony bleeding from the disrupted iliosacral joint tends to be extrapelvic. In this type of fracture, attempted stabilization with a sheet or external binder will only promote further inward collapse of the iliac bones and cause increased bleeding. External fixation of the pelvis or open reduction and internal fixation (ORIF) is preferable.
Vertical Shear malgaigne pelvic fracture
Malgaigne pelvic fracture type of injury typically occurs when a large vertical load is placed on one leg, such as in a fall from height. The iliac bones are completely separated from the remainder of the pelvis by disruption of the anterior ring and both the anterior and posterior iliosacral ligaments. Venous and bony bleeding is not contained within the pelvis, and arterial bleeding must be ruled out. Initial stabilization requires traction on the injured side leg to reduce the vertical displacement, followed by external binding of the pelvis. Malgaigne pelvic fracture carries the highest mortality rate due to exsanguination.
The initial management of pelvic fractures follows the paradigm of the ABCs of trauma resuscitation. After the airway (A) and breathing (B) are considered, circulation and control of hemorrhage (C) are imperative. Adequate volume resuscitation is essential, and blood should be administered early to the hemodynamically unstable or metastable patient. The pelvic x-ray will provide essential details about the bony injury that are crucial early in the resuscitation phase. Trauma and orthopedic surgical consultations should be obtained for immediate evaluation. Abdominal and pelvic CT scans with intravenous contrast are performed to assess for other injuries and further define the pelvic fracture. It is important that the pelvic portion be reviewed by the physician in attendance of the patient immediately, looking for arterial extravasation of intravenous contrast. The finding of arterial extravasation warrants immediate arteriography with therapeutic angioembolization. Operative attempts to control such bleeding are usually unsuccessful. Bleeding from other solid-organ injuries (e.g., liver, spleen, kidney) can also be addressed at the time of angiography.
If laparotomy is necessary, an external fixator should be applied prior to the abdominal procedure. The bracing arms should be directed toward the feet instead of being placed in the usual position toward the head (overlying the lower abdomen). Orthopedic surgeons will sometimes object because this interferes with the patient sitting up. However, the patient will not be sitting up in the near future, and abdominal exposure is more urgent. Definitive fixation can be accomplished by revising the bracing arms or performing internal fixation when the patient is stable.