Zhiyong Hou, Haili Wang, and Shiji Qin

A total of 53 patients with 53 pelvic ring and acetabular fractures were investigated in the China National Fracture Study (CNFS). The fractures accounted for 3.01% of all patients with fractures and 2.89% of all types of fractures. The population-weighted incidence rate of pelvic ring and acetabular fractures was 9 per 100,000 population. The epidemiologic features of pelvic ring and acetabular fractures in the CNFS are as follows:

• More females than males

• The highest risk age group is 15–64 years

• The pelvic ring fracture is the most common pelvic ring and acetabular fractures

• Injuries occurred most commonly via falls and traffic accidents

Pelvic Ring and Acetabular Fracture by Sex in CNFS

A total of 14,420 patients with 14,555 fractures of the pelvic ring and/or acetabulum were treated in 83 hospitals of China over a 2-year period from 2010 to 2011. All cases were reviewed and statistically studied, comprising 3.48% of all fractured patients and 3.37% of all types of fractures. Of a total 14,420 patients, there were 685 children with 687 fractures, accounting for 1.25% of pediatric patients with fractures, and 1.20% of all types of fractures in children. The rest of the 13,735 adult patients had 13,868 fractures, representing 3.81% of adult patients with fractures, and 3.70% of all types of fractures in adults.

Epidemiological features of fractures of the pelvic ring and acetabulum are the following:

• More males than females

• The high-risk age groups are 36–40 and 41–45 years; while the high-risk age group for males is 41–45 years, the groups 36–40 and 41–45 years are at risk for females.

• Pelvic ring fractures occur more frequently than acetabular fractures.

Fractures of the Pelvic Ring and Acetabulum in Adults by Fracture Segment Based on the AO Classification

Fractures of the Pelvic Ring and Acetabulum in Children by Fracture Location

A total of 10,672 adult patients with 10,694 pelvic ring fractures were treated in 83 hospitals of China over a 2-year period from 2010 to 2011. All cases were reviewed and statistically studied, comprising 2.96% of all adult patients with fractures and 2.86% of all types of fractures.

Epidemiological features of pelvic ring fractures are the following:

• Slightly more females than males.

• The high-risk age group is between ages 36–40 and 41–45 years; while the age group 41–45 years is the high-risk for males, age group 36–40 years is at risk for females.

• The most common fracture type of segment 61 fractures is type 61-A, the same fracture type for both males and females.

• The most common fracture group of segment 61 fractures is group 61-A2, the same group for males, and the most common fracture group for females is group 61-A3.

Pelvic ring fractures involve direct or indirect mechanisms. The direct mechanism includes a direct blow, motor vehicle crash, crush injury, fall, etc. Based on the direction of the force, the injury mechanisms can be classified into the following types: anteroposterior (AP) compression, lateral compression, and vertical shear. Different forces can result in different types of pelvic ring fractures. Indirect forces usually result in avulsion fractures from the traction of muscles or tendons.

The force of AP compression usually produces an “open-book”-type injury, that is, a symphysis disruption, by acting on the posterior superior spine and symphysis pubis, or by forced external rotation through the hip joints unilateral or bilaterally. If more force is applied, the anterior ligaments of the sacroiliac joint and the sacrospinous ligament may also be injured, and the posterior dislocation of sacroiliac joint, which is the traditional dislocation of the sacroiliac joint, may occur. In rare conditions, enormous AP force can lead to “anterior” dislocation of sacroiliac joint, in which the ilium dislocates anterior to the sacrum and often combines with symphyseal diastasis and fractures of pubic rami and ilia. Different locations upon which the AP compression is applied may lead to different types of “open-book” injuries.

The force of lateral compression can be transmitted by a direct blow to the iliac crest, often causing an internal rotation of the hemipelvis, or the so-called bucket-handle fracture. Lateral compression may also cause an ipsilateral injury through the femoral head, occasionally causing contralateral injury. The injuries caused by internal rotation account for the majority of pelvic fractures.

Shearing forces in the vertical plane can cause marked displacement of bony structures of the pelvic ring, and gross disruption of soft-tissue structures.

Complex forces, resulting from a combination of these injury patterns, often cause associated acetabular fractures. The most common combined mechanism is lateral compression and vertical shearing. The combined injury of the acetabulum and posterior pelvic ring can be described by three patterns: (1) Acetabular fractures associated with ipsilateral posterior pelvic ring injuries. (2) Acetabular fractures associated with controlateral posterior pelvic ring injuries. (3) Acetabular fractures associated with bilateral posterior pelvic ring injuries.

Pelvic ring injuries are generally high-energy fractures and frequently associated with multiple injuries. Evaluation of the patient should begin with an initial assessment to form a general impression of the degree or severity of the injury, such as to assess hemodynamic status, and the presence of other severe associated injuries. Physical examination should note the morphology of the pelvis and hip joint, as well as the function of the lower extremities. A careful examination of the painful area should be performed. The pelvic compression and separation test, Gaenslen’s maneuver, and the Yeoman test can be used to assess an injury and point to appropriate imaging studies.

The radiographic evaluation includes the AP, inlet, outlet, and Judet views of the pelvis. An AP view of pelvis is usually sufficient to uncover most pelvic injuries. Abnormalities depicted on the AP view can direct the need for the next set of radiographs, which usually include inlet and outlet views of the pelvis in pelvic ring fractures, and Judet (oblique) radiographs of the pelvis in acetabular fractures. Inlet radiographs of the pelvis allow the evaluation of pelvic brim integrity, AP displacement of the hemipelvis, internal/external rotation of the hemipelvis, and sacral impaction. Outlet views of the pelvis allow for confirmation of vertical displacement of the hemipelvis. Judet views of the pelvis illustrate the anterior and posterior columns of the acetabulum, free of superimposition. Computed (CT) or magnetic resonance imaging (MRI) should be performed when plain diagnostic radiographs are inconclusive, with regard to pelvic fractures or the presence of concomitant visceral or neurovascular injuries are suspected.

Patients with hemodynamic instability require emergency rehydration, and temporary stabilization of pelvic fractures, such as by pelvic ring pocket and external fixation, to decrease hemorrhage. Interventional radiology therapy can be applied if necessary. For instance, patients who sustain type B or C injuries often have concomitant severe bony and soft tissue injuries; for example, massive internal bleeding is commonly associated with complete sacroiliac joint disruption. To prevent recurrence of hemorrhage in such patients, temporary fracture stabilization should be performed.

For hemodynamically stable patients, surgical intervention should be performed 5 to 7 days after the injury. Either an external fixation device or open reduction fixation is used for isolated anterior arch fractures. The preferred treatment of choice for unstable pelvic fractures is anatomic reduction and rigid internal fixation. In addition, minimally invasive methods, such as percutaneous iliosacral screw fixation for fracture dislocations of the sacroiliac joint, are increasingly applied in the clinical setting. The sacral pedicel axial view projection is an optimal radiographic technique for percutaneous placement of iliosacral screws in clinical practice. AO classification of pelvis fractures provides a guide in selecting appropriate surgical plans: type A2 and B1 injuries, in which symphysis separation is less than 2.5 cm, can be managed nonsurgically; if symphysis disruption is greater than 2.5 cm, either an external fixation device or plate fixation can be applied; type B2 injuries, being relatively mild, require only reduction and maintenance in proper position; type B3 injuries with shortening of the limb > 1.5 cm should be considered for internal fixation. Operative reduction and internal fixation should be performed if the fracture fragments protrude into the perineal region.