Pelvic Fractures

Howard J. O’Rourke
Georges Y. El-Khoury

Osseous Emergencies

Mechanisms and Patterns of Fractures of the Pelvis

The pelvis is a complex series of articulations supported by a strong ligamentous network. The posterior ligaments are the strongest ( Fig. 16-1 ). The sacroiliac joint has thin anterior and thick posterior ligaments. The sacrospinous and sacrotuberous ligaments are additional posterior ligaments that primarily serve to resist rotational deformity of the pelvis. The pubic symphysis is supported by a series of comparably weaker ligaments.

Figure 16-1

Pelvic ligaments.

Pelvic fractures are a potentially devastating injury encountered in emergency medicine with an overall mortality reported between 8% and 17%. Fractures of the pelvis may be classified as stable or unstable; with unstable fractures the pelvic ring is disrupted, particularly posteriorly. The most common cause of mortality is hemorrhage, which may be arterial, venous, or bleeding from fractured cancellous bone. The most widely used classification system is the Young-Burgess system, which seeks to classify fractures based on the vector of force at the time of injury.

Radiology plays a central role in the classification and management of pelvic ring disruption. A strict approach to the pelvic radiograph will help in identifying and classifying fracture patterns. One’s search pattern in a trauma patient should evaluate the iliopectineal and ilioischial lines as well as the obturator and pelvic rings ( Figs. 16-2 and 16-3 ). The sacroiliac joints and pubic symphysis should also be evaluated for widening and craniocaudal displacement.

Figure 16-2

Pelvic landmarks.

The normal iliopectineal (green line) and the ilioischial (blue) lines represent the anterior and posterior columns of the acetabulum, respectively. The anterior rim line (dotted line) and posterior rim line (dashed line) are also shown.

Figure 16-3

Both sides of the pelvis should appear symmetric. The normal pelvic (larger circle) and obturator (smaller circle) rings are shown.

According to the classification system proposed by Young and colleagues, fractures are defined as lateral compression, anteroposterior compression, vertical shear, and combined mechanical injury. Lateral compression and anteroposterior injuries are further subdivided into types I to III depending on severity of injury ( Table 16-1 ).

Table 16-1

Classification of Pelvic Fractures

Fracture Type Description
Lateral compression—internal rotation injuries I—Compression fracture of sacrum
II—Iliac wing fracture
III—Contralateral open-book injury
Anteroposterior compression—external rotation injuries I—Stretched but intact anterior sacroiliac, sacrospinous, and sacrotuberous ligaments
II—Torn anterior sacroiliac ligaments with intact posterior ligaments
III—Complete ligamentous disruption
Vertical shear Diastasis of symphysis or vertical rami fractures with vertical displacement at either sacroiliac joint, iliac fracture, or sacral fracture
Combined mechanism Combined other patterns

Arterial bleeding most prevalent.

Lateral compression (LC) injuries represent the most common type of pelvic ring fracture. So named for the direction of force, there is resultant internal rotation of the iliac bone ( Fig. 16-4 ). In LCI fractures the fractures of the rami are horizontal and overlapping. The posterior ring injury most often is a buckle fracture of the sacrum. Given the stability of the sacrospinous and sacrotuberous ligaments, the pelvis remains vertically stable ( Fig. 16-5 ). In LCII fractures the iliac wing fractures, and the fracture may extend posteriorly to the sacroiliac joint. LCIII fractures are LCI or LCII on the side of injury and a contralateral open-book injury. The mechanism is internal rotation on the side of injury and external rotation on the contralateral side. The contralateral side may show partial or complete disruption of the sacroiliac joint. LCIII injuries are rotationally and possibly vertically unstable.

Figure 16-4

Diagram of lateral compression fracture.

The lateral compressive forces cause horizontal pubic rami fractures, internal rotation of the ipsilateral iliac bone, and a compression fracture of the sacrum. (Used with permission from Hunter JC, Brandser EZ, Tran KA. Pelvic and acetabular trauma. Radiol Clin North Am . 1997; 35[3]:559-590.)

Figure 16-5

A, Lateral compression fractures. Anteroposterior (AP) view of the pelvis shows overlapping right rami fractures (arrows) , indicative of a lateral compression mechanism. B, Inlet view shows the displaced fracture in the right pubis and disruption of the left second arcuate line of the sacrum, indicative of a sacral fracture (arrow) .

Anteroposterior compression (APC) injuries account for 15% to 20 % of all pelvic ring injuries. The vector of force leads to diastasis of the symphysis pubis with or without diastasis of the sacroiliac joint or fracture of the iliac bone. APCI injuries show less than 2 cm widening at the pubic symphysis and little to no widening of the sacroiliac joint. Vertical rami fractures may be seen. More severe APC injuries cause disruption of the sacroiliac joint, ranging from either anterior widening to disruption of the entire joint ( Fig. 16-6 ). Complete separation of the hemipelvis precludes the tamponade of vascular injury. The proximity of the superior gluteal arteries and internal pudendal arteries to the sacroiliac joint contributes to the incidence of significant hemorrhage with APC injuries ( Figs. 16-7 and 16-8 ).

Figure 16-6

Diagram of anteroposterior compression (APC) fractures.

The pubic ligaments are disrupted, but with increasing force, the sacroiliac and pelvic floor ligaments become disrupted as well. Posterior disruption may be either unilateral or bilateral.

Figure 16-7

Anteroposterior compression (APC) injury.

A, Anteroposterior (AP) pelvic radiograph shows diastasis of the symphysis pubis and right sacroiliac joint (black arrow) . B, Vascular and visceral injuries are common. Computed tomographic (CT) scan demonstrates extravasation of contrast material from a rupture of the urethra.

Figure 16-8

Anteroposterior compression (APC) injury.

Outlet view shows mild diastasis of the symphysis pubis and both sacroiliac joints (arrows) .

Vertical shear injuries occur because of axial loading of the pelvis, as with a fall from height on an extended leg ( Fig. 16-9 ). Characteristic radiographic findings include vertical rami fractures or diastasis of the symphysis and dislocation of the sacroiliac joint or sacral fracture. Furthermore, the hemipelvis displaces superiorly and posteriorly. In combined mechanical injuries, a combination of two or more vectors results in complex pelvic fractures ( Fig. 16-10 ).

Figure 16-9

A, Diagram of vertical shear fractures. The vector of force causes vertical rami fractures and dislocation through the sacroiliac joint or fracture through the sacrum. B, Anteroposterior radiograph of the pelvis shows vertical inferior and superior (white arrows) rami fractures and vertical fracture through the sacrum (black arrow) . ( A used with permission from Hunter JC, Brandser EZ, Tran KA. Pelvic and acetabular trauma. Radiol Clin North Am . 1997; 35[3]:559-590.)

Figure 16-10

Malgaine fracture.

A, This vertical shear injury results in bilateral superior and inferior pubic rami fractures (straight arrows) , as well as fracture of the sacrum (curved arrow) . B, Three-dimensional computed tomographic (3-D CT) reconstructed images optimally demonstrate all of the fractures.

Sacral Fractures

Sacral fractures are an important yet difficult-to-recognize injury. Mechanistically injuries can be associated with high-energy trauma or simply normal stress on insufficient bone. The most widely used system for describing sacral fractures was created by Denis and coworkers in 1988 ( Fig. 16-11 ). The sacrum is divided into three zones. Zone 1 fractures involve the region of the sacral ala; L5 is occasionally injured with zone 1 fractures. Zone 2 fractures involve the region of the sacral foramina. These frequently cause sciatica and rarely bladder dysfunction. Zone 3 fractures occur more centrally, and the patients experience saddle anesthesia and sphincter dysfunction.

Figure 16-11

Zones of Denis.

Anatomy of the sacrum, highlighting zones 1, 2, and 3.

Radiographs are relatively insensitive in detecting sacral fractures due to significant overlying soft tissues and bowel gas. Radiologists should be sensitive to the disruption of sacral ala on anteroposterior (AP) pelvis radiographs. A bone scan is very sensitive to the presence of a sacral insufficiency fracture ( Fig. 16-12 ). Fractures are optimally characterized at computed tomography (CT). Traumatic sacral injuries frequently occur in association with other pelvic fractures.

Jun 30, 2019 | Posted by in EMERGENCY RADIOLOGY | Comments Off on Pelvis

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