Similar to other anatomic areas, fractures of the pelvis and acetabulum may present as high-energy injuries, yet increasingly manifest as fragility fractures in the elderly. High-energy trauma to the pelvis is not only associated with severe blunt injuries to other organ systems but is also itself associated with potential life-threatening hemorrhage requiring prompt diagnosis and intervention. Classification of pelvic ring injuries focuses primarily on the diagnosis of mechanically unstable patterns that would benefit from surgical intervention. Outcomes of pelvic injuries are dependent on reestablishing stability, restoration of ring morphology, and extent of soft-tissue injury. For acetabular fractures, diagnosis continues to be based on the Letournel classification. Surgical intervention is indicated for unstable and displaced fractures to restore hip stability and to mitigate future risk of posttraumatic arthritis. Long-term outcomes depend on anatomic reduction, as well as fracture characteristics and patient factors.

Femoral head fractures occur rarely but are usually associated with posterior hip dislocations and occasionally clinically meaningful posterior wall acetabulum fractures. Surgery is indicated if the fracture fragments compromise the weight-bearing articular surface or stability of the hip. Both the anterior surgical approach and surgical hip dislocation are safe and effective strategies for managing femoral head fractures.

Pelvic ring disruptions are characterized by a bimodal distribution of high-energy blunt trauma and geriatric fragility or insufficiency fractures of the pelvis. Pelvic ring injuries are present in approximately 9% of high-energy blunt trauma.¹ High-energy pelvic ring injuries have a mortality rate of approximately 9% to 11%.²,³

Pelvic ring injuries are classified according to either the mechanism of injury or the implied stability of the injury. The Tile classification is still used to describe injuries based on perceived rotational and vertical stability after injury.⁴ The Young-Burgess classification is based on the vector of injury to the pelvic ring.⁵ The AO/Orthopaedic Trauma Association classification system uses features of the Tile and the Young-Burgess classification systems.⁶ Currently, each classification system remains limited in its ability to predict mortality, associated injuries,³ and treatment strategies.⁷

The AO Spine Sacral Injury Classification is a newer and reliable way to describe sacral and spinopelvic injuries. Type A lesions are lower sacrococcygeal injuries. Type B injuries are complete sacral fractures representing posterior pelvic ring injuries. Type C lesions describe spinopelvic injuries including nondisplaced (C0), stable (C1), and unstable, displaced (C3) injuries.⁸

The initial evaluation of suspected pelvic ring injuries includes an AP radiograph of the pelvis in the emergency department. The presence of a pelvic ring injury often suggests a high-energy mechanism and serves as a potential predictor of other blunt injury. Pelvic ring injuries are also associated with hemorrhage from the chest, abdomen, or long bones.⁹ Open wounds to the perineum, rectum, or vagina and soft-tissue degloving injuries (Morel-Lavallee lesions) should be identified. A neurovascular examination should be performed, and in sacral fractures, the sacral nerve root distributions should be examined.

Patients with pelvic ring injuries can have life-threatening hemorrhage into the retroperitoneal space. Therefore, in addition to resuscitation, circumferential wrapping (using a sheet or a pelvic binder) for volume-expanding injuries can close down the potential space and allow for tamponade.¹⁰ Circumferential sheets offer the ability to cut holes for access for external fixation, percutaneous fixation, or angiography, without having to be removed, which is a potential advantage over a binder,¹¹ although both are effective. In patients who have hypotension or hemodynamic instability with pelvic ring injury, and without other sources of hemorrhage from the chest or intraperitoneal space, angiography is an appropriate next intervention (depending on institutional access). This is a safe and efficacious technique to stem hemorrhage and should be available in a timely manner according to the American College of Surgery guidelines.¹² Retroperitoneal pelvic packing is also an option to mitigate ongoing hemorrhage but should occur in conjunction with relative stabilization of the pelvis, such as external fixation and resuscitation screws. Clinically meaningful pelvic packing can be technically challenging and is therefore potentially less generalizable than angiography to control active bleeding. There remains a lack of high-quality evidence comparing the two interventions. Newer interventions such as resuscitative endovascular balloon occlusion of the aorta offer additional hemorrhage control. Skeletal traction may also be helpful in selective injury patterns (eg, vertically unstable patterns with complete sacral fractures). External fixation with or without resuscitative posterior iliosacral screws may be used for damage control orthopaedics as part of the acute management.

Advanced imaging should consist of a CT scan of the pelvis and inlet and outlet views of the pelvic ring (obtained either through plain radiographs or as reconstructions from the CT).¹³ The AP pelvic radiograph alone is inadequate to detect U-type sacral fractures.¹⁴ In instances of frank hematuria or with blood at the urethral meatus, a CT cystogram is used to diagnose urethral or bladder injuries.

The most common pelvic ring injuries are lateral compression fractures. Although often the most benign injury of the pelvic ring, management of type I lateral compression (LC1) injuries remains controversial. There is evidence that minimally displaced (<10 mm) LC1 injuries may be managed nonsurgically with unrestricted weight bearing and early mobilization.¹⁵ Surgical treatment of patients with minimally displaced LC1 injuries may offer statistically significant early pain relief, but the clinical significance is uncertain.¹⁶ A subset of LC1 injuries, including complete zone 2 sacral fractures, and bilateral obturator ring disruptions injuries may demonstrate further radiographic displacement,¹⁷ and tend to undergo surgical fixation more often than isolated zone 1 fractures.¹⁸ However, compelling evidence is lacking that subsequent minor displacement with eventual healing is of clinical consequence (Figure 1, A through D). Nonetheless, identifying harbingers of substantial further displacement leading to an unacceptable malunion, including complete sacral fractures and bilateral superior and inferior rami fractures, is of interest.¹⁷ Another indication for surgical management in LC1 injuries is failed nonsurgical management (Figure 1, E through G). Although postmobilization radiographs can be used for serial imaging in patients treated nonsurgically, evidence suggests this intervention rarely changes management.¹⁵ Whether to fix posterior, anterior, or posterior with or without anterior aspects of the pelvic ring is also controversial.¹⁹ Posterior options include percutaneous iliosacral-style or transsacral-style screws. Anterior treatment options include percutaneous medullary screw placement, anterior external fixator, or internal application of an external fixator (INFIX). As with other types of trauma, a higher level of energy may predispose to more relevant instability, and similar injuries are more likely to require surgery, compared with fragility fractures.

Fractures of the posterior ilium with extension into the sacroiliac joint are potentially unstable and represent a relative indication for surgery. If displaced, the unstable ilium is manipulated through closed/percutaneous means or through a lateral window approach and reduced to the intact portion. Fixation can be achieved either with screws in the supra-acetabular corridor from the anterior inferior iliac spine toward the posterior
superior iliac spine (Figure 2) or with a buttress plate placed through a lateral window. If the iliac fracture exits low and posteriorly, or if there is also a complete sacroiliac joint injury, then additional fixation is achieved through iliosacral screws inserted after manipulative reduction. Lateral compression pelvic fractures are, in general, typically reduced through indirect manipulation of the anterior ring (Figure 3).

Historically, anterior-posterior compression I injuries with diastasis less than 2.5 cm were thought to be stable; however, it is critical to rule out occult instability, and many injuries within this range are now recommended to be stabilized. The concavity of the CT gantry can inadvertently reduce symphyseal diastasis and can mask some occult injuries.²⁰ Additionally, dynamic instability can be concealed on static imaging, and therefore dynamic radiographs or fluoroscopy may be of use.²¹ Single-leg stance radiographs (flamingo views) or examination under anesthesia can be used to diagnose occult instability.⁵,²¹,²² For unstable symphysis disruptions, reduction and fixation of
the anterior ring via a Pfannenstiel/midline rectus split approach can reduce the ring provided the posterior tension band is intact. Fixation of the anterior ring alone in these injuries does not always reduce motion at the sacroiliac joints²³ and can result in fixation failure in the event of an undetected/underdiagnosed posterior ligamentous injury. If the sacroiliac joint is well aligned in AP and craniocaudal planes after reduction of the anterior ring but remains wide, then a screw-based reduction can be performed along the vector of placement of a partially threaded lag screw. Otherwise, an open reduction of an unstable sacroiliac joint can occur through a lateral window approach (less commonly a prone paramedian approach). The number and size of screws needed and whether transiliac fixation is necessary to stabilize the sacroiliac joint remain topics of ongoing debate.

INFIX is another option for stabilization of the anterior pelvic ring.²⁴ Open fractures or urologic injury where definitive anterior internal fixation represents a risk of infection²⁵ are instances in which temporary placement of an anterior internal fixator can be considered. INFIX application can be more challenging in patients with very little abdominal subcutaneous adipose tissue. Lateral femoral cutaneous nerve injury, heterotopic ossification, and femoral nerve palsy are described complications after INFIX application.²⁶

Combined mechanism injuries and vertical shear patterns are typically considered rotationally and vertically unstable. Even in displaced injuries, the pelvic ring can be reduced indirectly via traction or reduction of the anterior pelvic ring, either with an anterior external fixator or an open reduction with a clamp. Alternatively, a sacral fracture can be reduced and clamped through a posterior approach and prone positioning if the patient’s physiology and soft-tissue envelope permit (Figure 4). (Anterior access to the sacrum is limited, and thus is not practical for reduction.) This is often easier to do with zone 1 fracture locations as there tends to be less comminution. The posterior ring is typically definitively stabilized with sacral screws. Lumbopelvic fixation may augment posterior ring fixation if there is lumbopelvic instability²⁷ or if patient anatomy precludes multiple points of transsacral pelvic fixation (Figure 4).

Sacral dysmorphism represents a spectrum of anatomic variation which, when present, merits special technical consideration for safe screw placement in contending with pelvic ring injuries.²⁸ The technical implications of sacral dysmorphism in the injured pelvis include that it may not be feasible to safely insert a transiliac transsacral screw. In pelvic ring injuries with complete posterior injuries in the presence of dysmorphism, percutaneous lumbopelvic fixation may be a useful adjunct to ensure durable fixation of the posterior ring.