eMedicine Specialties > Radiology > Musculoskeletal

Pelvic Ring Fractures

Author: D Dean Thornton, MD, Clinical Associate Professor, Department of Radiology, University of Alabama at Birmingham; Musculoskeletal Radiologist, Radiology Associates of Birmingham, PC
Contributor Information and Disclosures

Updated: Feb 11, 2009

Introduction

Background

Pelvic ring fractures occur as the result of high-energy blunt trauma, as may result from motor vehicle collisions and falls. These injuries are associated with significant morbidity and mortality, both from the complications of pelvic ring fractures and from commonly associated injuries. Recognition of the pattern of injury to the bony pelvis directs the search for associated soft tissue injuries and allows implementation of the appropriate therapy.^1,2,3,4,5

Pathophysiology

Three primary loading vectors result in pelvic ring fractures: anteroposterior (AP) compression, lateral compression, and vertical shear. Each of the forces leaves its mark in a characteristic pattern. The identification of 1 element of the pattern prompts a search for the remaining elements, allowing identification of all osseous and soft tissue injuries.^6,7

AP compression injuries most often result from head-on motor vehicle collisions in which the patient is a passenger. The injuries also result when a motorcycle accident occurs or when a pedestrian is struck by a vehicle. The force may be directed either from anterior to posterior or from posterior to anterior (see Image 1).

Frequency

United States

Table 1. Incidences of Pelvic Ring Fractures

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Mortality/Morbidity

With improvement in emergency management techniques, the morbidity and mortality rates of pelvic fracture have decreased in recent decades.

• The overall mortality rate in pelvic ring fractures is approximately 6%. Uncontrolled pelvic hemorrhage accounts for 39% of related deaths; head injury, 31%; and multiple organ failure, 30%. AP compression and vertical shear injuries are associated with a higher incidence of pelvic vascular injury and hemorrhage.
• Associated injuries are commonly found as a result of the powerful forces necessary to fracture the pelvic ring. Injuries to the peripheral nerve, urethra, and bladder are directly attributable to pelvic ring fractures. The frequencies of associated injuries are as follows:
  • Closed head injury — 51%
  • Long bone fracture — 48%
  • Peripheral nerve injury — 26%
  • Thoracic injury — 20%
  • Urethra (male) — 15%
  • Bladder — 10%
  • Spleen — 10%
  • Liver — 7%
  • GI tract — 7%
  • Kidney — 7%
  • Urethra (female) — 6%
  • Mesentery — 4%
  • Diaphragm — 2%
• Immediate complications may be observed.
  • Pelvic hemorrhage is the most serious immediate complication of a pelvic ring fracture. Disruption of the osseous pelvic ring leads to disruption of pelvic veins and/or arteries in as many as 75% of patients.
    • Venous bleeding may arise from the posterior pelvic veins (usually in the setting of sacral injury) or from the marrow space of broken pelvic bones.
    • Arterial bleeding occurs as the result of direct injury to a vessel close to an osseous injury. The injured vessels are typically branches of the internal iliac artery.
    • Posterior fractures, especially those through the greater sciatic notch, may injure the superior gluteal artery.
    • Anterior fractures or disruptions may injure the internal pudendal artery.
    • Pelvic hemorrhage is immediately treated by means of pelvic stabilization, either with sheets wrapped around the pelvis or with external fixator devices. In either case, the goal is to restore the normal anatomic relationships in the pelvis; this restoration serves to reduce the pelvic volume. The larger the pelvic volume, the greater the amount of bleeding that may occur. Uncontrollable hemorrhage requires angiographic evaluation and embolization of the bleeding vessels.
  • Bladder injury occurs as either an associated injury or a complication of a pelvic ring fracture.¹⁰
    • Extraperitoneal bladder rupture occurs more commonly (in approximately 80% of patients) than intraperitoneal rupture (20%). Extraperitoneal rupture results either from direct bladder injury caused by pelvic fracture fragments or from shearing forces near the base of the bladder.
    • Intraperitoneal rupture is usually the result of blunt trauma to a distended bladder.
    • Pelvic fractures need not be present in either type of bladder rupture; they are more often associated with extraperitoneal injuries. Traditionally, the diagnosis of bladder injury was made by use of conventional cystography; however, with the increased use of computed tomography (CT), CT cystography is now more routinely performed.
  • Urethral injury results from the same shearing forces that lead to extraperitoneal bladder rupture. Distraction of the anterior pelvic osseous support structures leads to stretching of the urogenital diaphragm, the most common location for urethral injury. The male urethra is longer and more mobile than the female urethra; therefore, it is more prone to injury.
    • In a type I urethral injury, the membranous urethra (above the urogenital diaphragm) is stretched and narrowed.
    • In a type II injury, disruption of the membranous urethra occurs near the base of the bladder.
    • In a type III injury, the disruption of the membranous urethra extends below the level of the urogenital diaphragm to involve the bulbous urethra.
  • Nerve injury occurs as both an immediate and a late complication of pelvic ring fracture. With fractures of the sacrum or sacroiliac (SI) joints, injury to the adjacent sacral plexus or sacral nerve roots may occur. With fractures extending into the region of the greater sciatic notch, injury to the sciatic nerve may occur. Posterior acetabular fractures also are associated with sciatic nerve injury. Nerve dysfunction may persist even after reduction and fixation of the pelvic fracture.
• Early complications may occur.
  • Blood loss in the preoperative and immediate postoperative period results in morbidity in several ways. Uncontrolled hemorrhage may result in exsanguination. Continued blood loss or inadequate volume repletion may result in shock and its clinical ramifications, such as coagulopathy and renal failure.
  • Infection may occur in a number of settings. The pelvic hematoma that accompanies most significant pelvic fractures may transform into an abscess. Open drainage or, if possible, percutaneous drainage is required. Patients undergoing open surgical fixation of a pelvic fracture are at risk for wound infection. Of course, all postsurgical patients are susceptible to a variety of infections, most notably those of the pulmonary system and urinary tract. Fixation devices, either external or internal, may become infected and require removal.
  • Thromboembolic disease is frequently encountered in the setting of pelvic fracture. The potential for coagulopathy coupled with inevitable temporary immobility of the patient serves to increase the risk. Deep venous thrombosis (DVT) in the lower extremities is readily visualized by using Doppler ultrasonography (US). However, most clinically significant and potentially deadly thrombi occur in the veins of the pelvis, an area not easily accessible to US. Magnetic resonance venography (MRV) is potentially useful in assessing the pelvic venous system.
• Late complications are possible.
  • Pain is the most common long-term complaint of patients with pelvic fractures. Pain most often is associated with abnormalities of the SI joint. Osteoarthrosis, malunion, and nonunion are potential etiologies of the pain.
  • Malunion of the fracture most often occurs in the setting of unreduced pelvic fractures. Leg-length discrepancies may result, resulting in gait abnormalities and pain.
  • Nonunion of the fracture develops in the setting of vertically unstable pelvic fractures. Treatment for this uncommon complication requires stable fixation of the pelvic disruption and correction of any malpositioning.

Race

Race is not a contributing factor in the incidence or pattern of pelvic ring fractures.

Sex

The incidence of motor vehicle collisions is higher in males, particularly young men, than in females. No difference is noted in the pattern of pelvic ring injuries between males and females. The incidence of urethral injury is higher in males (15%) than in females (6%).

Age

Compared with others, young adults are more likely to be involved in serious motor vehicle collisions. No difference is noted in the pattern of pelvic ring injuries between age groups. Elderly patients are more likely to have isolated pubic rami fractures secondary to osteoporosis.

Anatomy

The osseous pelvis is the bridge between the spine and the lower extremities. The pelvis comprises 3 bones: the sacrum and the 2 innominate bones. The innominate bones are formed by joining 3 ossification centers at the triradiate cartilage of the acetabulum: the ilium, the ischium, and the pubis. The sacrum posteriorly articulates with the 2 innominate bones at the SI joint, with the innominate bones joining anteriorly at the pubic symphysis. The posterior pelvic arch (sacrum, SI joints, and iliac bones) transmits the weight-bearing force from the lower lumbar spine to the acetabula (when a person is standing) or to the ischial tuberosities (when a person is sitting). During weight bearing, the anterior pelvic arch (pubic rami and symphysis) functions as a strut to maintain the shape of the pelvic ring.

Vertically oriented ligaments—that is, the long posterior SI, sacrotuberous, and lateral lumbosacral ligaments—oppose vertical displacement of the pelvis (see Image 6). The strongest of these ligaments, as well as the most important with regard to pelvic stability (especially vertical stability), are the short and long posterior SI ligaments. Interosseous SI ligaments provide an added level of support to the SI joints.

Presentation

The Young-Burgess^2,11,12,13 and the Tile^9,13 systems are 2 major classification schemes that have been developed for describing pelvic ring fractures. With both systems, injuries are classified on the basis of the direction of the injuring force. The Young-Burgess classification system focuses on the degree of injury (see Table 2).^2,11,12 The Tile classification system focuses on pelvic stability (see Table 3).⁹

• AP compression injury
  • The hallmark of the AP compression injury is pubic diastasis with or without disruption of the SI joints. The location and degree of diastasis is correlated with the magnitude of force imparted to the pelvis and with the amount of resulting instability. The AP compression causes the pelvis to open: one or both hemipelves undergo external rotation. According to the Young-Burgess classification system, 3 degrees of AP compression injury are identified.
    • Type I injuries: Less than 2.5 cm of the pubic diastasis is noted, either at the symphysis or through vertically oriented rami fractures. The SI joints and posterior ligaments remain intact, and stability is maintained.
    • Type II injuries: The amount of anterior diastasis exceeds 2.5 cm. In addition, diastasis occurs in 1 or both of the SI joints. This incomplete posterior arch disruption results in rotational instability. The posterior ligaments are not injured; therefore, vertical stability is preserved.
    • Type III injuries: These injuries extend to the posterior SI ligaments, which are disrupted. Consequently, the pelvis is vertically and rotationally unstable (see Images 7-8).
  • External rotation of the hemipelvis results in an increase in the volume of the pelvic cavity. This increased pelvic volume allows more pelvic hemorrhage to occur before the osseous and soft tissue structures cause tamponade. Exsanguination from a pelvic hemorrhage is a primary potential complication. Reduction of the increased pelvic volume is a primary goal in resuscitating a patient with an AP compression injury. Immediate reduction may be achieved by tightly wrapping the pelvis in sheets or a pneumatic antishock garment. The application of an external pelvic fixation device results in more definitive reduction. AP compression injuries are also strongly associated with brain and intra-abdominal injuries.

• Lateral compression injury
  • Lateral compression injury results in internal rotation of the affected hemipelvis. This internal rotation decreases rather than increases the pelvic volume. Consequently, pelvic vascular injuries and resulting hemorrhage are less common with this injury than with other injuries. Lateral compression injuries are associated with brain and intra-abdominal injuries.
  • The hallmarks of a lateral compression injury include sacral buckle fractures and horizontal pubic rami fractures. The Young-Burgess classification system describes 3 types of injuries.
    • Type I injuries: These involve a force directed posteriorly to the lateral aspect of the hemipelvis, which results in an ipsilateral sacral buckle fractures; ipsilateral horizontal pubic rami fractures; or, less commonly, disruption of the pubic symphysis with overlap of the pubic bones (see Images 9-11). The posterior ligaments remain intact; therefore, the pelvis is stable. Lateral forces directed anteriorly to the hemipelvis produce type II and type III injuries.
    • Type II injuries: These involve more internal rotation of the hemipelvis. As in type I injuries, ipsilateral sacral buckle fractures and horizontal pubic rami fractures are associated with fracture of the ipsilateral iliac wing or disruption of the ipsilateral posterior SI joint. The pelvis is rotationally unstable, but its vertical stability is maintained.
    • Type III injuries: The force continues from the ipsilateral side across the midline to affect the contralateral hemipelvis. The ipsilateral hemipelvis sustains either a type I or type II injury with associated internal rotation. The contralateral pelvis undergoes external rotation. This pattern has been described as a windswept pelvis (see Images 12-13). Contralateral vertical pubic rami fractures or disruption of the sacrotuberous and/or sacrospinous ligaments may occur. As in type II injuries, the pelvis is rotationally unstable but vertically stable.
• Vertical shear injury
  • A vertically oriented force applied to a hemipelvis, usually by the femur, results in a vertical shear injury. At the anterior aspect, vertically oriented fractures of the pubic rami occur. Posteriorly, the ipsilateral SI joint (or occasionally the contralateral SI joint) and its associated ligaments are disrupted (see Images 14-18).
  • The affected hemipelvis is displaced in a cranial direction. Complete disruption of the posterior ligaments yields a rotationally and vertically unstable pelvis.
  • Associated injuries seen in the vertical shear pattern are similar to those encountered in type III AP compression injuries.
• Complex injury
  • The forces applied to the pelvis may not conform to the primary vectors described for other types of injuries.
  • Complex injuries involve more than 1 pattern of injury. The specific findings of each pattern are still present.
  • Pelvic stability may be determined by use of the criteria outlined above.
• Ring-sparing injury
  • The Tile classification system includes fractures of the pelvis that do not significantly disrupt the pelvic ring (Tile type A). These injuries include avulsion fractures of the anterior iliac spine, iliac crests, and ischial tuberosities (see Image 19).
  • Also included are iliac wing fractures (see Image 20) and sacrococcygeal fractures that do not involve the SI joints. Minimally or nondisplaced pubic rami fractures resulting from a direct blow or straddle injury do not affect pelvic ring stability.

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Preferred Examination

Radiography^{1,10,12,14,15,16,17}

• AP radiography of the pelvis (see Image 21)
  • AP radiographs of the pelvis and chest and lateral radiographs of the cervical spine are included in the initial radiographic assessment of a patient with major traumatic injuries.
  • Radiographs are obtained with the patient in the supine position, with the x-ray beam passing in an AP direction.
  • Abnormalities depicted on the AP pelvis radiograph direct the need for the next set of radiographs, which include oblique (Judet) views of the pelvis in acetabular fractures,^18,19 and inlet and outlet radiographs of the pelvis in patients with pelvic ring fractures.
• Inlet and outlet radiography of the pelvis
  • Inlet radiographs of the pelvis are obtained with the patient in the supine position, with the x-ray tube positioned at the patient's head and angled 45° toward the feet (see Image 22). The x-ray beam is perpendicular to the pelvic brim (or inlet). This view allows the evaluation of pelvic brim integrity, AP displacement of the hemipelvis, internal/external rotation of the hemipelvis, and sacral impaction.
  • Outlet radiographs of the pelvis are obtained with the patient in the supine position, with the x-ray tube positioned at the patient's feet and angled 45° toward the head (see Image 23). The x-ray beam is perpendicular to the sacrum. This view allows confirmation of vertical (cranial) displacement of the hemipelvis and evaluation of the sacral neural foramina.
• Pelvic CT²⁰
  • During the initial trauma evaluation, CT images may be obtained of the pelvis in isolation, or CT scans of the pelvis may be obtained at the same time that scans of the abdomen are obtained.
  • Axial CT scans may be obtained, but helical CT scans (especially with multidetector CT) yield better 2-dimensional (2D) and 3-dimensional (3D) images.
  • CT allows the detection of subtle fractures and displacements not appreciated on radiographs.

Limitations of Techniques

Radiographs of the pelvis may not demonstrate subtle fractures that do not affect classification of the injury. Spatial orientation of fracture fragments and joints is visualized better on pelvic CT scans.

Pelvic CT scans require transport of the patient to the CT scanner; most patients need to undergo abdominal and pelvic CT for an assessment of visceral injury.

Differential Diagnoses

Acetabulum, Fractures
Pelvis, Insufficiency Fractures

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