Imaging Pelvic Fractures

Catherine M. Cooper, MS, RT(R)(CT)

  ^*Senior Instructor, University of South Alabama, Department of Radiologic Sciences, Mobile, Alabama.
  Address correspondence to: Catherine M. Cooper, MS, RT(R)(CT), Senior Instructor, University of South Alabama, Department of Radiologic Sciences, 307 N. University Boulevard, HAHN 3015, Mobile, AL 36688. E-mail: ccooper@usouthal.edu.

Disclosure Statement: Mrs Cooper reports having no significant financial or advisory relationships with corporate organizations related to this activity.

ABSTRACT

Patients with pelvic ring injuries present with fractures ranging from single pelvic fractures to those accompanied by many life-threatening injuries. Radiography is one of the first steps in the diagnosis and development of a treatment plan for these patients. A simple anteroposterior pelvis radiograph may not be sufficient to fully evaluate pelvic fractures. A radiographer should know how to properly perform additional radiographs of the pelvis, including inlet, outlet, and Judet views, and know the anatomy each view will demonstrate. Orthopedic surgeons rely on these images to determine the appropriate surgical approach. The goal of this article is to inform the radiographer of various types of pelvic fractures and specific radiographic images that will best demonstrate each fracture.

Introduction
The pelvic ring is a very important part of the human anatomy and has 2 main functions. It protects the pelvic viscera and provides stability to support the weight of the body. There are 2 main pathways in which weight bearing is transmitted through the body. When an individual is standing, the weight is transmitted from the upper body and trunk, through the spine, the sacroiliac joints, along the arcuate line of the pelvis to the superior dome of the acetabulum and continues down the femur. When an individual is in the sitting position, the weight is transmitted down the spine, the sacrum, and sacroiliac joints to the ischium.¹

Injuries to the pelvis usually occur as a result of motor vehicle collisions, pedestrians being struck by motor vehicles, crush injuries, or high-level falls. The severity of injury to patients with pelvic trauma ranges from those with single, isolated fractures of the pelvis to those patients who are critical and have multiple life-threatening injuries. Any victim of a serious trauma should be evaluated for pelvic fractures as well. All patients who present to the emergency department with multiple injuries should be stabilized prior to obtaining the necessary diagnostic radiographs.^2,3

Pelvic injuries have a reported 10% to 29% mortality rate due to complications resulting from displacement of the pelvic ring, which is usually associated with multiple injuries. Patients with pelvic fractures can have significant blood loss due to hemorrhaging of the iliac arteries, the presacral venous plexus, and a large volume of cancellous bone. The clinical examination on critically injured patients is usually limited, making it essential that diagnostic radiographs be obtained in an efficient manner in order to determine the appropriate plan of care.⁴

A single anteroposterior radiograph of the pelvis is commonly used in most trauma centers to evaluate the presence or absence of pelvic fractures. This view demonstrates the pelvis, sacrum, and coccyx and lumbosacral articulation and is sufficient for classification and management of most pelvic fractures. However, it may not reveal fractures of the sacrum, injuries to the sacroiliac joints, and the degree of bone displacement. In order to make a definitive treatment plan for pelvic ring fractures, additional radiographs are needed.^3,5,6

Anatomy of the Pelvis
The pelvis is a ring structure and is formed by the union of 4 bones: 2 hip bones, the sacrum, and the coccyx (Figure 1). The pelvic ring is formed by the union of the sacrum to the hip bones at the sacroiliac joints and the symphysis pubis.⁵ When a person is in the upright position, the center of the pelvis is the center of gravity. The pelvis provides structural support for the body by transmitting the weight from the trunk to the lower limbs and it provides attachment points for muscles. The strongest ligaments in the body hold the pelvic ring together. The ability of an individual to stand and bear weight requires stability of the pelvic ring.^3,7 This stability is a combined function of ligaments and bones in the pelvis.

The hip bones are often referred to as the ox coxae, and some literature continues to refer to them as the innominate bones. Each hip bone is formed by the fusion of 3 separate bones: the ilium, the ischium, and the pubis. These bones fuse together to form the acetabulum, which is a cup-shaped socket that joins with the head of the femur to form the hip joint. These bones are connected by cartilage in childhood and fuse into one bone by adulthood.^8,9

The ilium is the largest section of the hip bone and is located superior to the acetabulum. It is composed of a body and ala. The body is the lower portion of the ilium and forms two-fifths of the superior portion of the acetabulum. The ala is the superior portion of the ilium and is thin and flared.^8,9

The ischium is composed of a body and a ramus and is located posterior and inferior to the acetabulum. The body of the ischium forms the posterior wall of the acetabulum. The ramus projects inferiorly from the body and has an expanded portion termed the ischial tuberosity. When an individual is seated, the ischial tuberosities bear most of the weight of the body.^8,9

The pubis is composed of a body, the superior and inferior ramus, and is located anterior and inferior to the acetabulum. The body of the pubis forms the anterior wall of the acetabulum. The superior ramus projects medially and inferiorly from the acetabulum toward the midline of the body. The bone then curves into the inferior ramus, projecting inferiorly and laterally toward the ischium. The union of the pubis and ischium forms a large opening called the obturator foramen, which is the largest foramen of the human skeletal system.^8,9

The sacrum and coccyx comprise the distal end of the spinal column. The sacrum consists of 5 fused segments. The central portion is the body and each wing-like structure is termed the ala. The sacral foramina are the holes in the sacrum that allow for passage of nerves and blood vessels. The coccyx is referred to as the tail bone and is made up of 3 to 5 fused segments.

There are several ligaments that help provide stability of the pelvic ring. The symphysis pubis is formed by the union of the 2 pubis bones anteriorly. They are joined together by the interpubic ligaments. Forty percent of the pelvic ring stability is due to the anterior pelvic structures. The posterior aspect of the pelvic ring is supported by a series of strong ligaments at the sacroiliac joints. These are the major stabilizers of the pelvic ring. Any time there is a disruption of the sacroiliac ligaments, the normal weight-bearing function of the pelvic ring is altered.¹

Imaging Pelvic and Acetabular Fractures
When a patient presents to the emergency department with possible trauma to the pelvis, an anteroposterior (AP) pelvis is considered the baseline projection for hip and general pelvic pathology. This projection allows the physician to evaluate the overall pelvis, sacrum, and lumbosacral joints. In order to fully classify and plan the necessary surgical approach for pelvic and acetabular fractures, additional projections of the pelvis are required.⁸ These additional projections include the inlet and outlet views of the pelvis, along with Judet views to demonstrate the acetabulum.

Anteroposterior Pelvis
The AP projection of the pelvis is the baseline projection for the evaluation of pelvic fractures (Figure 2). The patient is placed supine on the radiographic table. The imaging cassette is placed crosswise in the bucky system with the top of the film 1 inch above the crest of the ilium. The central ray is projected perpendicular to the middle of the imaging plate and the midsagittal plane. The patient's feet need to be inverted 15° to 20° in order to overcome the anteversion of the femoral neck.⁹ This may not be possible in cases of significant trauma.

The radiographic image must be evaluated for diagnostic quality. Patient rotation can cause some fractures to be overlooked. Several anatomical landmarks are used to evaluate rotation of the pelvis. These include the size and shape of the iliac wings, the symmetric appearance of the obturator foramina, the alignment of the sacrum and coccyx with the symphysis pubis, and equal demonstration of the ischial spines.^3,9

In addition to evaluating the image for rotation, it must be evaluated for inclusion of all necessary anatomy. The entire pelvis and proximal femur should be visualized. The femoral neck should be fully demonstrated without superimposition and the greater trochanters should be visualized in profile, provided the patient was able to invert his or her feet for the radiograph. If the lesser trochanters are visualized, they should be demonstrated on the medial aspect of each femur.⁹

Inlet View of the Pelvis
The inlet view is considered one of the most useful pelvic projections obtained following pelvic trauma (Figure 3). The inlet view of the pelvis demonstrates posterior and superior displacement of fractures involving the posterior arch, widening of the sacroiliac joint, and fractures of the anterior arch that project inward.^3,5

In order to demonstrate the pelvic inlet, the patient is placed supine on the radiographic table with the patient's midsagittal plane aligned with the center of the grid. The central ray is directed 40° to 60° caudal and enters at the level of the anterior superior iliac spine. This view will demonstrate the pelvic inlet in its entirety. A properly positioned inlet view of the pelvis should demonstrate the superior and inferior ramus of the pubic bones superimposed medially, near superimposition of the superior pubic ramus and ischial ramus, and symmetry of the ischial spines.^5,9

Outlet View of the Pelvis
The AP axial projection of the pelvic outlet demonstrates the superior and inferior rami of the pubis and the ischia (Figure 4). This view provides a better demonstration of sacral fractures and injuries to the sacroiliac joints.^3,5

In order to demonstrate the pelvic outlet, the patient is placed supine on the radiographic table with the midsagittal plane aligned to the center of the grid. The central ray is directed 20° to 45° cephalic at the level 2 inches below the symphysis pubis. A properly positioned outlet view will demonstrate the superior and inferior rami of the pubis without the foreshortening seen in the AP projection. Symmetry of the obturator foramina should also be visualized.^5,9

Judet Views of the Acetabulum
Oblique or Judet views of the pelvis demonstrate the anterior and posterior columns of the acetabulum free of superimposition, obtaining true AP and lateral views of the acetabulum.^2,6 These views are obtained by obliquing the patient 45° toward and away from the involved side, with a perpendicular beam (Figure 5).

The iliac view is obtained by obliquing the patient onto the affected hip 45°. This view best demonstrates the posterior column, the ischial spine, the anterior wall of the acetabulum, and the entire iliac wing. The obturator view is obtained by elevating the affected hip 45°. This view best demonstrates the anterior column and the posterior lip of the acetabulum.¹² Some imaging facilities obtain these views with the central ray directed through the acetabulum of interest. Other imaging facilities will include both the affected and non-affected acetabulum for comparison. A properly positioned iliac view will clearly demonstrate the ilioischial column and the anterior rim of the affected acetabulum, and the properly imaged obturator view will demonstrate the iliopubic column and the posterior rim of the affected acetabulum.⁹

Computerized Tomography
Plain diagnostic radiographs are not always conclusive with regard to pelvic fractures. Computerized tomography (CT) has proven to be an effective diagnostic tool in the evaluation of pelvic fractures. Diagnostic radiographs fail to demonstrate approximately 30% of pelvic fractures that are visualized with CT. In addition, diagnostic radiography missed 29% of sacroiliac diastasis, 57% of acetabular rim fractures, and 34% of vertical shear fractures.⁴ Numerous advances in CT imaging software have expanded its use in demonstrating both bony and soft tissue injuries.¹

Computed tomography plays an important role in determining the nature of the injury to the posterior pelvic anatomy. When imaging pelvic fractures, the axial images obtained in CT allow for better visualization of anterior and posterior displacement of fractures. It is also effective in the evaluation of minor degrees of sacroiliac joint displacement, sacral fractures, crushing or shearing injuries, and other more subtle pelvic ring injuries.^1,5,11 For acetabular fractures, CT imaging can further clarify the fracture pattern, the presence of joint fragments, marginal impaction, and the status of the femoral head.^10,11

In order to have a clearer picture of fragment displacement and to visualize the fracture pattern accurately, the ideal slice thickness for pelvic and acetabular CT imaging is 1 mm. The smaller slice thickness allows for less partial volume averaging, allowing even the tiniest of fragments to be visualized. The smaller slice thickness allows for better 3-dimensional imaging (Figure 6). This supplies more information in the diagnosis of overall pelvic fracture displacement and aids surgical planning.^5,12

Although the benefits of CT imaging of the pelvis are numerous, the cost and radiation exposure received during CT examinations should be taken into account. CT imaging should not be utilized routinely on all pelvic fractures. Simple fractures that do not involve the acetabulum and are stable can be adequately evaluated on plain diagnostic radiographs.¹

Classifications of Pelvic Fractures
A classification is simply a description of the bone injury. When you define the injury, you need to look at several factors: the degree of displacement, how stable is the pelvic ring, the direction of the force applied, the condition of the soft tissue, and any other associated injuries.⁵ Accurate classification of pelvic fractures is essential in surgical planning, as well as providing important information regarding the prognosis of the patient. Fractures are typically classified by the type of fracture, the direction of dislocation, the position of the femoral head at the time of injury, and the direction of the applied force.¹²

Pelvic fractures are uncommon and represent only 3% of all skeletal fractures.¹ These fractures can involve a break in the pelvic ring, a fracture of a single bone without disruption of the pelvic ring, and fractures of the acetabulum. When evaluating pelvic fractures, it is important to determine whether it is stable or unstable. A stable fracture occurs when there is a single, nondisplaced break in the pelvic ring. The sacroiliac joints and the symphysis pubis remain intact. An unstable fracture occurs when 2 breaks are present, causing a risk of displacement.^1,2

Pelvic Fractures
There is no universally accepted classification system for pelvic fractures at this time. Two of the most widely used classification systems of pelvic fractures are the Tile classification and the Young and Burgess classification. Tile's system classifies the fractures by the stability of the fractures, whereas Young and Burgess classifies them according to how the injury was obtained.⁵

Tile's classification system is based on the stability of the pelvic ring and the integrity of the posterior sacroiliac complex. The classifications begin with stable pelvic ring fractures, which have minor complications, and increase to the complete instability of the posterior pelvic ring, involving more complex injuries. Type A fractures are the first level in Tile's classification system. These fractures have minor complications and have no major instability of the posterior ring. Type B fractures of the pelvic ring are partially stable. They may have some displacement anteriorly through the symphysis pubis and/or the pubic rami, but there is no vertical or posterior displacement. The final level of classification is Type C fractures of the pelvic ring. These are unstable and usually result from severe trauma. This type of injury involves the complete disruption of the posterior sacroiliac complex and can involve one or both sides of the pelvis.⁵

Young and Burgess group injuries according to the mechanism of injury. They believe it is important to look at 3 vectors of force and how they disrupt the pelvic ring. According to Young and Burgess, the most common vector of force is the lateral compression (LC). This force occurs when force is applied from the lateral side of the pelvis. The second vector of force is described as one that occurs from either the anterior or posterior direction (AP compression mechanism [APC]). The vertical shear (VS) is the last example of vector of force. If an individual has injuries that result from a combination of the aforementioned types of injuries, they are considered to have a combined mechanism (CM) pattern of injuries.⁵

Acetabular Fractures
Fractures of the acetabulum are uncommon, only comprising approximately 20% of pelvic fractures in adults. They are most common in younger patients and occur as a result of a high-impact injury. When there is a fracture to the acetabulum, it is often accompanied by injury to the femoral head.^3,12  

Letournel has classified acetabular fractures based on plain X-ray findings, and his classification is used by surgeons in choosing the appropriate surgical approach. He divided the acetabular fractures into 10 different types: 5 simple patterns that involve only 1 fracture line and 5 complex patterns which involve more than 1 fracture line.^10,12 The classification system has divided the acetabulum into anterior and posterior columns. The iliac wing, anterior wall, dome of the acetabulum, and the superior pubic ramus comprise the anterior column, and the sciatic notch, posterior wall of the acetabulum, quadrilateral plate, and ischium comprise the posterior column.¹¹ Letournel based his classification of acetabular fractures on the involved column.¹⁰

The 5 simple patterns described by Letournel involve 1 fracture of the posterior wall, posterior column, anterior wall, anterior column, or transverse fractures. The 5 complex fractures involve multiple fractures and include the T-shaped, posterior wall and posterior column, transverse and posterior wall, anterior with posterior hemitransverse, and both anterior and posterior column fractures.⁷

Evaluation and Treatment of Pelvic Fractures
In order to determine the appropriate course of pelvic care, pelvic fractures are divided into 3 different categories: nondisplaced fractures, displaced fractures, and acetabular fractures. Nondisplaced fractures of the pelvis occur when there is a single fracture in the pelvic ring. Nondisplaced fractures are mechanically stable because the sacroiliac joint and the symphysis pubis remain intact. A displaced pelvic fracture is the result of the pelvic ring being disrupted in 2 or more places, and represents only 15% of all pelvic fractures.¹ As stated previously, acetabular fractures are either simple or complex, based on the number of fracture lines present.^10,12

Nondisplaced Pelvic Fractures
The most common fracture of the pelvis involves the pubis bone. Nearly 70% of all pelvic fractures involve fractures of the pubis bone. This fracture usually occurs as a result of direct trauma to the area and is common in elderly patients who have fallen.³ Many patients who have hip fractures will also have fractures of the pubic rami.¹³ Fractures of the pubis bone are well visualized on the routine AP pelvis. If the radiologist or orthopedic physician feels the sacroiliac joint may also be involved, a CT scan is recommended to evaluate for sacroiliac joint disruption. If no other injuries are noted, the patient will be placed on bed rest for 3 weeks.¹

Nondisplaced fractures of the body of the ilium are very rare. These injuries usually occur as a result of a direct force pushing the ilium posterior and medially. Fractures of the ilium are usually adequately visualized on a routine AP pelvis. However, when this view is inconclusive, a CT scan is often helpful in delineating these fractures. Patients with this type of fracture will be treated with bed rest in a pelvic sling. When the patient begins to ambulate, the assistance of crutches will be essential. The total recovery time for an ilium fracture is 3 to 4 months.^1,7

Vertical sacral fractures result from an indirect trauma when an anterior force pushes the pelvic ring posteriorly. Nondisplaced vertical sacral fractures are rare because they are frequently associated with anterior pelvic fractures. The fracture usually begins next to the first and second sacral foramina, the weakest point of the sacrum. Even though a routine AP pelvis is usually adequate in viewing a sacral fracture, this type of fracture is better demonstrated with the outlet view.¹ A CT scan is often necessary to make a definitive diagnosis of sacral fractures as seen above in Figure 6.¹³ The treatment for a vertical sacral fracture is the same as for a nondisplaced fracture of the ilium, with recovery time lasting 3 to 4 months.¹

Displaced Pelvic Ring Fractures
The most common type of displaced pelvic fracture is a straddle injury, which generally occurs when a patient falls and straddles a hard object. This injury results in bilateral pubic rami fractures, or ipsilateral rami fractures with disruption to the symphysis pubis.³ An AP pelvis will demonstrate this type of injury. CT scans are often recommended to evaluate damage of the underlying soft tissue and organs. It is also recommended that patients with straddle injuries have radiographic imaging of the urinary tract, because up to 33% of patients with this type of injury have associated lower urinary tract injury. This type of injury requires operative fixation of the anterior pelvis, involving plates and screws being placed on the bilateral pubic rami.¹

The Young and Burgess Classification system is commonly used by orthopedic surgeons in classifying pelvic fractures. Therefore, it is used to divide the remaining displaced fractures. As noted earlier, the fractures in this classification system are divided according to the mechanism of injury into 4 subtypes: (1) LC; (2) APC (open-book injury); (3) VS; and (4) CM.

Lateral compression injuries result when the force is exerted from the lateral aspect causing the pelvis to implode, and usually occurs as a result of T-bone motor vehicle collision, when a pedestrian is struck from the side, or when an individual falls from a great height and lands on his or her side.⁵ The LC I injury involves a sacral impaction fracture posteriorly along with pubic fracture anteriorly. The outlet view of the pelvis best demonstrates the posterior elements in this type of fracture. However, most LC I injuries are best detected on CT scans of the pelvis. Patients with this type of injury will require bed rest with protected weight bearing on the side of injury. The patient should have repeat radiographs in 2 to 3 days to ensure further displacement has not occurred.¹

An LC II fracture involves transverse pubic rami fractures with a fracture of the iliac wing on the same side. A routine pelvis, along with inlet and outlet views of the pelvis will best demonstrate LC II fractures. This type of injury requires anterior and posterior stabilization. Either an external fixation device or open reduction fixation is used for anterior pubic fractures. Open reduction with a plate is required to stabilize iliac fractures posteriorly.¹

Lateral compression III (LC III) fractures occur when one side of the pelvis rotates externally while the hemipelvis on the side of impact rotates internally. The pubic rami on the side of impact are fractured with or without fractures to the ipsilateral ilium. In addition, the side opposite the impact has fractures to the pubic rami and disruption of the sacroiliac joint. The radiographs that best demonstrate LC III fractures are the routine AP pelvic view, along with the inlet and outlet views. In addition, CT scans are useful in determining the exact fracture pattern and the amount of displacement, allowing the surgeon to better plan the appropriate course of care. Patients with LC III fractures require both anterior and posterior stabilization, including plates and screws in the bilateral pubic rami and iliosacral screws.¹

Anteroposterior compression mechanism fractures are a result of a force being applied from the anterior portion of the pelvis. This type of injury can result when an individual's legs are spread apart during a motorcycle accident, causing the pelvis to widen from the force of the impact.⁵ The anterior injury to the pelvis will consist of either symphysis pubis diastasis or vertical fractures of the pubic rami. The subtypes of the APC fractures are defined by the injury to the posterior pelvis.¹

The APC I fracture is a stable injury that results in diastasis of the symphysis pubis or vertical fractures of the pubic rami without injury to the posterior pelvis. APC I fractures are rare and result from a low-to-moderate energy impact. The anterior ligaments of the sacroiliac joint are stretched, but do not tear. The ligaments of the symphysis pubis normally allow for movement from 0.5 to 1 cm. Any time the symphysis pubis is separated more than 1 cm, it is considered abnormal. Once the subluxation exceeds 2.5 cm, it should be considered unstable and classified as an APC II or APC III. A routine AP pelvis examination is adequate to classify this type of injury. Patients with APC I fractures are treated symptomatically with bed rest in the lateral position.¹

In the APC II injury, the diastasis of the pubic symphysis is accompanied by disruption of the anterior sacroiliac and pelvic floor ligaments. This results in diastasis of the pubic symphysis by more than 2.5 cm. These injuries are considered open-book injuries because the pelvis appears to open up from the symphysis pubis and typically result from head-on motor vehicle collisions (Figure 7).³ APC II injuries are visualized on routine AP pelvis, along with inlet and outlet views of the pelvis. CT scanning is recommended to determine the extent of displacement of the posterior segments. APC II injuries are mechanically unstable and have a high rate of hemorrhage. The immediate course of care is an external fixation device until the patient is stable for open reduction.^1,7,10

When there is an APC III injury of the pelvis, the anterior and posterior sacroiliac ligaments are injured along with the dislocation of the symphysis pubis. These fractures are very unstable and also are accompanied by vascular, visceral, and neurologic injuries. These patients are in critical condition and have a high mortality rate. In most trauma situations involving this type of injury, the speed of care is of utmost importance. Most trauma facilities perform the routine AP pelvic radiograph in these situations, followed by CT scanning of the entire abdomen and pelvis. The bony pelvis can be fully evaluated on the CT images. The immediate course of care is an external fixation device in order to control any hemorrhage. The external fixation device is in place for 8 weeks. Definitive treatment requires open reduction of anterior pubis fractures, as well as iliosacral screws posteriorly.^1,7

Vertical shear mechanism injuries generally occur when an individual lands on an extended lower extremity after jumping from a great height.⁵ VS injuries involve displacement of the anterior and posterior pelvis vertically. Disruption of the symphysis pubis is the usual anterior disruption, although some fractures to the pubic rami do occur. The posterior injury may occur in the ilium, sacrum, or the sacroiliac joint. When a patient presents with a VS injury, the lower extremity of the involved side is shortened. The routine AP pelvic view is adequate to evaluate this fracture. The inlet and outlet views of the pelvis will help determine anterior and posterior displacement of the fractured segments. A CT scan of the pelvis also evaluates for fracture patterns and amount of displacement. Patients with VS injuries may also have visceral injuries that require a complete radiographic evaluation. These patients are candidates for external fixation devices that remain in place for 12 weeks. Definitive treatment of VS injuries requires open reduction. If the posterior injury involves the sacrum or the sacroiliac joint, the patient will receive an iliosacral screw. The anterior structures also may require surgical fixation.¹

Combined mechanism fractures are very unstable, with the pelvic ring being completely abolished. These fractures are difficult to manage due to associated injuries, resulting in a high mortality rate. The routine AP pelvic view is generally the only image that will be obtained initially. If the patient becomes stable, more images, including inlet and outlet views of the pelvis and CT scans are beneficial in the evaluation of these fractures. Definitive treatment for CM injuries depends on the type of injury involved. An experienced orthopedic surgeon should handle this type of case.¹

Acetabular Fractures
Acetabular fractures are usually the result of automobile accidents. This high-energy trauma pushes the femur through the hip, such as when the knees of an individual are forced into the dashboard of an automobile.² The posterior column of the acetabulum is the most common site for fractures and is generally associated with posterior hip dislocations. If an acetabular fracture is suspected on the AP pelvis radiograph, Judet views need to be obtained in order to properly classify fractures of the acetabulum. Although these diagnostic radiographs adequately visualize fracture patterns of the acetabulum, they do not visualize intraarticular fragments in 80% of acetabular fractures. CT scans should also be obtained to evaluate for the presence of the fragments in the joint space and to aid in surgical planning.^1,6

Many fractures of the acetabulum are stable and are treated nonoperatively. These include fractures where there is no dislocation of the hip. Nondisplaced fractures of the weight-bearing dome of the acetabulum require the patient to be placed in traction. This helps prevent further displacement of the fracture. If displacement of the acetabular fracture is less than 1 cm or the fracture does not involve the weight-bearing dome of the acetabulum, the patient should be placed on bed rest and allowed to ambulate as tolerated.^10,12,13

The goal of acetabular fracture surgery is to anatomically restore the joint surface in order to regain the normal relationship between the head of the femur and the acetabulum. This will provide stability and congruency of the hip joint, allowing for better patient mobilization.^11,12 Surgery is indicated if the femur is subluxated or for fractures that are displaced more than 2 mm. The reduction involves a plate and screws placed along the fractured column. Complex fractures may require several modes of fixation in different locations.^1,12

Radiography in the Operating Room
The goal of all surgical fixations of pelvic fractures is to restore proper anatomical relationships. No patient should leave the operating suite without confirmation of acceptable reduction and fixation (Figure 8). For acetabular fractures, this includes confirmation that the joint space is free of hardware. An experienced radiographer can operate the image intensifier successfully, saving time and frustration in the operating suite.¹²

Case Studies
Case 1: APC III
Case 1 involves a 26-year-old male who presented to the emergency department following a head-on collision. The initial AP pelvis radiograph was obtained in the emergency trauma room with bedside radiography. The image visualized superior diastasis of the symphysis pubis, as well as the right sacroiliac joint, or an open-book fracture (Figure 9). In order to stabilize the patient, an external fixating device was applied. Radiographic images of the pelvis, including AP and inlet and outlet views were obtained after the fixation device was applied. The inlet view demonstrates no posterior displacement of the symphysis pubis. The outlet view demonstrates minimal superior displacement of the symphysis pubis (Figure 10).

Once the patient was stabilized, he underwent operative fixation of the symphysis pubis and sacroiliac joints. Postoperative radiographs demonstrate the plates and screws used to reduce the separation of the joints, resulting in improved anatomical alignment (Figure 11).

Case 2: Acetabular Fracture
Case 2 involves a 26-year-old male who presented to the emergency department following a motor vehicle collision. He was the driver of the automobile and received his injuries when the dashboard was forced back into the passenger compartment of the automobile. The patient was transported to the radiology department for an AP pelvis and Judet views of the pelvis. The images demonstrated a posterior hip dislocation with an acetabular fracture (Figure 12).

A CT scan of the pelvis was ordered in order to fully evaluate the extent of the fracture. The images demonstrated a fracture of the posterior column of the acetabulum. Three-dimensional images were reconstructed to aid in surgical planning (Figure 13). The patient underwent operative fixation of the acetabulum. Postoperative radiographs demonstrate the surgical plate and screws utilized on the posterior aspect of the acetabulum, with the femur in normal anatomical alignment (Figure 14).

Conclusions
Patients who present to the emergency department with suspected pelvic trauma have to be treated effectively and efficiently. Their injuries range from single, non-displaced fractures to multiple pelvic fractures accompanied by other life-threatening injuries. Radiographers should be able to provide the radiologist and orthopedic surgeon with acceptable diagnostic radiographs in order to help them evaluate and treat all pelvic fractures. Radiography plays an important role in the diagnosis, treatment, and follow-up care of patients with pelvic fractures.

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