Trauma Imaging of The Pelvis


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The pelvis is commonly injured as a result of high impact blunt trauma such as a motor vehicle accident or a pedestrian being hit by a car. This article covers plain film radiography and CT imaging of the pelvis. The emphasis of this article is traumatic injury and how radiographers image the pelvis. It also discusses fluoroscopic cystogram, retrograde cystogram, CT cystogram, and interventional angiography as a diagnostic and therapeutic tool to control hemorrhage.
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Author: Joseph, Nicholas
Credits: 1.5

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Instructions:

This activity may be available in multiple formats or from different sponsors. ARRT does not allow CE activities such as internet courses, home study programs or directed readings to be repeated for CE credit in the same or any subsequent biennium”

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Objectives

Outline

Introduction

Section 1.1: Anatomy of the Pelvis

Section 1.2: Pathophysiology of Pelvic Injury

Section 1.3: Plain Film Imaging of Trauma Pelvis

Section 1.4: CT Imaging of the Bony Pelvis

Section 1.5: Radiographic Findings In Pelvic Trauma

Section 1.6: Trauma Cystogram and Retrograde Urethragram

Section 1.7: Angiography and Therapeutic Control of Pelvic Hemorrhage

Section 1.8: Short and Long-Term Effects of Pelvic Ring Fractures

Summary and Points to Ponder

References

Bottom


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Objectives

Upon completion you should be able to:
  • State the number one cause of pelvic ring fractures.
  • List primary of causes of acute mortality from pelvic injuries.
  • List the three main vectors of high-energy force that causes predictable patterns of pelvis injury.
  • State the type of high-energy force that produces a characteristic sacroiliac joint diastasis.
  • State which type of pelvic injury is associated with the highest risk of vascular injury and hemorrhage.
  • State the diagnostic criteria for the portable AP pelvic view for acute trauma.
  • State why part-tube-film alignment is especially important when imaging patient on a spine board using a Stryker type bed in the emergency room.
  • State why the AP view of the pelvis is important and why it is not the sole determinant of pelvic injury.
  • State the importance of the pelvic inlet view and tell what is demonstrated by this view.
  • State the degree of tube angle and direction required for the pelvic inlet view.
  • State the importance of the pelvic outlet view and tell what is demonstrated by this view.
  • State the degree of tube angle and direction required for the pelvic inlet view.
  • State the diagnostic criteria for plain film imaging of the pelvic inlet and outlet views.
  • State the advantage of CT imaging of the pelvis for acute multisystem trauma with suspicion of possible pelvic injury.
  • State the reasons for CT imaging of the pelvis following known pelvic injury seen on the plain film radiograph.
  • State the CT protocol for imaging the pelvis from the chest/abdomen/pelvis series commonly acquired for multisystem injuries.
  • State the reasons for 2D and 3D imaging of the pelvis for acute pelvic trauma.
  • Discuss the potential complications of severe pelvic ring fractures using bladder rupture and urethral shear as examples.
  • Discuss the radiographic procedures used to diagnose bladder and urethral shear injuries.
  • Discuss fluoroscopic cystogram, retrograde urethrogram, and CT cystogram as means to diagnose bladder and urethra injury.
  • Discuss hemorrhage as the primary cause of mortality and morbidity from pelvic ring fracture.
  • Discuss angiography as a means of diagnostic and therapeutic treatment of pelvic vascular injury.

Outline

  • 1.0 Introduction
  • 1.1 Anatomy of the Pelvis
  • 1.2 Pathophysiology of Pelvic Injury
  • 1.3 Plain Film Imaging of Trauma Pelvis
  • 1.4 CT Imaging of the Bony Pelvis
  • 1.5 Radiographic Findings In Pelvic Trauma
  • 1.6 Trauma Cystogram and Retrograde Urethragram
  • 1.7 Angiography and Therapeutic Control of Pelvic Hemorrhage
  • 1.8 Summary Points
  • 1.9 References

1.0 Introduction

Pelvic fractures most often occur from a variety of mechanisms that involve high-energy blunt force trauma. About 60% are caused by motor vehicle accidents; while falls account for approximately 30% of pelvic fractures that statistically usually involve the elderly. Crush injuries and stress from overuse or misuse account for the remaining 10% of injuries. Injuries that involve the pelvic ring have a high morbidity and significant mortality (approximately 6%). Hemorrhage is the leading cause of death in patients with a pelvic fracture1. Bone injury is not the only concern with pelvic ring fractures, soft tissue components such as the bladder, urethra, rectum, and uterus may also sustain injury requiring immediate appropriate therapy. Often pelvic injuries are so extensive that the emergency physician is unable to control pelvic hemorrhage caused by discontinuity of pelvic veins and arteries. This account for about 35-40% of deaths from pelvic ring fractures. Pelvic fracture is a severe and life-threatening injury that requires treatment by a dedicated team5. In addition, there are associated multi system injuries, which occur at relatively high frequencies. For example, closed head injury occurs 48% of the time. Spine injury (20%), liver and/or spleen injury (17%), and bladder or urethra injury (25%) also frequently occur as multi system injuries. Understanding the force(s) that cause fractures of the pelvic ring, its potential consequential injuries, and acquiring appropriate radiographic images and diagnostic studies are the subjects of this learning module.

1.1 Anatomy of the pelvis

Before we discuss the radiography of the pelvis its anatomy should be briefly discussed. The pelvis is a term meaning 'a basin' referring anatomically to a ring of bone formed by the two innominate bones, sacrum and coccyx. It is where the trunk and lower limb meet to effect upright motility of the human. Besides bearing and transmitting weight to the lower extremity the pelvis can be appreciated for it’s obstetric, forensic, anthropological, and paleontological presentations. Our discussion of the anatomy of the pelvis will review the ossification and osteology of the composite bones that form it.

  • Pelvis is a strong osseous girdle bridging the trunk and lower extremity.
  • Its primary function is to facilitate locomotion.
  • Has the most obvious differences between male and female anatomy.
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The male pelvis is narrower and presents with a more acute angle of the pubic arch, whereas the female pelvis is broader and wider. The female pelvis is adapted for childbearing, which accounts for the major differences between the genders.

Every technologist should review basic anatomy of the pelvis from time to time. The best time to review it is when radiographs are being critiqued prior to sending them for interpretation. This will keep the anatomy “fresh” in the mind and promote growth beyond basic anatomy as you are practicing clinical radiography. Briefly look at the anatomy on the radiograph below and make sure you are familiar with all labeled parts and those that are not labeled, like the soft tissue structures.

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  • Iliac crest (A)
  • Iliac wing (B)
  • Sacroiliac joint (C)
  • ASIS (D)
  • Acetabulum (E)
  • Femoral head (F)
  • Femoral neck (G)
  • Greater trochanter (H)
  • Lesser trochanter (I)
  • Ischium (J)
  • Superior pubic ramus (K)
  • Inferior pubic ramus (L)
  • Obturator foramen (M)
  • Symphysis pubis (N)
  • Sacrum (O)

Ossification

Each of the two innominate (hip) bones is formed by three primary ossification centers that will ossify by endochondrial growth to become the ilium, ischium, and pubis bones. At birth parts of these bones are still cartilaginous including the acetabulum, which is not completely formed for bearing weight. In the adult pelvis these bones are fused at the acetabulum into a single composite bone called the innominate or hip bone. The two innominate bones are joined anteriorly at symphysis pubis and posteriorly to the sacrum at the sacroiliac joints. The pelvic ring is strongly held together by durable ligaments.

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Labeled on this radiograph are the three bones that form the innominate bone, which is called the hipbone. (A) ilium, (B) pubis superior ramus, and (C) ischium. The two hipbones, sacrum, and coccyx form the pelvis.

Osteology

The pelvis is arbitrarily divided into a greater and lesser segment called the false and true pelves. Posteriorly the sacral promontory separates the pelves and the lineae terminales elsewhere. The lineae terminales is a continuous line formed by the iliac arcuate line, iliopectineal line, and pubic crest. Above this line is the false pelvis and below is the true pelvis. The greater (false) pelvis consists of the iliac wings and parts of the ilium above the lineae terminales. Because the pelvis is inclined, the false pelvis has no anterior wall. As such the abdominal contents and pelvic contents are not separated and have little bony protection. The lesser pelvis is known as the true basin because it encloses soft tissues within its walls. The pelvic inlet is of great obstetrical importance. Three measurements are given to describe the opening. The true conjugate measures the anteroposterior diameter. It is the distance between the sacral promontory and symphysis pubis. The transverse diameter is the widest distance of the true pelvis. It is measured across the linea terminalis, but for partition it is measured from ischial spine to ischial spine. The oblique diameter is measured from the iliopubic eminence to the opposite S.I. joint. Several other planes are used in obstetric practice, which are outside the scope of this lesson. Within the bony true pelvis lies the rectum posteriorly, the bladder anteriorly, and the uterus between them in females.

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The blue line in this 3-D volume rendered CT image (above) represents the linea terminales that separates the false pelvis, which is above it from the true pelvis below it. The false pelvis consists of the iliac wings and has no anterior wall. The pubis bones, sacrum and coccyx, and both ischium bones delimit the false pelvis.

The pelvic inlet is of great obstetrical importance. The inlet is the opening into the true pelvis that houses the urinary bladder, uterus, and rectum among other important pelvic structures. Three measurements are routinely given to describe the size of this opening. The true conjugate measures the anteroposterior diameter. It is the distance between the sacral promontory and symphysis pubis. The transverse diameter is the widest distance of the true pelvis. It is measured across the linea terminalis, but for partition it is measured from ischial spine to ischial spine. The oblique diameter is measured from the iliopubic eminence to the opposite S.I. joint. Several other planes are used in obstetric practice, which are outside the scope of this lesson. The true pelvis houses the urinary bladder and rectum; in females the uterus is between these two structures.

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This 3D volume rendered CT image shows the three common linear measurements of the pelvic inlet: (A) anterior to posterior diameter, (B) transverse diameter, and (C) oblique diameter.

The pelvic outlet holds special importance to surgeons and obstetricians. The pelvic outlet has an anteroposterior diameter that in females ranges from 9.5 cm to 11.5 cm. Mobility of the coccyx plays a role in this variation in diameter. The transverse diameter is approximately 11 cm. For obstetric purposes the transverse diameter is measured as the distance between the ischial spines. This may represent the widest distance of the outlet for delivering the fetus. This picture shows an inferior view of the pelvis and its outlet. These measurements are important when referencing traumatic injury that alters the pelvic dimensions.

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This 3D CT volume rendered image demonstrates the inferior view of the pelvis showing the two of the main linear dimensions of the pelvic outlet, its AP (A) and transverse (B) diameters are demonstrated.

Pelvic Stability

One of the main functions of the pelvis is to transmit weight from the trunk and lower lumbar vertebrae to the lower extremity. For example, when standing weight is transmitted from the trunk through the posterior pelvic arch, sacrum and sacroiliac joints. Then this weight is transmitted through the acetabula to the femurs. The anterior arch functions like a strut maintaining the shape of the pelvic ring during active weight-bearing movements. Passive weight bearing such as during sitting is transmitted to the ischial tuberosities.

The bony pelvis lacks inherent structural stability, and so is stabilized by a system of tightly woven ligaments that provide support for the bony frame. Strong ligaments arranged transversely resist forces that can externally rotate the pelvis, thereby opening it. Among these strong ligaments is the short posterior SI ligament, the anterior SI ligament, the iliolumbar ligament, and sacrospinous ligaments. These function in a counteraction mechanism apposing forces such as AP compression. These ligaments fail when force exceeds their ability such as in acute AP compression injury. Vertical stability of the pelvis is primarily due to the short and long posterior SI ligaments. Interosseous ligaments within the sacroiliac joints also provide some additional vertical stability.

Some ligaments that stabilize the pelvis
  • Short posterior S.I. ligaments
  • Long posterior S.I ligaments
  • Anterior S.I. ligaments
  • Iliolumbar ligaments
  • Sacrospinous ligaments
  • Interosseous ligaments
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These ligaments are not appreciated on plain films and to some degree with the CT scan. But MRI is very useful for evaluating these ligaments when the pelvis is severely fractured. Consider the examples below of the complexity the dense ligaments that stabilize the pelvis.

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These three 3-D volume rendered CT images depict some basic patterns for dense broad ligaments that support the bony pelvis. The picture on the left shows these ligaments from the AP perspective; the middle picture shows how these ligaments attach to the posterior frame to support from behind. The far right picture is a lateral view that demonstrates the array of ligaments attached to the sacrum/coccyx and the hipbones. Many ligaments support and provide short stabilizing struts for the pelvis. The greater sciatic notch forms an opening bridged by ligaments that guard the entrance into and out of the pelvis. The lesser sciatic notch provides an opening to the perineum. It is important to understand the complexity of these ligaments and their relationship to known patterns of injury.

1.2 Pathophysiology of Pelvic Injury

There are three main vectors of high-energy force that causes predictable patterns of injuries involving the pelvis. These vectors may occur as a single force or as composite forces. The patterns of injury due to complex forces are: anteroposterior (AP) compression, lateral compression, and vertical shear. With any pelvis injury the physician evaluates the patient for all of these predictable patterns for injury. The report to the physician about the type of trauma can be extremely useful in determining suspicion for pelvic injury. Pelvic compression in the AP diameter results from a high impact vector from anterior to posterior or from posterior to anterior direction. Examples of this force would be a pedestrian is struck by a motor vehicle at waist level, or a motor vehicle accident in which the front seat passenger is thrown forward making contact with a solid force at waist level. The AP forced compression is evidenced by pelvis injuries that may include the characteristic symphyseal and/or sacroiliac joint diastasis.

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This AP Portable radiograph of the pelvis demonstrates multiple pelvis injuries characteristic of an AP vector. Diastasis or widening of the symphysis (white line) and sacroiliac joint shifting are classical indicators of AP compression injury. Also seen in this radiograph are other injuries, which are not described here.

Lateral compression injuries occur when a high impact force strikes the side of the pelvis. This is commonly seen when a significant force like a motor vehicle collides with a pedestrian. The hallmarks of a lateral compression injury include sacral buckle fractures and horizontal pubic rami fractures. With lateral compression injury the affected side of the pelvis sustains an internal rotation. This type of injury is characterized by horizontal fracture(s) of the pubic ramus and sacral fracture(s). A consequence of lateral compression injury is internal rotation of the affected hemipelvis, which decreases the pelvic volume. Consequentially, vascular injuries within the pelvis and resulting hemorrhage are less common with this injury than with other types. Anteroposterior compression and shear injuries have a much higher incidence of vascular injury and acute hemorrhage related mortality. When lateral compression injuries occur as part of multisystem injuries there is a high association with brain and intra-abdominal injuries.

A third type of injury is vertical shear that generally occurs as a result of a fall from a height. The force is a complex pattern of vectors. Like lateral compression, vertical shear injuries usually involve a hemipelvis. Complex forces directed caudocranially usually causes this type of injury. Both AP compression and vertical shear injuries can cause a disruption of the pelvic vasculature and cause profound hemorrhage. If the force is powerful enough the results can be difficult to uncontrollable bleeding. The majority of blood loss derives from injured retroperitoneal veins and broad cancellous bone surfaces1. Uncontrolled hemorrhage accounts for 39% of related deaths. Along with bleeding, when the pelvic ring is broken there may be damage to peripheral nerves, the urinary bladder, or even the urethra.

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This portable AP pelvis radiograph shows multiple fractures sustained from a motor vehicle accident. These injuries are a result of complex high-impact vectors that show AP compression, vertical shear, and lateral compression injuries. Note the dislocation of the right sacroiliac joint, fractures of the sacrum, complex compound fractures of the pubic rami, and fracture of the right femur. The patient will need to undergo further testing to determine injuries to the bladder and urethra. This patient is at high risk for life threatening injuries due to hemorrhage.

There are two major classification systems that describe fractures involving the pelvic ring. The Young-Burgess classification system describes the degree of injury to the ring. Pelvic stability is described using the Tile classification system. These are their brief descriptions:

  • Classification of AP compression injury using the Young-Burgess system
    • The hallmark indicator of AP compression injury is the degree of pubic diastasis. Whether or not there is sacroiliac joint disruption is also considered in the classification scheme. Furthermore, there is correlation with the amount of known force required to cause each type of injury, and is correlated with the amount of resulting instability. The AP compression occurs the pelvis is compressed open causing external rotation of the hemipelves. The Young-Burgess system identifies 3 types of types of observed AP compression injuries:
      • Type I – Separation of the symphysis (<2.5 cm) or vertical fractures of the pubic rami with the SI joints stable and intact.
      • Type II – Wide separation of the symphysis (>2.5 cm), posterior rotational instability but stable vertically, and diastasis of one or both SI joints.
      • Type III – Injuries result in rotational and vertical instability of the pelvis.


  • The Tile classification system is descriptive including an appraisal of the stability of fractures.
    • The Tile classification system describes pelvic fractures that do not appreciably disrupt the pelvic ring (Tile type A).
      • Type A, posterior arch intact stable fractures including avulsions of the iliac spine, iliac crest, ischial tuberosity, wing fracture, unilateral and bilateral pubic rami fracture, sacral fracture, or sacrococcygeal fracture. These are ring sparing injuries and fractures that do not affect the stability of the pelvic ring and do not involve the SI joints.
      • Type B, incomplete posterior arch disruption occurring with pubic diastasis, anterior SI joint disruption, anterior sacral buckle fracture, AP and lateral compression injuries, internal and external rotational injuries, and accountability for stability of rotational and vertical injuries.
      • Type C, complete posterior arch disruption. These are the most severe types of pelvic ring fractures caused by vertical shear, shear and AP/lateral compression. These occur with ipsilateral and contralateral internal or external rotation of the pelvis due to SI joint fracture/dislocation, and are rotationally and vertically unstable.

A rotational injury of the hemipelvis causes serious anatomical disruptions of the pelvic cavity. An external rotation of the hemipelvis increases the volume of the pelvic cavity causing pelvic hemorrhage. This type of injury must be reduced as soon as possible and bleeding controlled. Often paramedics who arrive on the scene of injury will immediately wrap in a pneumatic antishock suit. In severe cases the patient may remain in this condition until hemorrhaging can be stopped and therapeutic external fixation reduction can be achieved. If bleeding is not stopped, vascular embolization by interventional radiology may be called upon to attempt to control the bleeding.

Section 1.3 Plain Film Radiography of the Pelvis

Trauma imaging of the pelvis usually begins with a portable x-ray image. The AP view taken in the emergency room to evaluate the patient who has sustained traumatic injuries is a good survey image. The clinical criteria for the standard AP pelvis film warrants imaging for any patient who sustains a high-impact, blunt multiple trauma. Usually a person who sustains a high impact trauma will receive a portable chest and pelvis x-rays in the emergency room as part of the screening process. Portable pelvis x-ray is a good screening tool to determine if the patient has a fracture that may need further investigating.

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This portable trauma AP pelvis radiograph was taken in an emergency room along with a horizontal beam lateral cervical spine, chest x-ray, and AP abdomen radiographs. Multiple injuries have destabilized this pelvis, and the emergency room trauma team worked expediently to stabilize this patient and get the patient through other diagnostic testing and ultimately to the operating room.

The sensitivity of pelvic radiography is low, and it is not reliable for determining if the pelvic injury is stable or not. A study in Helsinki, Finland showed that the accuracy of plain film imaging of the pelvis while is necessary for quick evaluation of pelvic trauma is only marginally reliable. Using inclusion criteria for blunt trauma and plain film radiography followed by multi-detector row computerized tomography (MDCT), CT showed 629 fractures. Radiography depicted 405 fractures in these 226 patients, giving an overall sensitivity of 55%. The sensitivity of radiography was mainly good in the anteroinferior parts of the pelvis, fair in the acetabulum and ileum, and poor in the posterior ring3. The AP pelvis view provides a good study of most anterior pelvic structures and detects most injuries; however, other views of the pelvis may be required to evaluate the acetabulum, and other posterior elements. Additional views that may be required are the pelvic inlet, pelvic outlet, and Judet views. Plain films are an important part of imaging of the traumatic pelvis. These views have specific imaging criteria beginning with the required anatomy for diagnosis; correct positioning of the part, and adequate radiographic exposure technique.

AP Pelvis View

Often the technologist is called to the emergency room to respond to a trauma team alert (TTA) in which portable radiographs are anticipated. When called upon, the AP portable pelvis radiograph is usually taken with the patient in the “as is “position. If the patient is on a spine board the radiograph is taken through the spine board. The cassette is placed under the spine board and not directly under the patient to minimize movement and agitation of the patient. If the patient is on a Stryker type bed use of the cassette tray beneath the mattress is recommended. The Stryker type bed contains a special cassette tray beneath the mattress of the gurney. This allows the technologist to place a cassette beneath the patient for imaging. The advantage of this device is that the patient is not moved to place a cassette directly beneath the spine board. Using a Stryker type bed is an excellent way to maintain spine and pelvic precautions for patients under suspicion of multisystem injuries for which they should not be directly moved.

Understanding the workings of a Stryker type bed in order to correctly position the patient in the center of the cassette requires skill and experience. Accurately positioning a grid cassette in the tray beneath the patient requires accurate tube-part-cassette alignment. Alignment of the cassette to the top of the patient’s iliac crest is achieved by adjusting the longitudinal lock on the cassette slide tray (see picture below). Besides including the required anatomy the technologist must make sure grid cut-off does not occur. So use the maximum source-image-distance allowed by the grid focus range and portable unit. Part-tube-cassette alignment is critical to getting a good radiograph. Object film distance is also an important factor when imaging through a Stryker type bed because it can be a cause of excessive part magnification. Patient size, body composition, the spine board material, and mattress through which the x-ray beam must pass are to be considered when setting the radiographic exposure technique. A summary of the important factors to be considered when making an AP portable radiograph are: positioning of the patient, tube-part-cassette alignment, OID/SID, grid alignment, clearing metallic artifacts, and using an acceptable radiographic exposure technique.

The diagnostic criteria for the AP Pelvis view are:

  • Include the anatomy from the top of both iliac crest superiorly through the ischial tuberosities, and the inclusion of both lesser trochanters of the femurs.
  • The lateral margins of the film (14 X 17) should include the anterior portions of the iliac wings, which is the anterior part of the pelvis. Do not internally rotate the femurs during trauma imaging of the pelvis.
  • The radiographic exposure technique should demonstrate good bone detail. Soft tissue shadows should include the urinary bladder, pelvic portion of the iliopsoas muscle, rectum, and bowel gas.

If the diagnostic criteria are not met as a portable radiograph it must be repeated to include the entire criteria. This may be accomplished when the patient is stable enough to receive further diagnostic imaging in the radiology department. Otherwise, it must be repeated as a portable exam. Consider the radiograph below of a normal AP pelvis taken for trauma that meets the diagnostic criteria.

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This normal plain film AP pelvis demonstrates radiographic anatomy that must be demonstrated when imaging the pelvis. This radiograph encompasses the entire diagnostic criteria for a pelvis image whether portable or in department. Here the femurs are not internally rotated because this is a patient who sustained high impact trauma; however, non-trauma pelvis imaging the femurs is always internally rotated.

The diagnostic criteria must be met for all radiographs of the pelvis whether imaged for pathological changes, or for trauma. In the radiograph below we see that the diagnostic standard has been met for this radiographic trauma survey. Because this image was taken in the department on a standard x-ray table using a reciprocating bucky the problems encountered with mobile imaging are not a significant factor. Grid cutoff due to the cassette not being level does not occur with a reciprocating Potter bucky apparatus. This is because it is in the table and is not dependent on technologist positioning. However, alignment of tube-part-bucky must be accurately achieved if the proper radiograph is to be made.

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This abnormal AP pelvis radiograph demonstrates the anatomy required for interpretation according to the diagnostic criteria. Soft tissues and bone detail is seen on this image. Because this radiograph meets the diagnostic criteria the physician is able to make an assessment of the patient and request additional studies to further evaluate the visualized injuries. This radiograph was taken in the radiology department on the imaging table.
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These two pictures of a Stryker type bed demonstrate the trauma bed used in most emergency rooms when receiving a critically injured patient expected to need mobile radiographic assessment. The picture on the right shows a spine board positioned on the gurney. Note the position of the tray, which can be moved longitudinally to align the top of the grid cassette with the top of the iliac crests. The patient can be moved on the spine board with proper spine precautions if needed to center the patient’s mid-sagittal plane to the center of the cassette.

As all experienced radiographers know, it is sometimes difficult to include the entire pelvis, hip joints, and proximal femurs on the radiograph when using a Stryker type bed. Using a bed with a cassette tray may eliminate off angle grid cut-off, but at the same time may present the challenges of vertical misalignment and magnification. The basic scenario is that the patient is on a spine support board, and possibly wrapped in a pneumatic pelvic support apparatus. Along with the mattress on the gurney a sufficient part to image receptor distance will exist. This is to be expected because the degree of uncontrollable magnification may be out of the technologist’s control. The goal in this case is to entirely include the two innominate bones, sacrum and true pelvis contents as is seen in the radiograph below. Both femurs may not always be entirely seen; however the radiograph below demonstrates enough of the anatomy to warrant further imaging.

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This portable AP pelvis radiograph demonstrates how OID can affect even the most competently positioned part. We see a lot of image magnification due to excessive OID. It is not of great concern here because additional views of the pelvis will be taken once the patient is stabilized.

The AP view is very important because is gives the trauma physician a quick assessment of the pelvis so that other potential injuries can be evaluated. The most serious of injuries may include pelvic ring fracture, acetabular fracture, rupture of the urinary bladder, and transection of the urethra. Abnormalities depicted on the AP pelvis radiograph direct the need for additional radiographs. These may include inlet and outlet images and oblique (Judet) views of the pelvis if acetabular fractures are seen.

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This AP pelvis radiograph reveals a pelvic ring fracture on the left involving the acetabulum. To completely evaluate these findings inlet, outlet, and Judet views are also needed.

Pelvic Inlet and Outlet views

The pelvic inlet is formed by two arching lines that begin posteriorly with the sacral promontory and extends anterolaterally as the arcuate lines and pectin on the superior pubic rami. The pelvic inlet is the opening into the true pelvis, which houses the urinary bladder and rectum in both genders, and the uterus in females. The inlet view is an important view of the pelvis when there is posterior displacement of the SI joint and/or rotation of the hemipelvis. The inlet view is taken with the patient supine and the x-ray tube angled 45 degrees caudal and perpendicular to the pelvic brim. The following are some of the determinations permitted by the inlet view:

  • The degree of posterior displacement at the SI joint.
  • The degree of internal or external rotation of the hemipelvis.
  • The degree of pubic diastasis or overlap.
  • The presence of subtle sacral fractures or sacral impaction.

The primary purpose of the outlet view is to demonstrate the magnitude of vertical hemipelvis displacement. The sacral foramina are better depicted on the outlet view than with the AP view. Additionally, some sacral and pubic rami fractures are better visualized with the outlet view.

  • Can corroborate vertical displacement of the hemipelvis.
  • Demonstrates the sacral neural foramina better than the AP view alone.
  • Some pubic fractures are also better demonstrated in this view.
  • Outlet view is obtained with the patient in the supine position, with the x-ray tube angled 45 degrees cephalic and perpendicular to the sacrum.
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This view of the pelvic inlet demonstrates the diagnostic criteria. Notice that the entire pelvis is included on the film from the iliac crests through the lesser trochanters. The x-ray tube is properly angled and the pelvic inlet is presented opened on the film. Note that there is no rotation of the pelvis evidenced by the visualization of both ischial spines. The radiographic exposure technique is adequate for bone and soft tissue detail. The same picture is shown on the right with arrows that point to a fracture of the pelvic ring.

It is important when imaging the pelvic inlet not to clip the inferior portion of the pelvis. Both pubic bones should be entirely visualized on the inlet view. The picture below shows an inlet view that is a good radiograph in all regards, except that part of both pubic rami are clipped. This amount of omission is enough of a breach in the diagnostic criteria to warrant repeating the radiograph.

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Evaluation of the inlet view seen above requires complete inclusion of the pubic rami. The fractured right superior pubic ramus is part of the pelvic inlet; therefore, by it being clipped breaches the diagnostic criteria for this view. The technologist should repeat this view to include all required anatomy.

The outlet view is obtained with the patient in the true AP position and the tube is angled 45 degrees cephalic. The floor of the pelvis and sacroiliac joints are demonstrated. The diagnostic criteria for the evaluation of the pelvic outlet are:

  • Include the entire pelvis from the inferior pubic rami and ischial tuberosities to the top of the iliac crests superiorly.
  • Both sacroiliac (S.I.) joints and the entire sacrum/coccyx should be visualized.
  • The acetabulum and femoral heads should be included on the radiograph.
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The radiograph above is a pelvic outlet view. Both iliac crests are not entirely included on the film making this radiograph an incomplete view; however, the pelvic outlet is completely demonstrated. Because the outlet is well demonstrated, and the degree of vertical displacement could be determined from this radiograph the technologist did not repeat this view.

Consider the radiograph below of the pelvic outlet in which the iliac wings are entirely included.

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This outlet view of the pelvis demonstrates the entire pelvis not just the outlet. The iliac wings, sacroiliac joints, pubis bones, and ischial bones are profiled. Notice the fracture of the right acetabulum.

Oblique Pelvis (Judet) Views

Sometimes an injury involving the acetabulum is in question and a better presentation of the acetabula is helpful. An acetabular fracture may occur in addition to a pelvic ring fracture and must be distinguished from pubic rami and iliac wing fractures. In such case the acetabular fracture must be discretely analyzed. The plain film studies of choice for this are the Judet views (so named because Judet stressed the use of these views for trauma imaging. The patient is positioned with the mid-sagittal plane 45 degrees to the tabletop and the central ray perpendicular to the image receptor. Usually both oblique views are made unless specified as a unilateral examination. The Judet views are internal and external oblique views, which are very useful for visualization of nondisplaced acetabular fractures.

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These two radiographs are 45-degree oblique views of the pelvis called Judet views. They are so named because Dr. Judet stressed the importance of these views in evaluating the pelvis, especially the acetabulum. The left radiograph is a LPO view. It demonstrates a fracture of the right acetabulum very well. Before CT, this was a very effective method of diagnosing fractures along the posterior portion of the acetabulum. The radiograph on the right shows the RPO view and profiles both acetabula as well.

1.4 CT Imaging of The Trauma Pelvis

The trauma pelvis is usually included when indicated with the abdomen CT and the chest depending on the patient’s condition. CT scanning offers the advantage of thin helical tomographic images through the pelvis. Because the scan is algorithm based both soft tissue and bone detail can be acquired from a single scan. And with multi-slice CT scanners, images can be reconstructed to thin slices from a thick slice acquisition. A tremendous amount of diagnostic data is gathered from the helical scan, which can be reconstructed, into 2D and 3D images. A bone detail algorithm is recommended if the pelvis is scanned separately from the abdomen. The trauma pelvis should be retro reconstructed into a bone algorithm if the data is acquired from a soft tissue pelvis CT. Thin slice axial CT images no greater than 1.25 X 1.25 mm is needed and 1.25 X 0.625 mm or 0.625 X 0.625 mm or thinner is recommended for 2D and 3D image reconstructions.

The recommended protocol for CT of the bony pelvis depends on whether or not there is a fracture with displacement of bone seen on the initial axial helical scan. The protocol this learning module uses is derived from a Level I trauma center in St. Paul, Minnesota. The radiologist views all trauma images from the CT console and gives a preliminary reading to the trauma team physicians. At this time a protocol for the pelvis is given to the technologist. In our lesson we will consider the worst-case scenario and protocols to follow. This is not a case study; therefore, several different patient images are used to make our point about diagnosis and protocols. The CT protocol we will discuss is the acquision of axial images in the helical format of the entire pelvis as follows:

  • The entire pelvis is acquired as a helical scan. The top of the scan should begin above the iliac crests to include all of L5. The inferior landmarks are to entirely include the ischial tuberosities and inferior pubic rami, and through the lesser trochanters of the femurs.
  • These axial images should be acquired at 1.25 X 1.25 mm if possible or the thinnest possible cut for the type of scanner being used. For example, using a 16-MDCT scanner, a second set of reformatted axial images at 0.625 X 0.625 mm should be made in case 3D images are requested.
  • Thin slice 2D coronal reconstructions through the entire pelvis. These should be thin slice images too. Use the thinner reconstructions (0.625 X 0.625 mm images) to make the coronal and sagittal images. It is important that the slice grid is adjusted so that symmetry of the anatomy is achieved in each slice. For example, the pubic bones should be presented at the same anatomical locations in each slice.
  • Sagittal 2D reconstructions through any affected areas such as the iliac wing, or the acetabulum if a fracture is noted. These images are important because they provide images at 90 degrees to the coronal plane, and provide exceptional information about complex fractures of the acetabulum and complex fractures of the sacrum.
  • If there is displacement of any fracture component then 3D reconstruction with at least 20 images through 360 degrees of image rotation should be made. The number of images can be changed so that the angle between images is great or small depending on institutional protocol.
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These sixteen axial helical thin slice CT images demonstrate the importance of CT scanning of the pelvis in cases with complex fractures of the hip bone(s). Shown here are selections from the scan taken at 1.25 mm X 1.25 mm, and reformatted to 0.625 mm X 0.625 mm thin slices anticipating the need for 3D imaging. The selected series of images are continued below:
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The white arrow in the picture above (image #28) shows buckling of the superior ramus of the left pubis bone. The scan protocol ends just a little below the lesser trochanters. Axial images show a very good perspective of bony injury of the pelvis not fully appreciated on the plain film images.

Coronal CT reconstructions

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The nine coronal reconstructed images above are from axial CT data. These selected images demonstrate the value of CT coronal reconstruction of the pelvis. Note the fracture of the sacrum, left iliac wing, and right pubis bone (white arrows). While only nine images are shown here the complete set consisted of 80 thin slice reconstructed coronal images. Coronal images give a better representation of the acetabula and sacrum than plain film images.

Another advantage of coronal reconstructed images is the detail characterization of complex multiple fractures it provides. Coronal CT images demonstrate these fractures involving the posterior pelvic ring better than plain film images. Descriptive interpretation and the reality that surgical repair will be necessary in most cases of posterior ring fracture makes coronal images valuable. Consider the importance of the detail characterization of the multiple fractures seen in the 2D coronal reconstructions below. Repairing pelvic fractures that involve the sacrum must be precise. Coronal images provide the diagnostic and surgical information that has led to advancements in orthopedic surgery of the pelvis. A good CT technologist realizes the importance of reformatting good coronal images. The standard for good coronal reconstructions is to have symmetry of the anatomy in each slice. For example, the femoral heads and the pubic rami anatomy should be demonstrated at the same slice level. This makes the entire coronal set easier to appreciate. Consider the selected coronal slices below that illustrate this point.

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Notice the symmetry of the pelvis at the pubis bones, both ilium, and femoral heads. Symmetry on the coronal slices is especially important to characterizing and planning surgical repair of displaced fractures. These coronal images demonstrate a very complex set of fractures to the left hip bone. Notice the fracture at the upper part of the ilium, and comminuted fracture involving the left acetabulum. These fractures were identified on plain film images, but poorly described relative to CT coronal images.
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Because the technologist achieved symmetry when reconstructing the coronal slices, that symmetry is followed through the posterior part of the pelvis including the sacrum. Notice the symmetry of the sacral slices and the SI joints. This is very important when demonstrating coronal images of the pelvis because this is an area that is poorly described on plain film images.

Sagittal CT imaging of the pelvis

As we have stated, sometimes the imaging protocol requires sagittal images to compliment data needed for surgical repair. Part of this needed information may be sagittal images of the pelvis, especially the acetabula. When there are complex fractures involving the sacrum or acetabula such as multiple fractures seen on the plain pelvis radiograph below, then CT images should include sagittal reconstructions. In the sagittal selections below several fractures involving the left hemipelvis is demonstrated.

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The CT image above demonstrates the planes of reconstruction of the sagittal images of the pelvis. Sagittal images are not routinely made unless there is displacement of the posterior pelvic brim or acetabular fracture.
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These twelve sagittal CT images demonstrate the importance of 2D reformats in pelvic imaging especially of the acetabulum. We all know how important 90 degree images are to routine plain film imaging. These sagittal slices are complimentary to coronal imaging. The arrows point to several fractures involving the iliac wing, acetabulum, and pubic ramus.

CT 3-D Imaging

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These volume rendered images of the whole pelvis demonstrates the power of 3D imaging. These nine images show complex multiple fractures of the pelvis. This pelvis is very unstable due to the injuries. The complexity of surgical repair is apparent from these images, and the risk of pelvic hemorrhage is fully appreciated from these views.

Any physician who has treated a patient that suffered complex multiple fractures before the use of CT and 3D modeling know how difficult the recovery is when multiple surgeries are required. Nowadays orthopedic surgeons are able to achieve remarkable bone alignments and fixations of complex fractures primarily due to good radiological information. 3D imaging is partially responsible for the drastic reduction in multiple surgeries. Cost and recovery times are significantly reduced and physical therapy follow up is enhanced due to innovative surgery techniques. At the center of these recent developments is CT imaging, in particular 3D reformatted imaging. The amount of information the surgeon has before a surgery is critical to the success of any operation. Volume rendered images show the full effect of complex fractures of the pelvis.

Multidetector Row CT (MDCT) has greatly enhanced the performance of CT scanners, which has in turn vastly improved imaging of the musculoskeletal system. Fast, high resolution scanning is now possible, along with reformats that can include volume viewing. The advantages of volume rendered 3D imaging such as multiplanar reconstructions (MPRs) for isotropic viewing, and thick slice (wedge) MPRs is the enablement of accurate assessment of complex anatomical areas like the pelvis. 3D imaging promises to be a CT format of choice for viewing essential diagnostic imaging information available from CT. Many institutions are exploring the use of 3D imaging to complement those CT formats that remains necessary like coronal and sagittal reformats.

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These 3D reconstructions from axial CT data demonstrate the power of 3D imaging. These images were made in a transparent bone window to provide see through images. Picture labeled #1 is an anterior presentation of the pelvis. Image #2 and image #4 are about 45 degrees oblique similar to the Judet views. Notice the fracture of the right acetabulum involving the posterior rim. This fracture is really appreciated on image #3, which is the posterior view, and on image #4, which is a LPO view. Like all 3D image series there can be many images through the full 360 degrees of rotation.

1.5 Radiographic Findings In Acute Pelvic Trauma

Now that we have looked as some of the ways different imaging modalities handle trauma pelvis surveys, let’s discuss some findings with radiographic imaging and the consequences. When the AP pelvis is viewed it should have a normal space between the symphysis pubis of approximately 5 mm width. Any measurement greater than 1 cm is considered abnormal and represents diastasis. Diastasis – (Gr. Separation) is a form of dislocation in which there is separation of two bones normally attached to each other without the existence of a true joint; as in separation of the pubic symphysis. Normally both superior pubic rami should be at the same horizontal placement and should not overlap their joining at the symphysis. The horizontal presentation of the inferior pubic rami should also be symmetrical. As a result of AP compression the fibrocartilagenous connection between the two pubic bones may become disrupted causing symphyseal diastasis. To demonstrate these findings the pubis bones must be entirely visualized on the plain film radiographs, and CT images.

The pubis bones are an interesting location for investigating pelvis injury. If overlap of the pubic bones at the symphysis is noted, a lateral compression injury is suggested. The superior pubic rami should be at the same level as they join at the symphysis. In a vertical shear injury, one side is displaced usually in a cranial direction. It is the lower margins of the rami that are used to suggest injury since nonalignment of the upper margins may be a normal variation. The orientation of pubic rami fractures provides additional clues to the mechanism of injury. For example, horizontal overlapping fractures of the superior and inferior pubic rami are associated with lateral compression. With AP compression sometimes there is no symphyseal diastasis, instead a vertical fractures of the rami without cranial displacement of the hemipelvis occurs. Vertical rami fractures with cranial displacement are a hallmark of vertical shear injuries. Minimally displaced fractures of the pubic rami also occur without any other injuries. This usually occurs in individuals with osteoporosis who sustain a relatively slow speed fall that does not disturb the integrity of the pelvic ring.

The direction of hemipelvis displacement is also an indicator of the mechanism of injury. External rotation of the hemipelvis, sometimes is referred to as open-book pelvis, occurs with severe AP compression. Lateral compression causes the opposite phenomenon of internal rotation of the pelvis, which closes the pelvis. Vertical shear injuries result in vertical displacement in the cranial direction of the hemipelvis. Often seen are iliac wing fractures. Isolated iliac wing fractures may occur as a result of a direct blow without disruption of the pelvic ring. Major trauma such as a motor vehicle accident that causes wing fracture with extension towards the vicinity of the SI joint is seen in the more severe lateral compression injuries. Less commonly seen is an avulsion of the ischial spine(s), which may occur in external rotation or vertical displacement of the hemipelvis. Avulsion fractures with maintenance of the pelvic ring often occur in the iliac crest, anterior superior iliac spine, and ischial tuberosities. The iliolumbar ligament is inserted at the tip of the L5 transverse process, and so an avulsion fracture at this level is associated with disruption of the posterior SI ligament complex. A L5 transverse-process avulsion fracture may be the only indicator of complete pelvic instability so always includes all of L5 with pelvis images.

The anterior and posterior aspects of the sacroiliac joints are closely examined for diastasis. A spacing of approximately 2-4 mm width is considered normal. Disruption of a SI joint with external rotation of the ipsilateral hemipelvis is characteristic of AP compression. If only the anterior SI joint is widened, the posterior ligaments are usually intact and the vertical stability of the pelvis is preserved. If the SI joint suffers diastasis both anteriorly and posteriorly, the pelvis is completely unstable. As we have already stated, this is a finding in vertical shear injuries. Displaced vertical fractures through the sacrum or the iliac wing adjacent to the SI joint have the same implication as direct SI joint diastasis. An anterior crush fracture of the sacrum, called a buckle fracture, is the hallmark of lateral compression injury. These fractures may be isolated to the sacral ala, pass through the neural foramina, or extend centrally into the sacral spinal canal. Being vertical fractures, these radiographic findings on plain film may be subtle. The sacral promontory and arcuate line are carefully examined for cortical disruption. A good point with fractures is that horizontal fractures of the sacrum below the level of the S2 do not affect the integrity of the pelvic ring.

1.6 Trauma Cystogram and Retrograde Urethragram

There are many other considerations with pelvic ring fractures than just bony injury. There is the risk of bladder rupture, urethra transection, and of course profound life threatening bleeding from ruptured pelvic vessels. Death from pelvic hemorrhage occurs in an estimated 30% of cases. Interventional radiology has developed several techniques that include embolization that has significantly reduced this figure. Pelvic arch fractures have a nearly 20% injury rate involving the bladder and/or urethra. When there is a pelvic arch fracture the physician may request a retrograde cystourethrogram (RUG). This should occur prior to inserting a urinary catheter since blind insertion may create a false passage. The RUG is a better trauma study than the intravenous cystourethrogram or voiding cystourethrogram. It can quickly identify any transaction of the urethra and distal bladder extravasations.

In the adult the empty bladder lies in the true pelvis, posterior to the pubic bones where it is separated from them by a small retropubic space. In infants and children usually up to the age of six it lies in the abdomen. Slowly the bladder enters the false pelvis and by puberty is within the true pelvis. An important characteristic of the bladder that makes it susceptible to injury, especially when it is full is that it is a distensible tissue. That is it is able to stretch with filling and is folded into ruga when empty. The stomach is another tissue that is distensible. With this being the case, forces that cause pelvic ring fractures can more easily injure the bladder when it is full. Although it lies inferior to the peritoneum on the pelvic floor, it may distend when full into the abdomen nearly to the level of the umbilicus. It is described as having a base, which is the posterior surface, and the anterior surface is referred to as the apex. The inferolateral surfaces converge to form the neck, which in males rests on the prostate gland.

Injury to the bladder may occur as a complication of a pelvic ring fracture, or as an associated injury without ring fracture. Fifteen percent of patients with pelvic ring fracture sustain bladder or urethra injury (60% urethra injury, 30% bladder injury, 10% both). Rupture of the superior part of the bladder occurs when it is full as has been stated. Primary candidates for this are persons who have consumed large quantities of alcohol, and sustained high impact trauma that ruptures the pelvic ring. This frequently results in tears of the peritoneum causing extravasation of urine into the peritoneal cavity. Posterior bladder rupture results in extravasation extraperitoneally.

  • Extraperitoneal bladder rupture is more common than intraperitoneal rupture. Extraperitoneal rupture occur 4 times more often or approximately 80% of patients vs. 20% that occurs intraperitoneal.
  • Direct bladder injury due to pelvic ring fracture fragments piercing it, or shear forces from the base of the bladder are the cause of extraperitoneal rupture.
  • Direct blunt trauma to a distended bladder is the primary cause of intraperitoneal rupture.
image032a image032b
Traditionally, the diagnosis of bladder injury is made using conventional fluoroscopic cystography. These two radiographs demonstrate different routes of filling the bladder to assess potential rupture of the bladder. The radiograph on the left demonstrates intravenous filling of the bladder. This is the most common method used because a trauma patient is usually given intravenous contrast to evaluate the abdomen as part of the trauma chest/abdomen/pelvis CT scan. The point of this radiograph is that it demonstrates how little the bladder is filled by intravenous method. Part of this is due to inadequate time for filling since the patient is on the scan table for about 10 minutes following I.V. contrast administering. Pelvic fracture fragments from the pubic bones can injure an empty bladder causing extraperitoneal rupture. The radiograph on the right is a retrograde cystogram, which involves placement of a urinary catheter and active filling of the bladder. The radiograph on the right demonstrates a fully distended bladder. Retrograde filling through a urinary catheter allows us to achieve complete filling of the bladder. This provides a better diagnostic evaluation than does intravenous filling. We can see why forces that may not be strong enough to cause pelvic ring fracture can rupture a full bladder. While either of these two methods of filling the bladder are acceptable depending on the trauma scenario it should be remembered that these studies are limited to evaluating the bladder.
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These three cystogram radiographs demonstrate the value of a full bladder when diagnosing potential injury. Indentations to the smooth contour of the bladder may indicate a hemorrhage of blood vessels. The radiographs above are normal, the left image is an RPO, and the right radiograph is a LPO view. These oblique views allow for visualization of part of the posterior walls of the bladder. Notice that the full bladder poses risk for injury from traumatic high impact forces. The apex and neck lies in close proximity to the pubic bones, which can fragment and pierce it.

Another important issue with pelvic arch fracture is the potential fracture of the urethra. In females the urethra is short only about 4 cm long, whereas in males the urethra is long (15-20 cm) passing through the prostate gland. Because of its length, the male urethra is more commonly injured than the female urethra (incidence is 15% in males, and 6% in females) when associated with pelvic fracture. Classical signs of urethral injury are: 1) prostate is not palpatable on rectal exam, 2) Blood seen in the urethral meatus, 3) bloody urine that clears in the distal stream, 4) Patient is unable to void yet the bladder is palpated.

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These two radiographs are of a voiding cystourethrogram. The urethra is short indicating this is a female patient. To study the urethra by this method in a trauma situation would require the cooperation of the patient to void at request. This can be difficult to accomplish, which is why this is not a preferred method for trauma evaluation.
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These two radiographs demonstrate why the retrograde urethrogram is the preferred method of demonstrating the urethra. Retrograde filling of the urethra demonstrates the urethra better than with a voiding cystourethrogram. Notice that there is transection of the urethra and extravasation of contrast (white arrows).

CT Evaluation of the Urinary Bladder

The CT Cystogram is a very efficient way of imaging the bladder of a patient who has sustained acute pelvic trauma with fractures. The CT cystogram is the preferred method of diagnosing bladder rupture in patients with known pelvic and multiple organ injuries. Patients who are catheterized can simply have the catheter clamped to fill the bladder. When a trauma patient receives an abdomen/pelvis CT, the technologist should clamp the catheter as soon as the patient is placed on the CT table. If it is decided to evaluate the bladder using delayed antegrade filling, the contrast will solubolize with urine to show the bladder. Those who are not catheterized should not be permitted to void until after the CT scan of the pelvis is completed. In both cases the bladder is filled passively and imaged as a delay study following administration of intravenous iodinated contrast agent. When the patient is passively filled via the intravenous route the amount of filling of the bladder is dependent on renal filtration rate. The bladder although filled is rarely fully distended by intravenous route. Full distension of the bladder is not necessary to evaluate it for rupture. Passive intravenous filing of the bladder relying on renal filtration can provide a sufficient study. The sagittal CT image below demonstrates how passive filling may not fill the anteriosuperior portions of the bladder because the patient is imaged in the supine position.

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This Sagittal CT image demonstrates the bladder filled with contrast via intravenous administration. Notice the entire bladder wall is demonstrated although the anterior and superior portions are not filled. The bladder is not fully distended but does permit evaluation for rupture. The CT cystogram is the study of choice for acute trauma imaging of the urinary bladder.

We could ask, what does the CT cystogram offer in terms of diagnostic imaging that the fluoroscopic cystogram does not offer? The answer is simple. A single scan can be acquired and can be reformatted into coronal, sagittal and 3D images, which gives a complete perspective of the bladder. The slice-by-slice presentation of the contrast filled bladder and the true pelvis in several formats is quite informative. Consider the sagittal images below that demonstrate a contrast filled bladder:

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These six samples of coronal images show the intravenously filled bladder. Coronal image planes demonstrate the superior, inferior, and lateral margins of the bladder from anterior to posterior. Intraperitoneal or extraperitoneal rupture would be easy to identify. The need for CT cystogram is clearly demonstrated by the diastasis of the pubic bones (image #1, white line).
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These sagittal CT images show the bladder very well. Its relationship in the minor pelvis to the rectum is also shown. An injury to the bladder would be easily seen in these views. Together with the sagittal views, coronal images make CT Cystogram the method of choice to demonstrate the bladder following traumatic pelvic ring fracture.

We stated that the CT cystogram is a good method of imaging the bladder because it offers sagittal, coronal and 3D viewing in addition to axial helical images. 3D imaging is sometimes done to demonstrate images of the bladder through 360 degrees of rotation. This allows many different image views not just the traditional 45-degree oblique and lateral views seen with fluoroscopic cystography.

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These six volume rendered images demonstrate the power of 3D imaging of the bladder from a CT pelvis trauma protocol. Any number of images through 360 degrees of rotation can be made. The images above are selected form a case in which 30 images were made at 12-degree increments from AP to PA. These views give a good look at the filled portion of the bladder wall. Arrows in image #1 and #6 shows the fractured pubic bone and diastasis warranting imaging of the bladder. Picture six shows the posterior view of the pelvis. Notice there is no leakage of contrast material from the bladder.

1.7 Pelvic Angiography and Therapeutic Control of Pelvic Hemorrhage

The most serious complication of pelvic ring fracture is hemorrhage. It is the single most common cause of morbidity due to ring fracture. Disruption of pelvic veins and/or arteries is estimated to occur in as many as 75% of those suffering acute pelvic ring fracture.

  • The internal iliac artery or branches of it are directly injured due to their proximity to bone and can cause severe bleeding.
  • Venous bleeding usually occurs from disrupted pelvic veins involving sacral fractures.
  • Severe bleeding occurs when the superior gluteal artery is injured. This may be a complication of posterior ring fracture, especially those that involve the greater sciatic notch.
  • The internal pudendal artery is another at risk vessel from anterior ring fractures.

Both the location and degree of fracture displacement are keys to estimating the site of bleeding. The size of the pelvic volume is also a key to controlling bleeding. The larger the pelvic volume the greater the amount of bleeding, therefore, a goal is to quickly stabilize the pelvis with external fixation Restoring the normal pelvic volume helps to control bleeding. Diagnosing the source of bleeding and controlling it is the main concern. The gold standard for diagnosing and treating uncontrolled hemorrhage of pelvic vessel associated with pelvic fractures is angiography. This is because angiography is not only a diagnostic tool, but is also a therapeutic tool that uses embolization techniques to control bleeding. Patients who are hemodynamically unstable are given emergent angiography. The term emergent angiography applies to those who are hemodynamically unstable and require immediate embolization to stabilize blood loss. Those who are stable but likely to have or develop bleeds are given preemptive angiography as soon as possible.

Because angiography is a highly successful direct method of controlling bleeding it should be performed as soon as possible upon recognizing pelvic fracture and hemodynamic instability. It is advantageous to laparotomy and ligation of bleeding vessels because it avoids retroperitoneal contamination, avoids problematic hematoma entry, and preserves tamponade protective effect that occurs in the retroperitoneal space. In most cases, shock is not a reason to delay an angiographic procedure because it can be life saving. Clinical and statistical data have identified three indicators that can predict a 95% probability of pelvic hemorrhage. These factors are emergent angiography, greater than 55 years of age, and absence of long bone fracture. In the absence of these predictive independent indicators the probability of bleed is still 18%. Angiography as a whole identifies the source of bleeding in approximately 10-15% of cases. Even with early angiographic embolization a high suspicion for recurrent arterial hemorrhage must be maintained when there are multiple injuries to the patient. There are no criteria that exclude patients with traumatic injuries from the possibility of internal bleeding; therefore, patients should be given angiographic testing in selected cases liberally.

Interventional angiography is successful because it can block the blood flow through suspected discontinuous vessels. Interventionalists use three methods to embolize vessels: clotted blood, coils, or Gelfoam (gelatin sponge). Some common complications of embolizing pelvic vessels include bladder wall necrosis, emboli to normal vessels, necrosis of the buttocks, secondary coangulopathy, and sciatic or femoral nerve paresis.

Selective left Pelvic Angiogram

Angiography in the pelvis is usually selective based on the patient’s injury and the vasculature that supplies the affected area. The case below involves a patient who was hemodynamically stable allowing this study to be performed preemptively rather than as an emergent procedure. A catheter is placed into the femoral artery using a single wall puncture technique and a 5-French sheath over a guide wire. The obturator branch of the anterior division of the left internal iliac artery was first selected. A supraselective pelvic arteriogram was performed at the region of the patient’s left pelvic fracture.

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These six fluorospot image selections are from a pelvic angiogram that will include the left internal iliac artery, and obturator branch of the anterior division of the left internal iliac artery. These vessels are selected because of their close proximity of the fracture site. There is no active extravasation of the contrast media noted on these images. On image #5 the right ureter is demonstrated as contrast is excreted into the ureter following renal uptake from the vascular system.
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These images are a continuation of the same angiographic evaluation of vessels supplying the left pelvis as above. Vessels are selectively filled that supply the anterior, posterior, and general areas of the left pelvis. No extravasation is seen from the two vessels selected so far in this study. Image #4 uses bone subtraction technique to demonstrate the vasculature; the other views show the bone orientation of the vessels.
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This particular portion of the selective angiogram demonstrates the arteries in the region of the femur and acetabulum. Image #1 displays a good portion of the arterial branches in bone subtraction. Image #2 shows the vessel orientation to bone. Image #3 shows a wash out phase of the arteriogram. Notice that there is no extravasation of contrast material or pseudoaneurysm demonstrated. Image #4 is taken following complete contrast washout, there is no residual extravascular contrast present. Had there been extravasation these vessels would have been embolized.

Section 1.8: Short and Long-Term Effects of Pelvic Ring Fractures

Clinical medicine, orthopedic management, diagnostic and therapeutic treatments of injured patients has significantly improved. Clearly there is a sharp decline in the morbidity and mortality rates of pelvic fractures in recent decades. But those who suffer pelvic injury still have to overcome all sorts of challenges in their short and long-term recovery process. While we have discussed diagnostic imaging and interventional approaches to pelvic trauma there are still serious obstacles for recovering survivors. Most complications stem from pre and postoperative blood loss or infection due to pelvic abscess. Then there is the complication that thromboembolitic disease may develop. Still those who survive these obstacles face immediate and chronic pain and long-term effects like gait disturbance, and osteoarthritis. The work of orthopedic physicians is never ending to alleviate these hard to reduce factors that contribute to the morbidity of pelvic ring fractures.

Interventional radiology is now on the front line in the treatment of pelvic hemorrhage. Even with emergent angiography patients are still at great risk for continued bleeding if all hemorrhages are not identified at the initial diagnostic therapeutic treatment. These patients often have to undergo multiple embolizations to completely stop bleeding. Therefore these patients suffer the consequence of significant blood loss complicated by postoperative blood loss when uncontrolled for a long period. These conditions may lead to exsanguinations that when drained can lead to volume depletion, shock, coagulopathy, renal failure, and other of clinical conditions. None of these conditions are easy to treat considering the patient may have multiple medical concerns all with grave consequences. For example, a pelvic hematoma commonly transforms into an abscess and may require percutaneous drainage under CT or ultrasound. Pelvic repair may leave the patient vulnerable to infections due to an infected wound, or development of an infection from contamination of the fixation device. Prolonged bed rest makes the pulmonary and urinary systems susceptible to infections. So the patient’s problems can continue on and on during prolonged bed rest during recovery.

Because pelvic ring fractures require complete bed rest the patient finds himself or herself temporarily immobilized for a long recovery. A long stay in bed is a prime condition for coangulopathy and risk of thromboembolitic disease especially when fractures like the femur and pelvis are involved. Deep vein thrombosis (DVT) is frequently encountered in these situations. When the patient develops symptoms that lead to suspicion of DVT a Doppler ultrasound is usually required. Unlike those thrombus that develop in the deep veins of the legs these may develop within the deep veins of the pelvis, a location not so easily seen with ultrasound. CT is not a good option for imaging these veins either because the venous phase of pelvic veins is difficult to demonstrate with tomography. Magnetic resonance venography (MRV) is emerging as a strong potential for diagnosing these clots, but is there is not enough scientific information available to make this a common procedure. But research is mounting for development of optimal imaging techniques in MRI to make the diagnosis.

Patients who recover from pelvic ring fractures are generally plagued by chronic pain. Most often in the sacroiliac joints and hips. The etiology for pain is still an idiopathic subject. Osteoarthritis and malunions of some components of the injured pelvis are believed to be the source of most chronic pain. Sometimes-imaging years later reveal small nonunion of pelvic components that would be considered insignificant except for complaint of chronic pain. Patients who sustain vertical fractures and those separations involving the hemipelvis complicated with rotation seem to have more long-term pain issues. Persistent pain may require additional surgeries when possible to correct any know cause for it. Radiology continues to play an important role in providing diagnostic information for acute and chronic management of pelvic injuries.

  • 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 can 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 a guaranteed temporary immobility of the patient serves to increase the risk. Deep venous thrombosis 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 with US. Magnetic resonance venography (MRV) is potentially useful in assessing the pelvic venous system.

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These two pictures demonstrate the placement of an inferior vena cava filter (IVC filter) used to prevent acute deep vein thromboses from embolizing to other areas like the lungs. The white arrow points to a contrast visualized IVC where the filter is placed. Anticoagulant therapy and early detection using ultrasound and CT can help reduce the morbidity associated with thrombolitic disease due to pelvic fractures.

Summary and Points to Ponder

  • Pelvic fractures most often occur from a variety of mechanisms that involve high-energy blunt force trauma. About 60% are caused by motor vehicle accidents, while falls account for approximately 30% of pelvic fractures and usually involve the elderly.
  • Injuries that involve the pelvic ring have a high morbidity and significant mortality (approximately 6%).
  • Hemorrhage is the leading cause of death in patients with a pelvic fracture. Bone injury is not the only concern with pelvic ring fractures, soft tissue components such as the bladder, urethra, rectum, and uterus may also sustain injury requiring immediate appropriate therapy.
  • The pattern of injuries that causes pelvic fractures is known as anteroposterior (AP) compression, lateral compression, and vertical shear.
  • Lateral compression injuries occur when a high impact force strikes the side of the pelvis. This is commonly seen when a significant force like a motor vehicle collides with a pedestrian. The hallmarks of a lateral compression injury include sacral buckle fractures and horizontal pubic rami fractures.
  • Uncontrolled hemorrhage accounts for 39% of pelvic fracture related deaths; the majority of blood loss derives from injured retroperitoneal veins and broad cancellous bone surfaces.
  • There are two major classification systems that describe fractures involving the pelvic ring. The Young-Burgess classification system describes the degree of injury to the ring. Pelvic stability is described using the Tile classification system.
  • The hallmark indicator of AP compression injury is the degree of pubic diastasis.
  • The sensitivity of pelvic plain film radiography is low, and it is not reliable for determining if a pelvic injury is stable or not.
  • Some important factors to be considered when making an AP portable radiograph are: positioning of the anatomy, tube-part-cassette alignment, OID/SID, grid alignment, clearing metallic artifacts, and using an acceptable radiographic exposure technique.
  • The hip or innominate bone is a composite bone formed by the ilium, ischium, and pubis bones that fuse at the acetabulum.
  • Within the true pelvis from anterior to posterior are the urinary bladder, uterus (in females), and rectum.
  • Three main vectors cause known patterns of injury. These are AP compression, lateral compression, and vertical shear, or combinations of these.
  • The radiographic characteristic of AP compression is symphyseal and/or sacroiliac joint diastasis.
  • Hallmarks of lateral compression injury are sacral buckle fractures and horizontal pubic rami fractures, and internal rotation of the affected hemipelvis.
  • A third type of injury that occurs from forces similar to those caused by a fall from height is called vertical injury. These are caudocranial forces that result in rupture of the pelvic vasculature resulting in profound pelvic hemorrhage. Uncontrolled bleeding accounts for up to 39% of related deaths.
  • Two classifications systems are used to describe pelvic ring fractures and pelvic instability. These are the Young-Burgess and Tile classification systems. Young-Burgess describes fracture types, and the Tile classification describes pelvic stability.
  • When called upon to make an AP portable pelvis radiograph, the femurs should not be internally rotated. The femurs should be left in the “as is” position.
  • A Stryker type bed is advantageous for portable imaging of the pelvis because the x-ray cassette can be placed in a tray under the gurney. This eliminates grid cut-off due to angulation of the grid cassette.
  • Diagnostic criteria for the AP pelvis View: Include the top of both iliac crests and the entire L5 verterae through the ischial tuberosities and lesser trochanters of the femurs. Lateral margins of the radiograph should include the anterior aspect of the pelvis. Radiographic exposure should demonstrate good bone detail, soft tissue detail like the bladder, rectum, iliopsoas muscle, and bowel gas pattern.
  • Pelvic inlet view is important for demonstrating posterior displacement of the SI joints or rotation of the hemipelvis. X-ray tube is angled 45 degrees caudal.
  • For the pelvic outlet view the patient is supine and the CR is angled 45 degrees cephalic. Demonstrates the sacral neural foramina better, and evaluates displacement of the hemipelvis, and some types of pubic fractures.
  • Judet is an oblique view of the pelvis in which the mid-sagittal plain of the patient is positioned 45 degrees to the image receptor and the CR perpendicular to the tabletop.
  • Retro-reconstructed CT scans for the bony pelvis acquired using the abdomen/pelvis soft tissue algorithm for abdominal organs should be made in the bone algorithm.
  • 2-D and 3-D reconstructions of the pelvis should be made from the thinnest possible axial slices. Using MDCT it is recommended that the slices be 1.25 mm X 1.25 mm or thinner.
  • The axial CT scan should include from above the iliac crest, inclusive of L5 vertebra, down through the lesser trochanters of the femurs.
  • When 3-D reconstructions are requested do include a sufficient number of images through 360 degrees of rotation (at least 20 images). This will include sufficient AP, PA, and oblique images at small degrees of viewing between images.
  • A strong advantage of coronal CT images is it demonstrates complex multiple fractures of the posterior ring better than plain film images.
  • The key to good coronal images is to achieve symmetry of the anatomy in each slice. For example, the femoral heads and pubic rami should be seen at the same level and anatomical relationship.
  • Sagittal 2-D images of the pelvis are extremely valuable because they give the advantage of thin slices at 90 degrees to the coronal plane. This is especially useful when complex fractures involve the acetabulum or the sacrum.
  • When the AP pelvis is viewed it should have a normal space between the symphysis pubis of approximately 5 mm width. Any measurement greater than 1 cm is considered abnormal and represents diastasis.
  • An anterior crush fracture of the sacrum, called a buckle fracture, is the hallmark of lateral compression injury. These fractures can affect pelvic stability; however, horizontal fractures below S2 do not affect pelvic stability.
  • Pelvic arch fractures have a nearly 20% injury rate involving the bladder and/or urethra. When there is a pelvic arch fracture the physician may request a retrograde cystourethrogram (RUG).
  • Injury to the bladder may occur as a complication of a pelvic ring fracture, or as an associated injury without ring fracture. Fifteen percent of patients with pelvic ring fracture sustain bladder or urethra injury (60% urethra injury, 30% bladder injury, 10% both).
  • Because of its length, the male urethra is more commonly injured than the female urethra (incidence is 15% in males, and 6% in females) when associated with pelvic fracture. Classical signs of urethral injury are: 1) prostate is not palpatable on rectal exam, 2) Blood seen in the urethral meatus, 3) bloody urine that clears in the distal stream, 4) Patient is unable to void yet the bladder is palpated.
  • The CT Cystogram is a very effective way of imaging the bladder of a patient who has sustained acute pelvic trauma with fractures. The CT cystogram is the preferred method of diagnosing bladder rupture in patients with known pelvic and multiple organ injuries.
  • Passive intravenous filing of the bladder relying on renal filtration can provide a sufficient study. Sagittal CT images will show incomplete filling of the anteriosuperior portions of the bladder because the patient is imaged in the supine position.
  • The most serious complication of pelvic ring fracture is hemorrhage. It is the single most common cause of morbidity due to ring fracture. Disruption of pelvic veins and/or arteries is estimated to occur in as many as 75% of those suffering acute pelvic ring fracture.
  • Both the location and degree of fracture displacement are keys to estimating the site of bleeding. The size of the pelvic volume is also a key to controlling bleeding. The larger the pelvic volume the greater the amount of bleeding, therefore, a goal is to quickly stabilize the pelvis with external fixation.
  • The gold standard for diagnosing and treating uncontrolled hemorrhage of pelvic vessel associated with pelvic fractures is interventional angiography.
  • Patients who are hemodynamically unstable are given emergent angiography. The term emergent angiography applies to those who are hemodynamically unstable and require immediate embolization to stabilize blood loss. Those who are stable but likely to have or develop bleeds are given preemptive angiography as soon as possible.
  • In most cases, shock is not a reason to delay an angiographic procedure because it can be life saving. Clinical and statistical data have identified three indicators that can predict a 95% probability of pelvic hemorrhage. These factors are emergent angiography, greater than 55 years of age, and absence of long bone fracture.
  • Angiography as a whole identifies the source of bleeding in approximately 10-15% of cases. Even with early angiographic embolization a high suspicion for recurrent arterial hemorrhage must be maintained when there are multiple injuries to the patient.
  • Three major short-term concerns are preoperative and postoperative blood loss, infection due to pelvic abscess, and thromboembolitic disease. Those who survive these obstacles still face chronic long-term effects like chronic pain, gait disturbance, and osteoarthritis.

References

  • Archive Orthopedic Trauma Surgery, 2005 Jun 24; Control of severe hemorrhage using C-clamp and arterial embolization in hemodynamically unstable patients with pelvic ring disruption Sadri, H., Nguyen-Tang, Sern, R., Hoffmeyer, P., Peter.
  • J Bone Joint Surg Br. 2005 Apr;87(4):530-3, Major pelvic fractures: identification of patients at high risk, O’Sullivan, R.E., White, T.O, Keeting, J.F.
  • Eur Radiol.2005 Aug;15(8):1533-7, Diagnostic value of pelvic radiography in the initial trauma series in blunt trauma, Their, M.E, Bensch, F.V, Koskien, S. K, Handolin, L, Kiuru, M.J.
  • Eur J Radiol, 2004 Apr;5(1):96-105, CT of pelvic fractures, Falchi, M, Rollandi, G.A.
  • Journal. Isreal Medical Association, 2005 Oct; 7(10):619-22, Pelvic fractures in a level I trauma center: a test case for the efficacy of the evolving trauma system in Israel, Brazilay, Y, Liebergall, M, Safran, O, Khoury, A, Mosheiff, R.
  • Textbook of Radiographic Positioning 4th ed. 1997 Mosby Co., Chapter 7 Proximal Femur and Pelvis, pp 221-246, Bontrager, Kenneth L.
  • Anatomy-A Regional Atlas of the Human Body, 3rd ed. 1897 Urban & Schwarzenberg Co. Part IV The Perineum and Pelvis, Fig 388-398, Clemente, Carmine D.
  • Clinically Oriented Anatomy 2nd ed. 1984 Williams & Wilkins Co. Chapter 3 The Perineum and Pelvis pp. 298-395, Moore, Keith L.
  • The Radiology of Emergency Medicine 3rd ed. 1981 Williams & Wilkins Co. Chapter 10 Pelvis, Acetabulum, and Hips pp. 693-818.Harris, John H.Jr., Harris, William, Novelline, Robert A. H





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