Film Critique of the Lower extremity - Part 1


This article reviews the anatomy of the pelvis and proximal femur, and hip joint. It also reviews the important issues in critique of radiographs of the pelvis and hip joint.

Author: Nicholas Joseph Jr. R.T.(R)(CT) B.S. M.S

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Instructions:

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Objectives:

Upon completion, the reader should be able to:

  • Identify radiographic anatomy of the pelvis, sacroiliac joint, hip joint and proximal femur.
  • Describe the positioning of the patient for the AP, lateral and frog lateral projections of the hip joint.
  • Tell how trauma imaging of the hip for suspected fracture differs from imaging an ambulatory patient who suffers chronic pain.
  • Discuss how leg rotation affects the relationship of structures seen in the proximal femur on an AP and lateral projection of the hip.
  • State the diagnostic criteria for imaging the different views of the hip joint and proximal femur.
  • Discuss optimal exposure technique for imaging the hip and discuss the radiographic appearance of bone and soft tissue structure of an optimal radiograph.
  • Describe how the anatomical structures of the proximal femur are displayed when the leg is positioned at different angles from the tabletop for the frogleg hip projection.
  • Describe the correct anatomical relationships in the proximal femur of a properly positioned axiolateral hip projection.


Article Navigation:

Introduction

Anatomy of the Pelvis, Hip, and Proximal Femur

Pelvic Stability

Anatomy of the Proximal Femur and Hip Joint

Diagnostic Criteria for the AP Pelvis Projection

Diagnostic Criteria for the Pelvic Inlet and Outlet Views.

Diagnostic Criteria for the Judet View

Radiographic Imaging of the Hip Joint

Diagnostic Criteria for the AP Hip Projection

Diagnostic Criteria for the Frogleg and Axiolateral Hip Projections

Summary Points

References

Test



Introduction

Radiologic technologists make and review hundreds of thousands of films daily as part of our routine job performance. Acquiring an acceptable radiograph or digital image requires knowledge of the anatomy, positioning criteria, radiographic exposure, and other skills. In addition the radiographer must know and meet specific diagnostic imaging criteria in order to provide the radiologists images suitable for interpretation. A knowledgeable radiographer assesses acquired images as a point of quality control to make sure it meets the diagnostic criteria. No radiographer wants to pass on poorly made radiographs to the radiologist but when hundreds of images are taken daily it is easy to slack and become complacent. Achieving high quality diagnostic images when hundreds of different images are taken each day requires a conscious effort to maintain quality. Radiographers can at one moment make images of the hand and the next moment called upon to image the foot; the next patient may need abdominal or chest imaging. Not to mention the patient has a role in how images are acquired and their cooperation may vary from extremely cooperative to belligerently uncooperative. Yet the responsibility for achieving a high quality diagnostic image remains with the radiographer. Combining imaging skills with patient skills is truly an artful use of scientific principles and people skills. Occasionally we must be creative in order to present anatomy in a way that meets the diagnostic criteria. For example, a patient may present with extreme pain caused by trauma. The patient may have a deformed limb because of a fracture. Immobility of the affected part may require a creative approach without sacrificing image quality.

Knowing what is to be included in each view and the proper radiographic exposure technique for optimal subject detail is a must for any discussion on image critique. As we view images contained in this module we will also address two important issues: what anatomy should be presented in a specific view, and how should that anatomy be presented. Discussions will also include critique of radiographic exposure technique. For example, a radiograph that is positioned correctly and demonstrates the proper anatomy must also have optimal exposure technique to yield maximum diagnostic value. The diagnostic criteria for each view in our critique series is given; however, these should already be committed to practice, as this is actually a review of the current standards practiced in radiography. The intent of this learning module is to reaffirm that our universal imaging practices conform to the achievement of specific diagnostic criteria. It is commonly thought by laypersons and some medical workers that radiographers just put the part on a cassette and exposes it, which is far from the truth about how we acquire diagnostic images. Likewise, students are often too busy in school to go beyond what the textbook teaches. For example, the textbook may reference the AP hip projection by discussing the positioning of the part and the point of entrance of the central ray (CR) and degree of tube angle. Time constraints in the classroom may not have permitted your instructor to discuss film critique in sufficient detail, like the anatomical relationships seen on each radiographic projection. Now you can take your time and focus on radiographs we commonly image and review each diagnostic criterion.

You will notice that this critique takes a simple approach to viewing radiographic images. First, the anatomy of each part is reviewed, then the diagnostic criteria for the projection are given, and finally, a discussion is made critiquing the radiograph. This is the template for discussion of each image. By knowing the diagnostic criteria you can compare each radiograph and ask, “Did this radiograph meet the diagnostic criteria?” When a radiograph does not meet the diagnostic criteria then you must decide if it should be repeated or not. Keep in mind that just because a radiograph does not meet all aspects of its diagnostic criteria does not mean it is without diagnostic value. Sometimes diagnostic criteria are met using a series of images for a particular view. So consider this film critique relative to patient presentation and how we perform clinically. At times, additional views may be necessary to complete a diagnostic criterion. For example, the proximal femur is adequately displayed, but the acetabulum is underpenetrated requiring the projection to be repeated. The pattern of this critique is that first a radiograph is presented for you to observe. You should jot down your own critique of the radiograph using the diagnostic criteria as a guide. You should do this before you read the author’s review of the radiograph, as this will help you improve your critique and imaging skills. Then the author using the stated diagnostic criteria as a reference presents a discussion. Your notes should discuss what should be done to correct an unsatisfactory radiograph including positioning, anatomy demonstrated, and radiographic exposure technique. Hopefully this process will become a permanent pattern for you as you review your images before presenting them to the radiologist who gives a diagnostic reading. Share your image critique with your colleagues to get their opinion and to stimulate professional discussions.

Final radiographs are affected immensely by exposure technique selected and whether or not the patient is cooperative. Not all images that are eye pleasing when casually viewed are diagnostic to the keen eye of a radiologist. Radiographers must combine their knowledge of diagnostic criteria and image quality to assure quality diagnostic radiographs are made during a diagnostic study. Film critique greatly reduces repeat imaging and patient callbacks because of nondiagnostic radiographs. Paramount to diagnostic viewing is the ability of radiographers to present high quality diagnostic medical images time after time no matter how the patient presents. The hallmark of a good radiographer and an important result of critiquing any radiograph are to routinely acquire quality radiographs, even under difficult circumstances. While most patients cooperate for imaging procedures there are times when a patient is too young to understand the need for them to cooperate, or the manifestation of alcohol use is a factor, or even a language barrier that can hinder instructions to the patient and may diminish cooperativeness. Yet no specific circumstance inherently lowers or raises the bar for malfeasance or nonfeasance that haunts poor imaging. Often with today's shortages of radiologic technologists inexperienced radiographers are set on their own to clear images for interpretation without the precious benefit of critique by a seasoned professional technologist.

Experienced radiographers know that in order to evaluate any radiograph for technical excellence a solid foundation in how the four radiographic densities (muscle, fat, bone, air) are balanced when exposure factors are selected. A good exposure technique must provide adequate density and good subject contrast that maximizes the visualization of bone, muscle, fat and air. Balancing these densities require a good understanding of how exposure factors like milliamperage (mA), kilovoltage (kVp), source-to-image distance (SID), object-to-image distance (OID), use of grids, and patient body habitus, and various tissue types are distributed in the part being imaged. Bone is the most radiopaque of the four radiographic densities. Air is the most radiolucent density, which is dark on a radiograph. Between the light density of bone and the dark radiographic density of air are intermediate densities caused by muscle and fat. Together these four radiographic densities create a mosaic of gray tones that detail subject contrast and background density. A fifth density, metal, may be a part of the radiograph in the form of a prosthetic implant, or radiopaque iodinated contrast agent.

When present, metal also contributes to subject contrast. Metal is more radiopaque than bone and is the main component of implanted prosthetic devices. Metal is used extensively in radiology to enhance subject detail. Special formulations of iodine and barium are used in radiographic contrast agents and are the opacifying moiety in these materials. Using a contrast agent such as barium sulfate or iodine solutions allow us to demonstrate information about some structures better than if without it. For example, diagnostic detail of the alimentary tract not seen on routine radiographs, but can be seen when an oral contrast agent is used. Distinction of pathology in the esophagus, stomach and colon are best seen using barium sulfate or oral iodinated media. Likewise, blood vessels, lymph nodes, and solid organs such as the liver, kidneys, spleen, pancreas, and such are best demonstrated using intravenous iodine radiopaque contrast agents for some radiological studies. Intrathecal administration of a sterile water-soluble contrast agent can demonstrate the subarachnoid space and menenges in the spine. Altering subject contrast is necessary to enhance diagnostic value for many radiological studies. As technologists, we are able to use radiographic technique selection to enhance the display of many structures with and without using contrast agents. Technique selection is especially important when imaging bone for fine detail and to demonstrate sharp contrast of cortical bone margins.

Evaluating radiographic density, subject contrast, image detail, and anatomical presentation of each radiographic projection is part of film critique. Prior to submitting a radiograph for interpretation the technologist should evaluate subject contrast. Bone, muscle, fat, and air should be well balanced throughout the radiograph along with displaying good background density. As we present many radiographs in this module it is our goal to improve your ability to evaluate radiographs prior to submitting them for interpretation. It is our hope that you critique each radiograph in a way that encourages perfection at using diagnostic criteria, which are the standards by which we image. We also image using the standard of practicing ALARA (as low as reasonably achievable) in administering radiation for diagnostic purposes. Therefore, it is the purpose of this critique to instill the principles of diagnostic criteria and getting it right with the first radiographic exposure. Reducing radiation dose without compromising diagnostic quality is also a primary goal.

Radiographs of the lower extremity are commonly taken, so the radiographer should be very familiar with the anatomy, positioning, and proper imaging exposure techniques to make a quality radiograph. Imaging of the lower extremity can be divided into imaging of the pelvis, hip and proximal femur, distal femur and knee, knee and proximal tibia, leg, ankle, and foot. We will begin our critique with the pelvis, hip and proximal femur. Imaging of the hip and pelvis often becomes routine so some radiographers regard the hip as an uncomplicated structure anatomically. The result is that it may not get the attention to diagnostic criteria it deserves. Hopefully we will change this point of view (if you have it) by the time you have completed this module. The hip joint is not a simple joint; in fact it has the most extensive motions of all joints of the lower extremity.



Anatomy of the Pelvis, Hip, and Proximal Femur

Pelvis and hip injuries occur frequently from falls, automobile accidents, sports activities, work related injuries and so forth. Chronic pain is also an indicator that frequently requires radiographic imaging. In order to properly image the hip the radiographer must be familiar with its anatomy and how to properly position it for correct diagnostic referencing. Good radiographic imaging should always begin with a solid understanding of the anatomy of the part to be demonstrated. Radiography involves projecting anatomy in its proper anatomical position using standard criteria acceptable for diagnosis. Anatomy is often a first course in any radiology educational program because it is basic to all imaging studies and radiological procedures. In this section we will discuss the basic anatomy of the hip relative to plain film imaging. Even if you are a computed tomography (CT) technologist or a magnetic resonance imaging (MRI) technologist, or other type of imaging professional, you too can benefit from the anatomy portion of this module. Our purpose is to understand how we should present hip anatomy and soft tissue structures for diagnostic interpretation. Knowledge of radiographic anatomy is the basis for accurate diagnostic positioning. Finally, as radiographer’s we must understand the importance of characterizing bone pathology, especially fractures. For example, a pelvic ring fracture must be characterized as stable or unstable in addition to determining the type of fracture. Knowing what part of the pelvis anatomy is used to determine pelvis stability is important when discussing image quality. Adjunct views such as the pelvis inlet or outlet views help better see structures that determine pelvic fracture stability. It is our responsibility to understand what is demonstrated by various projections of a part. Also, we must provide radiographs that allow the radiologist to diagnose injuries and fully characterize them in a manner that leads to treatment.

The astute student will continue to gain knowledge about those normal anatomical variations that can even confound physicians. The unwary technologist may be fooled by ossification centers that mimic fractures. Experienced technologists can work around traumatic or chronic pain when positioning for radiographs. Inexperience may lead to poor positioning that fail to meet diagnostic imaging standards. For example, improper positioning can cause improper overlap of structures that can simulate abnormality. Radiologists are aware of positioning gamut’s and anatomical variants when interpreting radiographs. However, the role of the technologist is to present radiographs that meet known diagnostic criteria void of ambiguity. One of the primary purposes of this film critique is to review the diagnostic criteria and provide you the tools needed to determine when they have been met for any particular projection. The diagnostic criteria references positioning, anatomy demonstrated, and optimal radiographic exposure and subject contrast.

Let’s begin our discussion with the pelvic girdle, a term referring specifically to the two hipbones (a.k.a innominate bone, os coxae, pelvic bone). Each innominate bone is a composite of the ilium, ischium, and pubis that fuse at the acetabulum that receives the head of the femur. The ilium is the largest part and forms the superior portion of the innominate bone and acetabulum. The ischium forms part of the inferior and posterior portions of the acetabulum and innominate bone. The pubis forms the anterior and inferior parts of the innominate bone and acetabulum. The fusion of these bones is completed in the mid teens. The term pelvis includes the sacrum, coccyx, and the two innominate bones.

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This radiograph of a pediatric pelvis demonstrates the development of the three bones of the hip (Ilium-A, Pubis-B, Ischium-C) that will later fuse at the acetabulum. The ilium, ischium, and pubis bones form the innominate or hip bone. Notice that the acetabulum is not completely formed in the child, neither is the femoral head. The fusion of these three bones becomes the hip bone, which is a composite bone in the adult skeleton. The two hip bones and the sacrum/coccyx form the adult pelvis.
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This 3-D computed tomography image shows a lateral view of the pelvis with the femur removed to demonstrate the acetabulum (D). The acetabulum is formed by the fusion of the ilium, ischium (H), and pubis (E). Some parts of the ilium that are demonstrated are: iliac crest (A), anterior superior iliac spine (B), anterior inferior iliac spine (C), ala or wing (F), and posterior superior iliac spine (G).
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Radiographers should be familiar with the following labeled parts of the pelvis seen in the radiograph above: 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).

There are several reasons the pelvis may be imaged including trauma evaluation, chronic pain, and developmental abnormalities. When imaged, it is important to properly demonstrate the pelvic ring and sacrum. When we speak of the pelvic ring we are referring to that ring of bone forming the upper limit of the true pelvis. This ring is formed posteriorly by the sacrum and the two innominate bones form the sides and front. Strong articulations join the hip bones to the sacrum at the sacroiliac joints, and to each other at their pubic bone articulation forming the symphysis pubis. One reason it is important to understand anatomical relationships in the pelvis is so that we properly demonstrate areas where functional stability can be evaluated. Particularly important is the pelvic ring because when it suffers disruption the pelvis can become unstable. Instability of the pelvis means it cannot bear weight or is impaired in transferring forces through the femurs to the foot and ground. Ring fractures also place structures within the true pelvis, like blood vessels and the urinary bladder at risk to injury.

When we talk about critique of the pelvis and hip it is important to understand that the sacrum is one of the keystone functional parts of the pelvis. It distributes weight vectors through the femorosacral plane (a.k.a. femorosacral arch) supporting and aligning the spine evenly with the legs during gait. Anteriorly the pubic rami perform stabilization functions; however, anterior stabilization is less critical following pelvic injury than is posterior ring stabilization. When imaging the pelvis for trauma the radiographer must provide images that allow the radiologist and orthopedic surgeon to distinguish stable fractures from unstable fractures, that is, identify and characterize fractures involving the posterior pelvic ring or sacrum. Acetabular and hip fractures must also be demonstrated in a way that allows them to be characterized. The goal of the specific diagnostic criteria to be presented is to assure all technologists are imaging the entire pelvis in a way that meets universally accepted diagnostic standards.

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The anterior pelvis (Ant) presents the pelvic ring (blue dotted circle) formed by the sacral promontory posteriorly, and the arcuate ridge of the ilium and superior pubic ramus of each innominate bone. The posterior pelvis (Post) shows the articulation of the innominate bones with the sacrum. The upper portion of the sacroiliac joint (white arrow) is a strong fibrous articulation that gives great ligamentous stability to the joint. The lower portion of the S.I. joint (yellow arrow) is a synovial joint that gives some mobility to the joint, but contributes little to the stability of the pelvic ring.

There is no anatomical separation between the abdominal and pelvic cavities; however, some anatomists emphasize an arbitrary division of the true and false pelvis. The false pelvis is that portion of the pelvis above the pelvic brim; the true pelvis is that portion of the pelvis below the pelvic brim. An importance of this division is to emphysize that the true pelvis contains some soft tissue structures. Located in females (from anterior to posterior) are the urinary bladder, female reproductive organs, and the rectum. The male genitals are located outside the pelvis proper. Not only does the pelvis form a bony frame around these structures, but also it limits the space available for birthing. One can see distinct differences between the male and female pelvis. Differences between the male and female pelvis is one of the most important way to differentiate gender based on anatomy.

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The female pelvis (left) has a greater pubic angle than the male pelvis (right). The wings of the ilium are more flared in females than males, and the true pelvis is broader in females to accommodate passage of the fetus. Pelvic features can be appreciated for obstetric, forensic, anthropological, and paleontological concerns.
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These two 3-D images made from axial CT data show the pelvis of a pregnant woman. The fetus (white arrow) has not entered the birth canal of the true pelvis. Notice the fracture of the left pelvic ring and left acetabulum demonstrated by the yellow arrows. These features can also be seen on the 3-D surface rendered image on the right. It is important to properly image the pelvis in both males and females, especially in context of implications to child bearing following injury to a female. Alignment of the pelvis following injury is of great concern to orthopedists. It is important to demonstrate the pelvis, especially the female pelvis, in its correct anatomical orientation during trauma imaging.



Pelvic Stability

The bony pelvis lacks inherent structural stability, and so is stabilized by a system of tightly woven ligaments and muscle that provide its support. Strong ligaments arranged transversely resist forces that can externally rotate the pelvis, thereby opening it. Among these is the short posterior SI ligament, the anterior SI (sacroiliac) ligament, the iliolumbar ligament, and sacrospinous ligaments. Their function is to counter apposing forces such as AP compression. These ligaments fail when force exceeds their ability causing 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.

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A dense array of ligaments holds the bony pelvis together; some are illustrated on the 3D volume rendered CT images above (blue lines). While it is not our purpose to name all of these ligaments it is important to understand the general distribution of ligaments and their role in stabilizing the pelvis. For example, the sacrotuberous ligament is a long band of fibrous tissue that extends from the posterior superior and posterior inferior iliac spines and from the back and sides of the sacrum/coccyx down to the ischial tuberosities. Their role is to resist posterior rotation of the lower sacrum. We can see some of the muscles and their tendons and ligament that stabilize the pelvis on MR images below.

The take home point is that with pelvic fractures structural ligaments can be disrupted. Separation of the sacroiliac joints and fractures of the sacrum can cause instability of the pelvis. Of interest are the iliospinous ligaments that attach to the fifth lumbar vertebra transverse processes and to the ilium. This is illustrated on the posterior view above. Avulsion type fractures of the fifth lumbar transverse process may be the single indicator of pelvic instability when seen on plain film x-ray. For this reason the AP pelvis view should include the entire fifth lumbar vertebra as well as the iliac crests.

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These three coronal MR images show a portion of the tremendous network of ligaments and muscles that stabilize the bony pelvis. They also can cause the pelvis to shift due to unopposed pull when high impact forces separate bone or joints causing pelvic opening. Pelvic compression can also separate bones and often results in rupture of major blood vessels causing profound life-threatening intrapelvic hemorrhaging.
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The schematic lines on the 3D CT image on the left (blue) represent some of the ligaments supporting and closing the true pelvis. Many ligaments of the pelvis are named according to their origins and insertions. Blue lines show some of the well known ligaments that stabilize the pelvis. From superior to inferior is the posterior SI ligaments, sacrospinous ligaments, sacrotuberous ligaments, and sacrococcygeal ligaments. These ligaments also provide a soft tissue passageway for blood vessels and nerves to enter and exit the true pelvis and perineum. The greater sciatic notch (A) guards the entrance into and out of the true pelvis. The lesser sciatic notch (B) provides an opening into the perineum. The coronal MR image on the right shows some of the muscle and ligaments supporting the pelvis.


The Tile classification system provides a descriptive appraisal of fractures affecting pelvic stability. The Tile classification system can also be used to describe pelvic fractures that do not appreciably disrupt the pelvic ring (Tile type A).

  • Type A, posterior pelvic brim arch is intact; however, stable fractures may be present. Stable fractures include avulsions of the iliac spine, iliac crest, ischial tuberosity, wing fracture, unilateral and bilateral pubic rami fracture, sacral fracture, or sacrococcygeal fracture. The pelvic brim and SI joints are spared making these less severe injuries.
  • Type B, incomplete posterior arch disruption occurring with pubic diastasis. Other injuries may occur such as: anterior SI joint disruption, anterior sacral buckle fracture, AP and lateral compression injuries, internal or external rotation of the pelvis, and other types of rotational or vertical shear injuries that account for stability of the pelvis.
  • Type C, complete posterior arch disruption. These are the most severe types of pelvic ring fractures caused by vertical shear, anterior/posterior compression, or lateral compression. These occur with ipsilateral and contralateral internal or external rotation of the pelvis due to SI joint fracture/dislocation, or sacral fracture. These types are rotationally and vertically unstable and cause severe life-threatening hemorrhaging of pelvic blood vessels.

A rotational injury of the hemipelvis causes serious anatomical disruptions in the pelvic cavity. An external rotation of the hemipelvis increases the volume (pelvic opening) of the pelvic cavity causing life threatening hemorrhage. This type of injury must be reduced as soon as possible to control bleeding. Often these patients are immediately wrapped in a pneumatic antishock suit until permanent fixation reduction can be achieved. If bleeding is not stopped, vascular embolization by interventional radiology may be called upon to attempt control of bleeding. It is important that when imaging the pelvis the radiographer is aware that they are demonstrating pelvic components in a way that helps determine possible cause of hemorrhaging. Hemorrhage is the most serious complication of pelvic fracture and is life-threatening in most cases.




Anatomy of the Proximal Femur and Hip Joint

The femur is the longest and strongest bone in the body. It functions to transfer the weight of the body down through the lower extremity to the foot to facilitate locomotion. The proximal femur has distinct features that allow it to articulate with the hip bone. Because of the function of weight transference and shifting during gait, the hip and knee joints are often the source of chronic pain. These joints are also more likely to be injured due to trauma like a fall from height, or a high impact motor vehicle accident. Now let’s review the anatomy of the proximal femur and its articulation with the acetabulum at the hip joint.

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The proximal femur and hip is seen from the anterior view on the 3-D volume rendered CT image on the left. The right CT image shows the posterior aspects of the proximal femur and hip joint. Structures that should be reviewed are: superior pubic ramus (A), inferior pubic ramus (D), ilium (B), head of femur and hip joint (C), and ischium (E). From the posterior view structures demonstrated are: the neck of the femur (F), greater trochanter (G), and lesser trochanter (H). The intertrochanteric crest is seen as a sharp ridge of bone on the posterior side of the proximal femur between the lesser and greater trochanters.
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This AP hip radiograph demonstrates some of the important parts of the hip and proximal femur that should be identified. Structures demonstrated are: acetabulum (A) with the femoral head articulation, greater trochanter (B), femoral neck (C), and lesser trochanter (D). Notice that the femoral neck is not foreshortened and the entire proximal femur and hip bone are well penetrated. Reviewing radiographic anatomy with each projection taken daily is a good way to keep it fresh in one’s mind and it leads to critiquing each radiograph before sending it for interpretation.

Standard views of the hip consist of the AP projection (seen above), and horizontal beam lateral or the frog-leg lateral projections; therefore the radiographic anatomy seen by these views should also be reviewed at this time. Understanding what anatomy is demonstrated on a particular radiographic view is invaluable in understanding the diagnostic criteria for that projection. Consider the frogleg and horizontal beam lateral radiographs below on which some radiographic anatomy is identified.

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This radiograph demonstrates the anatomy that should be seen on the AP axial frogleg projection. This view is often taken when the clinical history does not involve trauma. The x-ray beam is vertical for this projection. Identified on this frog leg view are the following: wing of ilium (A), acetabulum and hip joint (B), greater trochanter (C), femoral neck (D), lesser trochanter (E), ischium (F), superior ramus-pubis bone (G), and inferior ramus of the pubis bone (H).
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This radiograph demonstrates the axiolateral projection (a.k.a. Inferosuperior projection). The labeled parts of the hip and hip joint are the femoral head (A), neck of femur (B), greater trochanter (C), Shaft of the femur (D), ischial tuberosity (F), lesser trochanter (E), and the acetabulum (arrowheads).



Diagnostic Criteria for the AP Pelvis Projection

Throughout this module we will use standard radiology terminology to describe terms such as exposure technique, positioning error, and tube angle. For example, the term overexposure is used to describe a dark radiograph owing to too many photons producing the image. Inherently one should understanding that overexposure means excessive milliamperage/time (mAs) and the technique should be reduced. Underexposed, on the other hand, is a descriptive term for insufficient photon exposure and the mAs should be increased. Likewise, the term underpenetrated is a term meaning there is not enough energy in the x-ray beam to penetrate the part. Beam quality or penetrability is directly controlled by the kilovoltage selected (kVp). An underpenetrated radiograph can be corrected by increasing the kVp just as decreasing the kVp compensates for an overpenetrated radiograph.

When the patient is incorrectly positioned, which results in an unacceptable radiograph, this is called a positioning error or technologist positioning error. Keep in mind that medical radiographs must meet specific positioning diagnostic standards, although there is great variation in acceptable values. When a radiograph does not meet its diagnostic criterion for positioning it should be repeated. We discuss this type of error in the context of a positioning error. Tube error is a term that can mean improper point of entry of the radiation beam, specifically, the central ray (CR). It can also be due to an incorrect degree of tube angle, or improper direction of the tube, e.g. a vertical beam that should be horizontal, or a 20-degree angle that should be 45 degrees. These terms should not be confusing since they are commonly used in radiology and are standard descriptions in radiology.

Any object that can potentially obstruct the anatomy under investigation and can be removed should be removed. Objects such as ECG monitor leads, oxygen saturation monitor lead or cord, or even a necklace hidden under a cervical collar should be removed or repositioned out of the critical field of view. A foreign object causing an artifact superimposed on image pathology must be removed and the projection repeated. It makes since that internal devices such as a prosthesis or pacemaker cannot be removed. Anatomy that obstructs the subject, such as the hand over the pelvis, or the base of the skull superimposing the odontoid must also be repeated. Equipment artifacts like processor streaks, digital image artifacts, grid lines on the radiograph, quantum mottling, digital noise, or artifacts caused by dirty screens, must all be repeated and cannot be considered acceptable radiographs.

Now, let’s go on to our critique of the proximal femur and hip. These lessons are organized so that you can review anatomy and positioning of the most common views of the lower extremity. Radiographs are presented for you to critique using established diagnostic criteria, which are presented for each view. The author's critique of each image is presented for you to compare with your notes. The goal is to promote effective learning. So use a pencil and a writing pad to jot down your critique of each image prior to reading the authors critique. Compare your notes and see how accurately you are critiquing each radiograph. Obviously only the main points of critique are presented as you may have other observations worth mentioning above the author’s notes. Upon completion you may take brief generalized examination, which presents questions from samples of the topics and images in this module. Remember, this is a three-part module and you must complete all three sections to get credit for this article.



Glossary of terms:
  • Overexposure (too much mAs)
  • Underexposure (too little mAs)
  • Overpenetrated (too much kVp)
  • Underpenetrated (too little kVp)
  • Positioning error (patient position)
  • Tube error (improper tube angle)
  • Image fog (loss of subject detail caused by scatter radiation)
  • Image noise (deficiency of photons making a digital image)


AP Pelvis Critique

For the AP pelvis view the lower extremity and feet are internally rotated 15-20 degrees from vertical. Internally rotating the lower extremity places the femoral necks parallel to the image receptor and maximally demonstrates the femoral neck angle. Placing the anterior superior iliac spines (ASIS) of each hip bone equal distance to the tabletop assures the pelvis is not rotated. Palpating the iliac crest will allow you to adjust its position 1 to 1½ inch below the upper margin of the cassette. This will allow you to include the entire fifth lumbar vertebra. The entire pelvis and proximal femora should be seen on the radiograph. The greater trochanters should be seen in profile laterally and the lesser trochanters seen on the medial border of the femora. The ischial spines should be equally demonstrated with symmetry of the iliac wings. The midsagittal plane of the sacrum and coccyx should be aligned with the pubic symphysis on a radiograph without pelvic rotation.


Diagnostic Criteria for the AP Pelvis View
  • The pelvis is formed by the two innominate bones (ilium, ischium, and pubis), sacrum, and coccyx. These bones must be entirely included on the AP view. The inferior margins of the displayed anatomy should extend below the lesser trochanters of the femora.
  • Sacrum and coccyx aligned with the pubis symphysis and the ischial spines, when seen are aligned with the pelvic brim.
  • Internal rotation of the femurs to profile the greater trochanters unless the patient presents with acute trauma and leg or hip deformity, traumatic external rotation of the hip or leg, or pain suggestive of an acute fracture.
  • When properly positioned the femoral necks will not be foreshortened, the greater trochanter of each femur is demonstrated in profile laterally, and the lesser trochanter superimposed by the neck of the femur or slightly projected medially.
  • Radiographic technique should demonstrate good penetration of the bony pelvis especially the iliac wings, sacrum, acetabulum, and hip joint. Soft tissue visualization of muscle, fat, and air densities, especially around the hip should be demonstrated.
  • Soft tissue structures that should be seen within the true pelvis include the urinary bladder and air contrast in the rectum.

Radiograph #1

image001 This AP Pelvis radiograph was taken on a patient with a history of chronic right hip pain. Does this radiograph meet the diagnostic criteria for a non-traumatic pelvis x-ray?

Critique of Radiograph #1

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    This radiograph is good in that it includes all of the anatomy required for diagnosis. The entire ilium and iliac crest is demonstrated superiorly, inferiorly the proximal femora are seen including the lesser trochanter. The pelvis is not rotated and the sacrum/coccyx is midline to the pubic symphysis. The only positioning error seen is that the right hip is not internally rotated, which causes foreshortening of the neck of the femur. Comparing the neck and greater trochanter of the right femur to the left femur demonstrates this. A second coned AP of the right hip joint with internal rotation should be added to this AP pelvis view to complete the requirements for image quality. The acetabulum is well penetrated, as are the sacroiliac joints (SI joints). Soft tissue detail is sufficient to show blood or sinus tracts that indicate an open fracture. This is overall a good radiograph in terms of the anatomy included and radiographic technique.

Radiograph #2

image002 This AP Pelvis radiograph was taken for history of trauma (motor vehicle accident). Does it meet the diagnostic criteria; give reasons for your answer?

Critique of Radiograph #2

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    This radiograph is not acceptable because the right hemipelvis is underpenetrated. Likewise, the right sacroiliac joint and acetabulum are also underpenetrated. This is caused in part by sclerotic changes in the right hemipelvis. Getting a balanced between mAs and kVp to display optimum subject contrast is what is needed. Use the 50/15 rule to make appropriate adjustments in exposure technique. Although the spine is well penetrated an increase in kVp is still needed. You may also need to slightly increase the mAs. Overall, the left side will show excessive density when the right side is correctly penetrated due to sclerotic changes and fracture healing. So keep this radiograph and supplement it with the adjusted projection.

Radiograph #3

image003 This AP Pelvis radiograph was taken for chronic left hip pain. Does it meet the diagnostic criteria; give reasons for your answer?

Critique of Radiograph #3

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    At first glance it may look like the left hip is not properly rotated; however, closer inspection reveals a congenital abnormality of the femoral head and neck. So the pelvis is properly positioned and all required anatomy demonstrated. Yet, this is not an acceptable radiograph because some areas are underpenetrated. Compare the right and left hip joints and sacroiliac joints. The spine is also underpenetrated. The subject is displayed using a high contrast technique, which is why the pelvis is underpenetrated. Strive to achieve a balance in contrast to demonstrate good penetration of the femora heads and sacroiliac joints. Unfortunately, this radiograph must be repeated because the right hemipelvis and sacrum is underpenetrated. The SI joints and sacrum must also be optimally penetrated since this could be the source of the left hip pain.

Radiograph #4

image004 This AP Pelvis radiograph was taken to evaluate the pelvis and left hip s/p ORIF left hip. A lateral left hip was also taken. Does this AP view of the pelvis meet diagnostic standards for the pelvis?

Critique of Radiograph #4

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    This radiograph is taken to evaluate the surgical fixation of the left hip. With this in mind it we should evaluate this image primarily on the radiographic quality of the hip. In most cases it would be wise to clarify the order with the requesting physician to determine if the left hip should be specifically imaged. As for the pelvis, keep in mind that the sacral relationships should be demonstrated as well. The positioning provides a good look at the pelvis and both hips with minimum rotation. The general appearance of the pelvis suggests it is underpenetrated. The arrow points to the lumbar spine that is poorly penetrated and without detail. High contrast pelvis x-rays should not be taken because the sacrum, lumbar spine, and acetabula may not be optimally demonstrated. There is a lot of bowel gas and fecal material that makes this radiograph particularly difficult to image. Repeating this radiograph at this time may not give good results because of this. Considering that this is a post-operative radiograph one should repeat this radiograph increasing the kVp at least 15%.

Radiograph #5

image005 This patient suffered blunt trauma to the abdomen and pelvis during a motor vehicle accident. This radiograph was taken during a trauma team alert in which the patient was receiving continuous medical care. Based on your experience with trauma team imaging does this radiograph meet the diagnostic criteria for a portable AP pelvis; give reasons for your answer?

Critique of Radiograph #5

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    Often the radiographer is called upon to take high quality diagnostic radiographs while the trauma team administers care to a critically injured patient. Radiographs are generally taken in the “as is” position because the main concern is to include as much anatomy as possible quickly. However, it is within reason that all metal be removed from the field of view prior to exposure. Image artifacts caused by metal will obstruct the image and can cause delay in giving diagnostic evaluation and care. Artifacts from the spine board are to be expected since removing it may compromise a spinal cord injury. The other issue with this radiograph is that the pelvis is rotated, which can make diagnosing pelvic injury difficult. Notice that the left obturator foramen is narrowed and the sacrum/coccyx is rotated towards the right hip. This is caused by rotation of the pelvis towards the left (LPO). It is important for the radiologist to distinguish a rotated pelvis due to trauma (indicating pelvic instability) from a positioning error. The left femoral neck is foreshortened and the lesser trochanter is seen in profile. This is caused by external rotation of the left leg. Placing each ASIS equidistant from the tabletop will insure the pelvis is not rotated. The femurs can be internally rotated to correct foreshortening of the femoral necks since there is no identified fracture on this radiograph. The main reason this radiograph should be repeated is because of the metal artifacts. Positioning the pelvis is contraindicated for the initial portable exam of a trauma patient.

Radiograph #6

image006 This patient was brought to a local emergency room by ambulance following a fall. Chief complaint is left hip pain and inability to stand. Does this radiograph meet the diagnostic criteria for a portable AP pelvis; give reasons for your answer?

Critique of Radiograph #6

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    This radiograph of the pelvis is adequate for evaluating the hip joint for fracture or dislocation. It is an obvious that there is a dislocation of the left hip joint. When prosthesis is present it must be entirely demonstrated. This radiograph meets the diagnostic criteria for the pelvis. The ordering physician should be consulted with to see if a separate request of the left hip could be made. The reason we need to see the entire prosthesis is that it must be determined whether a fracture occurred distal to the prosthesis. This determination should be made prior to reduction of the hip joint. A coned AP hip projection should be made to include the entire prosthesis, and a lateral view of the left hip may also be requested to determine if this dislocation is anterior or posterior. Consulting with the requesting physician about the findings is the next best approach. Radiographic exposure technique is adequate for the pelvis, but overexposed for the femurs and soft tissues of the proximal thigh are seen. Decrease the kVp 15% with no change in mAs, or reducing the mAs to half without change in kVp will provide proper density and contrast if the left hip is imaged separately.

Radiograph #7

image007 This is a post surgical radiograph taken to evaluate the alignment of the pelvis and to evaluate the proximal femoral rod and left hip. The left hip fracture is from a previous trauma; however the left pelvic ring fracture is acute. Does this radiograph meet the diagnostic criteria for the AP pelvis view?

Critique of Radiograph #7

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    This is an acceptable radiograph that meets the diagnostic criteria for the AP pelvis projection. Both femurs are accurately positioned and there is minimal rotation of the pelvis. It is important for the technologist to be familiar with the different surgical procedures when we talk about film critique. For example, you cannot include the entire left hip’s internal fixation on the film because it is a femoral rod that extends to the knee. There are some types that can be entirely included on the pelvis projection. As for the radiographic technique, it adequately displays the bony structures of the pelvis and hips. Soft tissue detail is excellently balanced with bone detail. This is an excellent radiograph that meets the diagnostic criteria for the AP pelvis view.

Radiograph #8

image008 The patient’s history for this exam involves acute trauma to the left pelvis and left hip due to a fall. Does this portable AP pelvis radiograph meet the diagnostic criteria for the AP pelvis, and tell what should be done to make this a complete diagnostic radiograph?

Critique of Radiograph #8

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    The iliac wings and left hip are clipped. The lateral portion of the left proximal hip including the greater trochanter and surrounding soft tissues is completely omitted. These finding require that the radiograph be repeated. When a hip fracture changes the angle of the femoral neck (arrow) both hips are difficult to demonstrate on the AP pelvis view. Consult with the ordering physician about adding a 2 view hip series to the AP pelvis is the best approach. Keep in mind that entire pelvis including the iliac wings, both hip joints, the proximal femora and all surrounding soft tissue must be included on the repeated radiograph. Notice that the pelvis is not rotated as the obturator foramina are opened and the pubic arches are symmetrical. Adjust the cassette so that the long axis is aligned with the pelvis and use maximum SID to reduce magnification. Radiographic exposure adequately displays subject contrast and soft tissues as well.

Radiograph #9

image009 A fracture of the left pelvic ring was discovered at a rural hospital. The patient was transferred to a level I trauma center for suspicion of injury to the urinary bladder. A CT scan of the abdomen and pelvis was performed. Forty minutes later this AP pelvis view was taken to evaluate the urinary bladder. Does this radiograph meet the diagnostic criteria for the AP pelvis projection?

Critique of Radiograph #9

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    This is a very good radiograph in terms of demonstrating the required anatomy for the AP pelvis projection. The problem is that the exposure technique shows high contrast throughout the upper pelvis and L5 vertebra. The purpose for this view is to evaluate potential injury to structures within the true pelvis (bladder, uterus, rectum) resulting from the left innominate bone fracture (arrows). The technologist answered two important concerns: 1) relationship of displaced left pelvic ring fracture to the urinary bladder, and 2) whether or not there is rupture of the urinary bladder. The radiographic technique inadequately demonstrates the bladder relative to the bony pelvis. This radiograph should be repeated paying attention to technique selection. Adjust the contrast by increasing the kVp sufficiently to penetrate the sacrum and lumbar spine. It may be necessary to decrease the mAs to compensate for density changes.

Radiograph #10

image010 This patient is an ambulatory patient who presented with hip pain and a chief complaint of “fall 2 days prior.” This radiograph was taken in the radiology department; does it meet the diagnostic criteria for the AP pelvis projection?

Critique of Radiograph #10

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    This radiograph shows the required anatomy for the AP pelvis view. Soft tissue within the abdomen and pelvis and surrounding the femora is properly displayed. The pelvis is slightly rotated; however, not significantly. Placing the ASIS equal distance from the tabletop corrects mild rotation of the pelvis. Overall, the exposure technique and positioning is adequate. No need to repeat this radiograph, it meets the diagnostic criteria for the AP pelvis view.

Radiograph #11

image011 An orthopedic surgeon requested that the pelvis be imaged to include both hips. The request for the examination specifically stated, “pelvis x-ray to include both hip prostheses.” Did the technologist produce this radiograph in keeping with the diagnostic criteria for the study as requested?

Critique of Radiograph #11

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    Paying close attention to the patient history that goes with each study will eliminate unnecessary exposure and allow one to practice within the guidelines ALARA. This radiograph represents the AP pelvis view, which meets the diagnostic criteria in a strict interpretation. However, a second radiograph to include both hip prostheses is needed. That portion of the pelvis above the yellow line can be omitted. The identification marker in the left lower part of the radiograph should not be allowed to obscure anatomy. A gonadal shield should be used when exposing the pelvis on the second view. While this radiograph does not need to be repeated it is important that the additional images of the hips do include the entire prosthesis and surrounding soft tissues on a single film. With this point in mind this radiograph does meet the diagnostic criteria for the AP pelvis view. Radiograph exposure technique adequately demonstrates bone and soft tissue.

Radiograph #12

image012 Give your critique of this AP pelvis radiograph, which was taken upright to evaluate both hip joints as a weight-bearing study?

Critique of Radiograph #12

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    When performing the weight-bearing study both legs are in the neutral position rather than internally rotated in an unnatural standing position. The femoral necks are minimally foreshortened, which is to be expected. The entire pelvis from the iliac crests through the lesser trochanters of the femurs is included on this radiograph. The pelvis is not rotated, nor is it tilted laterally, and both obturator foramina are opened and fairly symmetrical. The positioning is good reflecting the anatomical and functional relations of the subject accurately. Exposure is good showing well-penetrated bone structures such as the acetabula and sacrum. There is good bone detail and contrast throughout the pelvis and good soft tissue detail for the bowel, urinary bladder, and surrounding soft tissues. This is a good radiograph that meets the diagnostic criteria for the AP pelvis view.

Radiograph #13

image013 This AP pelvis radiograph was taken to evaluate the pelvis and hips, chief complaint, “chronic bilateral hip pain.” Does this radiograph meet the diagnostic criteria for the AP pelvis view?

Critique of Radiograph #13

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    This radiograph does not meet the diagnostic criterion for the AP pelvis view because a portion of the right ilium and right proximal femur are clipped. Although the femur is not an anatomical part of the pelvis, including it is part of the diagnostic criteria for the AP pelvis view. Also, the femurs are not internally rotated which would significantly reduce foreshortening of the femoral necks and profile the greater trochanters laterally. Radiographic exposure technique shows adequate penetration of the acetabulum and sacrum, and good subject contrast throughout the remainder of the pelvis. Soft tissue detail is good, so no change in exposure technique is needed. However, this radiograph should be repeated to include all of the required anatomy, specifically the right proximal femur and right ilium with the femora internally rotated.

Radiograph #14

image014 This patient presents with a history of acute trauma from a fall. The injured area is the left pelvis and especially the left hip. Does this AP pelvis radiograph meet the diagnostic criteria?

Critique of Radiograph #14

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    The most obvious observation is that subject contrast is too high. This is evidenced by underpenetration of the sacrum and “burn out” of the femurs. High contrast caused by low kVp and high mAs is always unacceptable for imaging the pelvis. A good measure of proper contrast is to look at the upper sacrum and lower lumbar spine. This area should be well penetrated, as should the acetabula and femur. No bone anatomy or surrounding soft tissue should be overexposed. Notice that the patient’s left hand guards the left hip (which could obscure a possible fracture). Guarding is a typical response to acute pain; therefore, make certain the entire area of exposure is clear before exposing the part. This radiograph should be repeated because of the hand overlies the left hip. Also, the exposure shows high contrast with underpenetration of the sacrum and overexposure of the femora.

Radiograph #15

image015 This patient was brought to a local emergency room on a spine board suspected of having multiple traumatic injuries. The initial films taken in the emergency room consisted of chest, abdomen, and pelvis x-rays. Does this radiograph meet the diagnostic criteria for a portable AP projection of the pelvis?

Critique of Radiograph #15

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    Imaging for trauma in the emergency room as part of the trauma team requires experience and skill to get the best radiograph on the first attempt. This portable AP pelvis radiograph demonstrates enough of the anatomy to give the trauma physicians a general assessment of the patient’s injuries. It is not uncommon to clip a minimal amount of anatomy when the patient is on a spine board and the image taken on a Stryker bed. This is because there is usually considerable object-to-image distance (OID), which causes significant image magnification. Using maximum source-to-image distance (SID) can only partially compensate for excessive OID. Proper centering of the patient would have allowed the left pelvis and left proximal femur to be included on the radiograph. There is adequate radiographic contrast and detail seen on this film, for example, the fracture of the left acetabulum and pelvic ring is easily observed. The technique is inadequate for complete diagnosis because the posterior pelvic elements, mainly the sacrum is underexposed. This radiograph should be repeated when the patient is stable and can be brought to the radiology department. Repeating this projection is necessary because the left proximal femur and left pelvis are not entirely included, and the exposure technique does not adequately demonstrate bone detail throughout the sacrum.

Radiograph #16

image016 This is a repeat of radiograph #15 above. The patient has been taken off of the spine board and the AP pelvis repeated. Does this radiograph meet the diagnostic criteria for the AP projection of the pelvis?

Critique of Radiograph #16

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    The patient is well centered; both hip joints and proximal femurs are included on the radiograph. All required anatomy is demonstrated in proper anatomical position. This follow-up to the portable radiograph shows good bone detail, especially the left pelvic ring and left acetabular fracture. The sacroiliac joints are faintly demonstrated as are the soft tissue structures like the urinary bladder and visualized bowel. The radiographic exposure technique is adequate for most of the posterior portion of the pelvis. However, the sacrum, SI joints, and lower lumbar spine are poorly penetrated and show poor bone detail. As a result, the sacrum and posterior pelvis is indeterminate for fracture and pelvic stability. Although this radiograph meets the diagnostic criterion for demonstrating the anatomy it should be repeated because the exposure technique poorly defines the posterior pelvis, especially the sacral margins. The AP pelvis view alone is not always sufficient to determine stability of the pelvis so additional projections like the inlet and outlet views, or a CT scan may be used to further characterize ill-defined features in the posterior pelvis.

Radiograph #17

image017 This patient was brought to a local emergency room on a spine board after suffering acute trauma. The patient was a pedestrian who was hit by a motor vehicle. Does this radiograph meet the diagnostic criteria for the portable AP projection of the pelvis?

Critique of Radiograph #17

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    This radiograph tells the story of a life-threatening injury involving the pelvis. Under great pressure to perform the technologist has done a fine job of not clipping pertinent anatomy. The pelvis is well centered and all of the required anatomy is present. The radiographic exposure technique shows good bone detail in the posterior pelvis where a fracture of the sacrum and femur (arrows) is noted. Because the technologist performed professionally and did achieve the diagnostic criteria for the AP pelvis view, crucial interventional time was saved. As a result, the patient was transported to the CT department for a complete chest, abdomen, and pelvis CT scan. The results of the CT scan indicated that interventional radiology was needed immediately to attempt to manage uncontrollable pelvic hemorrhaging. Surgical intervention was performed timely to stabilize the bony pelvis.

Radiograph #18

image018 This patient was brought to a local emergency room on a spine board after suffering acute trauma. This patient is also a pedestrian who was hit by a motor vehicle. Does this radiograph meet the diagnostic criteria for the portable AP projection of the pelvis?

Critique of Radiograph #18

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    The magnitude of injuries seen on this radiograph, like the previous one, tells the story of serious, potentially life-threatening injuries. Good timely diagnostic radiographs are important during trauma imaging since early diagnosis and treatment may in some cases increase chance of survival. We see that most of the pelvis is included on this radiograph including right hip and right hemi-pelvis, which is dislocated and displaced, respectively. An optimal radiograph would have included the entire left side: proximal femur, iliac wing. The inferior ramus of the right pubis bone is also clipped. Separation of the symphysis pubis (a condition called diastases) may indicate significant injuries to structures within the true pelvis. Symphysis widening seen on this radiograph may also suggest injury to the urethra and/or urinary bladder. Also, the patient identification marker should always be placed in an area that does not obstruct any anatomy. The metal strap from the spine board seen obscuring structures should have been removed. Radiographic technique is excellent. This radiograph should be repeated with the metal removed, and all omitted anatomy demonstrated.

Radiograph #19

image019 This radiograph was taken on a trauma patient who presented with the right hip in external rotation and extreme pain. Clinical history, “motorcycle accident.” Does this radiograph meet the diagnostic criteria for the AP projection of the pelvis?

Critique of Radiograph #19

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    When a trauma patient presents with external rotation of the lower extremity the technologist should not internally rotate the hip. External rotation of the leg following trauma often indicates a fracture of the proximal or distal femur, or acetabulum. This radiograph reveals a complex pattern of injuries that include a fracture of the right acetabulum, right pelvic ring, and fractures involving both iliac wings. The right iliac wing is clipped and so is a portion of both iliac crests. The external rotation of the right hip is to be expected and is not indicative of poor position on the part of the technologist. I suspect that magnification due to increased OID may be the reason for clipping the pelvis; another cause is failure to properly center the part. Better centering of the part to the image receptor to take advantage of the entire image area would reduce the chances of a positioning error. The exposure technique shows a well-penetrated pelvis with good bone detail through the acetabula, pubis bones, iliac wings, and sacrum. The exposure is adequate to permit radiographic interpretation of the entire pelvis. This radiograph should be repeated to include the required anatomy for the AP pelvis view. The best way to include all anatomy on this radiograph is to use proper part-tube-image receptor alignment.

Radiograph #20

image020 Give your critique of this postoperative radiograph given the clinical history, “evaluate internal fixation of the pelvis.” Does this radiograph meet the diagnostic criteria for the AP pelvis view?

Critique of Radiograph #20

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    This is a good postoperative radiograph because it demonstrates the entire pelvis. A portion of the left proximal femur and associated prosthesis is not demonstrated. Then again, it is not required to be entirely included unless the left hip is also specified in the exam request. Specifying the left hip to be evaluated along with the pelvis requires a separate left hip radiograph to include the entire prosthesis. This radiograph adequately demonstrates all surgical fixations of the pelvis. The field of view extends from above the iliac crests to below the lesser trochanters. The sacrum is not aligned with the pubic symphysis, which indicates that the pelvis is rotated. The rotation is negligible and due to traumatic displacement not to positioning. The radiographic exposure technique displays good penetration of bone and proper contrast between metal fixation devices and bone. Soft tissue structures such as the urinary bladder and bowel gas presentation is balanced with good bone detail.

Radiograph #21

image021 Give your critique of this portable AP pelvis radiograph. Clinical history is “to evaluate the left hip prosthesis. Could anything have been done to make this a better radiograph?

Critique of Radiograph #21

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    This radiograph fails to meet the diagnostic criteria for image quality and positioning of the part. The basic scenario is that the technologist forgot to take a grid and decided to try and get by without it. When the part measures more than 10 cm the scatter produced to cause excessive image fog. A grid must be used because it helps to clean up scatter by absorbing it before it reaches the image receptor. This in turn results in higher radiographic contrast and better subject detail. As the kVp increases, the amount of scatter radiation produce also increases. Since high kVp is needed to penetrate the pelvis a radiographic grid such as an 8:1 or 12:1 is needed to clean up most of the scatter that will be produced. When using a grid there must be a concomitant change in exposure factors. An increase in the mAs will be needed to account for photon absorption by the grid. Think ALARA at all times and avoid repeat patient exposure. The other problem with this radiograph is that the left acetabulum is not entirely included. Improper alignment of the patient caused the pelvis to be tilted placing the right acetabulum below the left acetabulum. Good alignment is a very important because symmetrical alignment of same structures makes for easier interpretive viewing.

Summary: AP Pelvis Film Critique

  • The AP pelvis view should include the entire ilium, ischium, pubis bones, and the entire L5 vertebra. The FOV should extend from above the iliac crests through the lesser trochanters of both femurs and include their surrounding soft tissues.
  • The femurs are internally rotated if the patient’s condition permits. A trauma patient who presents with trauma, or pain associated with the femur in external rotation should be taken in the “as is” position.
  • Radiographic exposure should penetrate the acetabula, innominate bones, and the sacrum. The iliac wings should show sharp bone detail and clearly diffrentiated bone trabeculae. The posterior pelvis mainly the sacrum and visualized lumbar vertebrae should be well penetrated having sharp bone edges. All soft tissues surrounding the pelvis including the skin should be demonstrated for any penetrating injury.

Pelvic inlet/outlet

The pelvic inlet and outlet views are generally taken to supplement the AP pelvis view. 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 pelvic inlet (brim) is formed posteriorly by the sacral promontory and extends along an oblique plane that passes through the arcuate line of the ilium, along the pecten pubis and pubic crest (a.k.a. linea terminalis). Within the true pelvis are the bladder, rectum, and portions of the urogenital organs.

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This CT midsagittal view of the pelvis demonstrates the inlet and outlet of the true pelvis. A line drawn from the sacral promontory to the crest of the superior pubic ramus (white line) represents the superior aperture or inlet. A line drawn from the coccyx to the inferior pubic ramus (blue line) represents the inferior aperture or pelvic outlet. These two lines represent the boundaries of the true pelvis. Within the true pelvis in females from anterior to posterior are the urinary bladder (B), uterus (U), and rectum (R).

The inlet view is important because it can immediately identify narrowing or widening of the pelvic ring. It is useful to identify posterior displacement of the pelvic ring, sacroiliac joint dislocation, and rotation of the hemipelvis. Also identified are pubic diastasis or pubis overlap, subtle sacral fractures and/or sacral impaction. The inlet view is taken with the patient supine and the x-ray beam angled 25-45 degrees caudal and perpendicular to the pelvic brim.



The following are some 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.
image281
This pelvic inlet view of the pelvis demonstrates the importance of seeing the posterior element of the pelvic inlet along the sacral border. An area of the pelvis (circle) is magnified on the right to show a vertical fracture (arrow) of the pelvis that is not easily characterized using the AP pelvis view alone. The inlet and the outlet views better demonstrate posterior ring fractures and injuries involving the SI joints than the AP view alone.

The pelvic outlet bound by the sacrum/coccyx posteriorly, the symphysis pubis anteriorly, and flanked by the ischial tuberosities laterally. The primary purpose of the outlet view is to demonstrate the magnitude of vertical displacement of the hemipelvis. The sacral foramina are better seen on the outlet view than on the AP pelvis view. It presents the anterior ring without superimposition on the posterior ring, almost showing a volume effect. Additionally, some sacral and pubic rami fractures are better visualized on the outlet view than the routine AP pelvis view. Proximal or distal displacements of the ring are better appreciated on this view. The outlet view is obtained with the patient in the true AP position and the tube angled 45 degrees cephalic.



The following are some determinations permitted by the outlet view:

  • Can corroborate vertical displacement of the hemipelvis, visualize the SI joints in profile, and show displacement of the hip joint.
  • Demonstrates the sacral neural foramina better than the AP pelvis view.
  • Some pubic fractures are better seen with the outlet view than the AP view alone.

When the outlet view is taken as part of a trauma series, both femoral heads should be included on the radiograph. This is because when a hip dislocation is present the outlet view can demonstrate its anterior or posterior displacement. A 45-degree cephalic angulation will cast the shadow of an anteriorly displaced femoral head above the acetabulum. The shadow of a posteriorly displaced femoral head is projected below the acetabulum. This projection also demonstrates the sacroiliac joints very well as the posterior rim of the true pelvis is seen in profile. The anterior margin of the pelvic brim is demonstrated without obstructing bone anatomy. As you can see on the radiograph below the pubic rami are also seen in profile along with the obturator foramen and pubic arch.

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The pelvic outlet view demonstrates the pubic rami, obturator foramina (O), and the anterior and posterior margins of the pelvis. The full pelvis view on the left demonstrates the anatomy demonstrated by the outlet projection. Notice that the femoral heads are demonstrated on this trauma pelvis radiograph. On the right is a magnified area involving the pelvic ring. Notice the borders of the posterior elements, mainly the sacrum (arrows) and SI joints are well demonstrated. The anterior pelvic rim is seen in profile.
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This coronal CT image shows in part the structure of the pelvic ring. Notice the continuity of bone from the sacroiliac joints to the visualized portion of the superior pubic rami anteriorly. The pelvic brim is a solid structure that forms the opening into the true pelvis. Note the bowel and urinary bladder, which are soft tissues of the abdominal pelvic cavities, are partially seen. The hip bone is a solid structure that when fractured can affect stability of the entire pelvis.
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This 3-D volume rendered CT image shows the outlet from the inferior opening of the true pelvis. This opening is bound posteriorly by the coccyx (arrow) and anteriorly by the inferior pubic rami. Strong ligaments bridge the opening but make an expandable space available for passage of the fetus during child birthing.

Diagnostic criteria for the Pelvic Inlet and Outlet Views
  • For both the pelvic inlet and outlet views include the entire pelvis from the top of the iliac crests superiorly through the ischial tuberosities and pubic rami inferiorly. Both SI joints and the entire sacrum should be demonstrated. The femoral heads must be included on the radiograph since anterior or posterior displacement can be determined from the outlet view.
  • The floor of the true pelvis should be demonstrated on the outlet view; the inlet view should show the opening into the true pelvis (pelvic ring) in profile.
  • There should not be any rotation of the pelvis on either view determined by the obturator foramina being open and symmetrical.
  • Radiographic exposure technique should penetrate the sacrum, SI joints, acetabula, and iliac wings. Bone detail should show good bone trabecular pattern throughout the pelvis and differentiation of the spinous processes of visualized lumbar vertebrae. The sacrum should be well penetrated and have good bone detail showing sharp margins of the sacral foramina and S.I. joints.

Radiograph #22

image022 Does this radiograph meet the diagnostic criteria for the pelvic inlet projection of the pelvis?

Critique of Radiograph #22

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    This inlet view shows sharp margins of the pelvic brim. The left portion of the ring is distorted because the pelvis is slightly rotated. When accurately positioned the ischial spines are aligned with the pelvic brim and the sacrum/coccyx aligned with the pubic symphysis. To avoid rotation of the pelvis check the distance from the ASIS to the tabletop on each side of the pelvis to make sure they are equidistant. There appears to be no displacement of the pelvic brim, but there is a right acetabular fracture. The femoral heads and necks are seen in profile and demonstrate no dislocation of the femora. At least a 45-degree caudal angle should have been used to elongate the ring better. This view should not be repeated for these positioning errors in keeping with ALARA. The exposure technique shows optimal bone detail throughout the pelvis and proximal femurs.

Radiograph #23

image023 This inlet view of the pelvis was taken following an AP view, which revealed a pelvic ring fracture. Does this radiograph meet the diagnostic criteria for the inlet projection?

Critique of Radiograph #23

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    The tube angle used to make this radiograph gives a better projection of the pelvic inlet than was seen in radiograph #22 above. The patient is positioned in a true AP without rotation of the pelvis. There is good presentation of the pelvic ring and a smooth contour of the ring on the right. On the left there is obvious bone irregularity caused by disruption of the pelvic brim (white arrows). A fractured left inferior pubic ramus is also nicely demonstrated. The radiographic exposure technique shows a well-penetrated sacrum (notice the vertical fracture of the left sacrum) and a well-penetrated left acetabulum. Soft tissue structures like the urinary bladder and gas in the rectum are optimally visualized. This is a properly positioned radiograph that shows optimal exposure and detail in the posterior pelvis.

Radiograph #24

image024 This patient had an unstable pelvic fracture involving the sacrum, as well as pubic rami fractures and a dislocated left hip prosthesis. Does this postoperative radiograph meet the diagnostic criteria for the inlet view?

Critique of Radiograph #24

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    It is important with post-operative imaging that the entire pelvis is demonstrated. The pelvic brim is adequately demonstrated without rotation of the pelvis. However, the entire sacrum is not demonstrated. Demonstrating from the first lumbar vertebra and iliac crests, through the inferior portion of the hip bones and including the lesser trochanters of the femurs is required for this view. The tube angle properly demonstrates the pelvic inlet. This patient suffered an unstable injury of the pelvis so the posterior pelvic elements must be seen in their entirety. Radiographic exposure is adequate for imaging the pelvis. This radiograph should be repeated to include the entire sacrum, lateral portion of the left proximal femur, and anterior portions of the pelvis.

Radiograph #25

image025 This inlet view was requested following an AP portable pelvis x-ray that revealed a left pelvic ring fracture. Does this radiograph meet the diagnostic criteria for the inlet pelvis view?

Critique of Radiograph #25

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    This radiograph does not meet the diagnostic criteria for several reasons. Among them is the failure to include the entire pelvis, and the other reason is inadequate penetration of the acetabula and proximal femurs. The tube angle is sufficient for demonstrating the pelvic inlet. We can see an obvious interruption of the pelvic ring on the left (arrow). The exposure technique does not penetrate the pelvic brim very well. A complete evaluation of the left pelvic ring is not possible based on this exposure technique. This radiograph should be repeated using more kVp to penetrate the pelvis. Also, increasing the SID will decrease the magnification seen on this radiograph. Including all of the pelvis and the sacrum is an essential requirement for a diagnostic inlet view. There appears to be fractures involving the left iliac wing, acetabulum, and proximal femur.

Radiograph #26

image026 This radiograph was requested for pre-op evaluation of several fractures that include the left pelvic ring, left acetabulum, and right pubic rami. Does this radiograph meet the diagnostic criteria for the inlet pelvis view?

Critique of Radiograph #26

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    When positioning it is important to align the patient to the midsagittal plane as much as possible, especially when there is a known fracture. This radiograph shows the right acetabulum positioned lower than the left acetabulum. This makes comparing symmetrical parts throughout the pelvis more difficult. The cause of this asymmetry is the patient is not centered on the slide board. Always align the midsagittal plane to the midline of the image receptor by centering the patient on the slide board. Remember we are trying to demonstrate degree of vertical shift of the pelvis by evaluating the sacrum and S.I. joints. The problem with this radiograph is that the superior part of the pelvis and sacrum are clipped. Subject contrast is poor due to both exposure factors and patient motion. Increase mA and decrease exposure time to compensate for motion artifact. Subject contrast, especially sharp bone edges and detail is necessary. Reasons to repeat this radiograph are: improper patient centering, clipped anatomy, and poor subject contrast.

Radiograph #27

image027 Does this radiograph meet the diagnostic criteria for the inlet pelvis view (patient history is acute trauma)?

Critique of Radiograph #27

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    This is a good radiograph of the pelvic outlet although it is slightly rotated. The evidence of the pelvis being rotated is that the midsagittal plane through the sacrum/coccyx is not aligned with symphysis pubis. The obturator foramina are not symmetrical. What is good about this radiograph is that the entire pelvis and the femoral heads are demonstrated. The anterior and posterior portions of the pelvic brim are well delineated. The superior and inferior pubic rami, and ischium of each innominate bone are seen in profile. The sacrum, S.I. joints, and sacral foramina are seen in profile with good bone detail. The radiographic exposure technique provides excellent trabecular bone detail and balanced soft tissue presentation. This is an excellent radiograph that meets the diagnostic criteria.

Radiograph #28

image028 An orthopedic physician requested this pelvic outlet view after seeing the AP pelvis view. Does this radiograph meet the diagnostic criteria for the outlet view?

Critique of Radiograph #28

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    What is good about this radiograph is that it has minimal to no rotation of the pelvis. The coccyx and ischial spines are appropriately demonstrated. The fracture through the left acetabulum is also well visualized due to the excellent exposure technique selected. While this radiograph was not repeated because it was known there is no fracture involving the superior iliac wings and crest, these structures should have been included. Also the x-ray tube could be directed a bit more cephalic (about 45 degrees is recommended), which would project the coccyx inferior to the pubic symphysis. Otherwise this is a great radiograph. In keeping with ALARA this radiograph does not need to be repeated.

Radiograph #29

image029 This postoperative radiograph was taken to evaluate the pelvis, especially the internal fixation of the sacrum. Does this radiograph meet the diagnostic criteria for the outlet view?

Critique of Radiograph #29

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    The pelvis is stabilized with internal and external fixations. The radiologist is asked to evaluate the internal fixation of the sacrum. Notice that the patient is slightly rotated with the obturator foramina being asymmetrical. The midsagittal plane through the sacrum is not aligned with the symphysis pubis. The patient being uncomfortable following surgery may have caused this and the technologist did not want to add to the patient’s discomfort by properly positioning them. It is important that the sacroiliac joints are properly evaluated. A well-positioned radiograph of the pelvis will have the sacrum aligned with the symphysis and symmetry of the obturator foramina. When properly positioned the left hip prosthesis may obstruct the anterior portion of the pelvic brim. So, repeat this radiograph aligning the midsagittal plane of the sacrum with the symphysis. Check to make sure the ASIS are equidistant from the tabletop to avoid pelvic rotation.

Summary: Inlet/outlet views of the pelvis

  • The pelvic inlet and outlet views should show well-defined margins of the pelvic brim. Pelvic outlet should profile the pubic rami, and acetabulum along with the pelvic outlet.
  • Include the entire pelvis from the top of the iliac crests superiorly through the ischial tuberosities and pubic rami inferiorly. Both SI joints and the entire sacrum should be demonstrated on both views. The femoral heads must be included on the radiograph since anterior or posterior displacement can be determined from these views.
  • The floor of the true pelvis should be demonstrated on the outlet view; the inlet view should show the opening into the true pelvis and pelvic ring in profile.
  • There should not be any rotation of the pelvis as both obturator foramina should be open and symmetrical. The sacrum/coccyx should be aligned with the pubic synthesis and the midsagittal plane aligned with the image receptor.
  • Radiographic exposure technique should penetrate the sacrum, SI joints, acetabula, and iliac wings. Bone detail should show good bone trabecular pattern throughout the pelvis and differentiation of the spinous processes of visualized lumbar vertebrae.
  • Radiographic technique should include good bone detail and good penetration of the acetabulum, sacrum, and iliac wings without image “burn-out.”

Judet view

Sometimes an injury involving the acetabulum is in question and a slant perspective of the acetabulum is helpful. An acetabular fracture may occur independently or with a pelvic ring fracture. Acetabular injuries must be distinguished from pubic rami, or confusing isolated iliac or ischium fractures. First and foremost is that evaluate an acetabular fracture it must be seen. The purpose for the Judet view is to demonstrate the acetabulum in profile. The Judet view is named after Dr. Judet who stressed the use of the 45-degree oblique views for trauma imaging. The patient is positioned with the midsagittal 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 hard to see nondisplaced acetabular fractures.

To fully appreciate why the Judet view is sometimes ordered let’s look at a real clinical case involving an acetabular fracture. Three radiographs are presented below: Radiograph A is a standard AP pelvis view. If you look closely at it you may see the fracture fragment through the right femoral head, which is magnified and presented as Radiograph B. The Judet view, Radiograph C, is taken with a perpendicular x-ray beam and the patient turned 45-degrees (left posterior oblique position). This view demonstrates the posterior acetabulum in profile confirming a fracture.

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Often the AP view does not demonstrate a pelvic fracture of the acetabulum sufficiently to characterize it. Demonstrating a subtle fracture of the acetabulum is one of the most common reasons a physician may request Judet views. Dr. Judet stressed the importance of these views referencing a similar type of fracture seen in the radiographs above. Radiograph (A) demonstrates a hard to see fracture seen as a fragment superimposed on the right femoral head. Radiograph (B) is a magnified view of the right acetabulum, which poorly defines the acetabular fracture. Radiograph (C) is a LPO Judet view demonstrating this fracture, which involves the posterior rim of the acetabulum. The AP view is an important projection for determining fractures; however, the Judet view like the inlet and outlet views is sometimes needed to better distinguish certain features of the pelvis.

The Judet views demonstrate both acetabula and provide useful evaluation for suspected acetabular fractures. The Judet views are 45-degree oblique views with the patient in the LPO and RPO positions. These give a detailed look at the acetabulum to better visualize nondisplaced and displaced fractures is achieved. When the entire pelvis is demonstrated what is in profile is the iliac wing of the side down; the SI joint, an opened obturator foramen, femoral neck and greater trochanter of the side up. For the Judet view, the patient is turned so that the midsagittal plane is turned 45-degrees to tabletop. The tube is positioned vertical to the film. Unless specified, both the left and right posterior oblique views are generally taken when the Judet views are requested.

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These two radiographs demonstrate the Judet views, which are 45-degree posterior oblique views of the pelvis. They are so named because Dr. Judet stressed the importance of these views in evaluating the pelvis, especially the acetabulum. The left radiograph is the RPO view. It demonstrates a fracture of the right acetabulum very well. The radiograph on the right shows the LPO view, which profiles both acetabula.

Judet views help the radiologist to describe fractures involving the innominate bone, particularly the acetabulum. It is important that fractures involving the anterior and posterior columns of the acetabulum be described as such. The anterior and posterior walls of the acetabulum when fractured must be described as well. The AP view alone may miss some fractures in these areas or provide limited evaluation data when they are seen. Judet views help provide additional image data needed to help complete diagnostic interpretation of the acetabulum. The Judet views are often requested by orthopedic surgeons when needed to evaluate or plan treatment for acetabular fractures. image287

This CT axial image through the mid acetabular region shows the various proposed columns of the hip bone. A reference line (rl) is used to define the anterior (AW) and posterior (PW) walls of the acetabulum lateral to it. A line through the mid-coronal plane gives a division of the hip into an anterior column (AC) and a posterior column (PC). Letournel and Judet described these landmarks for evaluating the acetabulum; however, current understanding of structure and function of the hip bone is continually redefining descriptive landmarks.

Diagnostic Criteria for the Judet view
    • The entire pelvis is demonstrated on each oblique Judet view and should include the acetabula and proximal femurs.
    • · The patient is turned so that the midsagittal plane is 45 degrees to the tabletop. With the patient centered to the image receptor, the x-ray beam is directed vertical to the tabletop.
    • Radiographic exposure technique should provide adequate penetration of both acetabula without “burnout” of other structures. The iliac wings and pubic rami should be well penetrated displaying good bone detail. Soft tissue structures such as the bladder wall and bowel gas should show good contrast
    • The Judet view demonstrates acetabular fractures and hip dislocation. The side up or the side down may be the area of interest depending on the posterior oblique being evaluated. For example, when the right side of the Judet view allows for evaluation of posterior rim of the pelvis, right obturator foramen, and anterior portion of the right column. When the side down is of interest, for example the left side, the structures evaluated includes the left anterior rim of the acetabulum, left posterior ilioischial column, and wing of the left ilium.

Radiograph #30

image030 This radiograph was taken to evaluate the right hip when a fracture was seen on the AP view. Does this radiograph meet the diagnostic criteria for the Judet view?

Critique of Radiograph #30

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    Overall, this is a good radiograph because it shows both acetabula in profile. The positioning properly demonstrates in profile a right hip dislocation, right acetabulum, and the anterior portion of the right pelvic brim. The left pelvic wing, left hip joint, and proximal femur are properly demonstrated. However, the flaw of this radiograph is that a portion of the right proximal femur and superior portions of the pelvis are clipped. Unfortunately these positioning error should be corrected. The bone detail is excellent and there is sufficient penetration of structures to evaluate for a fracture or dislocation. In keeping with ALARA if the right greater trochanter is seen on the AP and RPO Judet views this radiograph may not need to be repeated.

Radiograph #31

image031 This Judet view was taken to evaluate the pelvis. It was known there were fractures of the right acetabulum and left iliac wing. In what ways does this radiograph meet the diagnostic criteria, or does not meet the diagnostic criteria?

Critique of Radiograph #31

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    All anatomy required for the Judet view is included on this radiograph. This radiograph meets the diagnostic criteria for positioning of the pelvis; however, this radiograph displays high contrast, which is not optimal for imaging the pelvis. A well-penetrated right acetabulum is demonstrated: however, the left acetabulum is slightly underpenetrated. Because the left hip is close to the film there is good subject detail. Notice the fracture of the left iliac wing profiled, but the high contrast exposure created burnout along the edge of the iliac crest. The fracture of the left acetabulum is seen, but cannot be characterized because of poor penetration. Exposure technique should be in the 75-85 kVp ranges for this view, which will give optimal bone penetration and good subject contrast.

Radiograph #32

image032 Does this radiograph meet the diagnostic criteria for the Judet view, why or why not?
Critique of Radiograph #32

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    This is a case of what seems to be a good radiograph is really not so good a radiograph. What is good about this radiograph is that all required anatomy is presented on the radiograph. Also, the patient is properly positioned at about 45-degrees from the midsagittal plane, which properly displays both acetabula. However, the problem with this radiograph is the exposure technique. There is minimal the loss of detail along the right pelvic ring (which is the area of concern). This makes it difficult to determine the extent of the pelvic ring fracture into the acetabulum. The only reason to not repeat this radiograph is if a CT scan of the pelvis is to be performed. Otherwise, correct the exposure technique by increasing the kVp to penetrate the acetabulum and right pelvic brim.

Radiograph #33

image033 Does this radiograph meet the diagnostic criteria for the Judet view? Discuss the exposure technique used and whether or not it is optimal.
Critique of Radiograph #33

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    The exposure technique shows well-penetrated acetabula without burnout of the iliac wings. Unfortunately the patient is rolled away from the image receptor too steeply. Notice the loss of contour of the pelvic brim. Compare this feature to that demonstrated in radiographs 30 & 31 above. The part is well centered although the crest of the left ilium is partially clipped. The left inferior pubic ramus and ischial tuberosity are entirely visualized. The head, neck, and acetabulum of the side up (left) are well demonstrated. The side down (right) shows the femur in extreme external rotation. This has foreshortened the right femoral neck making its evaluation minimal. Neutral positioning or slight internal rotation of the hip is recommended as long as the patient does not have a hip fracture. Otherwise, the ‘as is” position of the leg is acceptable for the side injured. Repeat this projection decreasing the angle of the midsagittal plane to 45 degrees.

Summary: Judet view critique

  • The entire pelvis is demonstrated on each 45-degree posterior oblique view. The patient is turned so that the midsagittal plane is 45 degrees to the tabletop. Also position the patient in alignment and centered to the image receptor. The x-ray beam is directed vertical to the tabletop. Omitting any part of the pelvic basin, acetabula, or proximal femurs may warrant repeating the radiograph.
  • Radiographic exposure technique should provide adequate penetration of both acetabula without “burnout” of the pubic rami or soft tissues within the true pelvis. The main focus of the Judet view is to evaluate displaced and nondisplaced fractures of the acetabulum. So the exposure should always demonstrate good bone detail and sharp bone edges about the acatebula. Because the iliac wings and pubic rami are also profiled they should be well penetrated with good bone detail too. Soft tissue structures such as the urinary bladder and bowel gas should not be overexposed.

Radiographic Imaging of the Hip Joint

The hip bone and the proximal femur form the hip joint. In the United States each year about 280,000 persons fracture their hip, more than 90% occur in the age 60+ age group. Hip fractures are more common in older women, one in three women compared to one in six men. The main contributor to hip fractures is osteoporosis. Osteoporosis is a bone loss disease caused by a reduction in mineral density of bone. Calcium in particular is a mineral that is stored in skeletal tissue; it gives bone its hardness. Bone tissue forms the internal frame of the body. Bone is not static like the foundation and walls of a building; it is made of living cells called osteocytes that carry out metabolic functions. Too perform their functions osteocytes must have oxygen and nutrients just like other cells of the body. To support the body’s frame, bone cells deposit calcium into bone and release calcium when needed for bio-functions like muscle activity. Bone fragility due to bone loss puts men and women at risk for bone fracture. It is estimated that about 34 million Americans have status low bone mass, a condition called osteopenia, which is a precursor to osteoporosis, and about 10 million Americans have osteoporosis.

A considerable amount of new information is forthcoming about osteoporosis. This information is being used to lower the risks of associated bone fractures. Efforts to disseminate information to the public about the causes of osteoporoses are ongoing. Some risks for osteoporosis include aging, smoking, family history, and low lifetime ingestion and absorption of calcium. Understanding these factors can help individuals to manage their specific risks. Women are especially at risk for bone mass loss during the years following menopause. Decreased estrogen levels can cause a loss of as much as 50% of the trabecular bone and up to 30% of cortical bone. This subjects postmenopausal women to high risk of hip and other bone fractures. Understanding risks and consulting with a physician for preventive treatment against osteoporosis is effective. Diagnostic testing such as dual-energy x-ray absorptiometry (DEXA) is also available as a screening tool to detect osteoporosis. Currently, DEXA is the gold standard test for bone density measurement associated with osteoporosis.

Hip dislocations are also relatively common, most often resulting from severe trauma. Posterior dislocations occur more frequently than anterior dislocations. Approximately 85-90% of the time the dislocation is posterior and may occur with or without acetabular fracture. The mechanism that causes posterior displacement is traumatic force along the long axis of the femur with the hip in flexion. An example of this mechanism is hitting the dashboard with the knee during a high impact motor vehicle crash while the hip is flexed as in sitting. With severe injury the posterior column of the acetabulum is often fractured. The ilioischial union forms the posterior column, and the iliopubic union forms the anterior column. The posterior column is the thicker than the anterior column and is stronger, and therefore provides most of the articulation and weight bearing of the joint socket. A quadrilateral bone plate forms the medial wall of the acetabulum. It too can be involved in traumatic injury, as can be the posterior and anterior columns.


Fractures of the Acetabulum
  • Simple
    • Posterior rim
    • Posterior column
    • Anterior rim
    • Anterior column
  • Complex
    1. Two or more simple fractures

Frequency of Fractures of the Hip
  • Femoral neck - 45 to 55%
  • Intertrochanteric - 35 to 45%
  • Subtrochanteric - 5 to 15%

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These two radiographs demonstrate two common types of fractures seen in the proximal femur. Radiograph A on the left demonstrates a fracture of the femoral head (arrow). Radiograph B on the right demonstrates an intertrocanteric fracture with displacement of the lesser trochanter. Both of these types of fractures can result from simple trauma, especially in older adults whose bone mass is decreased due to osteoporosis.

Hip fractures also occur in children. Although rare, most often they occur from trauma, such as being struck by an automobile as a pedestrian. Traumatic hip injuries in children often are accompanied by injuries to the head, thorax, or spine. Multisystem injuries occur in children and adults alike when they occur due to trauma such a motor vehicle accident. The type and location of hip and femur fractures, and hip dislocation vary by age, height of child, or whether or not the person is an adult. In children, hip dislocations are more common than hip fractures. Young children still undergoing cartilaginous transformation to bony skeleton in part accounts for variance in injury type and location. The process of bone development is called endochondrial bone growth, which is a process of the cartilage frame being replaced by bone. In young children the acetabulum is composed of a significant amount of cartilage that gives it flexibility hardened bone does not have. Another factor causing a variance in type of injuries seen in adults vs. children is that the child innominate bone is not fused. A fused bony acetabulum is more susceptible to fracture than to hip dislocation.

Degenerative joint disease (DJD) also called osteoarthritis is the most common type of joint disease. Some adults suffer chronic hip pain because of osteoarthritis (OA) and/or rheumatoid arthritis (RA). Degenerative joint disease has many causes with aging being the primary culprit. There are many causes of DJD; it is considered a multifactorial disease. Osteoarthritis occurs in both men and women and can develop as a result of joint trauma, developmental disorders, and genetic components. Nearly 1% of the population in the United States has some form of rheumatoid arthritis. Rheumatoid arthritis is an inflammatory disease that causes joint disfigurement, swelling, and chronic pain. Rheumatoid arthritis is nearly 3 times more common in women than men. In many cases the best remedy for both forms of arthritis is hemiarthroplasty or total hip arthroplasty (THA). When a THA procedure is performed the entire hip joint is replaced with a hip prosthesis.

Diagnostic Criteria for the AP Hip Projection

Because the hip is imaged routinely in radiology departments, it is important to know the diagnostic criteria for imaging the various projections of the hip. An accurately positioned AP hip radiograph will show the ischial spine aligned with the pelvic brim and the sacrum and coccyx aligned with the pubic symphysis. When properly positioned the obturator foramen is open. The position of the femur is also important and should be internally rotated 15-20 degrees. When properly rotated the femoral neck is not foreshortened. The greater trochanter is seen laterally in profile, and the lesser trochanter is superimposed on the femoral neck. This is what is seen when the leg is internally rotated properly with an imaginary line connecting the femoral epicondyles is parallel with the tabletop. Quite obviously the technologist should not force internal rotation of a potentially fractured or dislocated hip. Doing so may result in injury to the blood supply and nerves in the area of injury. Those likely to have a fracture or dislocation of the hip joint often present with pain, the affected leg in external rotation, and loss of joint function.

The following structures should be seen within the collimated field of view on the AP hip view: The lower one-third of the ilium, one half of the sacrum, coccyx, and symphysis pubis. The acetabulum, greater and lesser trochanters, femoral head and neck and all surrounding soft tissues should also be demonstrated. Some common errors seen on poorly positioned AP hip radiographs include misalignment of the midsagittal plane of the sacrum with the symphysis pubis, narrowing of the obturator foramen, and external rotation of the femur. When properly position and there is no rotation of the pelvis, the ischial spine is aligned with the pelvic brim. The ischial spine should be closer to the acetabulum than to the pelvic brim. When the ischial spine closer to the acetabulum the patient should be rotated towards the affected hip. Foreshortening of the femoral neck is caused by an externally rotated hip, which also places the lesser trochanter in profile. Correct positioning of the leg, in the absence of acute trauma, is to rotate it internally until the epicondyles of the femur are parallel with the tabletop.

There is a wide range of exposures used to image the pelvis and proximal femur. These exposures depend of the patient’s age, amount of bone mineralization, and whether or not film-screen imaging or digital imaging is being used. Generally, 60-85 kVp is used to image the pelvis or hip. The pelvis of infants and small children can be optimally demonstrated using the appropriate mAs and kVp in the range of 60-70. Adult size patients can be adequately imaged using 75-85 kVp. These exposures must be adjusted when the patient has either bone loss disease such as osteoporosis, or sclerotic disease such as Paget’s. Other than positioning errors, one of the most common reasons for repeating a radiograph is sub optimal exposure technique. The visualized sacrum and acetabulum must be well penetrated and have sharp clear bone edge contrast. Equally important is that patients are not routinely overexposed. With digital imaging in particular there is the tendency to overexpose the patient and have a diagnostic radiograph. Each manufacturer sets the optimal exposure for digital imaging when using their x-ray unit. Perhaps the best exposure practice, though highly unpopular, is to use a fixed technique exposure chart and use radiographic calipers to measure the part. Advanced charts will account for body mass index (BMI) as well. Measuring the part is one of the best ways to practice ALARA with film-screen and digital imaging. Summaries of the diagnostic criteria for the AP hip projection are listed in the table below.




Diagnostic Criteria for the AP projection of the Hip

    The AP view should demonstrate the hip joint (acetabulum and femoral head) with the femur internally rotated.

    • Include the entire pubis and ischium, and inferior third of the ilium. Half of the sacrum, coccyx, and the entire pubis bone of the affected side to include the symphysis joint. The femoral head, neck, greater trochanter, and lesser trochanter should be entirely seen. When the hip is requested and the patient has a hip prosthesis, the entire hip prosthesis must be demonstrated along with the anatomy required for the hip view.
    • Internally rotate the hip unless an obvious injury from trauma has occurred. These patients will present with groin pain on movement and an externally rotated leg. The leg is not internally rotated for the trauma hip projection.
    • Include the proximal femur through the lesser trochanter so not to miss an intertrochanteric fracture.
    • The ischial spine is aligned with the pelvic brim; the midline of the sacrum and coccyx is aligned with the pubis symphysis joint. The obturator foramen is opened without distortion. This is accomplished by making sure both anterior superior iliac spines are equidistant from the tabletop. The femoral neck is demonstrated without foreshortening with the greater trochanter profiled laterally and the lesser trochanter medially and slightly superimposed on the femur.

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These three radiographs demonstrate the proper positioning of the hip for the AP view. In each of these three scenarios the required anatomy for the AP hip radiograph is demonstrated. The radiograph on the left (A) is of a child as you can see from the incomplete union of the innominate bone at the acetabulum. The epiphyseal plates of the femoral head and greater trochanter also indicate the patient is a child. The middle radiograph (B) shows the anatomy and prosthesis from a THA. This radiograph shows the proper positioning when a hip prosthesis is the subject. When the hip is requested and the patient has a hip prosthesis, the entire hip prosthesis must be demonstrated along with the anatomy required for the hip view. The radiograph on the right (C) shows an adult hip in which the inomminate bone is fused into a composite bone at the acetabulum. These are optimal radiographs that meet all diagnostic criteria stated for the AP hip.
Radiograph #34

image034 This patient presented to the emergency room on a backboard following a traumatic fall. The patient reported extreme pain and had an externally rotated leg. Discuss the proper handling of the patient for the AP hip projection, and tell whether or not this radiograph meet the diagnostic criteria for the AP hip view?

Critique of Radiograph #34

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    This is a good radiograph of the left hip in terms of demonstrating the required anatomy. The normal angle between the axis of the femoral shaft and neck of the femur is 120-130 degrees. Here we see the angle is more acute approaching 90 degrees. Whenever a trauma patient presents with an externally rotated leg it should not be manipulated for imaging. The technologist properly imaged this patient in the “as is” position. The obturator foramen is open; the pubis and ischium are correctly displayed. The slight amount of rotation of the pelvis due to the midsagittal plane of sacrum not being aligned with the symphysis pubis is negligible. The pubis symphysis is entirely demonstrated and the field of view properly collimated. The radiographic exposure technique is adequate to visualize the acetabulum and proximal femur. Overall this is a high contrast exposure that has burned out the soft tissues. While bone pathology can be adequately characterized, soft tissue detail is missing and the sacrum is underpenetrated. This radiograph should be repeated!

Radiograph #35

image035 A medical history of chronic hip pain was given on the imaging request for this patient. Does this radiograph meet the diagnostic criteria for the AP hip projection?

Critique of Radiograph #35

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    The leg is internally rotated to profile the greater trochanter laterally. The femoral neck is in profiled demonstrating the intertrochanteric crest and lesser trochanter superimposed on the femur. It is required that the entire pubis bone be included on the unilateral hip view. More of the ilium and the lateral half of the sacrum should also be included. This exposure technique is optimal showing good trabecular bone pattern and sharp cortical bone edges. Soft tissue surrounding the hip is displayed in good detail. Radiographic technique adequately penetrates the acetabulum. Unfortunately, this radiograph should be repeated to include the entire pubis bone and symphysis, half of the sacrum, and the lower third of the ilium. No change in exposure factors is needed.

Radiograph #36

image036 This radiograph was taken for acute pain without a history of trauma. Discuss why this radiograph meets the diagnostic criteria for the hip projection. Also discuss what would make this a better radiograph.

Critique of Radiograph #36

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    This is a very good radiograph of the hip. It meets the diagnostic criteria for the AP hip view for several reasons. Notice that the technologist included the entire pubis and ischium bones. The distal third of the ilium is also included. This allows us to see the sacrum and obturator foramen so we can determine if the pelvis is rotated. The entire left pelvic brim is demonstrated along with the hip joint and proximal femur. Exposure factors selected are superb providing optimal bone penetration, excellent subject contrast, and optimal radiographic density.

Radiograph #37

image037 This person was brought to a local emergency room by ambulance following a fall at a local grocery store. Upon completing this radiograph the radiographer notice the patient had a recent THA. Does this radiograph meet the diagnostic criteria for the AP view of the hip based on the history given?

Critique of Radiograph #37

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    This radiograph is a great example of why we us a diagnostic criteria for every radiographic projection we make. For the hip radiograph it is required that the entire pubis bone and symphysis be demonstrated. There is a questionable fracture in the wall of the acetabulum; however, it is not completely demonstrated. Also the distal one-third of the ilium along with the entire prosthesis should be seen. This gives the radiologist the proper amount of anatomy to evaluate for trauma. If there are screws in the prosthetic cup they too are evaluated for signs of loosening or infection. This is a good radiograph as far as technique selection and positioning of the hip. There is good penetration of the prosthesis while preserving bone detail and subject contrast. What is good about this radiograph is the fine detail within the soft tissue of the hip. There is good bone detail and clear cortical bone edges. However, this radiograph should be repeated to include the required anatomy, especially the bone surrounding the prosthetic cup.

Radiograph #38

image038 This radiograph was taken because of a traumatic event and the patient has a history of having total hip arthroplasty prosthesis. The emergency room physician wanted a radiographic evaluation of the hip and prosthesis. Give your critique of this radiograph using the diagnostic criteria for the AP hip projection.

Critique of Radiograph #38

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    A hip prosthesis can be just a few centimeters long; others can extend down to the middle of the femoral shaft. It is common practice to use a 10 X 12 inch cassette; however, it may not always be long enough to include the required hip anatomy and the entire prosthesis. This is what has happened on this radiograph, the required anatomy (including the entire pubis bone and symphysis), and distal prosthesis are not seen. I like to use a 14 X 17 turned lengthwise for hip imaging when there is a known prosthesis. This is especially the case when using digital imaging because there is no film to waste. The digital image can be collimated to the area of interest so not to exposed unnecessary tissue. The radiographic exposure technique is adequate for this image; it demonstrates soft tissue and bone adequately. Repeat to include the entire prosthesis and pubis bone.

Radiograph #39

image039 Following surgery in which a THA was performed, the orthopedic surgeon requested AP and lateral views of the hip. Give your critique of this AP hip view using the diagnostic criteria.

Critique of Radiograph #39

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    This radiograph meets the diagnostic criteria for positioning of the hip. The prosthesis is entirely demonstrated and centered on the film. However, the radiographic exposure technique could be improved. Poor penetration of the hip bone, especially the acetabulum made this radiograph nondiagnostic. It appears that the kVp is inadequate to penetrate the acetabulum; however, using high mAs has produced overexposure. Increasing the kVp will improve bone penetration and maintain adequate density. A concommittant reduction in the mAs is needed to optimize overall density and contrast. This radiograph must be repeated with adjusted exposure factors to penetrate the acetabulum and provide greater bone detail.

Radiograph #40

image040 This patient slipped and fell on ice and presented to a local emergency room complaining of right hip pain. Clinical history included, “THA 6 months ago.” Give your critique of this radiograph using the diagnostic criteria.

Critique of Radiograph #40

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    There are several things that are good about this radiograph. First, the radiographic exposure technique displays great subject contrast. The main reason contrast is optimal penetration of the proximal femur. This resulted in good contrast between cortical and spongy bone. The positioning of the hip is also very good: the hip is in internal rotation, and the portion of the obturator foramen that is demonstrated appears to be open. The entire prosthesis, acetabular cup, and supporting screw are well demonstrated. The technologist was not at all generous with the collimator. A portion of the ilium and screw in the prosthetic cup is clipped. Also a portion of the pubis bone is omitted. However, the orthopedic surgeon approved that the radiograph did not need to be repeated.

Radiograph #41

image041 This radiograph was taken for trauma in which there were substantial multiple injuries to the pelvis. It was requested that a coned view of the left hip be made because it was clipped on the portable pelvis view. What is your critique of this AP hip view based on its diagnostic criteria?

Critique of Radiograph #41

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    There are multiple injuries involving the left side of the pelvis. The pelvic brim is disrupted, as is the posterior column of the acetabulum. The sacrum/coccyx is in the midline aligned with the pubis symphysis. The femoral head is separated from the acetabulum and possibly displaced. Demonstration of the pubic symphysis reveals diastases of this joint. In spite of these injuries the technologist was able to accurately position for the AP view. It would have been nice to see more of the sacroiliac joint; however, the amount demonstrated is within the guidelines of this diagnostic criterion. The radiographic exposure technique displays high contrast, which has limited the visualization of the greater trochanter and soft tissues surrounding the proximal femur. Overall this is a satisfactory radiograph that meets the diagnostic criteria for the AP hip view.

Diagnostic Criteria for the Frogleg and Axiolateral Hip Projections

To properly diagnose the hip, two projections at 90-degrees to each other are needed. The AP and lateral projections are the most commonly taken views of the hip. There are two basic projections of the hip that can be taken for the lateral view. One projection is the AP axial lateral (a.k.a. frogleg lateral). The other projection is called the true lateral (a.k.a. axiolateral, horizontal beam lateral, or inferosuperior) projection. The axiolateral projection is known as the trauma lateral because the x-ray beam is directed horizontally. This projection is taken whenever the patient history involves acute trauma in which manipulation of the femur is contraindicated. In the absence of trauma the AP axial lateral is an acceptable method to evaluate the proximal femur and hip joint. An advantage of the frogleg view is that is displays uniform contrast in the hip joint and proximal femur because there is less soft tissue to penetrate. When properly performed, this projection is also a functional image of the rotated hip joint.

The axiolateral projection is a true lateral view of the hip joint and femur. The downside to this projection is that the acetabulum while is seen is often sub optimally penetrated and lacks sharp bone detail. Several factors can make a horizontal beam hip projection optimal, for example, having correct tube-part-image receptor alignment, properly abducting the unaffected leg, and using a radiographic grid. The radiograph exposure technique, good collimation, and use of a compensating filter will also help improve the overall quality of the image. Excessive scatter caused by using high kilovoltage to penetrate the acetabulum as the beam passes through soft tissue can degrade subject detail. To reduce scatter that may degrade the image use a grid and apply tight collimation. All of these measures will reduce the amount of scatter reaching the image receptor. Sometimes backscatter from the cassette can diminish the quality of the radiograph by fogging it. Placing a lead blocker along the back of the cassette will reduce backscatter.

Incorrect tube-part-film alignment is perhaps the most common reason for repeating the axiolateral view. To properly demonstrate the affected hip, place the unaffected leg in maximum flexion, and then adduct it so that the femur is nearly vertical. This movement removes the soft tissues of the unaffected leg away from the affected hip joint so that it is better visualized. The reason the axiolateral view is so important is that it minimizes risk of injury to the femoral vessels and nerves, or causing displacement of unstable fracture fragments. Consider the course of the vessels like the femoral artery and vein through the pelvis and proximal femur. Keep in mind that the femoral nerve and the femoral vein also are in close proximity of the femoral artery. The CT images below show the course of the femoral artery. Keep in mind that the femoral artery runs a constant course lateral to the femoral vein as they emerge from behind the inguinal ligament. The femoral nerve is found lateral to the femoral artery so that the order from medial to lateral is the femoral vein, femoral artery, and femoral nerve. This relationship is fairly constant in most individuals. The goal of imaging the hip when a fracture is suspected is to not cause injury to vital vessels and nerves during the procedure.

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These two 3D volume rendered CT images demonstrate the course of the femoral artery (B) at its proximal origin from the external iliac artery (A). The femoral vein and femoral nerve runs along a course parallel to the artery. The CT 3D volume rendered image on the left gives an oblique projection to show the relationship of the artery at the hip joint. The iliac vessels pass over the pelvic brim without entering the true pelvis. The external iliac artery passes just anterior and medially to the hip joint in the proximal part of the limb. The relationships can be seen on the additional images presented below.
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The 3D volume rendered CT image with bone overlay is seen on the left. This image shows the course and branching of the common iliac artery into the external iliac artery becoming femoral artery. Of particular interest is the course of the femoral artery at the hip and knee joints. The sagittal maximum intensity projection (MIP) CT image (middle) and coronal (right) better demonstrate its course. The femoral nerve and vein run near and parallel with the artery and can be injured by bone fracture. Penetrating injuries such stab or gunshot injuries can injure these and other delicate vessels. Being aware of the location of the femoral artery will helps one understand the rationale for not manipulating the hip with certain types of trauma. Risk of injury to the femoral artery, nerve, or vein is the reason the horizontal beam lateral is the preferred projection when fracture of the femur is highly suspected. The AP Axial projection, also called the frogleg lateral can be performed in the absence of trauma in most cases.

The diagnostic criteria for the frogleg (AP Axial) hip projection:
      • For the AP frogleg lateral the ischial spine is aligned with the pelvic brim, the midline of the sacrum and coccyx is aligned with the pubis symphysis joint. The obturator foramen should appear open without distortion. This is accomplished by making sure both anterior superior iliac spines are equidistant from the tabletop.
      • The degree of hip and knee flexion and the angle of the femur to the tabletop will determine the relationship of the lesser and greater trochanters to the proximal femur. In a properly positioned frogleg lateral the femoral neck is demonstrated with minimal foreshortening, the greater trochanter is superimposed on the proximal femur, and the lesser trochanter is projected medially in profile.
      • Optimally, the femur is placed at an angle of 60-70 degrees with the tabletop. Abducting the femur away from the midline will demonstrate the femoral neck with the greater trochanter projected distal to it. Proper abduction of the femur will reduce foreshortening of the femoral neck. For example, abduction of the femur so that it rest on the tabletop will demonstrate the greater trochanter positioned high, near the level of the femoral head, and the neck of the femur almost on end. Likewise, when the femur is at about 30 degrees from vertical, the neck of the femur is not foreshortened, and the greater and lesser trochanters are near the same level. An improper position intermediate to the tabletop (about 45 degrees) shows partial foreshortening of the neck and the greater trochanter midway between the head of the femur and the lesser trochanter.


Diagnostic Criteria for the Axiolateral (Inferosuperior) Hip Projection:
      • On an accurately positioned axiolateral hip radiograph what should be demonstrated is: 1) the lesser trochanter in profile medially, 2) the greater trochanter superimposed on the femoral shaft, 3) the femoral neck in the center of the collimated field and not foreshortened, and 4) the articulation of the acetabulum with the head of the femur entirely demonstrated and well penetrated.
      • Good bone detail should be seen in the acetabulum, femoral head, femoral neck, greater trochanter, lesser trochanter, femoral shaft, and ischial tuberosity. The proximal femoral shaft should not be overexposed.
      • Because the x-ray beam passes through the affected hip and a gonadal shield cannot be used effectively, tight collimation should be used. An extension cylinder can also be used to reduce the amount of primary beam radiation exposing the patient. Tight collimation or using other beam limiting devices will also reduce the amount of scatter produced. Using tight collimation will greatly improve contrast, especially when used in combination with a grid.
      • Proper alignment of the tube-part-image receptor is achieved by placing the cassette parallel to the femoral neck and perpendicular to the central ray (CR). To assure the grid cassette is parallel to the femoral neck use a cassette holder. Unless contraindicated by injury internally rotate the affected leg 15-20 degrees to align the femur.
      • Radiographic exposure should penetrate the acetabulum and sharply demonstrate its bone edges. The proximal femur should not be overexposed.

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This frogleg axial lateral demonstrates the proper positioning of the hip joint in the absence of trauma. Notice the symphysis joint is included and the obturator foramen is open. The femoral neck is not foreshortened and the greater trochanter is seen below the neck. The acetabulum is well penetrated without burnout of the proximal femur or soft tissues within in the pelvis.
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This axiolateral hip view demonstrates the proximal femur in a “true lateral” projection. This patient suffered a fall and was suspected of having a fracture, which is seen at the arrow. The leg was not internally rotated because of the patient history of trauma. Notice that the femoral neck is not foreshortened, the acetabulum is well penetrated, the area of interest is well collimated, and the greater trochanter is projected below the neck. Because of tight collimation and good alignment of the tube-part-image receptor the contrast is evenly distributed and subject detail is optimal.
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This radiograph demonstrates a properly made axiolateral projection taken in the recovery room following a total hip arthroplasty procedure. Notice that the entire prosthesis is demonstrated on the radiograph, which is required for this clinical history. There is good positioning of the part, which has been slightly rotated internally. The neck of the prosthesis is not foreshortened and the prosthetic cup appears to have no distortion. The exposure technique shows good contrast between bone and metal. This too is an optimal radiograph.
Radiograph #42

image042 This set of radiographs was taken on a patient who fell about a month after a hip pinning. The emergency room physician requested to see if the hip had suffered an acute fracture from the trauma. The AP view is included to provide you with the complete study. What is your critique of the axial lateral (bottom radiograph) using the diagnostic criteria for each view?



Critique of Radiograph #42

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    The AP view (top) is positioned with the femur in internal rotation. The lesser trochanter is seen medial and the greater trochanter profiled laterally. It is assumed that the hip appears to not be rotated based on the obturator foramen being open. The relationship of the symphysis to the sacrum/coccyx is not demonstrated. The internal fixating pins from the previous surgery is entirely included on both radiographs. There is good penetration of the hip joint and acetabulum on both views. As for the frogleg lateral view (bottom) the positioning is adequate, but not optimal. The neck of the femur is slightly foreshortened. Abducting the leg away from the midline helps elongate the femoral neck. The radiographic exposure technique for both views shows a well-penetrated femoral head and acetabulum. Good bone detail is seen throughout the visualized field. Soft tissue structures like the urinary bladder and bowel gas in the rectum is displayed in balanced with bone detail. This is an excellent radiographic exposure technique.

Radiograph #43

image043 The radiograph was taken on an ambulatory patient whose chief complaint was pain in the hip area. There was a traumatic event 2 weeks prior to this radiograph being taken. The radiographer decided to take a frogleg lateral rather than a horizontal beam lateral view. Does this radiograph meet the diagnostic criteria for the frogleg projection?

Critique of Radiograph #43

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    Since this patient presents with a history of trauma the entire ischium and pubis bone should be demonstrated along with the hip joint. Including the required anatomy is important since the patient’s pain is not specific to the hip. This is an unacceptable radiograph because (1) the pelvis is rotated, (2) the femoral neck is foreshortened, and (3) the greater trochanter is superimposed on the femoral neck. When the pelvis is not rotated the sacrum is aligned with the symphysis pubis and the obturator foramen opened. The greater trochanter is projected to the level of the femoral head, and the lesser trochanter projected medially. Also the neck of the femur is not profiled in a way that demonstrates the smooth anatomical curvature from the femoral neck along the trochanters. To correct these positioning errors, decrease flexion of the femur to 60-70 degrees with the tabletop. To project the lesser trochanter medially, add slightly more adduction to the femur. This will also elongate the femoral neck and place the greater trochanter lower than the femoral head. The radiographic exposure for this projection adequately demonstrates the anatomy; however it should be repeated correcting stated positioning errors.

Radiograph #44

image044 This is a postoperative radiograph taken to evaluate placement of a hip prosthesis. This portable axiolateral (aka inferosuperior) projection was taken in the recovery room. Does this radiograph meet the diagnostic criteria for the horizontal beam lateral hip projection?

Critique of Radiograph #44

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    This would be considered an acceptable radiograph by most; however, it does not meet the diagnostic criteria for the horizontal beam lateral projection. If proper part-tube-cassette alignment been achieved this would have been an optimal radiograph. Aligning the tube-part-image receptor is critical to imaging the hip. This is especially important when using a grid because contrast can be affected by off-grid alignment. In this case, the acetabulum and prosthetic cup lacks proper contrast resolution and subject detail. The key to bringing out subject detail on the horizontal beam lateral is to properly center the part and have the central ray pass through the acetabulum. It is important that the acetabulum is well-penetrated and cortical bone displays sharp detail. Applying tight collimation will increase subject detail. In keeping with ALARA the field of view should be well centered and collimated. A coned down view of the acetabulum is all that is needed since tight collimation of the acetabulum will provide subject detail needed to evaluate the screws in the prosthetic cup.

Radiograph #45

image045 The technologist repeated radiograph #44 and this was the resulting image. Does this portable axiolateral projection of the hip meet the diagnostic criteria?

Critique of Radiograph #45

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    Again, the entire hip prosthesis did not need to be repeated. This could be limited to only a coned down view of the acetabulum. The entire prosthesis is included and the posterior portion of the pelvis. Good bone detail and contrast of the metal prosthesis is seen in the femur. The radiographic exposure technique is adequate; however, to improve detail around the acetabulum better collimation is needed. Notice that the screw holding the prosthetic cup in place shows poor subject contrast between it and the surrounding acetabulum. While this radiograph does not need to be repeated as images with the C-arm during surgery may be adequate to visualize this area, the technologist should always make sure to provide detail in this area. I would recommend a second coned down view of the acetabulum well centered to the cassette and central ray. This will provide detail of the pelvis the orthopedic surgeon needs to see. This is a good film overall and should be included with the study.

Radiograph #46

image046 This axiolateral (aka inferosuperior) projection of the hip was taken because the patient fell. The patient was rehabilitating from a total hip replacement approximately 3 weeks prior to the fall. The ordering physician wanted the radiologist to evaluate the hip prosthesis. Does this radiograph meet the diagnostic criteria considering the patient’s history?

Critique of Radiograph #46

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    This radiograph shows adequate positioning of the femur and proper tube angle to demonstrate the acetabulum. The reasons this radiograph should be repeated include: not demonstrating the entire prosthesis, linear artifacts throughout the image, and underpenetration of the acetabulum. The lines creating artifacts on the radiograph are not grid lines. Notice that they are irregularly spaced and contoured. These lines are caused by elastic in the patient’s garment. Generally elastic does not create artifacts, but in this case it obscures the image. Another problem with this radiograph is that the entire prosthesis is not seen. Often the technologist does not know the length of the prosthesis. We assume the prosthesis will be seen when using the standard 10 X 12 inch crosswise cassette. Unfortunately this was not the case with this prosthesis. Both the proximal and distal ends of the prosthesis must be demonstrated. Lastly, the radiographic exposure appears to be adequate for the femur; however, the acetabulum is underpenetrated. A couple of things can be done to better demonstrate this area, for example using tighter collimation and increasing the kVp. This radiograph must be repeated to better visualize the bone surrounding the prosthetic cup and demonstrate the entire prosthesis.

Radiograph #47

image047 This frogleg (AP axial) lateral radiograph was taken on an ambulatory patient whose chief complaint is chronic left hip pain. Does this radiograph meet the diagnostic criteria for this projection?

Critique of Radiograph #47

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    This radiograph should be repeated because poor positioning resulted in foreshortening of the femoral neck. The greater trochanter is on the same plane as the femoral head suggesting the femur should be adducted. To correct the positioning seen here the femur should be adducted from its current position to 45 degrees from the body. The radiographic exposure technique is good for the proximal femur. Structures like the intertrochanteric crest and acetabulum are well-penetrated. All required anatomy is seen including the symphysis pubis, one-half of the sacrum, and the lower one-third of the ilium.

Radiograph #48

image048 This frogleg lateral (AP axial) radiograph was taken on an ambulatory patient whose chief complaint is chronic left hip pain. Does this radiograph meet the diagnostic criteria for this projection?

Critique of Radiograph #48

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    This is an accurately positioned frogleg hip radiograph. Notice that the femoral neck is centered in a well-collimated field. The lesser trochanter is demonstrated in profile medially and the proximal femur is superimposed on the greater trochanter. This is a great radiograph in terms of the radiographic exposure technique. The acetabulum is well penetrated while preserving good contrast between bone and soft tissues of the thigh. If this radiograph been taken for trauma the entire pubis bone should be demonstrated! If the lateral one-half of the sacrum/coccyx and symphysis pubis is seen on the AP view this radiograph does not need to be repeated. Overall, this is a great radiograph!

Radiograph #49

image049 Discuss why the horizontal beam lateral view does not meet the diagnostic criteria for a post surgical radiograph of the hip?

Critique of Radiograph #49

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    This radiograph does not meet the diagnostic criteria because the prosthetic cup is not adequately visualized. While there is good detail of the visualized femur there is gross underpenetration of the acetabulum. The CR must pass through the acetabulum in order to properly see the prosthetic cup. Because of the patient’s size, some fat tissue may need to be pulled up and out of the path of the CR if possible. Otherwise using an extension cylinder type cone devise and increasing the kVp about 30% will demonstrate the required anatomy. But the most important modification needed to improve this radiograph is to get the unaffected leg out of the field of view. You may find this a difficult task for some patients; therefore you will have to be creative when taking this projection. Unless the CR passes through the acetabulum you will not get a good radiograph on this patient. Alignment of the CR to the part and image receptor, as well as using tight collimation is the only way to get optimal subject detail on this patient.

Radiograph #50

image050 This patient was brought to a local emergency room following a traumatic fall. Clinical signs of injury included acute pain, bruising, and swelling. Discuss why this horizontal beam lateral view does not meet the diagnostic criteria for the lateral projection of the hip?

Critique of Radiograph #50

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    Given a history of acute trauma the leg is not internally rotated. As a result, the trochanters are not positioned in radiographic profile. The key to imaging in this scenario is to align the CR perpendicular to the femoral neck. But what makes this radiograph unacceptable is that the part is not centered to the image receptor, nor is to CR aligned to the part. This has resulted in poor penetration of the acetabulum and femoral head. To properly penetrate these structures it is necessary for the part to be aligned with the center of the grid. This radiograph represents off-centered grid alignment, which has diminished subject detail and contrast. Also notice that the collimator is wide open demonstrating a significant amount of useless background density (arrow). So, applying good tight collimation, slightly increase the kVp, and aligning the tube-part-image receptor will greatly improve radiographic contrast and maximize image quality for this projection.

Radiograph #51

image051 Discuss why this horizontal beam lateral projection taken on an elderly patient for suspected fracture does not meet the diagnostic criteria for the lateral projection of the hip?

Critique of Radiograph #51

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    There is a significant amount of motion artifact seen on this radiograph. When imaging the axiolateral projection the unaffected leg is flexed and raised to the vertical position to move the thigh out of the collimated field. The unaffected leg is rested on the collimator or leg support out of the path of the x-ray beam. Properly supporting the unaffected leg is the best way to reduce motion. Technical factors that can be changed to reduce motion include increasing the mA and decreasing the exposure time. Also to better penetrate the acetabulum increase the kVp and decrease the mAs using the 15/50 rule. It is also recommended to use an extension cylinder to limit the beam. Combining proper tube-part-image receptor alignment with recommended technique change, will result in a well-penetrated radiograph. In any case, this radiograph should be repeated because of patient motion, poor centering that resulted in loss of subject detail, and poor penetration of the acetabulum.

Radiograph #52

image052 This patient presented at a local emergency room with a chief complaint of right hip pain. The concern for the patient at triage was possibility of a dislocation or fracture of the right hip prosthesis. Does this radiograph meet the diagnostic criteria for the axiolateral projection?

Critique of Radiograph #52

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    The clearest observation is that the hip joint is not centered on the radiograph. It appears that the CR passed through soft tissue (white X) whereas it should pass through the prosthetic cup (yellow X). Good tube-part-image receptor alignment is a critical component to making a good axiolateral hip radiograph. To accomplish the proper alignment of the subject, the cassette holder should be lowered and centered to the femur. The CR should enter the femur perpendicular to the femoral neck. Be sure to use tight collimation to enhance contrast between bone and metal, and enhance bone edge of the acetabulum. A goal of the exposure technique should be to show early signs of complications such as infection or loosening of the prosthetic cup. Improper centering of the part, poor collimation resulting in loss of subject detail, and poor penetration of the acetabulum are reasons this radiograph must be repeated.

Radiograph #53

image053 This patient presented at a local emergency room with a chief complaint of right hip pain. Triage of the patient revealed a recent fall; however, the patient was ambulatory at presentation. Does this radiograph meet the diagnostic criteria for the axiolateral projection?

Critique of Radiograph #53

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There are two major reasons for repeating this radiograph: the femur is not optimally positioned and the hip joint is not well demonstrated due to superimposition of soft tissue. The greater trochanter is projected posterior, and the lesser trochanter superimposed on the femoral neck. This indicates that the affected leg is externally rotated. To properly position the affected hip, internally rotate the femur until the epicondyles are parallel with the tabletop. This will place the lesser trochanter in profile medially and the greater trochanter superimposed on the neck of the femur. Radiographic technique is adequate to visualize the proximal femur; however, significant overlap of the unaffected thigh obscures the femoral head and acetabulum. To correct this problem the unaffected leg should be flexed and abducted. Sometimes it can be a little bit embarrassing to the patient, but have them pull excess tissue out of the collimated field. Use tight collimation and increase the kVp 15%, which will penetrate the acetabulum, improve subject contrast, and minimize patient dose.

Radiograph #54

image054 Does this post-surgical axiolateral hip projection meet the diagnostic criteria?

Critique of Radiograph #54

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    This radiograph displays optimal positioning and collimation of the hip. What is great about this radiograph is that it includes the entire prosthesis. What this radiograph is lacking is good penetration of the acetabulum, and bone detail against the metal of the prosthetic hip. I would suggest using an extension cylinder and center the CR to the hip joint to bring out detail of the prosthetic cup and acetabulum. This will give the surgeon the needed detail around the acetabulum. Because there is graininess and loss of detail around the acetabulum an increase in the mAs is necessary. Overall, this radiograph should be included in the hip study, and add a coned or collimated view of the hip joint to complete this axiolateral view.

Radiograph #55

image055 This axiolateral hip projection was taken on a patient who reported trauma post 2 weeks. Does this radiograph meet the threshold for a diagnostic radiograph, why or why not?

Critique of Radiograph #55

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    Normally when the patient history references trauma the femur is not internally rotated as is seen here. However, the clinical history is post 2 weeks trauma indicating there is a low probability of fracture and the pain threshold is low. Therefore, we can conclude that the positioning of the femur in external rotation is unacceptable. Notice that the femoral neck is not foreshortened, which indicates the CR is perpendicular to the part. FYI: the greater trochanter can be evaluated on the AP view of trauma patients whose leg is externally rotated for the axiolateral. The radiographic exposure technique is optimal for the hip joint, proximal femur, and surrounding soft tissues. There is good tube-part-film alignment. Repeat this radiograph with the femur in internal rotation and add 15% increase in kVp to better penetrate the acetabulum. Also use close collimation to increase subject contrast when increasing the kVp.

Radiograph #56

image056 These two radiographs, AP projection (top) and frogleg projection (bottom) are taken to evaluate the hip post trauma. Do these radiographs together meet the diagnostic criteria for the AP and lateral views of the hip?

Critique of Radiograph #56

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    These are both good radiographs that meet their respective diagnostic criteria. Pediatric trauma imaging of the hip is a bit different from adult imaging. These radiographs are shown to emphasize two important points about infant imaging: 1) only slightly internally rotate the femur, and 2) slightly abduct the legs (bottom radiograph). Some pediatric radiologists prefer simple abduction with slight internal rotation of the legs for the frogleg axiolateral view. Inquire at your institution which method is preferred. This positioning technique allows for evaluating the hip joints for conditions like transient (toxic) synovitis, or avascular necrosis of the hip. The technologist did an excellent job on imaging this patient. Good exposure technique was selected, and shielding applied to the upper abdomen in keeping with ALARA.

Radiograph #57

image057 Consider this frogleg hip radiograph taken because of a fall. The patient had good mobility of the hip so the technologist decided to take a frogleg projection. Does this view meet the diagnostic criteria for the frogleg lateral hip projection?

Critique of Radiograph #57

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    What should be demonstrated on a properly positioned frogleg lateral projection are the proximal third of the femur, greater and lesser trochanters, femoral neck, hip joint and acetabulum, entire ischium and pubis bone, symphysis pubis, and half of the sacrum and coccyx. The femoral head should be centered in a well-collimated field. As for this radiograph the greater trochanter is displayed slightly above the lesser trochanter resulting in foreshortening of the femoral neck. Optimally the femur should be flexed 60 to 70 degrees to the tabletop to properly demonstrate the trochanters and femoral neck relationship. The pelvis does not appear to be rotated; however, at least half of the sacrum and entire obturator foramen should be seen to determine this. Radiographic exposure technique shows a slightly high contrast. Decreasing the mAs slightly with a small increase in kVp will give better penetration of the acetabulum. Use tight collimation superiorly to include only the distal third of the ilium keeping with ALARA. This radiograph should be repeated due to underpenetration of the acetabulum.

Radiograph #58

image058 Consider this frogleg hip radiograph taken on a young male patient. His chief complaint is hip pain after playing basketball; no trauma. Does this view meet the diagnostic criteria for the frogleg lateral hip projection?

Critique of Radiograph #58

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    This radiograph demonstrated the required anatomy for the frogleg lateral projection. Good bone detail is seen in all structures demonstrated, especially the acetabulum and hip joint. The femoral neck is only slightly foreshortened, and the trochanters are well visualized though slightly dispositional projected. The cause of this is not the degree of flexion of the femur. Notice that the sacrum/coccyx is not aligned with the symphysis pubis and the ischial spine is not superimposed on the pelvic brim. This has caused incomplete opening of the obturator foramen. These finding indicate the pelvis is rotated, which caused the hip to be displayed incorrectly. To properly position the hip make sure the distance of the anterior superior iliac spines (ASIS) are equidistant from the tabletop when the femur is flexed and abducted for the frogleg projection. This amount of rotation does not require repeating of this radiograph in keeping with the practice of ALARA.

Radiograph #59

image059 This radiograph was taken for trauma. Does this axiolateral projection meet the diagnostic criteria?

Critique of Radiograph #59

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    This is outstanding positioning of the hip for the axiolateral projection. The greater trochanter, femoral neck, and proximal femur are well demonstrated. However, the head of the femur, acetabulum, and hip joint is poorly visualized. This is due to using high contrast imaging technique, and failure to get the unaffected femur flexed and abducted out of the field of view. Good tight collimation has been applied in keeping with ALARA, unfortunately, there is incorrect tube-part-image receptor alignment. The CR should pass through the acetabulum to get the most concentrated portion of the x-ray beam into the densest part. When this projection is repeated, be sure to center the part so that the CR enters the hip joint and the grid cassette is aligned parallel and centered to the femoral neck. Other factors that will make this an optimal radiograph is to increase the kVp 15% with a proportional decrease the mAs using the 50/15 rule, flex and abduct the unaffected femur so that soft tissues do not superimpose on the femoral head.

Radiograph #59b

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These three coronal CT images are reconstructed from axial data. These images are presented to demonstrate why thin slice CT imaging with coronal and sagittal reconstructions is the standard for characterizing complex fractures of the acetabulum. We can certainly appreciate the complexity of some fractures, like the one seen on these CT images. These images further emphasizes why it is important to penetrate the acetabulum on plain film hip radiographs, especially the horizontal beam lateral.



Radiograph #59c

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    These two sagittal reconstructed CT images taken at different slice/intervals demonstrate the complexity seen with some types of acetabular fractures. These images give a perspective similar to the horizontal beam plain film projection. The point here is that these types of fractures are hard to see with plain films unless the acetabulum is well penetrated and good bone detail demonstrated. These images demonstrate why CT thin slice imaging with sagittal and coronal reconstructions is the standard for imaging complex hip and pelvic fractures. Plain films are very important in identifying this types of fractures for further imaging.

Summary: AP and Lateral Hip Views

  1. The AP view should demonstrate the hip joint (acetabulum and femoral head) on internal rotation.
    • Include the entire pubis and ischium on the coned down AP view.
    • Internally rotate the hip unless an obvious injury from trauma has occurred. These patients will present with groin pain on movement and an externally rotated leg.
    • Include down below the lesser trochanter so not to miss an intertrochanteric fracture.
    • For the AP hip projection the ischial spine is aligned with the pelvic brim, the midline of the sacrum and coccyx is aligned with the pubis symphysis joint. The obturator foramen of the affected side is open and without distortion.
  2. The AP axial (frogleg lateral) view should demonstrate the acetabulum and femoral head relationship, the femoral neck in profile, and the greater and lesser trochanters.
    • Optimally, the femur is placed at an angle of 60-70 degrees with the tabletop. Abducting the femur away from the midline will demonstrate the femoral neck with the greater trochanter projected distal to it.
    • The frogleg lateral projection is taken when trauma is not reported, or the physician did not specify a true lateral. The patient must be able to flex the affected hip joint and abduct it.
    • A properly positioned frogleg view will demonstrate the ischial spine aligned with the pelvic brim, and the midline of the sacrum and coccyx aligned with the pubis symphysis joint. The obturator foramen will be open and without distortion.
  3. The axiolateral projection (horizontal beam lateral) should be taken when the injury is related to trauma.
    • On an accurately positioned axiolateral hip radiograph what should be demonstrated is: 1) the lesser trochanter in profile medially, 2) the greater trochanter superimposed on the femoral shaft, 3) the femoral neck in the center of the collimated field and not foreshortened, and 4) the articulation of the acetabulum with the head of the femur is entirely demonstrated and well penetrated.
    • Proper alignment of the tube-part-image receptor is achieved by placing the cassette parallel to the femoral neck and perpendicular to the central ray (CR). To assure the grid cassette is parallel to the femoral neck use a cassette holder and unless contraindicated by injury or disease, in the absence of trauma internally rotate the affected leg 15-20 degrees.
  4. Radiographic technique should show good detail about the acetabulum. Bone trabecular pattern should be seen in the pelvis and femur. Equally important is tight collimation. Collimation will reduce the amount of scatter reaching the image receptor, and it will slightly increase the contrast improving the image.
Always ask, "Have I achieved the diagnostic criteria for this view?"



Summary Points

  • The innominate or hip bone is a composite bone formed by the union of the ilium, ischium, and pubis bones.
  • The pelvic brim (ring) is that ring of bone forming the upper limit of the true pelvis. This ring is formed by the two innominate bones and the sacrum.
  • Fractures that spare the pelvic brim and SI joints are stable and less severe than those involving the posterior pelvic brim. Examples of less severe fractures of the pelvis include: avulsions of the iliac spine or iliac crest, ischial tuberosity fractures, wing fracture, unilateral or bilateral pubic rami fracture, some sacral fractures, and sacrococcygeal fracture.
  • Fractures or dislocations of the pelvis resulting in complete posterior arch disruption are most unstable and most severe. These types are caused by vertical shear, anterior/posterior compression, or lateral compression, and result in internal or external rotation of the pelvis. The main cause is SI joint fracture or dislocation, or sacral fracture. These types are rotationally and vertically unstable and cause severe life-threatening hemorrhaging of pelvic blood vessels.
  • The femur is the longest and strongest bone in the body. It functions to transfer the weight of the body through the lower extremity to the foot to facilitate locomotion. Because of the function of weight transference, the hip and knee joints are often the source of chronic pain in some individuals. Likewise, these joints are also likely to be injured due to trauma like a fall or high impact motor vehicle accident.
  • The AP axial frogleg projection (lateral view) of the hip is taken when trauma is not involved. For this projection the CR is directed vertically. When trauma has occurred, the horizontally directed x-ray beam is used for the axiolateral projection.
  • For the routine AP pelvis view, the femurs are internally rotated 15-20 degrees from vertical. Internally rotating the lower extremity places the femoral necks parallel to the image receptor and maximally demonstrates the femoral neck angle. Placing the anterior superior iliac spines (ASIS) of each hip bone equal distance to the tabletop assures the pelvis is not rotated.
  • Trauma imaging of the pelvis should include the 5th lumbar vertebrae because a fracture of the transverse process can be the single indicator of pelvic instability.
  • The pelvic ring (brim) is formed by the two innominate bones and sacrum. Injuries to the pelvic ring can make the pelvis unstable.
  • Posterior pelvic brim fractures are the most serious because they can cause ring opening or ring closing disstabilization. Causes of posterior ring instability include vertical shear, anterior/posterior compression, and lateral compression of the pelvis.
  • Injuries involving the pelvic ring can cause profound hemorrhaging of pelvic vessels.
  • For the AP projection of the pelvis the leg is internally rotated 15-20 degrees to place the femoral neck angle parallel with the image receptor.
  • Internal rotation of the femur will profile the greater trochanter laterally, present the femoral neck without foreshortening, and place the lesser trochanter in slight superimposition on the medial femur. The femur should not be internally rotated when the patient presents with deformity or external rotation of the femur or pain caused by acute trauma.
  • When the pelvis is not rotated, the midline of the sacrum and coccyx is aligned with the pubis symphysis; the ischial spines, when seen are equally aligned or superimposed on the pelvic brim.
  • The inlet view is important because it can immediately identify narrowing or widening of the pelvic ring, identify posterior displacement of the pelvic ring, sacroiliac joint (SI joint) disruption, and/or rotation of the hemipelvis, pubic diastasis or pubic bone overlap, or subtle fractures or impaction of the sacrum.
  • The inlet view is taken with the patient supine and the x-ray beam angled 25-45 degrees caudal and perpendicular to the pelvic brim.
  • The pelvic outlet bound by the sacrum/coccyx posteriorly, the symphysis pubis anteriorly, and flanked by the ischial tuberosities laterally. The primary purpose of the outlet view is to demonstrate the magnitude of vertical displacement of the hemipelvis. The sacral foramina and displacements of the pelvic ring are better appreciated on the outlet view than on the AP pelvis view.
  • The outlet view is obtained with the patient in the true AP position and the tube angled 45 degrees cephalic.
  • Can corroborate vertical displacement of the hemipelvis and visualize the SI joints, and demonstrates the sacral foramina better than the AP pelvis view alone.
  • Both femoral heads should be demonstrated on the outlet view because an anteriorly displaced femoral head is projected above the acetabulum and a posteriorly displaced femoral head is projected below the acetabulum.
  • The Judet view demonstrates the acetabula in profile. The Judet view is named after Dr. Judet who stressed the use of these views for trauma imaging. For the Judet view the patient is positioned with the midsagittal plane 45 degrees to the tabletop and the central ray perpendicular to the image receptor.
  • The Judet view demonstrates both acetabula with side up being profiled, the femoral neck and greater trochanter of side up is also profiled, and the entire ilium of side down is seen. Both the left and right posterior oblique views are generally taken when the Judet views are requested.
  • In the United States each year about 280,000 persons fracture their hip, more than 90% occur in the age 60+ age group. Hip fractures are more common in older women, one in three women compared to one in six men.
  • Osteoporosis is a bone loss disease cause by a reduction in mineral (calcium) density of bone. Calcium gives bone its hardness. It is estimated that about 34 million Americans have a status of low bone mass, a condition called osteopenia, which is a precursor to osteoporosis, and 10 million Americans have osteoporosis.
  • Women are especially at risk for bone mass loss during the years following menopause. Decreased estrogen levels can cause a loss of as much as 50% of the trabecular bone and up to 30% of cortical bone.
  • Degenerative joint disease (DJD) also called osteoarthritis is the most common type of joint disease. Degenerative joint disease has many causes with aging being the primary culprit. Osteoarthritis occurs in both men and women and can develop as a result of joint trauma, aging, developmental disorders, or genetic components. Nearly 1% of the population in the United States has some form of rheumatoid arthritis. Rheumatoid arthritis is an inflammatory disease that causes joint disfigurement, swelling, and chronic pain. Rheumatoid arthritis is nearly 3 times more common in women than men. In many cases the best remedy for both forms of arthritis is hemiarthroplasty or total hip arthroplasty (THA). When a THA procedure is performed the entire hip joint is replaced with a hip prosthesis.
  • The femur is internally rotated 15-20 degrees in the absence of trauma so that the femoral neck is not foreshortened. In this position, the greater trochanter is seen laterally in profile, and the lesser trochanter is superimposed on the femoral neck.
  • The reason the axiolateral view is so important is that it minimizes risk of injury to the femoral vessels and nerves, or causing displacement of comminuted unstable fracture fragments.
  • Internal rotation of the femurs to profile the greater trochanter should be achieved for the AP pelvis view, unless the patient presents with acute trauma with leg or hip deformity, traumatic external rotation of the hip or leg, or pain suggestive of an acute fracture.
  • The AP pelvis view should include the entire ilium, ischium, pubis bones, and the entire L5 vertebra. The FOV should extend from above the iliac crests through the lesser trochanters of both femurs and include their surrounding soft tissues.
  • Radiographic exposure for the AP pelvis should penetrate the acetabula, innominate bones, and the sacrum. The iliac wings should show sharp bone detail and clearly diffrentiated bone trabeculae. The posterior pelvis mainly the sacrum and visualized lumbar vertebrae should be well penetrated having sharp bone edges. All soft tissues surrounding the pelvis including the skin should be demonstrated for any penetrating injury.
  • The inlet view is important because it can immediately identify narrowing or widening of the pelvic ring. It is useful to identify posterior displacement of the pelvic ring, sacroiliac joint dislocation, and rotation of the hemipelvis. Also identified are pubic diastasis or pubis overlap, subtle sacral fractures and/or sacral impaction.
  • The primary purpose of the outlet view is to demonstrate the magnitude of vertical displacement of the hemipelvis. The sacral foramina are better seen on the outlet view than on the AP pelvis view.
  • The outlet view is obtained with the patient in the true AP position and the tube angled 45 degrees cephalic. The inlet view is taken with the patient supine and the x-ray beam angled 25-45 degrees caudal and perpendicular to the pelvic brim.
  • When the outlet view is taken as part of a trauma series, both femoral heads should be included on the radiograph. This is because when a hip dislocation is present the outlet view can demonstrate its anterior or posterior displacement. A 45-degree cephalic angulation will cast the shadow of an anteriorly displaced femoral head above the acetabulum. The shadow of a posteriorly displaced femoral head is projected below the acetabulum.
  • Both the pelvic inlet and outlet views should show well-defined margins of the pelvic brim. Both SI joints and the entire sacrum should be demonstrated on both views, and the femoral heads. Pelvic symmetry is achieved when both obturator foramina are open and symmetrical. The sacrum/coccyx should be aligned with the pubic synthesis.
  • The purpose for the Judet view is to demonstrate the acetabulum in profile. When the entire pelvis is demonstrated what is in profile is the iliac wing of the side down; the SI joint, an opened obturator foramen, femoral neck and greater trochanter of the side up.
  • The Judet views are 45-degree oblique views with the patient in the LPO and RPO positions.
  • In the United States each year about 280,000 persons fracture their hip, more than 90% occur in the age 60+ age group. Hip fractures are more common in older women, one in three women compared to one in six men. The main contributor to hip fractures is osteoporosis.
  • Diagnostic testing such as dual-energy x-ray absorptiometry (DEXA) is also available as a screening tool to detect osteoporosis. Currently, DEXA is the gold standard test for bone density measurement associated with osteoporosis.
  • The position of the femur is also important and should be internally rotated 15-20 degrees. When properly rotated the femoral neck is not foreshortened. The greater trochanter is seen laterally in profile, and the lesser trochanter is superimposed on the femoral neck. This is what is seen when the leg is internally rotated properly with an imaginary line connecting the femoral epicondyles is parallel with the tabletop.
  • Generally, 60-85 kVp is used to image the pelvis or hip. The pelvis of infants and small children can be optimally demonstrated using the appropriate mAs and kVp in the range of 60-70. Adult size patients can be adequately imaged using 75-85 kVp.
  • For the frogleg lateral of the hip the femur is placed at an angle of 60-70 degrees with the tabletop. Abducting the femur away from the midline will demonstrate the femoral neck with the greater trochanter projected distal to it.
  • On an accurately positioned axiolateral hip radiograph what should be demonstrated is: 1) the lesser trochanter in profile medially, 2) the greater trochanter superimposed on the femoral shaft, 3) the femoral neck in the center of the collimated field and not foreshortened, and 4) the articulation of the acetabulum with the head of the femur entirely demonstrated and well penetrated.
  • Proper alignment of the tube-part-image receptor is achieved by placing the cassette parallel to the femoral neck and perpendicular to the central ray (CR). To assure the grid cassette is parallel to the femoral neck use a cassette holder and unless contraindicated by injury or unstable pathological bone disease, and in the absence of trauma, internally rotate the affected leg 15-20 degrees.
  • On an accurately positioned axiolateral hip radiograph what should be demonstrated is: 1) the lesser trochanter in profile medially, 2) the greater trochanter superimposed on the femoral shaft, 3) the femoral neck in the center of the collimated field and not foreshortened, and 4) the articulation of the acetabulum with the head of the femur is entirely demonstrated and well penetrated.



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Copyright image Copyright 2006 Nicholas Joseph Jr.






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