Acetabular Fractures: Anatomic and Clinical Considerations

Transcription

1 Musculoskeletal Imaging Review Lawrence et al. cetabular Fractures Musculoskeletal Imaging Review Downloaded from by on 01/28/18 from IP address Copyright RRS. For personal use only; all rights reserved FOCUS ON: David. Lawrence 1 Kirsten Menn 1 Michael aumgaertner 2 ndrew H. Haims 1,2 Lawrence D, Menn K, aumgaertner M, Haims H Keywords: acetabular fracture, acetabulum, Judet-Letournel classification system DOI: /JR Received December 19, 2012; accepted after revision February 7, Department of Diagnostic Radiology, Yale University School of Medicine, 333 Cedar St, PO ox , New Haven, CT ddress correspondence to. H. Haims (ndrew.haims@yale.edu). 2 Department of Orthopaedics and Rehabilitation, Yale University School of Medicine, New Haven, CT. CME/SM This article is available for CME/SM credit. WE This is a web exclusive article. JR 2013; 201:W425 W X/13/2013 W425 merican Roentgen Ray Society cetabular Fractures: natomic and Clinical Considerations OJECTIVE. Classifying acetabular fractures can be an intimidating topic. However, it is helpful to remember that there are only three basic types of acetabular fractures: column fractures, transverse fractures, and wall fractures. Within this framework, acetabular fractures are classified into two broad categories: elementary or associated fractures. We will review the osseous anatomy of the pelvis and provide systematic approaches for reviewing both radiographs and CT scans to effectively evaluate the acetabulum. CONCLUSION. lthough acetabular fracture classification may seem intimidating, the descriptions and distinctions discussed and shown in this article hopefully make the topic simpler to understand. pproach the task by recalling that there are only three basic types of acetabular fractures: column fractures (coronally oriented on CT images), transverse fractures (sagittally oriented on CT images), and wall fractures (obliquely oriented on CT images). We have provided systematic approaches for reviewing both conventional radiographs and CT scans to effectively assess the acetabulum. The clinical implications of the different fracture patterns have also been reviewed because it is critically important to include pertinent information for our clinical colleagues to provide the most efficient and timely clinical care. cetabular fractures are a challenging topic for radiologists and orthopedists. The classification scheme developed by Judet et al., first described in 1964, is still currently widely used in classifying acetabular fractures [1]; indeed, it has been confirmed to be exceedingly accurate and useful with the development of advanced cross-sectional imaging. efore the 1964 study [1], most acetabular fractures were managed with closed reduction. This landmark study examined fracture patterns in 173 patients with acetabular fractures in an attempt to improve management. The work by Judet et al. allowed successful management strategies driven by operative approaches that were determined by understanding the 3D aspects of the fracture types. The rise of MDCT, particularly in the setting of trauma, has led to the reexamination and subsequent confirmation of the original Judet-Letournel classification system that was based on conventional radiography. s MDCT scans become more prevalent in the setting of trauma, so too has the need to understand these complex fractures and their 3D relationships. In this article, we will discuss the osseous anatomy of the pelvis, the pivotal role the acetabulum plays in weight transference from the axial to the appendicular skeleton, the 3D relationships of the bony pelvis and acetabulum with reference to the classic description of acetabular fracture classification, and the clinical and management implications of different acetabular fractures. natomy of the ony Pelvis and cetabulum The bony pelvis is composed of the sacrum, coccyx, and the two innominate bones. The innominate bones are formed by the fusion of the ilium, ischium, and pubis (Fig. 1). The ilium contributes to the superior part of the acetabulum; the ischium, to the posterior part of the acetabulum; and the pubis, to the anterior part of the acetabulum. The bones of the pelvis form a ring, with the iliac bones articulating with the sacrum through the sacroiliac joints posteriorly and the two pubic bodies articulating at the pubic symphysis anteriorly. long the lateral surface of each innominate bone lies the acetabulum, which articulates with the femoral head. key reference point in the acetabulum is the cotyloid fossa that is, the central JR:201, September 2013 W425

2 Lawrence et al. Downloaded from by on 01/28/18 from IP address Copyright RRS. For personal use only; all rights reserved nonarticular aspect of the acetabulum below the acetabular roof (Fig. 1). One of the main functions of the bony pelvis is to transfer weight from the vertebral column to the ischial tuberosities when sitting and acetabula and lower extremities when standing (Fig. 2). Weight is transferred from the fifth lumbar vertebra to the upper three sacral segments, across the sacroiliac joints to the thick strut of the ilium known as the sciatic buttress, and down to the ischial tuberosities when sitting and down to the acetabula and subsequently the lower extremities when standing. The anterior column is defined as the strut of bone that extends from the sacroiliac joint to the ipsilateral pubic ramus (Fig. 3). The anterior column includes the superior pubic ramus, anterior half of the acetabulum, anterosuperior and anteroinferior iliac spines, and anterior iliac crest. The iliopectineal (also called the iliopubic) line on radiographs approximates the anatomic anterior column (Fig. 4). The posterior column is the bony strut extending from the posterosuperior iliac spine to the ischial tuberosity (Fig. 3). The posterior column includes the portion of the ischium from the ischiopubic junction of the obturator foramen to the greater sciatic notch and posterior half of the acetabulum. The ilioischial line on radiography approximates the anatomic posterior column (Fig. 4). The walls of the acetabulum extend from the corresponding columns, consequently forming the acetabular cup, and stabilize the hip joint (Fig. 3). The posterior wall is larger and extends more laterally; the anterior wall is smaller and stabilizes the hip joint anteriorly and has been described as extending to the pelvic brim [2]. Imaging Techniques Radiography cetabular fracture classification by Judet and Letournel requires oblique radiographs of the pelvis. standard radiograph series consists of an anteroposterior view and left and right Judet views. Judet views are right posterior oblique (also known as right iliac oblique or left obturator oblique) and left posterior oblique (also known as left iliac oblique or right obturator oblique) views of the pelvis (Fig. 5). ppropriate positioning of the obliquity is confirmed by ensuring that the coccyx projects over the ipsilateral femoral head: In the right posterior oblique projection, the coccyx should project over the right femoral head. The obturator oblique view splays open the contralateral iliac wing and allows visualization of the ipsilateral iliopectineal line and posterior wall. For example, with a right obturator oblique view, the right iliopectineal line, left iliac wing, and right posterior wall are best visualized. n iliac oblique view shows the ipsilateral ilioischial line and the anterior wall. Thus, the right iliac oblique view will show the entire right ilium en face, the right anterior wall, and the left posterior wall. These views are critical to orthopedists because these views are the intraoperative views used to judge reduction. CT ecause CT has become more prevalent, acetabular fractures are initially imaged using CT rather than standard pelvic radiography. Evaluating the bony anatomy was difficult with early CT technology, and the lack of adequate multiplanar reformatting made CT classification of acetabular fractures challenging. However, as MDCT has become increasingly prevalent, many studies have reevaluated the utility of CT to examine and classify acetabular fractures [3, 4]. MDCT offers the benefits of isotropic imaging and multiplanar reformatted images. In addition, modern CT allows better assessment for intraarticular fragments and better visualization of the articular surface of the acetabulum [3, 5]. Furthermore, CT offers better soft-tissue assessment for rapid evaluation of visceral structures in the multitrauma patient. With the prevalence of MDCT use, imagers have incredible amounts of anatomic information to relay to the treating orthopedic surgeons. Radiologists must be aware of the fractures, their classification, and their implications to provide pertinent information for appropriate treatment plans. In the following sections, we will discuss the Judet classifications of acetabular fractures and describe how they appear on CT with radiographic correlates. Judet-Letournel Classification There are several acetabular fracture classification schemes, with the most widely used classification scheme being the Judet-Letournel classification scheme. nother classification system is the Harris-Coupe classification system, which uses axial CT based on an analysis of 112 randomly selected acetabular fracture patients [6]. This system assigns the acetabular fracture a category from 0 to 3, with subcategories also existing [6 8]. However, this system has shortcomings, and many would argue in favor of the diagnostic and clinical management strengths of the Judet- Letournel system [9]. ecause the Judet-Letournel system is the prevailing classification system used by most radiologists and orthopedists, we will concentrate on this system. In the Judet-Letournel classification system, acetabular fractures are classified into two broad categories: elementary and associated fractures. The associated fracture patterns are composed of a combination of at least two of the elementary fracture patterns. The importance of this classification system lies in the fact that different acetabular fractures are repaired by different surgical approaches and techniques [10]. Elementary fractures include wall, column, and transverse fractures. These fracture types can easily be remembered by recalling the basic functional anatomy of the acetabulum: Elementary fractures involve a single wall, involve a single column, or are purely transverse. The simplest elementary fractures are two-part fractures. It is important to note that the term transverse fracture should be reserved to describe a diagnostic type of acetabular fracture, whereas the term transverse should be avoided when describing the orientation of a fracture because it may quickly become confusing as to which type of fracture is present. ssociated fracture patterns have at least three major fracture fragments and include a posterior column fracture with a posterior wall fracture, a transverse fracture with a posterior wall fracture, an anterior column fracture with a posterior hemitransverse fracture, a T-type transverse fracture, and associated both-column fractures. lthough there are 10 fracture patterns, 90% of acetabular fractures that occur are one of five types: associated both-column, T-type, transverse, transverse with posterior wall, and elementary posterior wall fractures [11, 12]. Some investigators have advocated concentrating only on these common fractures; however, commonly acetabular fractures do not fit perfectly in one of the fracture patterns in the classification scheme. We advocate a conceptual understanding of these fracture patterns. Different Way to Remember cetabular Fractures Instead of attempting to memorize all of the elementary and associated fracture types, it is much easier to remember three fracture patterns: column, transverse, and wall fracture patterns. Column Fractures Column fractures have a coronal fracture line running caudad to craniad. Thus, these fractures break the acetabulum into two halves: a front half and a back half. y definition, the weight- W426 JR:201, September 2013

3 cetabular Fractures Downloaded from by on 01/28/18 from IP address Copyright RRS. For personal use only; all rights reserved bearing function of the acetabulum has been disrupted. It is important to note that nearly every column fracture will extend inferiorly to involve the obturator ring. To look at it a different way, if the obturator ring is involved in an acetabular fracture, there is almost always either a column fracture or a T-type transverse fracture. n anterior column fracture will separate the anterior portion of the anterior weightbearing aspect of the acetabulum from the remainder of the bony pelvis, allowing the anterior fragment to float freely in space. Thus, one could, in theory, grab on the anterosuperior iliac spine and it would no longer be associated with the weight-bearing portion of the body. Conversely, a posterior column fracture will create a free-floating fracture fragment involving the posterior aspect of the acetabulum; one could, in theory, grab on the ischial tuberosity and it would no longer be associated with the weight-bearing portion of the body. Remembering these concepts will avoid erroneously calling a fracture of the root of the pubic rami that involves the joint surface a column fracture ; architecturally, these low fractures do not disrupt the weightbearing struts of the acetabulum. If the anterior column is fractured, the fracture line extends from the acetabulum craniad to involve the iliac wing on anteroposterior radiographs; consequently, the iliopectineal line will be disrupted. The extent of the iliac wing involvement will best be shown on iliac oblique views of the pelvis (Fig. 6). Posterior column fractures (Fig. 7) extend craniad from the acetabulum to the sciatic notch and will involve the ilioischial line. The iliac oblique view will show where the fracture involves the sciatic notch. Column fractures can be associated with other types of fractures, such as an anterior column fracture with a posterior hemitransverse fracture and a posterior column fracture with a posterior wall fracture. It is important to keep these possibilities in mind once the main fracture line is diagnosed because the additional component could have significant management implications. dditionally, it is important to note that disruption of the anatomic anterior column (i.e., the iliopectineal line) or anatomic posterior column (i.e., the ilioischial line) is not always diagnostic of an anterior or posterior column fracture. Other acetabular fractures, such as transverse fractures, will disrupt both of these anatomic columns. To distinguish among these fractures, remember that anterior column fractures will run cephalad up into the iliac wing and posterior column fractures will course cephalad into the sciatic notch. Column fractures will almost always be associated with pubic rami fractures. Very rarely, variant T-type transverse and posterior column fractures may skirt the obturator foramen posteriorly and exit through the inferior ischium. On CT, remember that column fractures have a coronal orientation at the roof of the acetabulum and will dissociate the fracture fragments from the weight-bearing portion of the body. The most common type of column fracture is the associated both-column fracture. In this fracture, both iliopectineal and ilioischial lines will be disrupted. The acetabulum in this case becomes dissociated from the weight-bearing strut that connects it to the axial skeleton. oth the iliopectineal and ilioischial lines will be disrupted in this fracture, and this fracture will be seen radiographically as Letournel s classic spur sign, which is pathognomonic for an associated both-column fracture (Fig. 8). The spur sign is shown only on the ipsilateral obturator oblique view and is created by medial translation of the distal fragment. The visualized spur fragment is simply the inferior end of the weight-bearing strut of bone in communication with the axial skeleton. On CT, this fragment is easier to see because one can trace down the weight-bearing strut of bone in continuity with the axial skeleton from the sacroiliac joint across the sciatic buttress. The fragment of bone never descends down to the acetabular surface in the setting of a both-column fracture, thus creating the CT spur sign (Fig. 8). In summary, column fractures are coronally oriented at the roof of the acetabulum and almost always involve the obturator ring. nterior column fractures extend superiorly to involve the iliac wing and posterior column fractures extend superiorly to involve the sciatic notch. ssociated both-column fractures will do both and the spur sign is pathognomonic. Remember that column fractures may be associated with other fracture components, leading to anterior column with posterior hemitransverse and posterior column with posterior wall fractures. Transverse Fractures Types of transverse fractures include the elementary transverse, T-type, and transverse with posterior wall. These fractures, by definition, separate the acetabulum into superior and inferior halves with the fracture line extending from anterior to posterior; thus, transverse fractures will show a sagittally oriented fracture line at the roof of the acetabulum on axial CT. With the elementary transverse fracture, anteroposterior views of the pelvis will show disruption of both the ilioischial and iliopectineal lines without the fracture extending in any other plane: The obturator ring is intact and the iliac wing is unremarkable (Fig. 9). To reiterate, these fractures run in the sagittal plane at the acetabular roof and do not extend cephalad into the anterior ilium or posteriorly and cephalad into the sciatic notch as anterior and posterior column fractures do, respectively (Fig. 9). The T-type fracture is a three-part associated fracture pattern that will also show a sagittally oriented fracture line at the roof of the acetabulum; however, this fracture will also extend inferiorly to disrupt the obturator ring, splitting the inferior component into anterior and posterior halves (Fig. 10). The distinction between the T-type and elementary transverse fractures is clinically important because the complexity of reduction will differ on the basis of the fracture pattern. The third type of transverse fracture is the transverse fracture with posterior wall, another type of associated fracture pattern. The fracture line, once again, is sagittally oriented along the roof of the acetabulum, but a separate fracture also extends to involve the posterior wall of the acetabulum (Fig. 11). combined transverse fracture with a posterior wall component is diagnosed only if the posterior wall is a separate fragment; stated another way, the an elementary transverse acetabular fracture may extend to involve the posterior wall but it is not separate from the superior component of the transverse fracture. CT offers an excellent assessment of the articular continuity of the posterior wall and of whether an intraarticular fragment is present. lternatively, on radiographs the posterior acetabular wall can be inspected on both the anteroposterior and obturator oblique views for evidence of discontinuity. In summary, a transverse acetabular fracture is a sagittally oriented fracture that separates the bony pelvis into superior and inferior halves, with the superior component lateral and the inferior component medial at the roof of the acetabulum. The fracture may be elementary (i.e., with no other fracture component involving other portions of the bony pelvis); however, if the fracture also has a coronal component that extends inferiorly and disrupts the obturator ring (splitting the inferior half into anterior and pos- JR:201, September 2013 W427

4 Lawrence et al. Downloaded from by on 01/28/18 from IP address Copyright RRS. For personal use only; all rights reserved terior components), then a T-type fracture is present. lternatively, if there is an additional fracture line that separates the posterior wall of the acetabulum into a separate fragment, then a transverse fracture with a posterior wall fracture is present. For column fractures as well as elementary transverse and T-type transverse fractures, the level of the intraarticular fracture line is clinically important and is defined with regard to its relationship to the cotyloid fossa: supratectal, juxtatectal, or infratectal. Fractures above the fossa are in the middle of the weight-bearing surface and the femoral head subluxes medially with the displaced column, which is a negative prognosticator for preservation of the native joint. n infratectal fracture is within the cotyloid fossa and the femoral head stays within the intact acetabulum; thus, posttraumatic osteoarthritis develops later in a joint with an infratectal fracture than in one with a supratectal fracture. juxtatectal fracture occurs through the top of the cotyloid fossa and the joint may or may not develop osteoarthritis. Wall Fractures cetabular wall fractures most commonly involve the posterior wall but occasionally involve the anterior wall. It is important to note that wall fractures are unique from the two other fracture patterns because the loadbearing mechanism of the acetabulum may not be disrupted. Thus, the main morbidity associated with wall fractures is hip instability [13]. Cadaver studies have shown that if greater than 40% of the posterior wall is fractured, the risk of hip instability is increased [14]. Wall fractures have an obliquely oriented fracture line on axial CT images at the roof of the acetabulum, as opposed to the coronal and sagittal fracture lines described with column and transverse fractures, respectively. Posterior wall fractures show an irregularity of the lateral aspect of the posterior wall on the ipsilateral obturator oblique Judet view of the pelvis (Fig. 12). CT images will show an oblique fracture line (Fig. 13), and they can help determine the percentage of articular surface involved and the location of the fracture fragments; in particular, whether there is an intraarticular fragment of bone is important to note because this fragment can prevent successful closed reduction. dditionally, posterior wall fractures are almost always associated with at least transient posterior dislocation of the femoral head, which is associated with an increased risk of femoral head cartilage damage and avascular necrosis [15]. Consequently, careful initial examination of the femoral head and follow-up studies are important to detect signs of early deterioration and avascular necrosis. nterior wall fractures are much less common than posterior wall fractures. n anterior wall fracture can be detected on the anteroposterior view of the pelvis, which will show any irregularity of the anterior wall of the acetabulum. The classic sign on an anteroposterior radiograph is a double break in the iliopectineal line. The iliac oblique view can be helpful in better visualizing the anterior lip if the anteroposterior view is not conclusive. CT images will provide a more definitive evaluation of the acetabulum (Fig. 14). common misconception is about the difference between anterior wall fractures of the acetabulum and high superior ramus fractures: True anterior wall fractures will involve a segment of the inner table of the pelvis (i.e., the pelvic brim), whereas high superior ramus fractures will not involve the pelvic brim and will not involve a significant segment of the articular surface [2] (Fig. 15). Synthesizing the Information s with any other type of radiographic study, it is important to use a systematic approach. First, the ilioischial and iliopectineal lines of both sides of the pelvis should be traced for any evidence of discontinuity. Second, the anterior and posterior walls should be examined using the anteroposterior image and the obturator oblique views. Third, the obturator ring should be examined for fracture, which is best shown on the obturator oblique view. Fourth, the iliac wings should then be examined on the iliac oblique views. Following this approach for radiographic evaluation, one should have a relatively good differential diagnosis about which type of fracture is present before the CT evaluation. When evaluating the CT images, we stress that the zone from the sciatic notch to the roof of the acetabulum is the key to diagnosis and prognosis. We recommend assessing the roof of the acetabulum first to determine the orientation of the fracture line. Remember that fractures running in a coronal plane are column fractures, fractures oriented in the sagittal plane are transverse fractures, and fractures in an oblique plane are wall fractures. Once this information is obtained, move to the obturator ring: Is it disrupted or not? If the obturator ring is intact, consider an elementary transverse fracture, transverse fracture with a posterior wall fracture, or an isolated wall fracture. Remember that there are rare exceptions when the vertical component of column fractures or T-type fractures may run anterior or posterior to the obturator ring. If the obturator ring is fractured, there must be a column fracture or a T-type fracture. Next, scroll cephalad and caudad through the acetabulum. nterior column fractures will extend cephalad and anterior into the iliac bone. Posterior column fractures will extend cephalad and posteriorly into the sciatic notch. If both the anterior and posterior anatomic columns are involved with disruption of the obturator ring, one must differentiate an associated both-column fracture from a T- type fracture. This distinction can be accomplished by tracing down the weight-bearing piece from the sacroiliac joint, across the sciatic buttress, and to the roof of the acetabulum. The diagnosis will be confirmed by the orientation of the fracture at the roof of the acetabulum (coronal = column, sagittal = transverse) and the presence or absence of a CT spur sign (present = associated both-column fracture, absent = a T-type fracture). Once you have determined the primary fracture, analyze the remainder of the acetabulum for additional fracture patterns that may add to the complexity of the fracture. The presence of a secondary fracture to the posterior wall will define several types of associated fracture patterns. lso remember that with a posterior wall fracture, it is important to determine the degree of articular involvement and whether intraarticular fragments are present. ssociated Soft-Tissue Injuries The full extent of pelvic injuries that are encountered in trauma patients is beyond the scope of this article. However, it is worthwhile to note injuries commonly associated with acetabular fractures. Hemorrhage accompanies pelvic fractures in approximately 75% of cases [16]. Hemorrhagic sequelae include shock, coagulopathy, secondary infection of the hematoma, and renal failure. leeding may be arterial or venous; if it is arterial, it is most likely arising from the internal iliac artery branches (Fig. 16). lso, remember the superior gluteal artery is in close proximity to the sciatic notch and posterior column fractures extend through that notch. The lower urinary tract is also important to closely examine for injury. The incidence of urethral injury in trauma patients has been reported to be as high as 17% and bladder disruption, as high as 25% [17, 18]. Retrograde W428 JR:201, September 2013

5 cetabular Fractures Downloaded from by on 01/28/18 from IP address Copyright RRS. For personal use only; all rights reserved urethrography to exclude urethral injury is the traditional approach. t our institution, given the frequency of CT studies performed for evaluation of trauma patients, delayed images through the pelvis are frequently obtained to evaluate for extravasation of contrast material from bladder rupture. Peripheral nerves may also be injured in acetabular fractures. The sacral nerve roots and sciatic nerve may be injured because of their close proximity to the sacrum, sacroiliac joints, and sciatic notch. The sciatic nerve passes posterior to the posterior aspect of the acetabulum and may be either lacerated or compressed from mass effect related to an adjacent soft-tissue hematoma. Summary lthough acetabular fracture classification may seem intimidating, the descriptions and distinctions discussed and shown in this article hopefully make the topic simpler to understand. pproach the task by recalling that there are only three basic types of acetabular fractures: column fractures (coronally oriented on CT images), transverse fractures (sagittally oriented on CT images), and wall fractures (obliquely oriented on CT images). We have provided systematic approaches for reviewing both conventional radiographs and CT scans to effectively assess the acetabulum. The clinical implications of the different fracture patterns have also been reviewed because it is critically important to include pertinent information for our clinical colleagues to provide the most efficient and timely clinical care. References 1. Judet R, Judet J, Letournel E. Fractures of the acetabulum: classification and surgical approaches for open reduction preliminary report. J one Joint Surg m 1964; 46: Lenarz CJ, Moed R. typical anterior wall fracture of the acetabulum: case series of anterior acetabular rim fracture without involvement of the pelvic brim. J Orthop Trauma 2007; 21: Griffiths HJ, Standertskjold-Nordenstam CG, urke J, Lamont, Kimmel J. Computed tomography in the management of acetabular fractures. Skeletal Radiol 1984; 11: O Toole RV, Cox G, Shanmuganathan K, et al. Evaluation of computed tomography for determining the diagnosis of acetabular fractures. J Orthop Trauma 2010; 24: Pascarella R, Maresca, Reggiani LM, oriani S. Intra-articular fragments in acetabular fracture-dislocation. Orthopedics 2009; 32: Harris JH Jr, Lee JS, Coupe KJ, Trotscher T. cetabular fractures revisited. Part 1. Redefinition of the Letournel anterior column. JR 2004; 182: Harris JH Jr, Coupe KJ, Lee JS, Trotscher T. cetabular fractures revisited. Part 2. new CTbased classification. JR 2004; 182: Harris JH, Coupe KJ, Lee JS, Trotscher T. cetabular fractures revisited: a new CT-based classification. Semin Musculoskelet Radiol 2005; Fig. 1 Sagittal schematic of pelvis and acetabulum. Green shaded area demarcates ilium, red shaded area demarcates ischium, and yellow shaded area demarcates pubis. Cotyloid fossa (also known as acetabular fossa), marked by asterisk, is circular nonarticular depression in acetabulum. = anterior, P = posterior. 9: Olson S. CT-based acetabular fracture classification. (letter) JR 2005; 185: ; author reply, Potok PS, Hopper KD, Umlauf MJ. Fractures of the acetabulum: imaging, classification, and understanding. RadioGraphics 1995; 15:7 23; discussion, randser E, Marsh JL. cetabular fractures: easier classification with a systematic approach. JR 1998; 171: Durkee NJ, Jacobson J, Jamadar D, Karunakar M, Morag Y, Hayes C. Classification of common acetabular fractures: radiographic and CT appearances. JR 2006; 187: Moed R, jibade D, Israel H. Computed tomography as a predictor of hip stability status in posterior wall fractures of the acetabulum. J Orthop Trauma 2009; 23: Keith JE Jr, rashear HR Jr, Guilford W. Stability of posterior fracture-dislocations of the hip: quantitative assessment using computed tomography. J one Joint Surg m 1988; 70: Em L. Judet R, Elson R. Fractures of the acetabulum, 2nd ed. erlin, Germany: 1993:xxiii, McMurtry R, Walton D, Dickinson D, Kellam J, Tile M. Pelvic disruption in the polytraumatized patient: a management protocol. Clin Orthop Relat Res 1980; 151: rosman S, Paul JG. Trauma of the bladder. Surg Gynecol Obstet 1976; 143: Colapinto V. Trauma to the pelvis: urethral injury. Clin Orthop Relat Res 1980; 151:46 55 JR:201, September 2013 W429

6 Lawrence et al. Downloaded from by on 01/28/18 from IP address Copyright RRS. For personal use only; all rights reserved Fig. 2 Surface-rendered 3D reformatted CT angiogram of healthy 27-year-old man. Image depicts weight transference (arrows) from axial to appendicular skeleton. Weight is carried down spine, across first three sacral segments, across sciatic buttress, onto acetabulum, and across hip joints to lower extremities. Fig. 4 nteroposterior radiograph of normal pelvis of healthy 38-year-old woman. Solid line depicts posterior wall of right acetabulum, dashed line depicts ilioischial line, and dotted line depicts iliopectineal line. Fig. 3 Schematic of columns and walls of pelvis. Green shaded area represents anatomic anterior column and red shaded area represents anatomic posterior column. lue line represents anterior wall of acetabulum and orange line represents posterior wall of acetabulum. Fig. 5 Left iliac oblique (right obturator oblique) Judet radiographic view of normal pelvis of healthy 38-year-old woman. Solid line depicts posterior wall of right acetabulum, dashed line depicts right iliopectineal, and dotted line depicts left ilioischial line. W430 JR:201, September 2013

7 cetabular Fractures Fig. 6 nterior column fracture. and, Left iliac oblique Judet radiographic view () and corresponding sagittal CT image () show anterior column fracture in 31-year-old man. Note that fracture extends up iliac wing (arrow). C, Sagittal anatomic drawing shows anterior column fracture. Note that fracture extends superiorly to involve iliac wing (arrow) and inferiorly to involve obturator ring (arrowhead). (Drawing by Menn K) Downloaded from by on 01/28/18 from IP address Copyright RRS. For personal use only; all rights reserved Fig. 7 Posterior column fracture. and, Sagittal () and axial () CT images show displaced posterior column fracture in 44-year-old man. Note that fracture line runs in sagittal plane (arrowheads, ). dditionally, note that fracture line extends to sciatic notch (arrow, ). C, Sagittal anatomic drawing of posterior column fracture. Note that fracture line extends to sciatic notch (arrow) and extends inferiorly to involve obturator ring (arrowhead). (Drawing by Menn K) C C JR:201, September 2013 W431

8 Lawrence et al. Downloaded from by on 01/28/18 from IP address Copyright RRS. For personal use only; all rights reserved Fig. 8 ssociated both-column fracture., nteroposterior radiograph of pelvis shows associated both-column fracture in 25-year-old man. Note disruption of both right iliopectineal (arrowhead) and right ilioischial (arrow) lines. Lines are intact on contralateral side., Right iliac oblique Judet view of associated both-column fracture in 25-year-old man shows classic spur sign (arrow) whereby weight-bearing strut of bone never reaches acetabular roof. C, Serial axial CT images from superior to inferior show acetabular fracture in 30-year-old man. cetabular fracture separates weight-bearing piece of bone (arrows) from acetabular roof. Orientation of fracture plane(arrowheads) is coronal at roof of acetabulum on most inferior image. Obturator ring was disrupted (not shown). D, Sagittal anatomic drawing of both-column fracture. Note that acetabulum is dissociated from weight-bearing strut that connects it to axial skeleton. (Drawing by Menn K) C D W432 JR:201, September 2013

9 cetabular Fractures Downloaded from by on 01/28/18 from IP address Copyright RRS. For personal use only; all rights reserved Fig. 9 Elementary transverse fracture., nteroposterior radiograph of pelvis of 39-year-old woman shows elementary transverse fracture involving left acetabulum. Iliopectineal and ilioischial lines (arrow) are disrupted, but there is no superior extension of this fracture into either ilium or sciatic notch., xial CT image of elementary transverse fracture of left acetabulum in 39-year-old woman. Note that fracture line (arrows) runs from anterior to posterior at roof of acetabulum. C, Sagittal anatomic drawing of elementary transverse fracture. Transverse fractures split pelvis into superior and inferior halves, where superior component is located laterally and inferior component is located medially. Note that obturator ring is intact in this type of fracture. (Drawing by Menn K) Fig. 10 T-type transverse fracture., xial CT image shows T-type transverse fracture in 33-year-old man. Note sagittally oriented fracture at roof of acetabulum (arrowheads) consistent with transverse fracture. In addition, there is coronal fracture line (arrow) splitting inferior half of acetabulum into anterior and posterior components, which extend inferiorly to disrupt obturator ring (not shown)., Sagittal CT image shows T-type transverse fracture in 33-year-old man. Note anterior (arrowhead) and posterior (arrows) components of this three-part fracture. C, Sagittal anatomic drawing of T-type transverse acetabular fracture. Note that it is three-part fracture that has component that extends inferiorly to disrupt obturator ring (arrowhead). This inferior component of fracture consequently splits into anterior and posterior parts. (Drawing by Menn K) C C JR:201, September 2013 W433

10 Lawrence et al. Downloaded from by on 01/28/18 from IP address Copyright RRS. For personal use only; all rights reserved Fig. 11 Transverse fracture with posterior wall fracture in 25-year-old woman., nteroposterior radiograph of pelvis illustrates transverse fracture with posterior wall fracture. Transverse fracture component interrupts both iliopubic and iliopectineal lines (arrow). lso notice fracture fragment of posterior wall (arrowheads)., xial CT image of transverse fracture with posterior wall left acetabular fracture. Note sagittal orientation of fracture (arrows). lso note displaced posterior wall fragment (arrowhead). Fig. 12 Posterior wall fracture in 41-year-old man., Left obturator oblique radiograph of posterior wall fracture of left acetabulum. Note posterior wall fragment (arrow)., Sagittal anatomic drawing of posterior wall fracture. Note that fracture line involves posterior rim of acetabulum (arrows). Importantly, superior fracture line is located lateral to medial cortex of posterior column. (Drawing by Menn K) W434 JR:201, September 2013

11 cetabular Fractures Downloaded from by on 01/28/18 from IP address Copyright RRS. For personal use only; all rights reserved Fig. 13 Posterior wall fracture in 19-year-old man., xial CT image of posterior wall fracture of right acetabulum. Note oblique course of fracture (arrow)., Surface-rendered 3D reformatted CT angiogram shows posterior wall fracture (arrow). Fig. 14 nterior wall fracture., nteroposterior radiograph of pelvis of 23-year-old man shows distinctive double break in iliopectineal line (arrows); this finding is characteristic of anterior wall fractures., Surface-rendered anterior 3D CT angiogram of anterior wall fracture in 23-year-old man. Note obliquity of fracture line (arrowhead) and how anterior aspect of pelvic brim is disrupted; disruption of pelvic brim is characteristic of anterior wall fracture. nterior wall fractures will involve segment of inner table of pelvis (arrow), whereas high pubic ramus fractures will not involve pelvic brim. C, Sagittal anatomic drawing of anterior wall fracture. nterior wall fractures will involve segment of inner table of pelvis (arrow), whereas high pubic ramus fractures will not involve pelvic brim. Importantly, note that although fracture line extends slightly cephalad, it does not continue up iliac wing, thus distinguishing it from anterior column fracture. (Drawing by Menn K) C JR:201, September 2013 W435

12 Lawrence et al. Downloaded from by on 01/28/18 from IP address Copyright RRS. For personal use only; all rights reserved Fig. 15 High superior pubic ramus fracture in 31-year-old woman. and, xial () and coronal () CT images illustrate high ramus fracture (arrows) without significant articular involvement or disruption of pelvic brim. Fig. 16 Three-dimensional surface-rendered CT angiograms of pelvis show normal findings in healthy 29-year-old man., Frontal view shows normal arteries adjacent to acetabulum including common iliac artery (white arrow), external iliac artery (black arrow), and internal iliac artery (arrowhead)., Left posterior oblique view shows normal arteries adjacent to acetabulum including common iliac artery (white arrow), internal iliac artery (arrowhead), anterior division of internal iliac artery (wavy arrow), and posterior division of internal iliac artery (black arrow). FOR YOUR INFORMTION This article is available for CME/SM credit. To access the examination for this article, follow the prompts. W436 JR:201, September 2013