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ECR 2016 / C-0823
Acetabular fractures: radiographic and CT characteristics
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Congress: ECR 2016
Poster No.: C-0823
Type: Educational Exhibit
Keywords: Trauma, Imaging sequences, Digital radiography, CT, Musculoskeletal system, Musculoskeletal joint, Musculoskeletal bone
Authors: V. Zecchi1, A. Leone1, A. Semprini2, M. Marino2, L. Tonetti2, C. Colosimo1; 1Rome/IT, 2Roma/IT
DOI:10.1594/ecr2016/C-0823

Findings and procedure details

 

Radiography

 

AF are primary evaluated with the anteroposterior (AP) (Fig. 1 a, b) and Judet views (Fig. 1 c-f), as they are able to demonstrate the following radiographic landmarks of each acetabular column: the anterior and posterior acetabular walls and the iliopectineal and ilioischial lines [1, 2, 5, 6] (Fig. 1).

 

 

Fig. 1: a) Diagram and b) corresponding AP view showing: 1. Iliopubic line, 2. Ilioischial line, 3. Acetabular roof, 4. Anterior acetabular wall, 5. Posterior acetabular wall. c) Diagram and d) corresponding obturator oblique view show: 1. Iliopubic line, 5. Posterior acetabular wall. e) Diagram and f) corresponding iliac oblique view show: 1. ilioischial line, 2. anterior acetabular wall.
References: Institute of Radiology, Catholic University, School of Medicine, Rome/Italy.

 

 

 

CT

 

CT is considered the reference standard for showing AF [7]. The new generation CT scanners with multiplanar reconstructions (MPR) and three-dimensional (3D) volume rendered images represent a more valuable visual tool for defining AF, especially in case of complex displaced fractures, for which mental reconstruction of the axial sections into a 3D configuration is a time-consuming effort [8,9]. CT scans are more sensitive than radiographs for demonstrating:

  • AF location and extent;
  • degree of fracture comminution;
  • impaction of the weight-bearing dome;
  • incarcerated fragments;
  • acetabular roof and quadrilateral plate;
  • injury to the femoral head;
  • sacroiliac joint integrity;
  • complications such as pelvic haematoma or gastrointestinal/genitourinary associated injuries.

 

Elementary fractures

 

  • Posterior wall fracture (Fig. 2). It’s the most commonly encountered of all acetabular fracture types and it typically results from indirect forces transmitted through the length of the femur with a flexed hip joint [10]. It always involve posterior articular surface. The fragment may be single or multiple, large or small. The fractures are identified radiographically by nothing, that only the posterior border is disrupted. CT scan is invaluable in evaluating marginal joint congruity and fragment size. 

 

 

Fig. 2: a) AP, b) iliac oblique, c) obturator oblique, and d) axial CT images show posterior wall fracture with a markedly displaced fragment (arrow in a, b, c, d).
References: Institute of Radiology, Catholic University, School of Medicine, Rome/Italy.

 

 

 

  • Posterior column fracture (Fig. 3). Detach typically the whole posterior column in one fragment. The fracture line usually originates in the greater sciatic notch, traverses through the obturator foramen. Radiographically the femoral head appears displaced medially, the ilioischial line is clearly disrupted, the posterior lip interrupted, whereas the anterior column is intact. CT scan usually reveals a significant “step” in the joint.

 

 

Fig. 3: a) The AP and b) the iliac oblique views show posterior column fracture with interruption of the ilio-ischial line (arrow in a, and b).
References: Institute of Radiology, Catholic University, School of Medicine, Rome/Italy.

 

 

 

  • Anterior wall fracture (Fig. 4). Pure are rare; often associated with an anterior dislocation of the hip. They may produce one fragment or multiple ones, and some may be marginally impacted. The diagnosis is made by identifying the characteristic displaced trapezoid fragment comprising a segment of the iliopectineal line without posterior injury. CT is invaluable for displaying the extent of the lesion.

 

 

Fig. 4: a) The AP view shows the characteristic displaced trapezoid fragment comprising a segment of the iliopectineal line (arrow). b) Axial CT scan better defines the anterior wall fragment (arrow).
References: Institute of Radiology, Catholic University, School of Medicine, Rome/Italy.

 

 

 

  • Anterior column fracture (Fig. 5). May produce one or multiple fragments. Several types are recognized; in all case the posterior column is intact.

 

 

Fig. 5: a) The AP and b) the obturator oblique views show the typical interruption of the ilio-pectineal line (yellow arrow in a, and b) and the fracture of the ischio-pubic ramus (white arrow in a, and b).
References: Institute of Radiology, Catholic University, School of Medicine, Rome/Italy.

 

 

 

  • Transverse fracture (Fig. 6Fig. 7). The transverse fracture transects both the anterior and posterior columns. Pure transverse fractures split the hemipelvis, though the acetabulum, into two large fragments: the upper iliac and the lower or ischio-pubic fragment.

 

 

Fig. 6: Schematic representation of the three variants of transverse fractures described by Letournel referring to the roof of the acetabular fossa: a) iuxtatectal fracture (usually at the junction of the roof and the cotyloid fossa), b) transtectal (occasionally through the roof), and c) infratectal (rarely through the cotyloid fossa cutting the horns of the acetabulum).These fractures typically transects both the anterior and posterior columns. Pure transverse fractures split the hemipelvis, through the acetabulum, into two large fragments: the upper iliac and the lower or ischiopubic fragment. Radiographically all vertical and oblique landmarks are disrupted, but the obturator ring is intact, which distinguishes this fracture from a T-shaped fracture. Furthermore, all projections reveal the roof segment to be attached to the iliac wing, which distinguishes this fracture from both columns injury.
References: Institute of Radiology, Catholic University, School of Medicine, Rome/Italy.

 

 

 

Fig. 7: The AP radiograph shows the interruption of the radiographic landmarks of each acetabular column (arrow), with interruption of both the iliopubic and ileoischial lines (arrow).
References: Institute of Radiology, Catholic University, School of Medicine, Rome/Italy.

 

 

 

 

Complex fractures

         

 

 

Fig. 8: a,b) Schematic representations of T-fractures, that associate a transverse fracture (of any variety) with an additional vertical split which divides the ischiopubic fragment into two parts. a) This split passes typically through the middle part of the obturator ring (a), but it may cut it obliquely either in a forward direction or backwards, and in some cases it descends through the ischium sparing the obturator foramen (b).
References: Institute of Radiology, Catholic University, School of Medicine, Rome/Italy.

 

 

 

Fig. 9: a) The AP view, b) the obturator oblique view and c,d) the axial CT scans show the transverse fracture (arrows in a, b, and c) associated with ischiopubic vertical split (long arrow in a and d) and posterior wall fragment (* in a, b, and c).
References: Institute of Radiology, Catholic University, School of Medicine, Rome/Italy.

 

 

 

  • Posterior column fracture associated with a posterior wall fracture (Fig. 10Fig. 11). This association comprises a posterior column fracture together with a fracture of a portion of the posterior wall. The posterior column fracture is not always complete and frequently little or not at all displaced. The posterior wall fragment is important and should be characterized by its site, posterior, postero-superior, or postero-inferior, by the number of fragments, and by the presence or absence of marginally impacted fragments. 

 

 

Fig. 10: Posterior column fracture associated with a posterior wall fracture in a 77-year-old man involved in a motor-vehicle accident. a) The AP, b) the obturator oblique and c) the iliac oblique views show the typical features of this uncommon fracture. The ilioischial line is displaced (arrow in a, and c) whereas the iliopectineal line is intact. A posterior wall fragment is clearly evident (small arrow in a, and b).
References: Institute of Radiology, Catholic University, School of Medicine, Rome/Italy.

 

 

 

Fig. 11: Axial CT scan show an osteo-cartilaginous fragment (small arrow), the displaced posterior column, the intact anterior column and a posterior wall fragment (arrow).
References: Institute of Radiology, Catholic University, School of Medicine, Rome/Italy.

 

  

 

  • Transverse and posterior wall fracture (Fig. 12Fig. 13). Are a frequent combination. The major component may be the posterior wall (single fragment, multi-fragmentary with or without marginal impaction) and only an “insignificant” transverse crack might be noted on radiography. The femoral head is most often dislocated posteriorly, but in some instances, it dislocates centrally. Careful radiographic study separates this group from pure transverse fractures. Obturator oblique view and CT scans do help in characterizing the posterior wall fragment. 

 

 

Fig. 12: Transverse and posterior wall fractures in a 32-year-old man injured in a motor-vehicle accident. a) The AP radiograph shows the transverse component (arrow). b) The obturator oblique view shows the size of the posterior wall fragment (arrow) and the integrity of the obturator foramen. c) The iliac oblique view demonstrates the position of the break in the posterior margin of the innominate bone by the transverse component (arrow).
References: Institute of Radiology, Catholic University, School of Medicine, Rome/Italy.

 

 

 

Fig. 13: a,b) The CT scans show the transverse fracture (anterior-to-posterior split) (arrows in a) and posterior wall fragments (white arrows in b). The largest one is a marginally impacted fragment (* in a) A small incarcerated fragment is also evident in b (yellow arrow in b).
References: Institute of Radiology, Catholic University, School of Medicine, Rome/Italy.

 

 

 

  • Anterior and hemitransverse fracture (Fig. 14). It's the association of an anterior wall or an anterior column fracture together with a split of the posterior column corresponding to the back half of a transverse fracture. The posterior component is usually located in the lower half of the posterior column and is minimally displaced. Unlike the both column injury, there is always an intact articular fragment attached to the iliac wing. The femoral head is usually anteriorly dislocated or subluxed. 

 

 

Fig. 14: Anterior plus posterior hemitransverse fractures in a 36-year-old man. a) The AP and b) the obturator oblique views show the iliopectineal line disruption (yellow arrow in a, and b), the fracture of the ischiopubic ramus (white arrow in a, and b) and a hemitransverse fracture (curved arrow in a). c,d) The axial CT scans, just above the dome of the acetabulum, better define the hemitransverse fracture (long arrow in c, and d) as well as the anterior column fracture (* and small arrow in c, and d).
References: Institute of Radiology, Catholic University, School of Medicine, Rome/Italy.

 

 

 

  • Fracture of Both Columns (Fig. 15Fig. 16). Fracture of both columns comprise the most complicated examples of acetabular fractures. This fracture is distinguished from all other fracture patterns in that no articular segment remains attached to a segment of iliac wing or sacroiliac joint. The posterior part of the fracture complex is similar to the single posterior column fracture. As the fracture line runs between the greater sciatic notch and the acetabulum, a second fracture line merges with it, and its configuration distinguishes two types of fracture of both column. 

 

 

Fig. 15: a) The AP and b,c) the Judet views show the typical appearance of a both column fracture where the fracture of the anterior column extends from the iliac crest to the superior pubic ramus (small arrows in a). The entire joint is displaced medially (arrow in a). The pathognomonic feature of this injury, the so called spur sign, is seen on the obturator oblique view (arrow in b). A subcapital femoral fracture is also noted (arrowhead in a, b, and c).
References: Institute of Radiology, Catholic University, School of Medicine, Rome/Italy.

 

 

 

Fig. 16: Same patient of figure 18. a,b,c) Axial CT scans showing the coronal nature of the iliac fracture (arrow in a), the spur sign (arrow in b), the subcapital femoral fracture (arrow in c), and the comminution. The asterisk in c indicates an anterior column fragment. d) The 3D CT reconstruction shows the split V section (*), and the coronal split along the pelvic brim with the femoral head peeking through.
References: Institute of Radiology, Catholic University, School of Medicine, Rome/Italy.

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