What are the patterns of acetabulum fractures seen on radiographs?

Updated: Jun 25, 2019
  • Author: David S Levey, MD; Chief Editor: Felix S Chew, MD, MBA, MEd  more...
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Answer

Isolated acetabular wall fractures typically do not involve the weight-bearing articular portion of the acetabulum. Fractures of the posterior wall are more common than are those of the anterior wall because of the preponderance of posteriorly directed forces responsible for acetabular fractures. Posterior wall fractures may occur in isolation (see the first three images below) or in combination with posterior column or transverse fractures. Anterior wall fractures are rare (see the last image below).

Posterior wall acetabular fracture. Anteroposterio Posterior wall acetabular fracture. Anteroposterior radiograph of the pelvis. The posterior wall of the left acetabulum is disrupted (arrow).
Posterior wall acetabular fracture. A left obturat Posterior wall acetabular fracture. A left obturator oblique radiograph of the pelvis. The posterior wall fracture (arrow) is better depicted on this view than on the anteroposterior view.
Computed tomography (CT) scan of a posterior wall Computed tomography (CT) scan of a posterior wall acetabular fracture. The oblique fracture of the left acetabulum is clearly depicted. The degree of displacement and marginal impaction can be determined more accurately with CT scanning than with radiography.
Anterior wall acetabular fracture. A computed tomo Anterior wall acetabular fracture. A computed tomography (CT) scan demonstrates an oblique fracture through the anterior wall of the left acetabulum (arrow). Such fractures are uncommon in isolation. The patient had other pelvic injuries.

Both-column fractures are the most common acetabular injury. As the name implies, the anterior and posterior columns are involved. On AP radiographs, a disruption of the iliopectineal and ilioischial lines, as well as the obturator ring, may be seen (see the first image below). An iliac wing fracture may be seen on the AP view, but often, it is appreciated only on the iliac oblique radiograph (see the second image below). The pathognomonic spur sign is present on the obturator oblique view (see the third image below) and confirmed on a CT scan (see the last 3 images below).

Both-column acetabular fracture. An anteroposterio Both-column acetabular fracture. An anteroposterior radiograph of the pelvis shows that the right ilioischial and iliopectineal lines are completely disrupted. A right iliac wing fracture is noted above the level of the acetabulum (arrow). A nondisplaced fracture of the right inferior pubic ramus is subtle.
Both-column acetabular fracture. A right iliac obl Both-column acetabular fracture. A right iliac oblique radiograph of the pelvis. The posterior column (arrowhead) and iliac wing disruptions are shown.
Both-column acetabular fracture. A right obturator Both-column acetabular fracture. A right obturator oblique radiograph of the pelvis best depicts nondisplaced fractures of the obturator ring (arrowheads). The iliopectineal line disruption (short arrow) signifies anterior column involvement. The pathognomonic spur sign (long arrow) of the both-column fracture is best appreciated on this view. The spur represents a strut of bone extending from the sacroiliac joint. The fracture of both columns disconnects this piece of bone from the acetabulum and causes its spurlike appearance.
Both-column acetabular fracture. A computed tomogr Both-column acetabular fracture. A computed tomography (CT) scan obtained at the level of the sacroiliac joints shows that the horizontal (coronal) column fracture begins superiorly at the iliac wing in the both-column fracture. The CT scan equivalent of the spur sign can be seen (arrow).
Both-column acetabular fracture. A computed tomogr Both-column acetabular fracture. A computed tomography (CT) scan obtained just above the level of the acetabular dome shows that the CT scan spur sign is present (arrow).
Both-column acetabular fracture. A computed tomogr Both-column acetabular fracture. A computed tomography (CT) scan obtained at the level of the acetabular dome shows the CT scan spur sign (arrow). Note how this spur does not connect to the articular portion of the acetabulum. In a both-column fracture, the articular surface of the acetabulum is completely disconnected from the axial skeleton.

Isolated anterior and posterior column fractures are uncommon. Anterior column fractures disrupt the iliopectineal line while preserving the ilioischial line. Conversely, posterior column fractures disrupt the ilioischial line but not the iliopectineal line (see the images below).

Posterior column acetabular fracture. An anteropos Posterior column acetabular fracture. An anteroposterior radiograph of the pelvis shows that the left femoral head is dislocated posteriorly. The ilioischial line is broken, but the iliopectineal line remains intact.
Posterior column acetabular fracture. Compared wit Posterior column acetabular fracture. Compared with the anteroposterior view, the left obturator oblique radiograph of the pelvis better depicts the posteriorly displaced posterior column, posterior wall, and femoral head.
Posterior column acetabular fracture. A left iliac Posterior column acetabular fracture. A left iliac oblique radiograph of the pelvis shows that the posterior column is markedly displaced.
Computed tomography (CT) scan of a posterior colum Computed tomography (CT) scan of a posterior column acetabular fracture at the level of the acetabular dome. The characteristic horizontal (coronal) orientation of the column fracture is appreciated easily by using CT scanning.
Posterior column acetabular fracture. A computed t Posterior column acetabular fracture. A computed tomography (CT) scan obtained at the level of the midacetabulum shows the horizontally oriented column fracture. The femoral head is relocated, but the recent posterior dislocation is evident in the anterior impaction fracture (arrow).
Posterior column acetabular fracture. A computed t Posterior column acetabular fracture. A computed tomography (CT) scan obtained at the level of the ischial tuberosities shows that posterior column fractures sometimes can exit through the ischial tuberosity (arrow) rather than through the obturator ring.

Column fractures divide the acetabulum into front and back halves (see the first image below). The posterior column fracture with a posterior wall fracture has the features of each of its components (see the second image below). The slightly more common anterior column fracture with a posterior hemitransverse fracture is the most complex acetabular fracture to classify.

Acetabular fracture orientation with a computed to Acetabular fracture orientation with a computed tomography (CT) scan. A CT scan of the left acetabulum obtained at the level of the dome shows that transverse-type acetabular fractures have a vertical (sagittal) orientation. Column-type fractures have a horizontal (coronal) orientation.
Acetabular fracture classification system. Judet a Acetabular fracture classification system. Judet and colleagues (1964) described the classification scheme that is most commonly used today. Of the 10 types, 5 are elementary fractures (top row), and 5 are associated fractures (bottom row). Elementary types involve 1 primary fracture plane. Associated types involve more than 1 fracture plane.

The combination of column fractures and transverse fractures may be difficult to appreciate radiographically (see the first image below). The iliopectineal and ilioischial lines are broken, and an iliac wing fracture should be evident. Unlike the both-column fracture, which shares these features, the obturator ring is intact and the spur sign is not present. On CT scans, the anterior column and the posterior transverse fracture planes may be appreciated (see the second image below).

Anterior column fracture with a posterior hemitran Anterior column fracture with a posterior hemitransverse acetabular fracture. An anteroposterior radiograph of the pelvis shows disruption of the iliopectineal (long arrow) and ilioischial (short arrows) lines. The obturator ring is intact.
Anterior column fracture with a posterior hemitran Anterior column fracture with a posterior hemitransverse acetabular fracture, as depicted on computed tomography (CT) scans obtained above and at the level of the right acetabulum. Left: The image shows an iliac wing fracture (arrow) that was not appreciated on the anteroposterior radiograph. (The oblique radiographs were not of good quality.) Middle: The image clearly depicts a column-type fracture (arrow) that is oriented horizontally on the CT scans. Right: The image again demonstrates the column fracture (long arrow), but now a transverse (vertically oriented) fracture can be seen posteriorly (short arrow).

Transverse fractures are transverse because of their appearance when the acetabulum is examined from the lateral view. The iliopectineal and ilioischial lines are interrupted, but the obturator ring is spared. On CT scans, the fracture is oriented vertically (front to back).

Transverse fractures divide the acetabulum into top and bottom halves, as seen on the lateral view of the acetabulum. The transverse fracture with a posterior wall fracture is a common fracture that incorporates the features of transverse and posterior wall elementary fractures (see the images below).

Transverse with posterior wall acetabular fracture Transverse with posterior wall acetabular fracture. An anteroposterior radiograph of the pelvis shows that the central dislocation of the left femoral head results in the disruption of the iliopectineal and ilioischial lines. In addition, the left posterior acetabular wall is disrupted.
Transverse fracture with a posterior wall acetabul Transverse fracture with a posterior wall acetabular fracture. Compared with the anteroposterior view, this left obturator oblique view of the pelvis view better demonstrates the anterior column and posterior wall disruption. The obturator ring is intact.
Computed tomography (CT) scan of a transverse frac Computed tomography (CT) scan of a transverse fracture with a posterior wall acetabular fracture. The vertically oriented transverse fracture (arrow) of the left acetabulum is well depicted on CT scans. Note the oblique posterior wall fracture (arrowhead). Posterior wall fractures often are associated with femoral head dislocation.

The T-shaped fracture is a fairly common acetabular injury. This fracture has the characteristics of an elementary transverse fracture with the addition of a medial acetabular wall fracture extending through the obturator ring (see the images below). The anterior column with posterior hemitransverse fracture is discussed earlier.

T-shaped acetabular fracture. An anteroposterior r T-shaped acetabular fracture. An anteroposterior radiograph of the pelvis shows that a transverse fracture (arrows) disrupts the left iliopectineal and ilioischial lines. The obturator ring also is interrupted (arrowheads). No iliac wing fracture is seen above the level of the acetabulum.
Computed tomography (CT) scan of T-shaped acetabul Computed tomography (CT) scan of T-shaped acetabular fracture. The transverse portion of the fracture has a vertical (sagittal) orientation (arrow). The extension of the fracture through the medial wall represents the stem of the T (arrowhead). More inferior CT scans demonstrated the obturator ring fractures.

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