What is the role of radiography in the workup of acetabulum fractures?

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

Radiography

AP radiography of the pelvis is used in the initial radiographic assessment of patients with major trauma that is suggestive of pelvic and/or acetabular injury (see the images below). Images are obtained with the patient in the supine position and with the radiographic beam passing in an AP direction. This is the typical first radiographic examination performed, as a patient may arrive on a stretcher in the hospital ED in acute, severe pain and extremis, and time is of the essence to establish an immediate working diagnosis. Abnormalities depicted on the AP pelvis radiograph direct the need for the next set of radiographs, if indicated. Acetabular fractures are imaged by using bilateral oblique (ie, Judet) views of the pelvis. Pelvic ring fractures are imaged by using inlet and outlet views of the pelvis.

Anteroposterior view of the pelvis. The left femur Anteroposterior view of the pelvis. The left femur has been removed for illustration purposes. The iliopectineal, or iliopubic, line is an important landmark for examining the anterior column of the acetabulum. The ilioischial line demarcates the medial border of the posterior column. The posterior wall of the acetabulum is larger and projects more laterally than does the anterior wall.
Anteroposterior (AP) radiograph of the pelvis. The Anteroposterior (AP) radiograph of the pelvis. The iliopectineal (or iliopubic) and ilioischial lines serve as landmarks for the anterior and posterior columns, respectively. The larger and more lateral posterior wall is visualized more easily than is the smaller, more medial anterior wall. The acetabular tear figure is a composite shadow of the inferomedial structures that compose the acetabulum. The ilioischial line should pass through the teardrop on a true AP view of the pelvis.

In a retrospective review of 133 patients who underwent acetabular revision for pelvic discontinuity, preoperative radiographic studies were reviewed, including anteroposterior pelvis (AP; N = 133), true lateral hip (N = 132), Judet (N = 47), false profile (N = 4), and computed tomography scans (N = 14). Using only the AP view, the fracture line was visible in 116 (87%), medial migration of the inferior hemipelvis in 126 (95%), and obturator ring asymmetry in 114 (86%). A fracture line was visualized in 65 of 132 hips (49%) evaluated with laterals, 36 of 47 hips (77%) evaluated with Judet views, 3 of 4 (75%) evaluated with a false profile view, and 10 of 14 (71%) evaluated with computed tomography. [21]

Oblique, or Judet, radiographs of the pelvis are obtained with the patient in the left posterior oblique and right posterior oblique positions (see the images below). The patient should be at a 45º angle relative to the radiographic beam, which remains perpendicular to the cassette. This technique results in 2 orthogonal radiographs of the pelvis. The patient must be moved to the oblique position; the radiographic tube is not moved so as to be at a 45º angle relative to the patient and film cassette. Angling the tube results in unacceptable radiographic distortion.

Left obturator oblique view of the pelvis. The lef Left obturator oblique view of the pelvis. The left obturator ring is seen en face. The anterior column and posterior wall of the left acetabulum are profiled in this position.
Left iliac oblique view of the pelvis. The left il Left iliac oblique view of the pelvis. The left iliac wing is demonstrated en face. The left posterior column and the anterior wall are seen in profile.

A common mistake in this radiographic technique is the positioning of the patient in an oblique position that is not steep enough, with a resultant angle of less than 45º. On an oblique view obtained with good positioning, with the aid of a blocking device or on-site technologist to hold the patient in place, the coccyx should project over the femoral head.


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