What is the role of CT scans 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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CT scanning

Pelvic CT scans may be obtained alone or in combination with abdominal CT scans during the initial trauma evaluation. Pelvic CT scans allow the detection of subtle fractures and displacements that are not appreciated on radiographs. [22] Axial CT scans may be obtained, but helical CT scanning yields better 2D and 3D reformatted images. [18]

In a retrospective review of suspected occult hip fractures detected by CT or MRI following negative radiographs, of 179 patients investigated (mean age, 82±13 years), the ultimate diagnosis was an occult hip fracture in 71 cases and pelvic or acetabular fracture in 34 cases. The average time to further imaging was 2.0±2.7 days but was significantly shorter for CT. [23]

As opposed to older CT scanners, newer scanners use 2D axial helical continuous volumetric acquisitions of patient anatomy. Using MDCT with 2D MPR images and 3D volume rendering is the current state of the art for image acquisition in North America. Sixteen-, 32-, 64-, 128-, and 256-slice scanners are widely available at the time of authorship. After fast axial image acquisition over 15-25 seconds, depending on equipment, the "slab" of continuous anatomy is then created during the image reconstruction phase, during which image reformatting may occur, allowing the patient to leave the CT suite and be transported to another area to be treated for his or her injuries.

Rapid image acquisition is important in acutely injured, unstable patients with highly painful injuries, as it allows for rapid scan times, decreased motion artifact, and large volumes of tissue acquired in a single setting.

Traditional classification into anterior column, posterior column, and complex 2-column fractures is facilitated. CT is especially useful in evaluation of the 2-column fractures in which unique information concerning the configuration of the fracture and integrity of the acetabular dome and quadrilateral surface can be obtained. Helical CT scanning is also useful in determining the presence or absence of loose bodies in the joint. Evaluation of the femoral head and sacroiliac joint is also emphasized, as these structures may participate in the traumatic process. Fracture may occur in any part of the proximal femoral metaepiphysis, or fracture extension into the sacroiliac joint and/or distraction forces that create sacroiliac joint space widening.

Virtually all acetabular fractures may be correctly classified after careful interpretation of AP and oblique radiographs of the pelvis. However, excellent patient care does not stop at simple fracture classification. Intra-articular fracture fragments may be difficult to recognize on radiographs, as are loose bodies, subtle clinically significant malalignment, and fracture extension outside of the region of the hip joint proper.

Compared with radiography, pelvic CT scanning allows a more precise determination of the degree of articular involvement, as well as of fragment displacement and orientation. As above, pelvic CT scanning also permits the identification of intra-articular fracture fragments. In complex acetabular fractures, 3D reformatted images, so-called "virtual imaging" of the acetabular and pelvic bones, may help conceptualize the fracture pattern and thereby aid in the planning of orthopedic surgical intervention.

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