eMedicine Specialties > Radiology > Musculoskeletal
Acetabulum, Fractures: Imaging
Updated: Feb 11, 2009
Radiography
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.
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 obturator oblique radiograph of the pelvis. The posterior wall fracture (arrow) is better depicted on this view than on the anteroposterior view.
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.
Findings
Brandser and Marsh devised a system of observations leading to the correct classification of most acetabular fractures.19 The answers to the following questions about the radiographic observations are used to determine the acetabular fracture pattern:- Is a fracture of the obturator ring present? A fracture of the obturator ring indicates either a T-shaped or a column fracture (with the exception of the hemitransverse type of fracture). An intact obturator ring eliminates these fractures from consideration.
- Is the ilioischial line disrupted? Disruption of the ilioischial line occurs in fractures involving the posterior column or fractures in the transverse group.
- Is the iliopectineal line disrupted? Disruption of the iliopectineal line indicates anterior column involvement or 1 of the transverse-type fractures.
- Is the iliac wing above the acetabulum fractured? Iliac wing fractures are observed in fractures involving the anterior column.
- Is the posterior wall fractured? Posterior wall fractures may occur in isolation or in combination with posterior column or transverse fractures.
- Is the spur sign present? The spur sign is observed exclusively in the both-column fracture. The spur is a strut of bone extending from the sacroiliac joint. Usually, this strut of bone connects to the articular surface of the acetabulum. In the both-column fracture, this connection is disrupted; a fractured piece of bone that resembles a spur remains. The spur sign is best depicted on the obturator oblique view (see Image 26). In addition, the spur sign can be appreciated on CT scans (see Image 27).
Table 2 shows the combined set of radiographic and CT scan observations that are useful in acetabular fracture classification.
Table 2. Radiographic Features of Acetabular Fracture Types 19Open table in new window
Table
| Fracture Type | Obturator Ring Fracture | Ilioischial Line Disrupted | Iliopectineal Line Disrupted | Iliac Wing Fracture | Posterior Wall Fracture | Pelvis Into Halves | Spur Sign | CT Scan Fracture Orientation |
|---|---|---|---|---|---|---|---|---|
| Both-column | Yes | Yes | Yes | Yes | No | Front/back | Yes | Horizontal |
| Anterior column | Yes | No | Yes | Yes | No | Front/back | No | Horizontal |
| Posterior column | Yes | Yes | No | No | No | Front/back | No | Horizontal |
| Posterior column with posterior wall | Yes | Yes | No | No | Yes | Front/back | No | Horizontal |
| T-shaped | Yes | Yes | Yes | No | No | Top/bottom | No | Vertical |
| Transverse with posterior wall | No | Yes | Yes | No | Yes | Top/bottom | No | Vertical |
| Transverse | No | Yes | Yes | No | No | Top/bottom | No | Vertical |
| Posterior wall | No | No | No | No | Yes | No | No | Oblique |
| Anterior wall | No | No | Yes | No | No | No | No | Oblique |
| Anterior column with posterior hemitransverse | No | Yes | Yes | Yes | No | N/A * | No | N/A |
| Fracture Type | Obturator Ring Fracture | Ilioischial Line Disrupted | Iliopectineal Line Disrupted | Iliac Wing Fracture | Posterior Wall Fracture | Pelvis Into Halves | Spur Sign | CT Scan Fracture Orientation |
|---|---|---|---|---|---|---|---|---|
| Both-column | Yes | Yes | Yes | Yes | No | Front/back | Yes | Horizontal |
| Anterior column | Yes | No | Yes | Yes | No | Front/back | No | Horizontal |
| Posterior column | Yes | Yes | No | No | No | Front/back | No | Horizontal |
| Posterior column with posterior wall | Yes | Yes | No | No | Yes | Front/back | No | Horizontal |
| T-shaped | Yes | Yes | Yes | No | No | Top/bottom | No | Vertical |
| Transverse with posterior wall | No | Yes | Yes | No | Yes | Top/bottom | No | Vertical |
| Transverse | No | Yes | Yes | No | No | Top/bottom | No | Vertical |
| Posterior wall | No | No | No | No | Yes | No | No | Oblique |
| Anterior wall | No | No | Yes | No | No | No | No | Oblique |
| Anterior column with posterior hemitransverse | No | Yes | Yes | Yes | No | N/A * | No | N/A |
* N/A indicates not applicable.
Degree of Confidence
By using Brandser and Marsh's system, the accurate classification of acetabular fractures is possible in almost every patient.
False Positives/Negatives
An accessory ossification center, the os acetabulum, may mimic an acetabular wall fracture. Its differentiating features include its characteristic superolateral location and well-corticated margins. Fractures of the anterior puboacetabular junction may be observed in pelvic ring fractures. These fractures may extend into the anterior column of the acetabulum, but they are not anterior column fractures per se. Such fractures are more correctly considered to be superior pubic ramus fractures.
Computed Tomography
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 orientation with a computed tomography (CT) scan. A CT scan of the left midacetabulum shows that wall fractures have an oblique orientation.
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.
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).
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).
Findings
Brandser and Marsh described several CT scan–based observations in the classification of acetabular fractures.20 The answers to the following questions may help in the classification of these fractures:
- Does the fracture divide the acetabulum into top and bottom halves or into front and back halves? Transverse-type fractures divide the acetabulum into top and bottom halves, as seen from the lateral perspective of the acetabulum. Column fractures divide the acetabulum into front and back halves. Isolated wall fractures do not divide the acetabulum.
- Can an intact strut of bone be followed from the sacroiliac joint to the acetabular articular surface? In other words, is the CT scan spur sign present? Only the both-column fracture causes the spur sign.
- What is the orientation of the major fracture line on CT scans? Transverse-type fractures have a vertical (sagittal) CT scan orientation. Column fractures have a horizontal (coronal) orientation. Wall fractures are oriented obliquely.
Table 2 shows the combined set of radiographic and CT scan observations that are useful in acetabular fracture classification.
Durkee and colleagues presented an algorithm for classification of the 5 most common types of acetabular fracture based on several observations.3 The observations are similar to those presented in Table 2.21,22,4
Degree of Confidence
Interpreted in conjunction with the pelvic radiographs, CT scans allow accurate fracture classification and appropriate surgical planning.
False Positives/Negatives
False findings can occur (see Radiograph Findings).
Magnetic Resonance Imaging
Findings
Magnetic resonance imaging (MRI) is not routinely used in the primary evaluation of acetabular fractures. Potter and colleagues described the use of MRI in the evaluation of occult femoral head injuries and in the detection of subclinical sciatic nerve injury.23 Intra-articular fracture fragments may be missed on magnetic resonance images.
Currently, the use of MRI in imaging deep venous thrombosis in patients with pelvic or lower extremity injuries is being evaluated. Magnetic resonance venography may be useful in depicting lower extremity and pelvic venous thrombosis.24,25,26
Ultrasonography
Findings
Ultrasonography is not used to evaluate acetabular fractures. Lower extremity Doppler ultrasonography is used to assess lower extremity deep venous thrombosis.
More on Acetabulum, Fractures |
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References
Hunter JC, Brandser EA, Tran KA. Pelvic and Acetabular Trauma. Radiol Clin North Am. 1997;35:559-590. [Medline].
Young JW. Pelvic Injuries. Semin Musculoskelet Radiol. 1998;2(1):83-104. [Medline].
Durkee NJ, Jacobson J, Jamadar D, Karunakar MA, Morag Y, Hayes C. Classification of common acetabular fractures: radiographic and CT appearances. AJR Am J Roentgenol. Oct 2006;187(4):915-25. [Medline].
Olson SA. CT-based acetabular fracture classification. AJR Am J Roentgenol. Jul 2005;185(1):277-8; author reply 278-80. [Medline]. [Full Text].
Lovric I, Jovanovic S, Leksan I, et al. Functional status of hip joint after surgical and conservative treatment of acetabular fracture. Coll Antropol. Mar 2007;31(1):285-9. [Medline].
Letournel E. Fractures of the Acetabulum. 2nd ed. New York, NY: Springer-Verlag; 1993.
Matta JM. Fractures of the acetabulum: accuracy of reduction and clinical results in patients managed operatively within three weeks after the injury. J Bone Joint Surg Am. Nov 1996;78(11):1632-45. [Medline].
Dakin GJ, Eberhardt AW, Alonso JE, et al. Acetabular fracture patterns: associations with motor vehicle crash information. J Trauma. Dec 1999;47(6):1063-71. [Medline].
Issack PS, Toro JB, Buly RL, et al. Sciatic nerve release following fracture or reconstructive surgery of the acetabulum. J Bone Joint Surg Am. Jul 2007;89(7):1432-7. [Medline].
[Best Evidence] Karunakar MA, Sen A, Bosse MJ, et al. Indometacin as prophylaxis for heterotopic ossification after the operative treatment of fractures of the acetabulum. J Bone Joint Surg Br. Dec 2006;88(12):1613-7. [Medline].
Harris JH Jr, Lee JS, Coupe KJ, et al. Acetabular fractures revisited: part 1, redefinition of the Letournel anterior column. AJR Am J Roentgenol. Jun 2004;182(6):1363-6. [Medline]. [Full Text].
Judet R, Judet J. [Fractures of the acetabulum]. Acta Orthop Belg. May-Jun 1966;32(3):469-76. [Medline].
Pitt MJ, Ruth JT, Benjamin JB. Trauma to the pelvic ring and acetabulum. Semin Roentgenol. Oct 1992;27(4):299-318. [Medline].
Tile M. Fractures of the Pelvis and Acetabulum. 2nd ed. Baltimore, Md: Williams & Wilkins; 1995.
Tile M. Fractures of the acetabulum. In: Rockwood CA, Green DP, Bucholz RW, et al, eds. Rockwood and Green's Fractures in Adults. 4th ed. Philadelphia, Pa: Lippincott-Raven; Lippincott-Raven Pub:1996.
Brandser EA, El-Khoury GY, Marsh JL. Acetabular fractures: a systematic approach to classification. Emerg Radiol. 1995;2:18-28.
Borrelli J Jr, Peelle M, McFarland E, Evanoff B, Ricci WM. Computer-reconstructed radiographs are as good as plain radiographs for assessment of acetabular fractures. Am J Orthop. Sep 2008;37(9):455-9; discussion 460. [Medline].
Citak M, Gardner MJ, Kendoff D, Tarte S, Krettek C, Nolte LP, et al. Virtual 3D planning of acetabular fracture reduction. J Orthop Res. Apr 2008;26(4):547-52. [Medline].
Brandser E, Marsh JL. Acetabular fractures: easier classification with a systematic approach. AJR Am J Roentgenol. Nov 1998;171(5):1217-28. [Medline].
Beaulé PE, Dorey FJ, Matta JM. Letournel classification for acetabular fractures. Assessment of interobserver and intraobserver reliability. J Bone Joint Surg Am. Sep 2003;85-A(9):1704-9. [Medline].
Harris JH Jr, Coupe KJ, Lee JS, Trotscher T. Acetabular fractures revisited: part 2, a new CT-based classification. AJR Am J Roentgenol. Jun 2004;182(6):1367-75. [Medline].
Ohashi K, El-Khoury GY, Abu-Zahra KW, Berbaum KS. Interobserver agreement for Letournel acetabular fracture classification with multidetector CT: are standard Judet radiographs necessary?. Radiology. Nov 2006;241(2):386-91. [Medline].
Potter HG, Montgomery KD, Heise CW, et al. MR imaging of acetabular fractures: value in detecting femoral head injury, intraarticular fragments, and sciatic nerve injury. AJR Am J Roentgenol. Oct 1994;163(4):881-6. [Medline].
Cabarrus MC, Ambekar A, Lu Y, Link TM. MRI and CT of insufficiency fractures of the pelvis and the proximal femur. AJR Am J Roentgenol. Oct 2008;191(4):995-1001. [Medline].
Hong RJ, Hughes TH, Gentili A, Chung CB. Magnetic resonance imaging of the hip. J Magn Reson Imaging. Mar 2008;27(3):435-45. [Medline].
Kwon JW, Huh SJ, Yoon YC, Choi SH, Jung JY, Oh D, et al. Pelvic bone complications after radiation therapy of uterine cervical cancer: evaluation with MRI. AJR Am J Roentgenol. Oct 2008;191(4):987-94. [Medline].
Further Reading
Clinical Guidelines and Trials:
ACR Appropriateness Criteria® developmental dysplasia of the hip. American College of Radiology - Medical Specialty Society. 1999 (revised 2005). 8 pages. NGC:004788
ACR Appropriateness Criteria® imaging after total hip arthroplasty (THA). American College of Radiology - Medical Specialty Society. 1998 (revised 2005). 8 pages. NGC:004649
Periacetabular Osteotomy.A Prospective Study With Reference to Cartilage, Migration and Bone Density
Role of Vacuum Assisted Closure (VAC) Device in Postoperative Management of Pelvic and Acetabular Fractures
Unipolar or Bipolar Hemiarthroplasty in the Treatment of Displaced Femoral Neck Fractures. A Randomized Trial of RSA Measurements of Acetabular Wear
Acetabular Fractures of Both Columns
A Clinical Investigation of the C2a-Taper™ Acetabular System
Clinical Study Evaluating an Acetabular Cup System After Total Hip Replacement
Safety and Effectiveness Study of the Reflection Ceramic Acetabular System
The Influence of "Operating Table Position Simulating Radiographs" on Acetabular Cup Angle During Primary Total Hip Replacement
Evaluation of Acetabular Perfusion After Ganz Osteotomy by Positron Emission Tomography
Keywords
acetabulum fracture, acetabulum trauma, acetabular trauma, femur trauma, femoral trauma
