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Obturator oblique; anterior-posterior position of the screw
12%
237/1967
Obturator outlet; cranial-caudal position of the screw
28%
545/1967
Obturator inlet; medial-lateral position of the screw
25%
497/1967
Obturator oblique; cranial-caudal position of the screw
21%
420/1967
Obturator outlet; anterior-posterior position of the screw
8%
154/1967
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This patient has a transverse acetabular fracture that can be partially stabilized by an anterior column screw. The view shown demonstrates the obturator outlet view which assesses the cranial-caudal position of the screw in order to remain extra-articular. Fixation of the anterior column can be performed percutaneously. The starting point for the antegrade placement of an anterior column screw is determined by a line drawn between the tip of the greater trochanter and the thick part of the iliac crest. The wire is then inserted and directed towards the pubic symphysis. Obturator outlet views and iliac inlet views are obtained to ensure the wire remains intraosseous. The obturator outlet view determines the cranial-caudal position of the wire in order to remain out of the hip joint. Starr et al. wrote a technique on percutaneous fixation of the columns of the acetabulum. They reported that in order to safely place an anterior column screw, the C-arm should be oriented perpendicular to the superior pubic ramus. The C-arm can then be rotated during screw placement between an iliac inlet view and an obturator outlet view. The iliac inlet view is used to ensure that the guidewire does not penetrate the inner cortex of the superior ramus, while the obturator outlet view is used to make sure the wire does not penetrate the hip joint. Mauffrey et al. performed a review of the radiographic evaluation of acetabular fractures. They reported that the acetabulum consists of two columns of bone arranged in an inverted Y-shaped configuration that is attached to the ilium. They report that radiographic evaluation and classification of acetabular fractures is necessary to guide treatment decisions. They concluded that CT scans provide invaluable information in classifying these injuries. Figure A is an obturator outlet view in a patient with a transverse acetabular fracture. Illustration A is an illustration demonstrating the path for an antegrade anterior column screw (Starr et al.). Illustration B is an illustration demonstrating the path for a retrograde anterior column screw (Starr et al.). Incorrect Answers: Answers 1 & 4: Though the obturator oblique may reveal intra-articular penetration, the obturator outlet view most clearly demonstrates this conduit of bone. Answer 3: The obturator inlet view has no role in the placement of an anterior column screw. It assists with placement of screws within the tables of the ilium. Answer 5: The obturator outlet view assists with the cranial-caudal position of the screw, while the iliac inlet assists with the anterior-posterior position of the screw.
2.0
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