What is the best way to order an x-ray (radiograph) for a suspected pelvic fracture?

Imaging Protocol for Suspected Pelvic Fracture

For hemodynamically unstable patients, obtain a portable anteroposterior (AP) pelvic X-ray immediately upon arrival; for hemodynamically stable patients, skip the plain X-ray and proceed directly to CT scan of the chest, abdomen, and pelvis with IV contrast. 1, 2

Hemodynamically Unstable Patients

Immediate portable AP pelvic radiograph is the first-line imaging study when patients remain unstable despite resuscitation efforts or require urgent interventions to stabilize vital signs. 1, 2 This approach allows for:

• Rapid identification of unstable pelvic injuries that require immediate hemorrhage control while resuscitation continues 1
• Concurrent evaluation with chest X-ray and E-FAST to rule out extra-pelvic sources of hemorrhagic shock 1, 2
• Time-critical decision-making regarding angiographic embolization, external fixation, or laparotomy without delaying bleeding control beyond 60 minutes from admission 2

Critical Caveat

Plain radiographs miss approximately 22% of pelvic fractures, with sacral and iliac fractures being the most commonly overlooked injuries. 3 However, in unstable patients, the speed of obtaining this screening study outweighs its limited sensitivity, as it identifies life-threatening injuries requiring immediate intervention. 1

Hemodynamically Stable Patients

Proceed directly to whole-body CT scan (chest, abdomen, pelvis) with IV contrast, bypassing plain radiographs entirely. 1, 2 The rationale is compelling:

• CT provides complete injury inventory including occult fractures, associated visceral injuries, and active arterial bleeding (sensitivity 82-89%, specificity 75-100% for contrast extravasation) 2
• Plain X-rays add no clinical value in stable patients who will undergo CT regardless, as demonstrated by studies showing 51% of patients are underdiagnosed by radiographs alone 3
• Reduced radiation exposure and cost by eliminating redundant imaging 4

Standard Radiographic Views (When X-ray is Indicated)

If plain radiography is performed, the proper technique includes:

• AP view of the entire pelvis (not just the symptomatic hip) to detect concomitant sacral and pubic rami fractures that occur in the majority of cases 1, 2
• Cross-table lateral view of the symptomatic hip to complete orthogonal imaging, as this view changes treatment decisions even when the AP appears clearly positive 1, 2
• Proper patient positioning with approximately 15 degrees of internal rotation for the AP view 1

Why Include the Entire Pelvis

Patients with proximal femur fractures frequently have associated pelvic fractures (sacrum, pubic rami) that may occur in isolation or concomitantly, and the contralateral side serves as an internal control for comparison. 1, 2, 5

Advanced Imaging for Occult Fractures

When initial imaging is negative but clinical suspicion remains high (persistent pain, positive physical examination with posterior pelvic tenderness):

• MRI without IV contrast is the next imaging study of choice with the highest diagnostic accuracy rating (9/9) for occult fractures 1, 2, 5
• CT without contrast is an acceptable alternative (rating 7/9) when MRI is contraindicated 1, 5
• At least 90% of proximal femoral fractures are visible on radiographs, so advanced imaging is reserved for the minority with negative initial studies 1

Special Considerations

Lower Urinary Tract Injury

Perform retrograde urethral and bladder opacification before attempting catheterization in patients with clinical symptoms of lower urinary tract injury (blood at meatus, perineal hematoma), especially in men, as contrast CT may miss bladder injuries when a catheter is already in place. 2

Angiography Planning

CT angiography should precede angiographic embolization when the patient's hemodynamic status permits, as it guides targeted intervention. 2

Common Pitfalls to Avoid

• Never rely on hip radiographs alone without including the pelvis, as this misses associated pelvic fractures in the majority of cases 2, 5
• Do not skip the cross-table lateral view when obtaining plain films, as orthogonal views are essential and alter treatment decisions 1, 2
• Avoid delaying CT in stable patients to obtain plain films first, as this adds no diagnostic value and wastes time 1, 3
• Do not dismiss negative radiographs when clinical examination reveals posterior pelvic tenderness (98% sensitive for posterior ring injury), as occult fractures require advanced imaging 6, 2