EMRad: Radiologic Approach to the Traumatic Hip/Pelvis

This is EMRad, a series aimed at providing “just in time” approaches to commonly ordered radiology studies in the emergency department [1]. When applicable, it will provide pertinent measurements specific to management, and offer a framework for when to get an additional view, if appropriate. Next up: the hip.

Learning Objectives

1. Interpret traumatic hip x-rays using a standard approach
2. Identify clinical scenarios in which an additional view might improve pathology diagnosis

Why the hip matters and the radiology rule of 2’s

The Hip

• Hip and thigh pain are common complaints in the ED [2].
• Hip fractures have a very high one-year mortality [2].
• Compared with CT, pelvic radiographs have a sensitivity of 64% to 78% for the identification of pelvic fractures in blunt trauma [3].
• 2% of occult hip fractures will be missed by CT. Consider MRI for patients with significant hip pain and negative x-rays [2]. MRI hip protocols can be done in as little as 5-15 minutes.

Before we begin: Make sure to employ the rule of 2’s [4]

• 2 views: One view is never enough
• 2 abnormalities: If you see one abnormality, look for another
• 2 joints: Image above and below the injury
• 2 sides: If unsure regarding a potential pathologic finding, compare to another side
• 2 occasions: Always compare with old x-rays if available
• 2 visits: Bring patient back for repeat films

An approach to the traumatic adult hip x-ray

1. Adequacy
2. Bones
   • Inner Pelvic Ring
   • Obturator Foramina
   • Sacral Foramina
   • Outer Pelvic Ring
   • Acetabulum
     • Iliopectineal Line
     • Ilioischial Line
   • Femur
     • Shelton’s Line
3. Cartilage/Joints
   • The SI Joint
   • Pubic Symphysis
4. Consider an additional view

1. Adequacy

• • A standard “hip series” consists of the AP view of the pelvis and a lateral view of the affected extremity.
    • There are multiple ways to perform the “lateral view”
    • For trauma: “Cross Table Lateral” or “Horizontal Beam Lateral” has these views
      • Require minimal movement of the affected painful hip
  • The AP radiograph of the pelvis should include the whole pelvis, proximal 3rd of the femur, and the lumbar spinous processes, coccyx, and pubic symphysis in a straight line [5].
    • The patient’s legs should be internally rotated to maximize visualization of the femur anatomy [6].
  • The lateral radiograph should include the acetabulum, ischial spine and tuberosity, and proximal femur.

2. Bones

• • Examine the “Three rings“: Inner Pelvic Ring and 2 Obturator Foramina. They should be smooth. If disrupted, think fracture.

• Figure 3: Inner Pelvic Rings. Case Courtesy of Dr. Jeremy Jones, Radiopedia.org. Annotations by Stephen Villa, MD.

  • Arcuate Lines of Sacrum should be smooth and symmetrical.

• Figure 4: Arcuate Lines of Sacrum. Case Courtesy of Dr. Jeremy Jones, Radiopedia.org. Annotations by Stephen Villa, MD.

  • Outer Pelvic Ring

• Figure 5: Outer Pelvic Ring. Case Courtesy of Dr. Jeremy Jones, Radiopedia.org. Annotations by Stephen Villa, MD.

  • Acetabulum: Look for any cortical breaks
    • Ileopectinal Line: Disruption suggests fracture of the anterior column of the acetabulum
    • Ilioischial Line: Disruption suggest a fracture of the posterior column of the acetabulum

• Figure 6: Acetabulum. Case Courtesy of Dr. Jeremy Jones, Radiopedia.org. Annotations by Stephen Villa, MD.

  • Femur
    • Evaluate the femoral head, neck, intertrochanteric region (between greater and lesser trochanters), femoral shaft.
    • Shenton’s Line – Line from the medial femoral neck to the inferior edge of the superior pubic ramus, disruption is concerning for a femoral neck fracture.

3. Cartilage/Joints

• • The SI Joints: should be 2-4 mm.
  • Pubic Symphysis: should be <5 mm.

4. Consider an additional view

Frog Leg Lateral View

• When: Because this view requires movement of the hips, it is not appropriate to obtain if concerned for fracture or dislocation. This view is used mostly in pediatrics.
• Why: Helpful when concerned for Slipped Capital Femoral Epiphysis or Legg-Calve’-Perthes as it allows for better visualization of the femoral head.

“Pelvic Inlet/Outlet” View

• When/Why: Do not perform when clinically concerned for fractures. The inlet view allows better visualization of the pelvic brim while the outlet view improves visualization of the SI joint/Sacral Foramina and the presence of vertical displacement.

“Judet” View

• When/Why: Allows for better visualization of acetabulum [7].

Learn More

Want a more in-depth review? Check out Taming the Sru, Startradiology, or radiopaedia.org, all of which have excellent reviews of the pelvic x-ray.

Dealing with polytrauma? Check out EMRad’s approach to the wrist, foot, elbow, shoulder, ankle, or knee.

Resources

1. Schiller P et al. Radiology Education in Medical School and Residency. The views and needs of program directors. Academic Radiology, Vol 25, No 10, October 2018. PMID: 29748056
2. Stein M et al. Emergency Department Evaluation and treatment of Acute Hip pain. Emerg Med Clin N Am. Volume 33. Issue 2. May 2015. PMID: 25892725.
3. Steele M, Norvell J. Chapter 269. Pelvis Injuries. In: Tintinalli’s Emergency Medicine. A Comprehensive Guide, 7th edition. New York: McGraw-Hill Education, 2011. P1841-1840
4. Chan O. Introduction: ABCs and Rules of Two. ABC of Emergency Radiology, Third Edition. Edited by Otto Chan. 2013 John Wiley & Sons, Ltd. Published 2013.
5. Sanville P et al. ABC of Emergency Radiology. The hip. BMJ. Volume 308. Feb 1994. PMID. 8136674
6. Lim SJ et al. Plain Radiography of the Hip: A Review of Radiographic Techniques and Image Features. Hip Pelvis. Volume 27. Issue 3. Sep 2015. PMID 27536615.
7. Hutt JR, Ortega-Briones A, Daurka JS et-al. The ongoing relevance of acetabular fracture classification. Bone Joint J. Volume 8. Aug 2015. PMID 26224834.

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