Ortho Hors D'oeuvres (Answer):
To review, this is a 42 year-old male with left hip pain after fall.
Questions and Answers:
1) Is there an injury on the radiographs? If so, what is it?
In the above films, linear radiographic lucencies can be seen extending both superiorly and inferiorly from the acetabulum, consistent with an acetabular fracture.
Acetabular fractures can involve the anterior half of the acetabulum or the posterior half of the acetabulum. These halves are referred to as columns, and knowledge of which column is involved can be helpful for both evaluation of associated injuries and surgical planning. Posterior column fractures are frequently associated with posterior hip dislocation and are often caused by axial force on a flexed knee; knees against a dashboard in high speed MVC is a good example of this injury pattern. Anterior column fractures are also caused by axial force, but are more likely to occur when the leg is in extension.
Briefly, radiographic evaluation for acetabular fracture should include the following: trace the ileopectinal line, ilioischial line, acetabular roof, anterior rim, and the "anatomical teardrop."
If the ileopectineal line or anterior rim are disrupted, this would indicate anterior column fracture. If the ilioischial line or the posterior rim are disrupted, this would indicate posterior column fracture. Disruption of the anatomical teardrop can indicate an occult acetabular fracture and warrants further imaging.
Nondisplaced fractures of the hip and acetabulum can be faint and easily missed on radiographs, even if slightly visible as in this case. Overall radiographic sensitivity for hip fractures using the standard AP and lateral view ranges from 90-98%.
2) What are the next steps in imaging? Patients with diagnosed acetabular fractures by radiograph may require Judet views to further characterize the fracture. In the Judet view, a patient lies supine with a 45 degree rotation towards the affected hip, so that the acetabular surface is more transverse to the x-rays and fracture lines more easily detected. Judet views can also be helpful in assessing whether a superior or inferior pubic ramus fracture extends into the acetabulum.
This is a Judet view of the patient's left hip; the patient's right side is resting on a 45 degree ramp so the left hip is in the dependent position and open to the xrays.
For operative planning and evaluation for associated injuries, these patients will also benefit from more advanced imaging with CT or MRI. This discussion should be made in concert with your orthopedic consult.
In patients with concerning mechanism or suspected osteoporosis and continued pain causing inability to ambulate, further imaging should be pursued to evaluate for occult fractures. The gold standard for nondisplaced bony fractures is MRI. However, based on small cased reports, 64-slice CT is 98% sensitive in the detection of occult fracture and recent larger retrospective review (174 patients) found CT to be 100% sensitive for occult fracture.
This patient received a CT scan which is seen below:
3) What are the next steps in management?
Acetabular fractures are high-energy injuries caused by the forceful impact of the femoral head on the acetabulum and thorough evaluation for associated injuries must be performed. The reported incidence of associated bodily injuries are as follows: 19% head injury, 18% chest injury, 12% abdominal or genitourinary injury, and 4% spinal injury. More specifically, these patients frequently have severe trauma to the knee that can go undiagnosed because of distracting hip pain. 29% of patients with acetabular fractures have associated knee fractures (either patella or distal femur), and 25% have ligamentous injuries of the knee. A patient who is diagnosed with an acetabular fracture should have a very thorough secondary evaluation, and if range of motion of the ispilateral knee is limited because of hip pain, the patient should get radiographs of the knee as well as the hip.
Acetabular fractures are always nonweight-bearing and almost always require surgical fixation. Indications for surgical treatment for an acetabulum fracture include loss of congruence between the femoral head and the acetabulum on any view, displacement of greater than 2 mm within the superior articular surface (weight-bearing dome) retained intraarticular fragments, and disruption of greater than 25% of the width of the posterior wall on CT. Orthopedics should always be consulted for these patients and they will require admission for pain control regardless of the operative planning by your consultant.
References:
Judet films courtesy of Dr Luke Danaher, Radiopaedia.org, rID: 39777
Cannon J, Silvestri S, Munro M. Imaging Choices in Occult Hip Fracture. J Emerg Med. 2009 Aug;37(2):144-52.
Hakkarinen DK, Banh KV, Hendey GW. Magnetic resonance imaging identifies occult hip fractures missed by 64-slice computed tomography. J Emerg Med. 2012 Jan;43(2):303-307.
Kempegowda et al. Knee Injury Associated with Acetabular Fractures: A Multicenter Study of 1273 Patients. J Orthop Trauma. 2016 Jan;30(1):48-51.
Rehman et al. Imaging of occult hip fractures: CT or MRI? Injury. 2016, http://dx.doi.org/10.1016/j.injury.2016.02.020
Rockwood CA et al. (2001). Rockwood and Green's fractures in adults. Philadelphia: Lippincott Williams & Wilkins.
Tintinalli JE, Kelen GD, Stapczynski JS. (2010). Emergency medicine: A comprehensive study guide. New York: McGraw-Hill, Med Pub. Division.
