IS Case 193: Posterior dislocation of the femoral head

Nate Johnson, MD

Imaging Sciences URMC 2008
Publication Date: 2009-05-22

History

A 15-year-old male felt a popping sensation after tackled while playing football.

Discussion

Posterior dislocations at the hip constitute 90% of hip dislocations. Imaging findings include a superolateral position of the femoral head on AP radiography and lateral view demonstrating a posterior location of the femoral head in relation to the acetabulum. Once the diagnosis of posterior hip dislocation is established it is important to assess for associated fractures that would complicate the reduction.

The most common clinical scenario for posterior hip dislocation is a patient presenting status post-motor vehicle accident or fall with adduction and internal rotation of the femur. The affected limb will also appear shortened and the hip and knee may be held in flexion.

Treatment goal is to reduce the dislocation within 6 hours because the risk of avascular necrosis increases with delay in reduction. If the reduction is achieved in less than 6 hours there is a 4.8% chance of osteonecrosis compared to 58.8% if delayed. Most of the reductions are achieved in a closed manor. Indications for open reduction include:

  1. Fracture of the femoral head or instability of the joint.
  2. Unsuccessful closed reduction.
  3. Neurovascular deficit after successful closed reduction.

References

  1. Greenspan A. Orthopedic Imaging: A Practical Approach. 4th ed. Lippincott Williams & Wilkins, 2004.

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