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Anteroposterior view
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Lateral view
A 34-year-old man presents to the emergency department after a motor vehicle accident with severe left hip pain and a lower extremity rotational deformity. He was the driver when he lost control and hit a pole. On examination, he has a shortened and externally rotated left lower extremity. Radiographs of the left hip show a posterior hip dislocation.
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Traumatic hip dislocations are caused by a high energy injury such as a motor vehicle accident. A posterior hip dislocation can occur as the flexed knee hits the dashboard and the femur is pushed out of the posterior pelvis. Posterior hip dislocations account for 90% of all traumatic hip dislocations. A posterior hip dislocation typically occurs in younger patients as the soft tissues give way before bone is fractured. Older patients will typically sustain a fracture before a dislocation occurs. A simple dislocation is a dislocation without fracture, and a complex dislocation occurs with a fracture.1
Standard pre- and postreduction radiographs are required for posterior dislocations. CT should be ordered postreduction to determine if any loose bodies or associated fractures occurred. A careful neurovascular exam should be documented after reduction to rule out sciatic nerve injury, which occurs in 10% to 20% of hip dislocations. Ipsilateral knee injuries can occur in up to 25% of patients. MRI arthrogram may be ordered in an outpatient setting if the patient has continued pain beyond 4 to 6 weeks. MRI helps identify associated labral tears, chondral lesions, and osteonecrosis. In American professional football players who sustain a posterior dislocation, an MRI is done at 6 weeks to rule out osteonecrosis before return to play clearance. A period of 4 to 6 weeks of protected weight bearing followed by a gradual return to activities is the typical treatment protocol for simple hip dislocations.1,2
Dagan Cloutier, MPAS, PA-C, practices in a multispecialty orthopedic group in the southern New Hampshire region and is editor-in-chief of the Journal of Orthopedics for Physician Assistants (JOPA).
References
- Weatherford B. Hip dislocation. Available at: https://www.orthobullets.com/trauma/1035/hip-dislocation. Accessed on March 23, 2018.
- Moorman CT 3rd, Warren RF, Hershman EB, et al. Traumatic posterior hip subluxation in American football. J Bone Joint Surg Am. 2003;85-A:1190-1196.
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