Ortho Hors D'oeuvres (Answer):

To review, this is a 70 year-old female with left hip pain after fall.

Questions and Answers:

1) What is the injury identified on radiographs?

In the AP radiograph of the pelvis, the left femoral head is just slightly outside and lateral to the acetabulum. The lesser trochanter is less apparent on the left side, consistent with internal rotation of the left femoral shaft. Finally, the left femoral head appears slightly smaller in comparison to the right femoral head, consistent with a position further from the x-ray tube (and therefore posterior).

​In the lateral radiograph, a posterior hip dislocation is identified. The acetabulum is empty and the femoral shaft is clearly directed posterior to the acetabulum.

2) What are frequently associated injuries with this fracture pattern?

Posterior hip dislocations account for 90% of hip dislocations, and are generally caused by high force directed posteriorly towards the flexed knee. Up to 70% of these injuries are associated with other life-threatening traumatic injuries, including splenic lacerations, liver lacerations, and intrathoracic pathology. Because a high mechanism is often required for these patients, excusion of concomitant injuries must be performed, either with CT or careful reassessment.

More locally, posterior hip dislocations often cause damage of the sciatic nerve (10%). As you can see here, the sciatic nerve runs just posteriorly to the acetabulum. Sciatic nerve function (sensation of the sole of the foot, and ankle dorsiflexion) should be evaluated both prior to and after a hip reduction.

Several important neurovascular structures run anterior to the hip and are theoretically at risk of injury during the forced flexion and internal/external rotation procedures performed during reduction. Thorough literature review revealed only one case report in which a patient had femoral nerve palsy after reduction of an uncomplicated posterior hip dislocation, and femoral nerve function had not been adequately documented prior to initiation of the reduction procedure and therefore might have been a result of the initial injury as opposed to the reduction. However, thorough neurovascular examination should be completed both prior to and after any dislocation-reduction.

3) What is the appropriate emergency department management of this injury?

Approximately 10% of patients with posterior hip dislocations go on to have avascular necrosis of the hip requiring arthroplasty, and recent studies show that a delay to reduction of greater than 12 hours is associated with a 5.6x odds ratio of having avascular necrosis. Time is of the essence. Formal recommendations state that attempts at closed reduction under procedural sedation should be performed 2-3 times and within 6 hours of the injury, with immediate progression to open reduction if unsuccessful.

There are several commonly-known hip reduction maneuvers, including the Allis, the Captain Morgan, and the Whistler, with published success rates of 60%, 92%, and 60% respectively. All of these techniques involve some variation of 1) inline traction, 2) gentle flexion to 90 degrees, and 3) internal-to-external rotation. A recent study by Dan et al describes a novel technique called the "rocket launcher" that has been used in a small case series and appears to have relatively good success. Images shown below from their 2015 paper:

After reduction, these patients should undergo a CT scan of the pelvis to assess for associated acetabular fracture or intra-articular bony fragments and have a thorough secondary survey and neurovascular examination. They should be placed in a hip-abductor and admitted for pain medicine, bed rest, and physical therapy. The affected extremity should be nonweightbearing for a minimum of 2 weeks and up to 6 weeks, depending on their orthopedic provider's recommendations.

References:

Dan M et al. Rocket launcher: A novel reduction technique for posterior hip dislocations and review of current literature. Emerg Med Australas. 2015 Jun;27(3):192-5.

Frew N et al. Femoral nerve palsy followint traumatic posterior dislocation of the native hip. Injury. 2013 Feb;44(2):261-2. Kain MSH, Tornetta P. Hip dislocations and fractures of the femoral head. In: Rockwood CA, Bucholz RW, Heckman JD, et al., editors. Rockwood and Green’s fractures in adults. 6th ed. Lippincott Williams & Wilkins; 2006. p. 1717-52

Kellam P, Ostrum RF. Sytsematic Review and Meta-Analysis of Avascular Necrosis and Posttraumatic Arthritis After Traumatic Hip Dislocation. J Orthop Trauma. 2016 Jan;30(1):10-6. Sahin V et al. Traumatic dislocation and fracture-dislocation of the hip: a long-term follow-up study. J Trauma. 2003 Mar;54(3)520-9.


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