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Year |
2001 |
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Question Number |
82. |
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Category |
Select |
Question
Which of the following factors will have the greatest affect on the stability of the hip after closed reduction of a posterior wall fracture-dislocation?
1- Magnitude of the posterior capsular disruption
2- Length of time until reduction occurs
3- Size of the wall fragment
4- Presence of femoral loose head depression
5- Presence of loose bodies in the fovea of the hip joint
Figures
Answer (click for answer)
Answer- 3 Some general principles of hip dislocations are frequently asked. 90% are posterior from a dashboard type injury. If the femur is in an abducted position then a posterior wall fracture will also occur. Treatment in the ER is to deal with life threatening injuries and stabilize the patient. The next step is to evaluate the fracture and check for concurrent femoral head, neck, shaft, or acetabulum fractures. If possible a closed reduction should be attempted in the ER. Time to reduction is the greatest risk factor for developing AVN. If reduction is unsuccessful, then an open reduction must be done emergently. If a closed reduction is successful then CT scans are used to evaluate for concentric reduction, associated head injuries and chondral fragments within the joint space. Also, stability is assessed at the time of reduction. Reducible but unstable, non-concentric reduction, and interposed loose bodies need to be operated on as well, but not emergently. These patients should remain in traction until surgery. Small fragments within the fossa that do not impinge on the head do not require excision.
The stability of the hip joint relies mainly on the bony constraints of the deep socket and ball joint. It is therefore the size of the wall fragments that most predicts stability. Lab studies have shown that involvement of more then 50% of the posterior wall results in instability but less then 25% almost never do. Current indications to fix the posterior wall fractures are a non concentric reduction on an view of the hip out of traction, displacement of >2 mm of the superior articular surface, any fragment greater then 25%, and retained loose bodies in the joint.
Reference: Stover MD Elementary Fractures of the Acetabulum in Trauma OKU Kellam JF, et al (eds) American Academy of Orthopaedic Surgeons, Rosemont, IL, 2000,pp. 283-284.