A 30-year-old man is involved in a motor vehicle collision and sustains a posterior dislocation of the hip. The hip must be reduced within what time frame to minimise the risk of avascular necrosis of the femoral head?
- A Within 12 hours of injury
- B Within 6 hours of injury ✓
- C Within 24 hours
- D Time to reduction is not a significant factor if the patient is haemodynamically stable
Correct answer: B. Within 6 hours of injury
Explanation
The risk of avascular necrosis (AVN) of the femoral head following traumatic hip dislocation increases substantially when reduction is delayed beyond 6 hours. The retinacular vessels (lateral epiphyseal arteries from the medial femoral circumflex) are tethered and kinking occurs during dislocation; prolonged ischaemia leads to femoral head osteonecrosis. AVN rates: <6 hours ~4–5%, 6–12 hours ~20%, >12 hours ~40–50%. Prompt closed reduction under sedation/anaesthesia is mandatory as an orthopaedic emergency.
Reference: Maheshwari Essential Orthopaedics, 6th ed.
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Written and medically reviewed by the StethoPrep medical team.