A 22-year-old man with known sickle cell disease presents with sudden onset left hip pain and limitation of movement, which has been worsening over the past 3 months. Plain X-ray shows flattening of the femoral head. Which is the MOST likely long-term complication responsible and the underlying mechanism?
- A Septic arthritis from Salmonella osteomyelitis
- B Marrow hyperplasia causing cortical thinning
- C Avascular necrosis due to vascular occlusion by sickled cells ✓
- D Pathological fracture due to bone infarct
Correct answer: C. Avascular necrosis due to vascular occlusion by sickled cells
Explanation
Avascular necrosis (osteonecrosis) of the femoral head is a major long-term complication of sickle cell disease, occurring in up to 50% of patients. The mechanism is occlusion of the terminal intramedullary blood vessels by sickled erythrocytes, leading to ischaemia and death of bone tissue. Flattening of the femoral head on X-ray is a late sign. Salmonella osteomyelitis is more common in the diaphysis and presents acutely with fever and periosteal reaction, not gradual joint destruction.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
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