A 45-year-old man on long-term corticosteroid therapy for systemic lupus erythematosus presents with progressive right hip pain. Plain radiograph is normal. MRI of the hip shows a T1 hypointense line paralleling the articular surface and a T2 hyperintense line just deep to it. What is the most likely diagnosis?
- A Transient osteoporosis of the hip
- B Stress fracture of the femoral neck
- C Avascular necrosis of the femoral head ✓
- D Osteoarthritis of the hip
Correct answer: C. Avascular necrosis of the femoral head
Explanation
The double-line sign on MRI, consisting of a T1 hypointense line paralleling the articular surface with a T2 hyperintense line deep to it, is pathognomonic for avascular necrosis of the femoral head. Corticosteroid use is a major risk factor. Transient osteoporosis shows diffuse marrow edema without the double-line sign. Stress fracture would show a fracture line, not this characteristic sign.
Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.