On MRI, the 'double-line sign' in the femoral head is pathognomonic of which condition?

• A Transient osteoporosis of the hip
• B Pigmented villonodular synovitis
• C Avascular necrosis (osteonecrosis) of the femoral head ✓
• D Stress fracture of the femoral neck

Explanation

The double-line sign on T2-weighted MRI of the femoral head is pathognomonic of avascular necrosis (osteonecrosis). It consists of an inner high-signal line (representing granulation tissue / hyperaemic reactive interface) and an outer low-signal line (representing sclerotic reactive bone or fibrosis) demarcating the necrotic segment. This sign is seen in approximately 80% of cases and confirms the diagnosis. Transient osteoporosis shows diffuse marrow oedema without a demarcating line. Stress fractures show a linear low-signal band.

Reference: Grainger & Allison's Diagnostic Radiology, 7th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.