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AVN MRI Double-Line Sign — SCE Rheumatology MCQ

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ModerateMusculoskeletal ImagingAVN MRI Double-Line SignSCE Rheumatology

A 65-year-old woman with rheumatoid arthritis has received long-term systemic glucocorticoid treatment. She develops progressive groin pain and restriction of hip movement. MRI demonstrates a subchondral lesion in the anterosuperior femoral head, bounded by a serpiginous low-signal rim on T1-weighted imaging. On T2-weighted imaging, parallel inner high-signal and outer low-signal lines are present at the interface with viable bone, with adjacent bone-marrow oedema. What is the most likely diagnosis?

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Correct answer: D — Osteonecrosis of the femoral head

The diagnosis is osteonecrosis (avascular necrosis) of the femoral head. The decisive feature is the T2-weighted double-line sign: an inner high-signal line and outer low-signal line at the interface between necrotic and viable bone. A serpiginous subchondral boundary and systemic glucocorticoid exposure provide additional support. Transient osteoporosis produces diffuse marrow oedema without a circumscribed serpiginous necrotic segment. A stress fracture produces a discrete fracture line, usually across the femoral neck or subchondral bone, rather than the double-line interface. Septic arthritis is suggested by joint effusion, synovitis and systemic inflammatory features, while osteoarthritis demonstrates cartilage loss, osteophytes and subchondral degenerative change.

Reference: Tasu J-P et al. Avascular osteonecrosis of the hip: The vision of the radiologist (radiology, MRI, CT and scintigraphy). Morphologie. 2021;105:85-93. https://pubmed.ncbi.nlm.nih.gov/33419657/