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Avascular necrosis of the femoral head in adults
Loss of blood supply to the femoral head kills the bone under the cartilage, leading to collapse and joint wear; MRI detects the disease before collapse, when the head may still be preserved, whereas after collapse treatment is usually joint replacement.
Why it matters in the exam
The typical stem describes a young adult aged 30–50 with worsening groin pain and asks for the risk factor and the right test. The main risk factors are prolonged corticosteroid treatment, heavy alcohol use, sickle cell disease, lupus, Gaucher disease, decompression (dysbaric) illness, radiation and trauma — a femoral neck fracture or hip dislocation that damages the medial femoral circumflex artery, the main blood supply to the head. Radiographs can be normal in early stages; the crescent sign indicates subchondral collapse. MRI is the most sensitive test and shows the double-line sign, and the disease is bilateral in a large share of patients, so both hips are imaged. The Ficat-Arlet classification describes progression from a stage with normal radiographs, through sclerosis and cysts, to collapse and joint wear. The treatment decision rests on whether the head has already collapsed: before collapse, core decompression can be tried, sometimes with bone graft, together with reducing risk factors; after collapse, and especially with joint wear, the usual treatment is hip replacement. In questions about children, necrosis of the femoral head is Perthes disease, a separate topic.
Key points
- Risk factors: steroids, alcohol, sickle cell disease, lupus and trauma.
- The medial femoral circumflex artery is the main blood supply to the head.
- MRI is the most sensitive test; the crescent sign means collapse.
- Before collapse — core decompression; after collapse and wear — hip replacement.
- Image both hips.
Summary table
| Stage (Ficat-Arlet) | Radiograph | MRI and symptoms | Usual treatment |
|---|---|---|---|
| I | Normal | MRI positive, mild or no pain | Reduce risk factors; core decompression |
| II | Sclerosis and cysts, round head | Groin pain | Core decompression, sometimes with bone graft |
| III | Crescent sign and subchondral collapse | Pain on weight-bearing and loss of motion | Usually joint replacement; in young patients sometimes preservation with graft |
| IV | Collapse with joint space narrowing and acetabular wear | Marked pain and stiffness | Hip replacement |
| Bilateral disease | Common | Finding on MRI of the other side | Image both hips and treat each side by its stage |
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Sources
- Campbell's Operative Orthopaedics, 14th ed. (2021) — Osteonecrosis of the Femoral Head
- Apley and Solomon's System of Orthopaedics and Trauma, 10th ed. (2017) — Osteonecrosis
Sources are given for further reading; the text is written afresh and not copied from them.
Reviewed by the Examqo AI Professor · 2026-11-06. The text may contain errors; when in doubt, check the source.