# Avascular Necrosis of Hip

> Avascular necrosis of the hip for NEET-PG Orthopaedics: Ficat and Steinberg staging, crescent sign, core decompression and arthroplasty timing.

- Canonical URL: https://prepelephant.com/topics/neet-pg/orthopaedics/avascular-necrosis-of-hip
- Exam / course: NEET-PG · Subject: Orthopaedics
- Publisher: PrepElephant (https://prepelephant.com) — Prepared and reviewed by the PrepElephant Academic Review Team
- First published: 2026-10-02
- Last updated: 2026-10-02
- How to cite: "Avascular Necrosis of Hip", PrepElephant, https://prepelephant.com/topics/neet-pg/orthopaedics/avascular-necrosis-of-hip

## Direct answer

Corticosteroids, alcohol excess and sickle cell disease top the cause list of femoral head avascular necrosis — a final common pathway in which the subchondral bone of the loaded dome dies, fractures microscopically, and collapses, converting a smooth sphere into a mushroom. The young adult (20-50) presents with groin pain, often bilateral, an antalgic limp and restricted internal rotation before any radiographic abnormality; MRI is both the sensitive and staging investigation, showing the double-line sign of reactive interface, while the crescent sign of subchondral fracture marks the point of no return. Ficat-Arlet (I-IV) and Steinberg staging drive treatment: pre-collapse disease gets core decompression with or without grafting, while collapsed heads (III-IV) are beyond salvage and head for total hip arthroplasty — unusually early in life, which is why prevention (limiting steroid dose, alcohol cessation, haemoglobinopathy screening) matters more than any operation.

## What you must remember

- **Causes in order:** corticosteroids and alcohol commonest; sickle cell disease the great Indian contributor via the central tribal belt; also decompression sickness, Gaucher disease, thrombophilia, pregnancy, radiation, femoral neck trauma — roughly a third remain idiopathic (Chandler disease).
- **Staging:** Ficat-Arlet — I normal radiograph, II sclerosis or cysts without collapse, III crescent sign and flattening, IV joint-space loss with secondary arthritis; Steinberg quantifies lesion size on MRI; ARCO synthesises both.
- **The crescent sign:** a radiolucent subchondral line from fracture of dead trabeculae beneath intact cartilage — the marker of impending collapse and the divider between joint-preserving and joint-replacing treatment.
- **Investigation logic:** normal radiographs do not exclude disease — MRI for suspicion (sensitivity above 90 per cent, double-line sign of granulation interface); screen the contralateral hip always, since bilaterality approaches half in steroid and sickle disease.
- **Joint-preserving options:** core decompression for pre-collapse Ficat I-II with small-medium lesions; adjuncts include vascularised fibular graft and rotational osteotomy.
- **Joint replacement:** total hip arthroplasty once collapse or arthritis is established — in younger patients, bearing-surface choice and revision expectations dominate counselling; arthrodesis survives only in select young heavy-labour indications.
- **Sickle cell specifics:** hydration, oxygenation and transfusion optimisation reduce crisis risk; cementless fixation generally preferred; the Chhattisgarh-Odisha-Maharashtra belt supplies advanced bilateral disease at first presentation.

## Walking through a steroid-associated case

A 32-year-old man with a renal transplant on maintenance prednisolone develops insidious left groin pain over four months; internal rotation is limited and painful. A radiograph shows subtle mottled sclerosis of the superolateral head — Ficat II. The right hip is imaged at the same sitting and looks normal; both go to MRI, which demonstrates a 25 per cent left-sided lesion with the double-line sign and a small right-sided lesion invisible to plain films — the bilaterality that makes screening mandatory.

Because both hips are pre-collapse, the plan is joint-preserving: left core decompression with or without bone graft into the track, protected weight-bearing for six weeks, and staged right-sided decompression for the smaller lesion. His immunosuppression is reviewed with the nephrologist — steroid sparing where feasible — and he is counselled that success depends on lesion size and the absence of collapse. Should he re-present with a flattened head and joint-space narrowing — Ficat IV at age 34 — the conversation is total hip arthroplasty with bearings chosen for youth, revision a near-certainty across a normal lifespan.

## Where students slip

The staging-to-treatment map is where marks are lost: candidates offer core decompression for collapsed heads — after the crescent sign and flattening, decompression restores nothing and the answer converts to arthroplasty — or they quote radiographs as reassuring in early disease, forgetting that MRI is the standard for the painful hip at risk. The double-line sign gets described without its meaning (a bright reactive rim on T2), the crescent sign without its mechanics (subchondral fracture through dead bone). Aetiology answers that stop at "steroids" miss sickle cell, decompression sickness, Gaucher and thrombophilia. In India the sickle cell belt concentrates bilateral young AVN presenting late at stage III-IV; the exam-worthy nuance is perioperative sickle management (hydration, oxygenation, transfusion targets) and cementless implants in these young hosts.

## Frequently asked questions

### Which investigation detects early avascular necrosis?

MRI — sensitivity above 90 per cent, showing marrow oedema and the double-line sign of reactive interface; plain films are normal in Ficat stage I.

### What does the crescent sign represent?

A subchondral radiolucent line from impaction fracture through dead trabecular bone beneath intact cartilage — evidence of collapse, defining stage III and the end of joint-preserving surgery.

### When is core decompression indicated?

Pre-collapse disease (Ficat I-II) with small to moderate lesions, where decompression relieves pressure and promotes revascularisation; collapsed heads need arthroplasty.

### Why must the other hip always be imaged?

Bilateral involvement approaches half of steroid-, alcohol- and sickle-related cases, frequently asymptomatic and radiographically occult — screening MRI changes prognosis and planning.

### What perioperative considerations apply in sickle cell AVN?

Hydration, oxygenation, avoidance of acidosis and hypothermia, transfusion to dilute sickle haemoglobin, and generally cementless fixation — measures that reduce crisis and infection risk.