Question 1

What is avascular necrosis (AVN)?

Accepted Answer

Avascular necrosis (also called osteonecrosis or bone death) is death of bone tissue from loss of blood supply. In the hip, it affects the femoral head (ball of the hip joint). Without adequate blood flow, bone cells die. Initially the bone looks normal on X-rays, but over months to years, the dead bone weakens and collapses under body weight. Once collapse occurs, the joint surface becomes irregular, causing arthritis. AVN is progressive and irreversible - dead bone cannot regenerate. The disease progresses through stages from early (pre-collapse, potentially reversible) to late (collapse, secondary arthritis).

Question 2

What causes AVN of the hip?

Accepted Answer

Most common causes: high-dose corticosteroids (prednisone, prednisolone) used for asthma, rheumatoid arthritis, lupus, organ transplants, or other conditions - accounts for 35% of cases. Chronic heavy alcohol use - 20-30% of cases. Hip trauma (femoral neck fracture, hip dislocation) - blood vessels damaged. Sickle cell disease. Other causes: blood clotting disorders, chemotherapy, radiation, caisson disease (the bends), autoimmune diseases, HIV. Idiopathic (no identifiable cause) - 30-40% despite thorough workup. The final common pathway is interrupted blood supply to femoral head, causing bone death.

Question 3

How is AVN diagnosed?

Accepted Answer

MRI is the gold standard for early detection. Shows classic band-like signal in femoral head months before X-ray changes appear. X-rays may be normal in early disease (stage 0-1). As disease progresses, X-rays show: increased bone density (stage 1), cystic changes (stage 2), crescent sign (subchondral collapse - stage 3), and eventually secondary arthritis (stage 4). If you have hip pain and risk factors (steroids, alcohol), insist on MRI even if X-rays normal - early diagnosis offers joint-preserving options. CT scan measures extent of collapse for surgical planning.

Question 4

What are the stages of AVN?

Accepted Answer

Multiple staging systems exist (Ficat, Steinberg). Simplified: Stage 0-1 (early/pre-collapse): normal X-ray but MRI shows changes. Potentially reversible with core decompression. Stage 2 (late pre-collapse): X-ray abnormal (sclerosis, cysts) but no collapse. Core decompression success 40-60%. Stage 3 (collapse): crescent sign on X-ray - subchondral bone collapsed. Core decompression under 30% success. Stage 4 (arthritis): secondary arthritis developed. Joint-preserving surgery not effective - needs hip replacement. Staging critical because it determines treatment - early stages benefit from joint-preserving surgery; late stages need replacement.

Question 5

Will I need a hip replacement?

Accepted Answer

Depends on stage when diagnosed. If caught in stage 0-1 (pre-collapse, early), core decompression has 60-80% success and may delay or prevent hip replacement. If stage 2, success drops to 40-60%. If stage 3+ (collapse or arthritis), core decompression rarely works - most patients need hip replacement. Natural history studies show: 80-90% of hips progress to collapse and need replacement within 2-5 years if untreated. Early diagnosis and treatment (core decompression) may delay replacement, but about 50% still need replacement eventually. The good news: hip replacement for AVN has excellent outcomes and reliably resolves pain.

Medical Disclaimer

Hip Bone Death (Avascular Necrosis)

📖What is Hip Bone Death (Avascular Necrosis)?

🔬What Causes It?

⚠️Risk Factors

You may be at higher risk if:

🛡️Prevention