Avascular Necrosis (AVN): Causes, Symptoms, Diagnosis & Management

Avascular Necrosis (AVN): Causes, Symptoms, Diagnosis & Management

Avascular necrosis (AVN)—also known as osteonecrosis—is a progressive condition in which bone tissue dies due to a loss of blood supply. Without adequate blood flow, the bone collapses over time, ultimately leading to joint destruction. AVN most commonly affects the femoral head of the hip but can also occur in the shoulder, knee, ankle, scaphoid, or other bones.

Early diagnosis is critical because early-stage AVN is reversible, whereas late-stage AVN often requires joint replacement surgery.

avascular necrosis


What Causes Avascular Necrosis?

AVN occurs when the blood supply to a bone is disrupted. Common causes include:

1. Trauma

A fracture or dislocation can damage blood vessels, especially around the hip joint.
Example: Femoral neck fractures frequently cause AVN.

2. Corticosteroid Use

Long-term or high-dose steroid therapy (e.g., for asthma, autoimmune disorders) is one of the most common non-traumatic causes.

3. Alcohol Abuse

Heavy alcohol consumption leads to fat deposition in blood vessels, reducing blood flow to bone.

4. Medical Conditions

  • Sickle cell disease

  • Systemic lupus erythematosus (SLE)

  • Gaucher’s disease

  • HIV infection

  • Pancreatitis

5. Idiopathic

In 20–30% of cases, no clear cause is identified.

Pathophysiology (How AVN Develops)

  1. Reduced blood flow →

  2. Hypoxia and ischemia →

  3. Death of osteocytes →

  4. Microfractures form →

  5. Collapse of bone structure →

  6. Joint degeneration and arthritis

The femoral head is especially vulnerable due to its limited vascular supply.

Signs and Symptoms

1. Pain

  • Gradual onset

  • Initially appears only during weight-bearing

  • Later occurs at rest

  • Pain often felt in hip, groin, thigh, or buttock

2. Stiffness & Limited ROM

Difficulty in walking, squatting, or hip rotation.

3. Limping

Due to collapse of the femoral head.

Stages of Avascular Necrosis (Ficat & Arlet Classification)

Stage Description
Stage I Normal X-ray, MRI shows early changes
Stage II Sclerosis, cysts visible; no collapse
Stage III Subchondral fracture (“crescent sign”)
Stage IV Bone collapse & secondary osteoarthritis

Early-stage (I–II) is reversible; late-stage (III–IV) often requires surgery.

Diagnosis

1. X-Ray

  • May appear normal in early stages

  • Later shows sclerosis, cysts, collapse

2. MRI (Best test)

  • Most sensitive test for early AVN

  • Detects bone marrow edema and necrotic changes

3. CT Scan

  • Used to assess severity of collapse

4. Bone Scan

Alternative when MRI is unavailable.

Management of Avascular Necrosis

Treatment depends on stage, location, and severity.

Conservative (Non-surgical) Management

Mainly effective in early stages (I & II).

1. Medications

  • NSAIDs for pain

  • Bisphosphonates (e.g., alendronate) may slow collapse

  • Statins help prevent steroid-induced AVN

  • Anticoagulants (if clotting disorders are present)

2. Reduced Weight Bearing

Using crutches can slow disease progression.

3. Physiotherapy

  • Pain management

  • ROM exercises

  • Strengthening of glutes & core

  • Gait training

4. Extracorporeal Shockwave Therapy (ESWT)

Shows improvement in pain and function in early AVN.

Surgical Management

1. Core Decompression

  • Most effective in early-stage AVN

  • Reduces pressure inside bone

  • Promotes revascularization

  • Success rate is highest before bone collapse

2. Bone Grafting

  • Vascularized or non-vascularized grafts used to support bone

  • Vascularized fibula graft is common

3. Osteotomy

Repositions bone to shift load away from necrotic area.

4. Total Hip Replacement (THR)

  • Indicated in late-stage AVN with collapse

  • Provides excellent long-term outcomes

Physiotherapy Management

Acute Stage

  • Pain reduction: hot/cold therapy

  • Non-weight-bearing exercises

  • Soft tissue mobilization

  • Gentle ROM exercises

Subacute Stage

  • Strength training (glutes, quadriceps, core)

  • Hydrotherapy

  • Stretching to maintain hip mobility

Chronic Stage

  • Gait retraining

  • Balance & proprioception

  • Functional strengthening

  • Post-operative rehab (if surgery performed)

Prognosis

  • Early diagnosis → better outcomes

  • Late diagnosis → high chance of femoral head collapse

  • 40–80% of untreated AVN cases progress to arthritis and require replacement

PubMed-Indexed References

  1. Mont MA, Jones LC, Hungerford DS. Nontraumatic osteonecrosis of the femoral head. J Bone Joint Surg Am. 2006. PMID: 16818966

  2. Moya-Angeler J, et al. Current concepts on osteonecrosis of the femoral head. World J Orthop. 2015. PMID: 26601055

  3. Assouline-Dayan Y, et al. Pathogenesis and natural history of osteonecrosis. Semin Arthritis Rheum. 2002. PMID: 12185279

  4. Zalavras CG, Lieberman JR. Osteonecrosis of the femoral head: evaluation and treatment. J Am Acad Orthop Surg. 2014. PMID: 24740663

  5. Lieberman JR et al. Core decompression for osteonecrosis of the hip. Clin Orthop Relat Res. 2004. PMID: 15232452

  6. Marker DR, Seyler TM, et al. Treatment of early-stage osteonecrosis of the hip. J Bone Joint Surg Am. 2008. PMID: 18381301


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