Published: 18 Jun 2025

ICD9: 733      ICD10: M87.0      ICD11: FB81

Avascular necrosis (AVN), also known as osteonecrosis, is a condition that occurs when blood supply to a bone is disrupted, leading to bone tissue death (necrosis).
Think of it like a small stroke within the bone.

Here's a breakdown of the key aspects:

Avascular: Means "without blood vessels"
Necrosis: Means "tissue death"
Osteo: Refers to bone

How it Happens:

1. Blood Supply Disruption: The problem starts when the blood supply to a section of bone is cut off or significantly reduced. This can happen due to various reasons (see "Causes" below).
2. Bone Tissue Death: Without a steady supply of oxygen and nutrients from the blood, bone cells (osteocytes) start to die.
3. Weakening and Collapse: As more bone cells die, the bone weakens. Over time, this can lead to tiny fractures and eventually collapse of the affected bone.
4. Joint Damage: If the bone that collapses is part of a joint, it can damage the cartilage (the smooth, protective covering) and lead to pain, stiffness, and arthritis.

Commonly Affected Areas:

While AVN can occur in any bone, it most commonly affects:

Hip: This is the most frequent site, affecting the femoral head (the ball-shaped top of the thighbone that fits into the hip socket).
Shoulder: Specifically, the humeral head (the ball-shaped top of the upper arm bone).
Knee: The femoral condyles (the rounded ends of the thighbone that articulate with the tibia).
Ankle: The talus bone.
Jaw: Can be caused by bisphosphonates.

Causes:

The exact cause of AVN isn't always clear, but some common risk factors and causes include:

Trauma: Fractures, dislocations, or other injuries can damage blood vessels and disrupt blood flow to the bone.
Corticosteroids (Steroids): Long-term use of high doses of corticosteroids (like prednisone) is a well-known risk factor. The mechanism isn't fully understood, but it's thought to involve fat deposition in blood vessels and impaired blood flow.
Excessive Alcohol Consumption: Heavy alcohol use can lead to fat deposits in blood vessels.
Medical Conditions: Certain medical conditions increase the risk, including:
Sickle cell anemia: Abnormally shaped red blood cells can block small blood vessels.
Lupus and other autoimmune diseases: These conditions can cause inflammation and blood vessel damage.
HIV/AIDS:
Gaucher's disease:
Caisson disease (decompression sickness or "the bends"): Nitrogen bubbles can block blood vessels.
Radiation Therapy: Radiation can damage blood vessels.
Bisphosphonates: medications that are used to treat osteoporosis and some cancers. These medications can cause osteonecrosis of the jaw.
Idiopathic: In some cases, there's no identifiable cause (idiopathic AVN).

Symptoms:

Symptoms vary depending on the affected bone and the stage of the condition. Early on, there might be no symptoms. As AVN progresses, common symptoms include:

Pain: Pain in the affected joint, which may be mild at first and gradually worsen. The pain can be constant or intermittent and may radiate to the groin, buttock, or thigh if the hip is involved.
Stiffness: Decreased range of motion in the affected joint.
Limping: If a weight-bearing joint like the hip or knee is affected.

Diagnosis:

Physical Exam: A doctor will examine the joint and check for pain, tenderness, and range of motion.
Imaging Tests:
X-rays: May show changes in the bone in later stages, such as bone collapse or arthritis.
MRI (Magnetic Resonance Imaging): The most sensitive imaging test for detecting AVN, especially in the early stages. MRI can show changes in blood flow and bone structure.
Bone Scan: Can help identify areas of bone damage.
CT Scan (Computed Tomography): May be used to assess the extent of bone damage and collapse.

Treatment:

Treatment depends on the severity of the AVN, the location of the affected bone, the patient's age and overall health, and the underlying cause. Treatment options include:

Conservative (Non-Surgical):
Pain medication: To relieve pain.
Physical therapy: To improve range of motion and strength.
Weight-bearing restrictions: Using crutches or a walker to reduce stress on the affected joint.
Medications: Medications such as bisphosphonates may be used to slow the progression of bone damage.
Surgical:
Core decompression: A procedure in which a hole is drilled into the affected bone to relieve pressure and stimulate new blood flow. This is often used in the early stages of AVN.
Bone grafting: Replacing damaged bone with healthy bone from another part of the body or from a donor.
Osteotomy: Reshaping the bone to reduce stress on the affected area.
Joint replacement: In advanced cases, when the joint is severely damaged, total joint replacement may be necessary.

Prognosis:

The prognosis for AVN varies. Early diagnosis and treatment can help slow the progression of the disease and preserve joint function. However, in some cases, AVN can lead to significant joint damage and require joint replacement surgery.

In summary, avascular necrosis (osteonecrosis) is a serious condition caused by a lack of blood supply to bone, leading to bone tissue death and potential joint damage. Early detection and appropriate management are crucial for improving outcomes.