Avascular necrosis (osteonecrosis)

Avascular necrosis

Avascular necrosis (osteonecrosis) Overview

Avascular necrosis (osteonecrosis) | The bones in the human body rely on a steady blood supply to remain healthy, as they consist of living cells. Osteonecrosis occurs when the blood flow to a section of bone becomes disrupted, leading to the death of bone tissue. Eventually, this can result in bone breakdown and joint collapse. Osteonecrosis is also known as:

• Avascular necrosis.
• Aseptic necrosis.
• Ischemic necrosis of bone.

Osteonecrosis can affect any bone, but it most commonly occurs in the ends of long bones, such as:

• Thigh bone (femur), particularly the upper part—the ball in the hip socket. The lower end, part of the knee joint, is also frequently affected.
• Upper arm bone (humerus), especially the upper part—the ball in the shoulder joint.

When osteonecrosis affects a portion of bone within a joint, it can lead to bone breakdown and subsequent arthritis. Less commonly, osteonecrosis may impact the bones of the elbows, ankles, feet, wrists, and hands.

Symptoms and Diagnosis

Pain is the primary symptom of osteonecrosis, with doctors typically diagnosing the condition using imaging techniques like x-rays or magnetic resonance imaging (MRI). Surgical intervention is often necessary to prevent further bone damage, safeguard the bones and joints, and enhance joint function.

Risk Factors and Causes

Osteonecrosis can affect individuals of any age, but it is most prevalent in those aged 30s and 40s. Traumatic cases of osteonecrosis stem from injury, while nontraumatic or atraumatic cases occur without a history of injury.

Various risk factors increase the likelihood of osteonecrosis, including:

• Injury: Damage to surrounding blood vessels from a broken or dislocated bone or joint injury can diminish blood supply to the bone, leading to osteonecrosis.
• Medications: Prolonged high-dose use of corticosteroids, such as those used for asthma or arthritis, heightens the risk of osteonecrosis.
• Excessive Alcohol and Tobacco Use: Overconsumption of alcohol and tobacco may decrease blood flow to the bone, increasing the risk of osteonecrosis.
• Medical Conditions: Certain blood disorders, cancers, and other medical conditions elevate the risk of osteonecrosis.
• Medical Interventions: Chemotherapy, organ transplantation, and radiation treatment may also heighten the risk of osteonecrosis.

Types and Symptoms

Osteonecrosis manifests in two forms: traumatic, following an injury, and nontraumatic, without an injury history. Symptoms may initially be absent, but as the disease progresses, pain—especially in weight-bearing bones—may develop. Osteonecrosis commonly affects the hip joint, with pain typically felt in the groin or buttock area. Over time, joint stiffness, loss of motion, and osteoarthritis may occur, potentially leading to intensified pain if bone collapse ensues.

Underlying Causes

Osteonecrosis arises when blood supply to a bone section is disrupted, depriving bone tissue of essential nutrients and oxygen. In traumatic cases, injury-related blood vessel damage likely causes the blood flow loss. Nontraumatic cases' causes are less clear but may involve factors like blood clotting, elevated bone pressure, genetics, alcohol or medication overuse, or other diseases.