What is Avascular Necrosis or Osteonecrosis?
Avascular necrosis is a condition of decreased blood supply resulting in the death of bone tissue. This is also known as osteonecrosis. Avascular necrosis usually leads to the tiny breaks in the bone forcing the bone to collapse eventually. The blood supply to a section of bone also gets interrupted in case of fractured or dislocated joints. Avascular necrosis or osteonecrosis is also associated with excessive alcohol intake and prolonged and high-dosage of steroid medications. This condition more commonly affects the hip joint and can occur to anyone. Avascular necrosis more commonly affects men in the age group of 30 and 60 years.
Types of Avascular Necrosis or Osteonecrosis
Avascular necrosis or osteonecrosis can broadly be classified into two types.
Trauma-Related Avascular Necrosis or Osteonecrosis: As the name suggests this type of avascular necrosis is a result of an injury such as a fracture or a joint dislocation.
Non-Trauma-Related Avascular Necrosis or Osteonecrosis: This type of avascular necrosis is mostly a result of alcohol abuse or long-term steroid use.
Epidemiology of Avascular Necrosis or Osteonecrosis
About 15,000 new cases of avascular necrosis or osteonecrosis are reported every year in United States. More than 10% of total hip replacement surgeries that are performed in the United States are due to avascular necrosis. Approximately 380 cases of osteonecrosis of the jaw associated with bisphosphonate use have also been reported recently.
Causes and Risk Factors of Avascular Necrosis or Osteonecrosis
Avascular necrosis or osteonecrosis is caused due to reduced or interrupted flow of blood to a bone. Causes may include:
Bone and Joint Injury: An injury caused by a trauma such as a fracture or a dislocated joint usually reduces the supply of blood to a portion of the bone resulting in the death of the bone.
Radiation treatment: This is generally a part of cancer treatment, which may result in weakening of the exposed bone and injuring the blood vessels.
Pressure Inside the Bone: Gaucher’s disease or sickle cell anemia usually increases the pressure inside the bone creating difficulty for fresh blood to enter.
Excessive Drinking: Consuming excessive alcoholic drinks daily for many years causes fatty deposits to develop in blood vessels, which restrict the blood flow to the bones. Daily habitual drinking is a very big risk factor for developing the condition of avascular necrosis.
Steroids: High dosage of steroids for prolonged periods may also cause avascular necrosis or osteonecrosis.
Osteoporosis Drugs: Bisphosphonates which often help in strengthening weak bones in patients of osteoporosis may also lead to osteonecrosis.
Other Causes: Diabetes, Sickle cell anemia, HIV/AIDS, Lupus, Dialysis, and Transplants of kidney or any other organ.
Signs and Symptoms of Avascular Necrosis or Osteonecrosis
Several individuals may not experience any symptoms in the initial stages of avascular necrosis of the bone.
Worsening of the disease may lead to pain in the affected joint just with putting weight on it. As the condition of avascular necrosis or osteonecrosis worsens further, the pain in the affected joint may be present even while lying down.
- Severe or mild pain could also be experienced, which is gradual in progression.
- Knee, hip, foot, hand and shoulder are the joints, which usually get affected by avascular necrosis.
- Avascular necrosis of the hip generally leads to pain in the thigh, buttock, and groin.
- Few individuals also experience avascular necrosis bilaterally such as in both knees or in both hips.
Tests to Diagnose Avascular Necrosis
A complete subjective and physical examination is performed to diagnose avascular necrosis or osteonecrosis. A physician will press around the joint in order to examine the tenderness. A joint is also rotated in different positions in order to check for reduced range of motion. Tests that assist in diagnosing avascular necrosis or osteonecrosis may include: Magnetic resonance imaging (MRI), X-rays, and Bone scan.
Treatment for Avascular Necrosis or Osteonecrosis
The treatment for avascular necrosis or osteonecrosis primarily concentrates on preventing future bone loss. Generally the treatment process depends upon the amount of damage caused to the bone.
In few of the cases, medications help in reducing the symptoms of avascular necrosis or osteonecrosis. These medications may include:
Nonsteroidal Anti-Inflammatory Drugs (NSAIDs): NSAIDs like naproxen and ibuprofen usually help in relieving the inflammation and pain caused due to avascular necrosis or osteonecrosis.
Osteoporosis Drugs: In some cases, osteoporosis medications like alendronate may also help in slowing down the progression of avascular necrosis.
Cholesterol Drugs: Decreasing the amount of fat in blood helps in preventing the vessel blockages that usually result in avascular necrosis or osteonecrosis.
Blood Thinners: Blood thinners like warfarin are also prescribed in order to prevent clotting of the blood vessels in the bones in patients with clotting disorder.
Rest: Decreasing the amount of stress and weight on the affected bone helps in slowing down the damage caused due to avascular necrosis. Restricting heavy amount of physical activity and using crutches may help in keeping the weight off from the affected joint for many months in case of knee and hip avascular necrosis or osteonecrosis.
Exercises: Some exercises may help in improving and maintaining the range of motion of the joint. These exercises can be performed with the help of a trained physical therapist.
Electrical Stimulation: Electrical stimulation helps the body in growing new bone for replacing the damaged area caused due to avascular necrosis or osteonecrosis. Electrical stimulation may be used at the time of surgery and is applied directly to the affected area. Electrical stimulation may also be performed externally by attaching electrodes to the skin.
Surgery for Avascular Necrosis or Osteonecrosis
Surgery may be required in cases where avascular necrosis or osteonecrosis is not identified until it reaches a fairly advanced stage. Given below are few of the surgical procedures used to treat avascular necrosis or osteonecrosis.
Core Decompression: Core decompression is performed by removing a part of the inner layer of the affected bone in order to reduce the pain. The extra gap present in the bone stimulates the growth of new blood vessels and healthy bone tissue.
Bone Transplant: Bone transplant helps in strengthening the area of affected bone. This procedure may involve a graft or a section of a healthy bone being taken from some other part of the body to be used at the necrosed site.
Bone Reshaping or Osteotomy: Bone reshaping is performed for removing a wedge of bone below or above a weight-bearing joint in order to release the pressure off of the affected joint. Bone reshaping may also provide an option of delaying the joint replacement.
Joint Replacement: This procedure is performed by removing an affected joint in order to replace it with an artificial joint made up of plastic or metal components. Joint replacement can either be partial or total depending on the condition of affected joint.