Avascular necrosis (AVN), also known as osteonecrosis, aseptic necrosis or ischemic bone necrosis, is a condition in which the blood does not reach the bone.
The femoral head (femur head) is the upper part of the bone that is fitted into the pelvis and forms the hip joint.
Since the femoral head, like all bones, is living tissue, it needs blood flow to maintain nutrients and remove waste products.
Interruption of blood circulation leads to the death of bone cells.
If no intervention is made, this process causes the disintegration of the femoral head.
Avascular necrosis most commonly occurs in the thigh and especially in the hip. Other areas of the body that can be affected by necrosis include: arm, knee, shoulder, leg, upper and lower jaw.
Who suffers from avascular necrosis
Over 20,000 people suffer from avascular necrosis every year. Most are between 20 and 50 years old. For healthy people, the risk of avascular necrosis is low.
Causes of femoral head necrosis
Most cases are the result of an underlying health problem or accident.
Possible causes are:
- Chronic use of corticosteroids. Long-term use of this drug for inflammation treatment, both orally and intravenously, is involved in 35% of all cases of non-traumatic avascular necrosis. Although the reason for this link is still not understood, doctors suspect that these drugs interfere with the body’s ability to break down fatty substances. These substances are deposited in blood vessels, narrowing them and reducing the amount of blood in the bone.
- Alcohol abuse. Just like cortisone, the increased consumption of alcohol can lead to deposits of fatty substances in the blood vessels and cause an undersupply of blood to the bone.
- Blood clots, inflammation and damage to the arteries.
- Dislocation or femoral fracture (femoral fracture). This type of injury can affect the blood supply to the bone and lead to avascular traumatic necrosis. Vascular necrosis can occur in 20% of people with hip dislocation.
All these disorders can block blood flow to the bone.
Other conditions associated with avascular non-traumatic necrosis include:
- Gaucher disease, an inherited metabolic disorder in which a harmful amount of a fatty substance accumulates in the organs;
- Sickle-cell anaemia;
- pancreatitis, which is the inflammation of the pancreas;
- HIV infection;
- Autoimmune diseases;
- Decompression sickness, a disorder that occurs when the body is exposed to a sudden decrease in ambient pressure, which leads to gas bubble formation in the blood.
Some medical procedures increase the risk of avascular necrosis.
Some examples are:
- cancer treatment, such as chemotherapy or radiotherapy;
- dialysis, a process of purifying blood after kidney failure;
- Transplantation of kidneys and other organs.
Symptoms of femoral head necrosis
Typically, femoral head necrosis does not cause symptoms in the early stages.
As the disease progresses, pain develops.
Initially, pain may occur with pressure on the hip, that is, when standing or walking.
Then the pain can become more constant. If the disease progresses, the bone and the surrounding joint collapse, severe pain may occur, which limits the load capacity of the hip.
The time that passes between the first symptoms and the collapse of the bone can vary from a few months to more than a year.
Diagnosis of femoral head necrosis
In many cases, this condition can be diagnosed by an X-ray.
However, X-rays do not always indicate avascular necrosis. The first signs of avascular necrosis can be diagnosed by magnetic resonance imaging (MRI) or bone scintigraphy.
Other ways of diagnosing this disease are computed tomography (CT) and biopsy (removal and analysis of a bone particle).
Complications of femoral head necrosis
Untreated avascular necrosis worsens over time.
In the end, the bone can break down to such an extent that it collapses.
If the bone loses its smooth shape, this can lead to severe arthritis.
Treatment and medication for femoral head necrosis
The goal of treatment for avascular necrosis is to prevent further bone loss.
The type of treatment that is performed depends on the extent of bone damage.
In some people, symptoms of avascular necrosis may be reduced by medications, such as:
- Nonsteroidal anti-inflammatory drugs (NSAIDs). Medications such as ibuprofen (Dolgit, Aktren, etc.) or naproxen (Aleve) may help relieve pain and inflammation associated with hip necrosis.
- Medications for osteoporosis. Some studies show that medications for osteoporosis, such as alendronic acid (Fosamax), can halt the progression of femoral head necrosis.
- Medications for cholesterol. Reducing the amount of fat (lipids) in the blood can counteract blockages of the veins, which often lead to avascular femoral head necrosis.
- Anticoagulant. If you have bleeding disorders, blood thinners such as warfarin (Coumadin) may be prescribed to prevent blood coagel formation in the vessels that supply the bone.
In the initial stages of hip necrosis, the doctor may recommend the following measures:
Rest. By reducing weight and stress on the affected bones, damage to avascular necrosis can be delayed.
It is recommended to limit the frequency and intensity of regular physical activity. In the case of avascular necrosis of the hip or knee, it may be necessary to use walkers for several months to take weight off the hip joint.
Exercises. Some exercises can help maintain or improve range of motion in the hip joint.
A physiotherapist can choose special exercises to do this and teach them to the patient so that he can perform them regularly.
Physiotherapy. Some instrument-based therapies, such as magnetic therapy, can stimulate the body to form new bone tissues that replace the necrotic zone.
Electrical stimulation can be done by electrodes that are attached to the skin.
Surgical intervention and other procedures
Since most people do not experience symptoms until the disease is relatively advanced, it may be necessary to consider surgical intervention:
Pressure relief of the core
In this operation, the surgeon perforates the bone and removes the inner necrotic part.
In addition to relieving pain, the empty space inside the bone stimulates the production of new and healthy bone tissue and new blood vessels.
Bone grafting (implantation)
This procedure can help strengthen the bone area affected by avascular necrosis.
The bone graft is a healthy piece of bone that has been taken from another part of the body.
Remodeling of the bone (osteotomy)
This procedure removes a bone wedge above or below a joint that supports the load to take the weight off the damaged bone.
Remodeling the bone can postpone joint replacement.
Joint prosthesis If the diseased bone has already collapsed and other treatments have not been able to reduce the symptoms, surgery may be necessary to replace the damaged hip areas with a plastic or metal prosthesis.