Some known causes of Avascular Necrosis AVN
It is all a bit of a mystery, many times there is no known cause, while others can be attributed to a known cause. Here we try and summarise some known causes of Avascular Necrosis AVN.
Idiopathic or unknown cause
This is all cases of AVN with no known or understood and obvious reason. For some reason, the body has become susceptible to the onset and developing of avascular necrosis AVN.
Trauma or Injury
Injury (fracture or dislocation) trauma to a joint can be attributed to the onset of AVN.
Long term steroid use has been proven as one of the main causes for AVN, unfortunately, in many of these cases, it goes on to develop bi-lateral (both hips or both knees) or in multiple joints through the body. It is thought that AVN from Steroid use accounts for over 50% of all recorded cases. The most common risk factor is the use of oral or IV steroid medications (Corticosteroids such as prednisolone). These medications are typically used for patients with asthma, inflammatory arthritis, Crohn’s disease, severe allergies, spinal cord trauma, and many other disorders. Although there is little risk of developing AVN with the use of limited steroids (like short-course steroid dose packs), there have been few reports in the literature of its possible risks.
A very common risk factor is excessive use of alcohol. The greater the consumption of alcohol, the higher the risk of developing AVN. The exact mechanism of how alcohol (or steroids) causes AVN is not absolutely understood, but it is believed that excessive fatty substances are produced and build up in the very small blood vessels of the bone. Blockage then occurs which decreases blood flow to the femoral head causing bone death.
Sickle cell disease Some medical conditions, such as sickle cell anaemia or Gaucher’s disease, can increase the pressure inside the bone — making it more difficult for fresh blood to enter, with the risk of developing AVN. Normally, your red blood cells are flexible and round, moving easily through your blood vessels. In sickle cell anaemia, the red blood cells become rigid and sticky and are shaped like sickles or crescent moons. These irregularly shaped cells can get stuck in small blood vessels, which can slow or block blood flow and oxygen to parts of the body.
Chemo steroids can contribute to a decreased blood flow to the area involved resulting in the onset of avascular necrosis, however it depends on dose and time.
Because radiation works to destroy cancerous cells through the deprivation of oxygen and vital nutrients, it inevitably destroys normal cells as well, damaging small arteries and reducing circulation. Not an infection itself, it is the bone’s reduced ability to heal and the resulting lesions, pain, and fragility. Insufficient blood supply to the irradiated areas decreases the ability to heal and can lead to AVN.
AVN due to cancer treatment
Avascular Necrosis can be a side effect of treatment for several different types of cancer.
The main risk factors for developing AVN as a result of cancer treatment include treatment with:
- Corticosteroids such as dexamethasone or prednisolone (these remain a leading cause of AVN
- Certain types of chemotherapy
- Radiotherapy to weight-bearing joints and Total Body Radiation
- Bone Marrow or Stem Cell Transplantation
- Patients who are being treated for acute myeloid leukaemia, acute lymphoblastic leukaemia, lymphomas, testicular cancer, ovarian cancer, breast cancer, and multiple myeloma have an increased risk of developing AVN regardless of the treatment they receive
- Being older than 10 years old whilst receiving treatment
The period of time from treatment to onset of AVN can vary greatly. Although it is usually diagnosed whilst undergoing cancer treatment, it can rarely be diagnosed years later when symptoms become apparent.
It is important to remember that although AVN can be an unwanted side effect of cancer treatment, it is very important not to discontinue any medication or reduce the dosage without the instruction of your medical team as the medicines that can cause AVN is also very effective at treating cancer.
Gaucher disease Some medical conditions, such as sickle cell anaemia or Gaucher’s disease, can increase the pressure inside the bone — making it more difficult for fresh blood to enter, with the risk of developing AVN. Gaucher’s disease occurs when certain harmful fatty substances accumulate to excessive levels in your liver, spleen, lungs, bone marrow and, less commonly, brain. This accumulation of fatty material in tissues interferes with how your body works and may cause organ enlargement and bone pain.
Divers decompression sickness
This has proven to contribute to the onset of Avascular necrosis AVN.Decompression illness, or DCI, is a term used to describe illness that results from a reduction in the ambient pressure surrounding a body. A good example is what happens to your body when you’re surfacing after a dive.DCI encompasses two diseases, decompression sickness (DCS) and arterial gas embolism (AGE). DCS is thought to result from bubbles growing in tissue and causing local damage, while AGE results from bubbles entering the lung circulation, traveling through the arteries and causing tissue damage at a distance by blocking blood flow at the small vessel level.
Lupus – systemic lupus erythematosus (SLE) can affect many parts of the body including joints. Surveys have shown there is between 5% and 12% risk of contracting Avascular Necrosis AVN.
Ref The Eular Journal