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Avascular Necrosis of the Hip (AVN)

Avascular necrosis means death of bone tissue due to a lack of blood supply. This can lead to tiny breaks in the bone and the bone’s eventual collapse. Avascular necrosis most often affects the head of the thighbone (femur), causing hip pain. But it may affect other bones as well.

Blood supply to the bone can be impaired for a number of reasons, including injuries. Avascular necrosis is also associated with long-term use of steroid medications and excessive alcohol intake. Body builders who take pulses of high dose steroids are particularly at risk.

Other risk factors or conditions associated with non-traumatic AVN include Gaucher’s disease, pancreatitis, radiation treatments, chemotherapy, decompression disease, and blood disorders such as sickle cell disease.

Avascular necrosis is often progressive, meaning it worsens with time. Managing the condition can be a lifelong process.

 

AVN-1-blood-supply-to-head-neck-femur

Symptoms

AVN may be present without any pain. In most cases, however, pain often develops dramatically, and increases in severity once the AVN has progressed. If the patient has hip pain, it is often due to flattening of the normally round femoral head, bone fragmentation, and eventual collapse of the femoral head.

Diagnosis

It is important to perform a complete physical examination and ask about past medical history, including your health problems, and medication history. As with any other diseases, early diagnosis increases the chances of treatment success.

X-ray may help identify the cause of hip joint pain, such as a fracture or arthritis. In the earliest stages of AVN, standard x-rays are often normal. If the x-ray is normal, you will probably have additional tests. A magnetic resonance image (MRI) is the most sensitive non-invasive method for diagnosis of AVN, and will show if there is any damage to the bone marrow, the bone itself, and the structures in and around the joint. In addition, MRI may show diseased areas that are not yet causing any symptoms.

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In addition, it is important to evaluate the opposite hip as well, because there is an 80% chance that the other hip is affected, even though there may be no symptoms at the time.

Treatment

The goal in treating avascular necrosis of the hip is to improve the patient’s use of the affected joint, stop further damage to the bone, and ensure bone and joint survival. Several treatments are available that can help prevent further bone and joint damage and reduce pain. To determine the most appropriate treatment, the following must be considered:

  • Age
  • The stage of the disease – early or late
  • The location and amount of bone affected – a small or large area
  • The cause of AVN – with an ongoing cause such as steroid or alcohol use, treatment may not work unless use of the substance is stopped
If a small percentage of the femoral head is involved, AVN may resolve without any further treatment. Non-operative (conservative) treatment consists of partial weight bearing with the use of crutches for six weeks then re-evaluation by your orthopaedic surgeon. However, non-surgically managed cases most often show an 85-92% risk of progression of the disease, and for this reason, it is usually best to treat the hip surgically.

On the other hand, if greater than 50% of the femoral head is involved, it will ultimately require surgery. Surgical treatment involves one or a combination of four different procedures:

  • Core decompression is a procedure that involves drilling into the femoral neck (hip bone), through the necrotic (dead) area in order to relieve the pressure in the bone and to allow the bone to regrow in the area and heal on its own. This surgical procedure removes the inner layer of bone, which reduces pressure within the bone, increases blood flow to the bone, and allows more blood vessels to form. Core decompression works best in people who are in the earliest stages of avascular necrosis, often before the collapse of the joint. This procedure sometimes can reduce pain and slow the progression of bone and joint destruction in these patients. Patients are required to use crutches for 6 weeks following this procedure in order to prevent the risk of fracture.
  • Osteotomy. There are several types of osteotomies; however, all of these procedures attempt to shift the diseased femoral head by relocating some viable (living) cartilage in the weight bearing area so that there is less pain when walking. After the procedure, activities are very limited for 3 to 6 months.
  • Arthroplasty (total hip replacement) entails replacing the hip joint with an artificial femoral head and part of the femur with an artificial stem. A total hip replacement appears to provide the best results, and leads to complete or nearly complete relief of pain and relatively normal function in 90-95% of patients. With modern surgical techniques and devices, these artificial hips should continue to function for at least ten to fifteen years in the majority of patients.

In addition to the above surgical and non-surgical treatments, doctors and researchers are exploring the use of medications, electrical stimulation, and various therapies to increase the growth of new bone and blood vessels. These treatments are used experimentally, alone, and in combination with other treatments, such as osteotomy and core decompression.