Avascular necrosis (AVN) of the hip may be caused by a fracture, joint dislocation, excessive alcohol intake, long-term steroid use or secondary to certain medical conditions.
Avascular necrosis (AVN) of the hip, also called femoral head avascular necrosis, is most common. The thigh bone is called the femur and the head of the femur is called the femoral head. This head attaches to the socket in the pelvic bone forming the hip joint. Other areas that may be affected are the shoulders, knees, hands and feet. The bone breaks down and eventually collapses.
AVN of the hip could be caused by fracture, joint dislocation, certain medical conditions, excessive alcohol intake or long-term use of high-dose steroid medications. The causes of AVN and the treatment used are the same, irrespective of which joint or bone is affected. The condition can affect anyone but is mostly seen in people 30 to 50 years of age.
What are the causes of avascular necrosis?
In about one-fourth of cases, the cause of avascular necrosis (AVN) remains unknown. However, in other cases, it is a secondary condition that occurs when blood flow is reduced or cut off, which can be caused by:
- Trauma to bone or joint
- Steroid therapy (especially in young people)
- Cancer treatments involving radiation to or near the bone or joint
- Fatty deposits in blood vessels or even fat emboli (fat clots), which can block the blood vessels that supply the bone and joint
- Certain medical conditions can reduce blood flow to the bone, such as:
Risk factors for developing avascular necrosis include:
- Prolonged high dose bisphosphonate use (a medication to increase bone density) that causes the osteonecrosis of the jawbone
- Excessive alcohol consumption
- Certain medical treatments, such as radiation therapy for cancer or organ transplantation
What are the signs and symptoms of avascular necrosis?
In the initial stages, avascular necrosis (AVN) may not have any symptoms. However, as the condition progresses, it presents itself with mild pain that increases in severity over time. While pain might only result from putting weight on it at first, eventually, the pain may arise even when you’re at rest. This is followed by a limited range of motion for the joint.
Pain from AVN of the hip typically centers on the groin, thigh or buttock. Though, other areas that may be affected include the shoulder, knee, foot and hand. Some people develop the condition on both sides (bilaterally), such as in both hips.
How is avascular necrosis diagnosed?
To diagnose avascular necrosis (AVN), your doctor will conduct a complete physical exam and advise the following tests:
- Blood tests to rule out rheumatoid arthritis, sickle cell anemia, human immunodeficiency virus (HIV) or acquired immunodeficiency syndrome (AIDS), lupus and coagulation profile
- X-rays, magnetic resonance imaging (MRI) and computed tomography (CT) scan
- Radionucleotide bone scan
- Bone biopsy
- Functional evaluation of bone (measuring the pressure inside the bone via surgical intervention)
How is avascular necrosis treated?
The treatment of avascular necrosis (AVN) aims to provide symptom relief and prevent the condition from worsening. Surgery may be done if needed.
Treatment for AVN of the hips could include:
- Nonsteroidal anti-inflammatory drugs to help relieve pain
- Osteoporosis medications, such as alendronate, may paradoxically slow down the progression of avascular necrosis if used in the right dose and frequency
- Cholesterol-lowering medication to reduce the amount of cholesterol in the blood, which may help prevent the blockage of blood vessels due to lipid plaques.
- Using blood thinners under supervision to prevent clots in the blood vessels supplying the bones
- Adequate rest and restricting physical activity
- Using crutches to decrease the stress over the joint
- Rehabilitation and exercises under the guidance of a physical therapist
- Electrical stimulation to stimulate new bone growth to replace damaged bones
- Stem cells from the bone marrow aspiration and concentration is a newer procedure.
- This may help in the early stages of avascular necrosis of the hip by potentially growing new bone.
- Research is underway to confirm the efficacy of this treatment.
Surgical procedures may be recommended for advanced disease and may include:
- Bone graft or transplant: A section of healthy bone from another part of the body is used to strengthen the area of the affected bone.
- Core decompression: Part of the inner layer of the bone is removed.
- Bone osteotomy (reshaping): A wedge of bone is removed from the joint to help reduce the weight on the damaged bone.
- Joint replacement: Done if the bone has collapsed or other treatments failed, the damaged parts of the joint are replaced with plastic or metal parts.
How is avascular necrosis prevented?
The following measures can help reduce the risk of avascular necrosis (AVN):
- Since low vitamin D levels are associated with AVN, discuss with your healthcare practitioner about routine monitoring of your vitamin D levels and supplementation
- Avoiding smoking
- Limiting alcohol consumption
- Keeping your cholesterol levels in check
- Monitoring steroid use with the help of the doctor
- Never using exotic supplements for muscle building because these may be contaminated with steroids