Familial avascular necrosis of the femoral head

Alternate names

Familial osteonecrosis of the femoral head; Primary avascular necrosis of the femoral head

Definition

Avascular necrosis of the femoral head (ANFH) is a degenerative condition which causes the upper ends of the thigh bones (femurs) to break down due to a disrupted blood supply and poor bone repair.

• It can lead to pain and limping, hip collapse, and cause the legs to be of unequal length.
• In children, ANFH is known as Legg-Calves-Perthes disease.

Epidemiology

• Around 20,000-30,000 cases are reported each year in the United States.
• This condition mainly affects young, active adults, but can occur in children as well.

Cause

• Although rare, there are some families that have an inherited form of ANFH.
• Genetic changes in the type II collagen gene (COL2A1) cause ANFH in a few families.
• This gene is responsible for making a protein that helps build cartilage.
• One other family was found to have a genetic change in the transient receptor potential vanilloid 4 gene (TRPV4).
• This gene makes a protein that helps regulate blood flow.

In the non-inherited types of avascular necrosis of the femoral head, the cause is not clear.

These are some of the factors have been associated with an increased chance to get ANFH:

• Steroid use
• Alcohol use
• Chemotherapy
• Auto-immune disease
• Medications that suppress the immune system
• Sickle cell anemia and other disorders of the blood
• Disorders that affect how the blood clots
• Too much fat in the bloodstream (hyperlipidemia)

ANFH can also develop in a person who has had a hip injury (like a fracture or dislocation) or hip surgery.

Inheritance

File:Autosomal dominant - en.svg

Autosomal dominant pattern, a 50/50 chance.

Most cases of avascular necrosis of the femoral head (ANFH) are not inherited in families. In a few rare families, ANFH is inherited in an autosomal dominant pattern.

Signs and symptoms

• In the early stages, avascular necrosis of the femoral head does not cause any symptoms.
• As the bone damage increases, people may have leg and hip pain, a limited ability to move the leg, and a limp.
• Some people may develop a difference in the length of their legs.
• Eventually, the hip joint breaks down and surgery may be required.

For most diseases, symptoms will vary from person to person. People with the same disease may not have all the symptoms listed. 80%-99% of people have these symptoms

• Groin pain

30%-79% of people have these symptoms

• Flattened femoral head(Flat head of thigh bone)
• Hip osteoarthritis
• Hip pain
• Impairment of activities of daily living
• Limited hip movement
• Lower limb asymmetry(Left and right leg differ in length or width)
• Short stepped shuffling gait(Short stepped shuffling walk)

5%-29% of people have these symptoms

• Generalized osteoporosis

Diagnosis

• Avascular necrosis of the femoral head is diagnosed based the symptoms, and by using imaging, such as X-rays or MRI.
• A physical examination can be helpful as well.
• People with the familial (inherited) form of ANFH may have other family members with the same condition.

Treatment

• Treatment for avascular necrosis of the femoral head may depend on how early it is diagnosed and the presence of an underlying condition.
• It is not clear if medications are helpful.
• Surgery may help in some cases.
• In the more advanced stages, total hip replacement is an option.

Prognosis

The long-term outlook for avascular necrosis of the femoral head depends on the stage that it is diagnosed. Most people with this condition will end up having arthritis in the joint as well as hip collapse. Children diagnosed with this condition have a better long term outlook than adults.

NIH genetic and rare disease info

• NIH info on Familial avascular necrosis of the femoral head

Familial avascular necrosis of the femoral head is a rare disease.