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Hip Osteonecrosis

What is hip osteonecrosis?

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Updated May 27, 2014

Hip osteonecrosis, also called avascular necrosis, impairs the blood supply to bone. Hip osteonecrosis occurs when there is an interruption of the blood supply to the head of the femur (the ball, of the ball-and-socket hip joint). The lack of normal blood supply causes a decrease in delivery of oxygen and nutrients to the bone, and the bone subsequently dies. When the bone dies, the strength of the bone is greatly diminished, and the bone is susceptible to collapse.

What causes hip osteonecrosis?
No one know exactly what causes hip osteonecrosis. When hip osteonecrosis occurs, the bone collapses and the joint surface, the cartilage, looses its smooth shape. Because the cartilage looses the support of the bone underneath itself, the joint surface is quickly worn away, and arthritis quickly progresses.

Most cases of hip osteonecrosis are associated with either alcoholism or steroid use. Other risk factors for developing hip osteonecrosis include sickle cell disease, trauma to the hip (dislocation or fracture), lupus, and some genetic disorders.

What are the symptoms of hip osteonecrosis?
Hip osteonecrosis usually has few warning signs. Patients often complain of new onset hip pain and difficulty walking. Common symptoms of hip osteonecrosis include:

  • Aching pain in the groin
  • Pain with movement of the hip
  • Difficulty walking or limp

How is the diagnosis of hip osteonecrosis made?
The two tests that are most helpful in diagnosing and treating hip osteonecrosis are X-rays and MRIs. The X-ray may be completely normal, or it may show severe damage to the hip joint. If the X-ray is normal, an MRI will be performed to look for early signs of hip osteonecrosis.

Other conditions that can have similar symptoms include osteoarthritis of the hip, transient osteoporosis of the hip, and back conditions.

What are the treatments of hip osteonecrosis?
Treatment of hip osteonecrosis is difficult because the problem tends to progress quickly despite intervention. In the early stages of hip osteonecrosis, crutches and anti-inflammatory medications can be helpful.

Surgical options in the early stages of hip osteonecrosis include hip decompression and vascularized bone grafting. Hip decompression is done to relieve increased pressure within the femoral head. This pressure build up may contribute to the problems with blood supply. A hip decompression is done with the patient asleep in the operating room. Small holes are drilled into the area of hip osteonecrosis to relieve the pressure within the femoral head. The vascularized bone graft moves healthy bone from the lower leg (along with the blood vessels attached to the bone), and places this into the area of hip osteonecrosis. The goal of this surgery is to deliver normal blood flow to the affected hip. Both of these procedures are done only in the early stages of hip osteonecrosis.

The most common surgical treatment of hip osteonecrosis is total hip replacement. If there is damage to the cartilage of the joint, then hip replacement is probably the best option. While hip replacement works well, the replacements will wear out over time. This presents a problem in young patients diagnosed with hip osteonecrosis. Another option for younger patients is called hip resurfacing surgery. This procedure is similar to a standard hip replacement, but removes less normal bone.

Sources:

National Osteonecrosis Foundation.

CJ Lavernia, RJ Sierra, and FR Grieco "Osteonecrosis of the femoral head" J. Am. Acad. Ortho. Surg., Jul 1999; 7: 250 - 261.

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