Osteonecrosis of the hip is a painful condition that occurs when the blood supply to the bone is disrupted. Because bone cells die without a blood supply, osteonecrosis can ultimately lead to destruction of the hip joint and arthritis.
Osteonecrosis is also called avascular necrosis or aseptic necrosis. Although it can occur in any bone, osteonecrosis most often affects the hip. More than 20,000 people each year enter hospitals for treatment of osteonecrosis of the hip. In many cases, both hips are affected by the disease.
Anatomy
The hip is a ball-and-socket joint. The socket is formed by the acetabulum, which is part of the large pelvis bone. The ball is the femoral head, which is the upper end of the femur (thighbone).
A slippery tissue called articular cartilage covers the surface of the ball and the socket. It creates a smooth, low friction surface that helps the bones glide easily across each other.
Cause
Osteonecrosis of the hip develops when the blood supply to the femoral head is disrupted. Without adequate nourishment, the bone in the head of the femur dies and gradually collapses. As a result, the articular cartilage covering the hip bones also collapses, leading to disabling arthritis
Risk Factors
Although it is not always known what causes the lack of blood supply, there are a number of risk factors that can make it more likely for someone to develop the disease:
Injury — Hip dislocations, hip fractures, and other injuries can damage the blood vessels and impair circulation to the femoral head
Alcoholism
Corticosteroid medicines — Many diseases, such as asthma, rheumatoid arthritis, and systemic lupus erythematosus, are treated with steroid medications. Although it is not known exactly why these medications can lead to osteonecrosis, research shows that there is a connection between the disease and long-term steroid use.
Other medical conditions — Osteonecrosis is associated with other diseases, including Caisson disease (diver's disease or "the bends"), sickle cell disease, myeloproliferative disorders, Gaucher's disease, systemic lupus erythematosus, Crohn's disease, arterial embolism, thombosis, and vasculitis
Incidence
Although osteonecrosis affects people of all ages, it most commonly occurs between the ages of 40 and 65. Men develop osteonecrosis more often than women.
Symptoms
Osteonecrosis develops in stages. Hip pain is typically the first symptom. This may lead to a dull ache or throbbing pain in the groin or buttock area. As the disease progresses, it will become more difficult to stand and put weight on the affected hip, and moving the hip joint will be painful.
How long it takes for the disease to progress through these stages varies from several months to over a year. It is important to diagnose this disease early, because some studies show that early treatment is associated with better outcomes.
Doctor Examination
After discussing your symptoms and medical history, your doctor will examine your hip to discover what specific motions cause you pain.
Increased pain during certain movements may be a sign of osteonecrosis.
Imaging Tests
Imaging tests that may help your doctor confirm a diagnosis include:
X-rays. These scans create pictures of dense structures, like bone. X-rays are used to determine whether the bone in the femoral head has collapsed and to what degree.
Magnetic resonance imaging (MRI) scans. Early changes in the bone that may not show up in an x-ray can be detected with an MRI scan. These scans are used to evaluate how much of the bone is has been affected by the disease. An MRI may show early osteonecrosis that has yet to cause symptoms (for example, whether osteonecrosis is developing in the opposite hip joint).
Treatment
Although nonsurgical treatment options like medications or using crutches can relieve pain and slow the progression of the disease, the most successful treatment options are surgical. Patients with osteonecrosis that is caught in the very early stages (prior to femoral head collapse) are good candidates for hip preserving procedures.
