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An Update on Osteonecrosis of the Hip

Posted on: 02/10/2011
In this update on osteonecrosis of the hip, two orthopedic surgeons on opposite sides of the globe team up to review diagnosis, causes, and treatment. Dr. G. C. Babis from the University of Athens and Dr. J. Parvizi from Thomas Jefferson University in Philadelphia explore this condition as it affects the head of the femur (thigh bone). They remind us of the many classifications and treatment options (nonoperative as well as surgical).

Osteonecrosis of the femoral head refers to death of the round ball of bone at the top of the femur that fits into the hip socket. Another term used for osteonecrosis is avascular or ischemic necrosis. Avascular and ischemic both mean a loss of blood supply to the area is the cause of the problem.

But what turns off the flow of blood to that area? That's the real cause or etiology. The authors provide a table of more than a dozen potential causes or etiological factors. From a broad perspective, the etiology of femoral osteonecrosis is the result of genetics, risk factors, and specific events. This is considered a multifactorial etiology.

Let's take a closer look at some of the more common causes and risk factors first. Number one is trauma: a hip fracture or hip dislocation with damage to the blood vessels supplying the femoral head is the most commonly reported cause. Most of the time, older adults are the prime group at risk.

Number two is the use of corticosteroids -- medications such as prednisone used to reduce inflammation and the immune system. Adults with arthritis, anyone who has had an organ transplantation, and cancer patients in treatment are just a few of the types of people taking corticosteroids. Usually long-term use of corticosteroids is the trigger but there have been reports of patients developing osteonecrosis within a month of starting these drugs.

Number three: lifestyle factors. Smoking and alcohol abuse compound the problem and increase the risk of femoral head osteonecrosis. Even occasional drinking (once a week) increases the risk of developing avascular femoral necrosis. But the odds are much higher for those who drink daily and especially if they drink more than one alcoholic beverage in a 24-hour period.

Then there is a long list of other diseases and conditions that are associated with increased incidence of femoral head osteonecrosis. These are referred to as nontraumatic causes. For example, there is a link between osteonecrosis and more commonly known problems like leukemia, sickle cell diseases, and HIV infection and less well-known diseases such as Gaucher disease, hyperuricemia, and Caisson's disease.

The etiology and risk factors for osteonecrosis of the hip are just one side of the coin. The other side (and the remainder of this article) is devoted to understanding classification and staging as part of the diagnosis and finally, treatment. The plan of care really depends on an understanding of the severity of the condition.

Through X-rays and MRIs, the physician is able to "stage" the condition. This classification process helps pinpoint the problems and identify the solutions. But there isn't one method of describing osteonecrosis that includes all the important variables to consider. Instead, there are at least six classification systems on record for osteonecrosis.

Even saying that imaging studies are used to stage the disease doesn't really describe the process and why so many systems are out there. That's because there are many, many different elements that can be examined using X-rays for example. The same can be said when using MRIs to determine exactly what's going on around and inside the hip joint.

All kinds of efforts have been made to treat femoral head osteonecrosis nonoperatively. But despite protecting the joint from weight, using various medications, and attempting electromagnetic stimulation and shock-wave therapy, the results have been poor.

That's why surgeons have turned to operative procedures to treat this problem. But even within the realm of surgical care, there many different options to choose from: decompression, osteotomy, and reconstruction head the list. And, of course, there are an equal number of ways to perform each of those procedures. For surgeons involved in treating patients with avascular femoral necrosis, the authors discuss in detail specific surgical techniques, grafts, fixation devices, and choices among joint resurfacing and hip replacements.

How does the surgeon decide what to do? Two tools are at their disposal. First, there is what's referred to as a treatment algorithm. That's a step-by-step process where each factor is examined and considered carefully when planning the treatment. Age and life expectancy, patient's goals and activity level, and general health and presence of other health problems are a big part of that equation.

Second, the surgeon knows the benefits and drawbacks of each surgical procedure available. Matching up the specific patient characteristics with the surgical options becomes the final step of the algorithm. For patients with poor health or a limited lifespan, more temporary measures may be advised.

For young, active adults, the more invasive but permanent reconstructive techniques may be selected. Severity of disease, length of time from diagnosis to treatment, and intensity of symptoms are also taken into consideration when planning treatment. You can see how this can range from minimal intervention for mild disease in patients with no symptoms to total hip replacement for those with bone death and deformity of the entire joint.

In summary, this review article examines many aspects of osteonecrosis of the femoral head. In the first half, the problem is defined, the causes and risk factors are outlined, and an understanding of the various classification systems is provided. In the second half, treatment is discussed -- both the specifics of what treatment to use and how to decide the best plan of care. Anyone with an interest in the topic of osteonecrosis of the femoral head will find this information useful.

George C. Babis, MD, PhD, et al. Osteonecrosis of the Femoral Head. In Orthopedics. January 2011. Vol. 34. No. 1. Pp. 39-48.

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