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Treatment of Asymptomatic Osteonecrosis of the Femoral Head

Adults who have a painful hip from osteonecrosis of the femoral head often have the same problem in the other hip but it is "silent" or asymptomatic. In other words, there's no pain. If it wasn't for the telltale signs on X-ray, the affected individual wouldn't even know there was a problem.

Is this a case of out of sight, out of mind? Is it best to leave it alone or treat the condition early to prevent any further damage that can occur within the joint? Let's take a closer look at osteonecrosis first and then see what the experts have to say.

Osteonecrosis means "bone death". Loss of blood supply, bone death, and collapse occur over a period of months to years. The femoral head is the round ball at the top of the thighbone that fits into the hip socket. Osteonecrosis can be caused by steroid use, alcohol, trauma, and blood-clotting problems like Sickle Cell Disease. In some cases, no cause can be found.

The first goal in treating symptomatic (painful, limiting) osteonecrosis of the femoral head is to save the bone. The second goal is to keep function while relieving pain. But what about that asymptomatic hip? Is treatment needed at all? What's the natural history (i.e., what happens over time if it is NOT treated).

Some surgeons advocate what is referred to as careful neglect. This is a watch-wait-and-see approach. Some of the phrases used to defend this position include no sense in muddying up the waters or best to leave well enough alone. But there are just as many orthopedic surgeons who say head it off at the pass. In other words, treat it early and prevent the problem from getting much worse.

The voice of reason and experience comes through loud and clear on this one: study patients who have this problem and see if there are any predictive factors of disease progression. Those patients who have significant risk factors for progression of disease without treatment should be teated early in the course of their disease development.

It is possible that the question of how (and when) it's best to treat asymptomatic osteonecrosis of the femoral head has already been answered but lies buried in the medical literature. That's why these surgeons reviewed all of the articles published on this topic up to the middle of 2008. This type of study is called a systematic review.

Information collected from the studies that were high enough quality to be part of the review included patient age, how long they were followed, location and size of the bone lesion, and use of certain medications (e.g., steroids) or excessive alcohol. They also looked at personal medical history of lupus, sickle cell disease, kidney disease, kidney transplantation, and human immunodeficiency virus (HIV).

By combining all the hips studied into one group, they found that 394 of the total 664 hips developed symptoms and eventual collapse. That's a percentage rate of about 59 per cent (more than half, almost two-thirds). The destruction took place over a period of time from as little as two months and as long as 20 years.

There were some telltale factors to help predict who might go on to a symptomatic phase. The size of the lesion was the main risk factor. The larger the lesion at the time of diagnosis, the more likely destruction and collapse were to occur in time. Patients with sickle cell disease were also at great risk of disease progresion. Patients with lupus were much less likely to progress to collapse.

The authors concluded that based on the systematic review there is enough evidence to support a more aggressive approach to treating asymptomatic hip osteonecrosis. Large lesions are likely to get worse, so don't wait. A wait-and-see approach may be okay for smaller areas of bone death but the patient should be followed closely. Any sign of progression should be addressed right away.

Medium-sized lesions present a different dilemma. In those cases, the surgeon may evaluate the location of the osteonecrosis when making a decision about the best treatment. Repairing damage along the medial (inside) portion of the femoral head is not as crucial as destruction along the lateral (outside) femoral head. X-rays and a series of MRIs taken from different angles might help show the full extent of the damage when making the decision of conservative (nonoperative) versus operative care.

In summary, both the lesion size and location are two big factors in making the wait-or-treat decision about asymptomatic femoral osteonecrosis. The bottom line is that every effort should be made to save the joint without subjecting the patient to unnecessary surgery. Knowing the natural history as it was presented here helps surgeons know how to educate and advise their patients who are trying to decide between conservative and operative treatment.

References: Michael A. Mont, MD, et al. The Natural History of Untreated Asymptomatic Osteonecrosis of the Femoral Head. A Systematic Literature Review. In The Journal of Bone and Joint Surgery. September 15, 2010. Vol. 92-A. No. 12. Pp. 2165-2170.

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