Osteonecrosis means “bone death”. Loss of blood supply, bone death, and collapse can 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.
Many people who have been diagnosed with osteonecrosis of the femoral head already have the same problem in the other hip. They just don’t know it because the disease can be “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.
The majority of people who have femoral osteonecrosis in one hip will go on to develop the same problem in the other hip. But this isn’t always the case and even if it does happen, treatment may not be needed.
So how does a person decide what to do? 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. Your surgeon will be able to advise you as to the best course of action for you.
That still doesn’t answer the question about what to do for that asymptomatic hip. Is treatment needed at all? What’s the natural history (i.e., what happens over time if it is NOT treated)?
In a recent systematic review of the literature, surgeons who conducted the study concluded that large lesions along the outer two-thirds of the femoral head are in the greatest danger of further destruction and collapse. Those should be treated right away. Small-to-medium lesions can be watched carefully and treated conservatively at first.
Any sign of progression of disease should be addressed immediately. Anyone with known risk factors (Sickle cell disease, prolonged use of steroids, alcohol abuse) should be watched closely as well.