Avascular Necrosis of the Hip

Avascular necrosis describes a process through which bony tissue dies due to not receiving an adequate blood supply. This can occur anywhere in the body, however, there are certain locations that are known to be more prone to develop avascular necrosis – for example, femoral head, talus and scaphoid.

There are a number of different potential causes of avascular necrosis: it has been shown to be associated with the use of certain drugs (e.g. prednisone), it can occur as a result of trauma, be associated with other medical conditions such as antiphospholipid syndrome or protein C or S deficiency, has been linked to excessive smoking, is associated with certain chemotherapy drugs and has even been shown to be associated with deep sea divers who experience “the bends” However, there are a good number of cases of avascular necrosis that occur without an obvious identifiable cause. We refer to these cases as “idiopathic”.

The period of time that it takes to develop avascular necrosis will largely depend on the cause. For example, for drugs such as prednisone or chemotherapy drugs to be present in sufficient quantities in a person’s bloodstream to be able to cause avascular necrosis, they need to be taking such drug for an extended period of time (usually over a number of months). However, if the cause is related to physical trauma then avascular necrosis can be detected as early as four to six weeks after the injury (e.g. talar avascular necrosis, where “Hawkins sign” can be used as a radiographic marker of the development of avascular necrosis in this area).

While the process of avascular necrosis is not reversable per se, it is possible to undergo treatment to prevent the progression of avascular necrosis from its early stages to full-blown tissue death and as such preserve some function in the joint that is affected. Traditionally, early stages of avascular necrosis of the femoral head are thought to have benefited from a procedure known as a core decompression, which essentially involves drilling into the avascular necrotic lesion to allow blood to reach the area and to prevent worsening of the hypoperfusion of the areas of the femoral head undergoing avascular changes. There are other areas of the body that do benefit from treatments of a similar type, for example in the talus retrograde drilling of an avascular necrotic lesion is a widely recognized treatment option with varying degrees of success.

For many people the first sign that they may be suffering from avascular necrosis will be development of pain in or around the affected area. For patients with avascular necrosis of the femoral head this will present as hip pain, for patients with avascular necrosis of the talus this will present as ankle or foot pain and broadly speaking whichever area of the body has undergone avascular necrosis will begin to become quite sore and painful, particularly with movement or weight-bearing. It is important to seek medical attention for any pain of this type, as avascular necrosis can show up on plain film x-rays even in its early stages. However, even if it does not, there are other ways to be able to diagnose the early stages of avascular necrosis that have not yet shown signs of developing on a plain film x-ray. CT scans and, more commonly, MRI scans are used to give your physician more information regarding the bone itself as well as the overlying cartilage in bones that form joints and the fluid content of the bone which may indicate an abnormal process. For patients with any type of persistent and refractory joint pain, consultation with a specialist orthopedic surgeon early on is beneficial in assessing avascular necrosis as it allows us to both diagnose the condition and establish, if any, the cause.

As previously mentioned, there are a number of surgical procedures that have been shown to yield some benefit in patients who have developed avascular necrosis in a bone, particularly in bones that form joints. However, while treating the patient surgically is often the best option, it is also important to try (wherever possible) to establish a clear cause of the avascular necrosis. If this is possible, cessation of the offending drug or treatment plays just as important a role in the treatment of the patient as does any possible surgical procedure that they may have to undergo. This presents challenges, as patients are often taking these medications in relation to other medical conditions, and it may be unfavorable to stop taking these medications with due consideration to the condition that they are treating. At this point in time it becomes important to discuss with your orthopedic surgeon as well as your treating physician for any other medical condition the development of avascular necrosis and the consequences of both continuing to take the medication as well as the consequences of stopping the medication and any possible alternatives to the medication that your physician may be able to offer you. Unfortunately, in cases where avascular necrosis has reached its advanced stages, it may not be possible to halt the progression of avascular necrosis further, or it may have caused destruction of the bone anatomy to such a point that more invasive surgery may be necessary. These surgical procedures can include osteochondral allograft, resections, arthroplasty and possibly even fusion.

The development of avascular necrosis in and of itself will not pose a threat to a patient’s life. Although it is death of bony tissue, it is most commonly bony tissue alone that is affected by his phenomenon. All of the basic human functions will go unaffected by this condition and as such this is not an emergency and there is no immediate threat to life. It does pose a risk, however, of decreasing the patient’s quality of life to a point that may exacerbate certain other conditions. For example, in avascular necrosis of the hip, if left untreated and undetected, patients may experience severe and debilitating hip pain that they are unable to exercise with or even comfortably ambulate with, and this may cause the patient to choose to become more sedentary. This sedentary lifestyle is often detrimental to cardiovascular health and in patients with diabetes it can significantly change the dynamics of their blood sugar control.

While significant and important developments are being made in the area of stem cell research, to date there have been no high quality studies that have demonstrated the ability of stem cells to regrow deficient bony anatomy as a result of avascular necrosis. At this point in time we simply cannot recommend stem cell therapy for avascular necrosis as it is not known if this type of therapy holds any benefits for avascular necrosis patients.

Although avascular necrosis around the joint can ultimately lead to the development of arthritis, not everybody who suffers from avascular necrosis will go on to develop arthritis necessarily. The term arthritis simply refers to inflammation within a joint and can happen for a great number of reasons, one of which is recognized to be avascular necrosis. However, avascular necrosis itself is the death of bone tissue related to poor blood supply, and although if left untreated and undiagnosed it can lead to arthritis in its later stages, there are a great number of patients who present to medical professionals in early stages of avascular necrosis and are able to be successfully treated so that they do not go on to develop arthritis as a result of this condition.

The possibility of suffering from avascular necrosis in multiple different parts of the body will entirely depend on the cause of avascular necrosis. For patients who suffer from this phenomenon due to a traumatic injury, the development is unrelated to any systemic issue and as such will be isolated to the area which was initially injured. However, if the cause is systemic (e.g. related to chemotherapy or corticosteroid use) then the possibility does exist that a patient will undergo avascular necrosis in different parts of the body. This is, however, exceedingly rare and it is most commonly only one area of the body that tends to be affected by avascular necrosis even from systemic causes. That being said, once avascular necrosis is diagnosed in one area of the body, it is important to continually monitor other areas of the body for pain so that, if avascular necrosis develops elsewhere, it can be caught and treated early in order to minimize risk of requiring invasive surgery.