...less medical jargon in a 'Quick Glance' format!
Osteonecrosis(ON) affects approximately 20,000 new patients per year in the United States. Although any age group may develop ON, most patients are between 20 and 50 years old, with the average age in the late 30's. The diagnosis of ON does not affect life expectancy, and for this reason several hundred thousand patients are living with this disease in the U.S. alone.
What is osteonecrosis? First, you should understand that bone is a living tissue with living cells and a blood supply. ON means death of bone which can occur from the loss of the blood supply or by some other means. It has been known by a number of other names including ischemic necrosis of bone, aseptic necrosis or avascular necrosis. AVN has been quite popular in its use because it is shorter to say and write. More recently the term ON has been adopted.
The symptoms of ON of the Jaw can range from minimal noticeable adverse effects, to very serious dental problems. Jaw necrosisis a painful and potentially disfiguring condition, and may require surgery to remove portions of the jaw bone.
The symptoms include:
infection of the gums or jaw infection
loosening of the teeth
poor healing gums
numbness or a feeling of heaviness in the jaw
exposed jawbone and drainage
There are two major forms of osteonecrosis, post-traumatic and non-traumatic. Examples of post-traumatic ON, a common cause of ON, include displaced fractures or dislocations. Minor trauma is not believed to cause ON. Even major injury does not often result in ON. Certain kinds of fracture, where the blood vessels to part of the bone have been physically damaged, may result in ON.
Non-traumatic ON occurs when their is no history of trauma. Scientists have identified a number of risk factors that may be associated with non-traumatic ON. We do not know how these risk factors may lead to the development of the disease. There are many different ideas. But these ideas have not been proven. There are some cases of osteonecrosis that occur in patients that are otherwise completely healthy with no detectable risk factors. This catagory is called "idiopathic", a word meaning "of unknown cause".
Before entering into a description of some of the treatments available for ON, it is important to understand the concept of risk/benefit ratio. Any surgical procedure has a certain element of risk involved. Even no treatment at all has the risk that the disease will progress, so doing nothing is not risk free. Some procedures may have a lower likelihood of success but have very little risk. Other procedures may have a higher degree of success, but also have a higher degree of risk. The physician must work with the patient in assessing all the factors that evaluate both risk and benefit for the patient in their particular circumstance. What is right for one patient may be absolutely wrong for another. This is particularly true for ON because each patient presents with a unique set of factors.
. . . Non-Surgical Treatment
Protected weight bearing canes, crutches or a walker are useful in alleviating the pain associated with osteonecrosis. They can also be useful in protecting the joint between the time of diagnosis and scheduling of elective surgery. Limiting weight bearing may also play a role in limiting progression while associated medical conditions are managed. However, protected weight bearing alone is never an adequate treatment for ON nor will it result in cure of the condition, no matter how long it is maintained. Rarely, an associated medical condition may result in a patient not being able to have surgery. In this case, protected weight bearing may be recommended for pain management.
. . . Pharmaceutical Treatment
There are no established drugs for the prevention or treatment of osteonecrosis. In order to treat the disease, we must first understand how the disease develops. In spite of considerable effort by researchers, we still do not know for sure what causes some forms of ON. We’ve identified several risk factors, but it is not known what effect eliminating or treating the risk factors has on the disease once the disease has begun. However, this is not meant to be a pessimistic outlook for the pharmaceutical treatment of ON. There are several studies that are being undertaken to evaluate the potential of pharmaceutical treatment. This article will summarize their findings to date.
There are several levels of evidence that can be used to support a position by the medical community. They range from the treatment of one patient to comprehensive studies evaluating large numbers of patients. Most of the studies concerning the pharmaceutical treatment of ON fall somewhere in between – with many being a report of a series of patients treated with a medication with no control group receiving a placebo. It is important to understand this so that you can place the significance of these reports in their proper context.
. . . Lipid Lowering Agents
Two hypotheses concerning osteonecrosis relate to fats. One hypothesis proposes that there is an increase in the number of fat cells in the bone marrow of the diseased joint. Another hypothesis is that there is an increase in the amount of fat contained within cells that eventually causes the cell to malfunction or die. With this in mind, scientists have investigated whether lipid-clearing agents can be used to prevent the development of ON.
. . . Anticoagulants
There is increasing evidence that there are abnormal levels of specific factors involved in the coagulation/blood clotting system in some patients.
. . . Hypertensive Medications
Hypertensive medications are drugs used to treat high blood pressure. Several studies have shown that osteonecrosis is associated with an increase in the pressure within the affected bone. One surgical treatment for this is core decompression. It is believed that a core biopsy or biopsies in the diseased bone relieves the pressure and thereby relieves the pain. Another approach to this would be to treat the patient with blood pressure lowering medications.
. . . Bisphosphonates
Bisphosphonates are a class of drugs that have been used to treat osteoporosis – a disease that is characterized by a low bone mass. Recently, in an effort to reduce bone loss, one bisphosphonate - alendronate has been evaluated in patients diagnosed with ON of the hip10. All patients had symptomatic improvement at one year. Although the follow-up time ranged from three months to five years, only a few patients progressed to the point of needing surgery. Recently, concern has been raised relating to a possible association between bisphosphonate therapy and an increased incidence of ON of the jaw.
. . . Drug Studies
You do not need to be in a drug study to receive pharmaceutical treatment for osteonecrosis. These medications are not experimental and can be prescribed by a physician. However, whether they will be prescribed for you is dependent on the physicians experience and your individual circumstance. All of these treatments must be evaluated more thoroughly before the medical community will accept them as standard treatment.