Osteonecrosis is a disease which ultimately results in the destruction of the joint if left untreated. It can affect any joint but occurs most frequently in the hip. There is no agreement as to what causes osteonecrosis, although a number of factors which contribute to the disease have been identified. Different treatment options are available depending on how far along the disease has progressed. Advanced stages require a total hip replacement. However, if the disease is detected early enough, other alternatives are available. One of these alternatives is a procedure called a core decompression. This procedure involves drilling a small hole in the diseased bone. It was developed by Arlet and Ficat in 1964. David Hungerford, M.D. introduced it to the United States in 1974. All of the orthopaedic surgeons at our center are trained and experienced in the core decompression procedure.

Why a core decompression?

We have shown, as published in numerous medical journals, that there is an increase in the pressure within the diseased bone. This increase in pressure is associated with pain which in some patients becomes intolerable. Core decompression Adecompresses@ the bone. That is, it relieves the pressure from within this rigid structure. The drill hole then fills with tissue and, in some cases, new bone forms within this area. It may increase the blood flow to the diseased area of bone and allow new blood vessels to form. The procedure appears to slow down the disease process in most cases and may even stop its progression in others.

Under the right circumstances, the results of core decompression indicate that it is an effective treatment for osteonecrosis. What are the right circumstances? First, the results are best for treatment of the early stages of the disease. Results after the joint has collapsed are less successful, although in some cases pain relief still occurs. Therefore, it is best used when a hip or other joint is painful but the x-rays are normal. Second, the procedure should be performed by a surgeon experienced with the procedure. Some surgeons have reported a higher rate of complications than we have experienced.

One of the features of a core decompression is that it does not limit further surgical treatment should the disease progress. It is a relatively simple procedure and recovery from it is fairly quick. Pain relief occurs rapidly.

What should you expect?

Pre-admission testing. Within two weeks prior to your surgery, you will be asked to undergo several laboratory tests and possibly an electrocardiogram and chest x-ray. This is called pre-admission testing. This will help us to tell whether there are any conditions which might increase the risk of surgery. A physical examination, performed by your own medical doctor or hospital staff here, is also a part of pre-admission testing.

Just Before Surgery. You will not be allowed to drink or eat anything after midnight and on the morning of the surgery. In some cases, you may be allowed to take a medication you normally take in the morning with a minimal amount of water. If instructed to do so, you will need to let the admitting nurse know that you have done this.

When you come into the hospital on the day of surgery, you may have some additional x-rays that might not have been taken previously and have a physical examination by your surgeon or resident. If you have not already done so, you will be asked to sign an operative consent form to state that you understand what is being proposed and that you are in agreement that we may proceed with the operation. Just prior to surgery, an intravenous line will be started and you will be taken into the operating suite.

Anesthesia. You will be seen by an anesthesiologist on the morning of surgery. The anesthesiologist can answer specific questions you might have. Most of our surgeries are performed under spinal anesthesia. This is a very safe form of anesthesia. It is safer than general anesthesia, which is one of the reasons why we recommend it. Spinal anesthesia disturbs the major body functions a lot less than general anesthesia. Unless there are some specific reasons why a spinal anesthetic should not be used in your case, this is our preferred method of anesthesia.

The anesthesiologist will give you some medication to make you sleepy so that you're not really aware of what=s going on in the operating room. You will not be totally asleep either. However, the area that will be operated on will be totally numb throughout the operation and for several hours after the surgery.

Surgery. As stated before, the surgery involves drilling into the diseased joint. This is done with a specialized instrument that creates a Acore@ of bone that can be removed. Therefore, a core track is left in the bone which first fills up with a blood clot but eventually fills up with tissue. The surgeon uses a specialized x-ray technique, called fluoroscopy, to help him locate the precise site that he would like to drill in to. Bone graft is sometimes used to fill the hole in the bone. The surgery usually takes about 2 hours.

Recovery Room. When your surgery is completed, you will go to the recovery room where you will be closely monitored until the effects of the anesthesia and intra-operative medicines are decreased and you are relatively awake and comfortable.

Orthopaedic Unit. When you have completed your stay in the recovery room, you will be transferred to your hospital room in the orthopaedic nursing unit. If only one site is undergoing a core decompression, you may not be admitted overnight and your length of stay usually is up to 23 hours. However, if you have more than one site done, you will likely be admitted overnight. You will be instructed in how to care for your wound site and what activities you should expect to be able to perform. If you have had a core decompression of the hip, you will be taught how to use crutches.

Risks. It is important that you understand that there are risks associated with any major surgical procedure and core decompression is no exception. This section is not meant to alarm you but you really do need to know these kinds of things in order to make the decision as to whether you wish to proceed with a core decompression. These risks include the risk of death. That's true of any major surgical procedure requiring anesthesia and blood transfusion. The risk of death in our hospital for core decompression is in the order of 1 per 1,000 cases so that you can see that the risk is very small, but it's not zero. The specific risk for you will depend upon your general medical condition, your age, and the difficulty of the surgical procedure, but the risk of death itself is really very small.

Although precautions are taken, there are other potential risks that need to be taken into account. These include fracture and infection. Although these do not occur frequently, you should be aware that they could occur.

As with any surgical procedure, there is a potential risk of infection. So far, probably because core decompression is such a small procedure, we have never had an infection. You will be receiving an antibiotic on the morning of surgery and this will be continued for 24-36 hours after surgery. In spite of the antibiotics and other preventive measures taken, it is possible that an infection could develop. This could generally be treated with antibiotics and cured.

Another risk of core decompression is a fracture. The drill hole creates a Astress riser or weak point in the bone. The incidence of fracture at our hospital is about 1 in 200 cases. It is important to minimize the weight and activity placed on this area during the healing process. With hips, this area is particularly at risk if you should fall. Therefore, it is important that you use crutches or a walker for 6 weeks.

Activity.

Your activity level will depend on which joint or joints have undergone a core decompression. As we have stated previously, with core decompression of the hip, you will be instructed to use crutches for six weeks, possibly longer depending on the severity of the disease. This is to protect against fracture through the A drill hole in the bone. After this, you should be able to return to the normal activity of daily living. Your ultimate maximum advisable activity depends on many factors and should be discussed with your surgeon.

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