April 2010 Newsletter

Archived Newsletters

Squeaky Joints
By Dr. Robert J. D'Agostini, Jr.

Recently, there have been articles in the media drawing attention to potential problems with new technology for joint replacements. These articles have stemmed from an article written in a professional journal that pointed out some problems with some of the newer artificial joint devices. This journal article was written by three orthopedic surgeons who are highly respected among their peers in the professional community. At least two of these authors have also produced their own joint replacement devices.

Total joint devices consistently evolve and improve. Currently of interest is improving bearing surface technology. The bearing surface is where the ball and the socket of a hip replacement come together to support weight placed on the joint. The materials that make up this bearing surface largely determine the longevity of the device.

Traditionally, the bearing surface has consisted of a metal ball that rubs against a polyethylene shell, which has been shown to be an extremely satisfactory construct. However, in time this type of artificial joint does wear out. The polyethylene liner wears away and the debris from this wear essentially causes the metal components of the device to come loose. If the patient who received this device is young, active, or overweight, the device can wear out sooner than it does in a person that is older, sedentary, or weighs less. As a result of this phenomenon of wear and subsequent loosening, there is ongoing research to find something better.

Alternative bearing surfaces that have been developed use ceramics and metals. Different devices include a ceramic ball with a plastic shell, a ceramic ball with a ceramic shell, and a metal ball with a metal shell. In the laboratory, these alternative constructs seem superior to the traditional metal ball with a plastic shell.

Many doctors around the country who are enthusiasts of this new technology have implicitly or explicitly told their patients that this new technology is superior. They have told patients that if they have a metal-on-metal hip or hip resurfacing implant, they can go out and perform sports without concern that the device will wear out.

Other doctors, myself included, who are enthusiasts for these new bearing surfaces, have explained these devices differently. To be truthful, it is not known at this time that these devices are superior when implanted in a human patient. Only time will tell if this is true. It can take 20 to 30 years to know if these new bearing surfaces are superior to the old bearing surfaces. What is true in the lab is not always true in practice.

Recent articles in medical literature point out that alternative bearing surfaces do have problems. Some of these problems are of great significance. Ceramic-on-ceramic devices make squeaky noises on occasion. Depending on the article that you read, it can sometimes be as high as 20%, though most surgeons think it is more on the order of 3% to 4% of patients with ceramic devices who experience this squeaking phenomenon. Metal-on-metal devices release ions of metal into the body, which end up in the liver. Though physicians do not think this is going to cause a problem, to be perfectly honest we are not positive. In addition, some patients have a reaction to the metal debris, which we call "metalosis." When this occurs, the patients have severe pain and inflammation and frequently the joint has to be removed immediately.

It is important for doctors to inform patients that all bearing surfaces fail eventually. New technology, by definition, has not stood the test of time. This does not mean that new technology is bad, however it may get a bad reputation if doctors trying to sell the new technology present it as “perfect.” It is equally important for other doctors to say that new technology should never be used because it has some problems.

The fact is that there is presently no perfect total hip device. No bearing surface is perfect. It is critical that patients understand this, and discuss the choice of bearing surfaces to be used for his or her device. It is the responsibility of the doctor, who is the professional, to present this data in a fashion that the patient can understand, so that the patient can make an informed decision on what device is right for them. This topic should be explored face-to-face with the surgeon prior to implantation of any device. The patient should not make his decisions based on articles in the media or over enthusiastic claims by irresponsible purveyors of the latest technology.