The most common joints replaced are hips and knees. Portions of these replacements are made from metals (such as titanium or chrome and cobalt alloys) and polyethylene plastic. There are some joint replacements which are made from a ceramic material or a specially treated zirconium product. The ceramic implants have a smoother surface, reducing friction and wear, but are at this time best suited for hip replacement use. The zirconium implants react with oxygen to create a ceramic-like surface—again, reducing friction and wear. These newer materials are also ideal in patients who are allergic to metals.
Elbow and shoulder joint replacement is still a more difficult proposition; the technology has not caught up with the quality of knee and hip prostheses. However, finger joint replacement is a relatively common procedure in patients with rheumatoid arthritis. In general, finger joint prostheses have been made of silicone, which allows for more flexibility; however, these silicone replacements do not fit as tightly into the finger bones compared to the fit seen with hip and knee replacements. Research is ongoing to perfect finger joint replacements made of metal and plastic which will have a better fit into the bones which make up the finger joint.
In hip and knee joint replacements, there are other options to consider besides the composition of those prostheses. For example, there are a variety of ways in which these joint replacements can be implanted—they can be chiefly cemented into place, partially cemented into place, or they can be essentially cementless. With the cementless implant, the components of the artificial joint that are placed into the bone are composed of a porous material which allows the patient’s own bone to grow into it. Cementless versions of the hip or knee joint replacement theoretically may last longer simply because there is no cement to loosen. However, the cementless version requires healthy bone which can grow sufficiently to create a strong bond; patients with osteoporosis may therefore be poor candidates for the cementless replacement. And cementless replacements appear to require a longer recovery period, as the bone needs time to grow into that porous material of the artificial joint. Obviously, a patient must discuss the options with his or her physician, because so much of the decision on joint replacement and the type of joint replacement will be dictated by other medical problems—or the lack of such. Prior to surgery the patient will undergo testing to make sure that he or she is a safe candidate for the particular procedure.
The benefits of joint replacement surgery include improved mobility, pain relief, and better alignment of deformed joints. The risks include the development of blood clots, infection, and (particularly if there is a pre-existing heart, lung, or kidney problem) worsening of other medical conditions. Blood transfusions are occasionally needed due to the blood loss that can come with hip or knee surgery; but many patients donate their own blood for transfusion during or after surgery—this lessens the risk for transfusion reaction, or the transmission of disease. Of course, recovery time varies among individuals, and the patient has to be willing to undergo intensive physical therapy after surgery. The patient may also sometimes find it necessary to make life style changes, as they may not be able to do the heavy physical activities they might have done in the past; in some cases they must learn how to maneuver about to avoid dislocating the joint.