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Total Knee Replacement

There is much written and advertised about the total knee replacement. Minimally invasive surgery (MIS) has become widely popular. Patient satisfaction rates are very high, with well over 90 percent of patients being totally satisfied. Over the past 50 years of use of total knees, the life expectancy or time that they are expected to last, has improved dramatically. Approximately 86 percent of total knees are still working well at 15 years follow-up.

There are many different designs of total knees. They can be classified into those that keep the posterior cruciate ligament and those that do not (posterior cruciate sparing and posterior cruciate sacrificing). The posterior cruciate ligament is often diseased in the arthritic knee. It may be very tight or even ossified, meaning that it has turned into bone. In Dr. Clyburn's opinion, most knees should be replaced with a posterior cruciate sacrificing design, and the sparing design used only in cases where the arthritic process is fairly mild. In Dr. Clyburn's practice, he usually chooses the posterior stabilized design. He also has, on many occasions, seen patients with a cruciate sparing design who either have stiffness or instability. These patients often improve dramatically when they are revised to a posterior stabilized design.

Total knee replacement can also be classified as either fixed bearing or mobile bearing. In the fixed bearing design, the polyethylene part is fixed to the metal plate of the tibial component. All of the movement of the knee occurs between the femoral component and the polyethylene. In the mobile bearing design knee, there is movement allowed between the polyethylene and the metallic tibial component, allowing this design to attempt to move in a more anatomically correct fashion. However, long-term studies of both the fixed and mobile bearings show similar results.

Advertising of Specific Total Knees

There is much marketing today with regard to specific total knee designs. One advertiser states that their knee is the only one designed to bend and rotate. Remember that this marketing is written by advertising executives working for the manufacturer. In fact, all knees are designed to bend and to rotate. Total knee replacement would not be successful today had they not been designed from the beginning to bend and rotate.

Another manufacturer, Zimmer, which is an excellent company, is aggressively marketing their gender specific knee. This design focuses on two general principles. One is that women's knees tend to vary more in size in the front to back (AP) and side to side (ML) proportions than men. They, therefore, changed the sizing slightly and added 1/2 sizes (like shoes). Also, because women tend to have more "knock-kneed" than "bowed" legs, their patellae (knee cap) function slightly differently than those of men. They, therefore, slightly changed the way the patellofemoral parts function. Other manufacturers have made similar modifications but did not market them as specifically for women. In some ways, it is similar to the tobacco industry which marketed cigarettes specifically for women, even though, for the most part, it was simply a cigarette. This type of design holds promise and deserves attention and study; however, there are currently no long-term or even mid-term studies showing superior outcomes of these implants.

Computers and "Navigation in Total Knee Replacement"

Dr Clyburn has been in the forefront in the use of computers and navigation in total knee replacement. We have performed a research study and clinical study of navigation.

We have not found this technology to offer an improved outcome and thus we do not use it routinely. However, we do continue to study this technology.