Session I: Long-Term Followup After Total Knee Arthroplasty

It is expected that more than 62 million people (18% of the United States population) will be older than 65 years in 2025. ¹ In those individuals 65 years and older the prevalence of arthritis, including osteoarthritis and rheumatoid arthritis, will continue to increase with age. ⁴ Therefore, the actual number of knee arthroplasties done each year in the United States will continue to increase. ¹ For this reason, long-term clinical results must support the surgeon’s decisions for selecting one implant over another. In addition, surgeons who do joint replacements will be called on to put implants into an increasingly younger population, which, in itself, may lead to failures.

Since the early 1980s when total knee replacement became critically dependent on instrumentation, the success rate from this operation has increased to 95% or higher. Unfortunately, there are many different types of implants and physicians are not always sure as to what implant to use for what type of arthritic condition and how durable it may be. There are few long-term followup studies on most of the implants and those that do have long-term followups may not all be manufactured anymore. ⁵

Before 1992, osteolysis only was associated with hip arthroplasties and was not even a clinical diagnosis. Because of design changes, modularity and the uses of various polyethylenes, osteolysis now is also a problem associated with knee arthroplasty. Therefore, surgeons not only have to worry about the durability of the implant, but also must worry about the mechanisms of prosthetic wear at the articular and modular surfaces of the implant. ²

The present five topics all surround the problems that confront the surgeon doing total knee replacement.

It has been shown that the major cause for osteolysis after total knee replacement is wear between the modular implant and the metal backing. ³ Clinical reports stated that no modular implant can avoid the problem of backside wear. This session will address the problem of nonmodularity as it relates to wear and long-term followup as has been reported previously. ⁵

Using a modular mobile-bearing type of implant that has an enormous amount of motion between the polyethylene surface and the metal backing and to date has shown very little problem with wear also will be discussed. As has been reported previously, this experience will offer great insight into the possible need for a mobile-wearing type of component. ⁵

Finally, whether to retain the posterior cruciate, a question that has been asked since the beginning of total knee replacement surgery will be addressed with long-term data.

With the increasing number of total knee arthroplasties done each year in the United States, surgeons who do joint replacements must feel comfortable with the decision-making process of selecting the best total knee replacement system for a given patient. This process should be based on long-term followup studies that clearly show enduring performance and durability of implants. The important long-term data presented will provide direction to the surgeon in selecting the most appropriate total knee replacement for each given patient.