Historically total hip and knee replacement were reserved for patients older than age 65 who were low demand, and patients would be dissuaded from more strenuous repetitive activity. This was based on original joint replacement generations which were projected to last only 15 years. Now nearing 5 decades into widespread use with several generations of materials and design advancements, modern joint replacements have proven remarkably durable. Today’s patient is often younger and does not wish to forgo any work-related or leisure time activity including competitive sports and high-demand recreation. Today’s older patients often also remain very physically active in their advanced years, and they too do not wish to compromise their fitness and independence.
The two factors that influence the longevity of an implant include fixation to bone and wear of the plastic insert. The former can be affected by the latter. Implant loosening historically could be caused by an inflammatory response created by wear debris from the plastic insert in hip and knee replacement. Through a process called cross-linking, modern manufacturing and sterilization techniques have yielded stronger bonds in the substance of the plastic that is highly resistant to wear over time. Extensive research over many years helped to determine factors that led to the internal breakdown of the plastic material through a process called oxidation. Creating more cross-linking between the molecules in the plastic and impregnating the material with anti-oxidants like Vitamin E can substantially lower the tendency for the material to wear with cyclical use.
Now that highly cross-linked polyethylene has become the standard in hip and knee replacement for the past several years, measurement techniques have determined that wear is negligible over time. We often now see patients who are more than 20 years after a hip and knee replacement and still have a well-functioning implant. Registry studies and long-term follow-up studies have now determined that 95% of hip and replacements are still functioning at 15 years and that forward projections of longitudinal failure predict that today’s implants may easily last 25-30 years and permits a high level of function.
In our practice, we understand that patients want to return to the activities they love, even those that may have lead to hip or knee arthritis in the first place. For this reason, we do not specifically restrict peoples’ activity level provided they have a well-functioning stable implant. Part of our AVATAR value proposition is faster recovery and better outcomes and this means restoring a high level of function without pain and provided a durable result that can withstand the physical demands of today’s patients. Fortunately, the implant industry has responded to the demands of the market and provided surgeons with the tools to deliver long-term success with joint replacement.