How Durable Are Hip and Knee Replacement Prosthetics?

Historically, hip and knee replacement surgery was performed to treat severe arthritis in those aged 65 and older. The common belief was that a prosthetic joint usually would last for 10 years, then wear out or loosen requiring more surgery. Often the results of the re-do surgery were not as effective as the initial implant and the recovery was more difficult.

Because a joint could be redone only once or twice at most, hip and knee replacement surgery typically was delayed for as long as possible. In fact, many patients were told they were not candidates because they were too young. Instead, they were advised to make lifestyle changes and “live with it” until they were older. At the other end of the spectrum, many elderly patients were told they were too old to survive the surgery, that the risks were too high and that they also needed to “live with it.”

So what’s changed? Joint replacement now is considered routine and the number of surgeries being performed each year has grown tremendously. Since the first joint replacement procedures performed nearly 50 years ago, surgery now is safer, less traumatic, more streamlined and the results are more predictable. The surgical tools and instruments which we now have, including computer assisted navigation for total knee replacement surgery, robotic assisted partial knee replacement and the Pelvic Alignment Guide (PAL) for hip replacement surgery, have been major game changers in my opinion, allowing surgeons to more accurately position prosthetics for better results and longevity.

Today, people no longer are willing to endure living with pain and disability or give up their active lives when there is a safe and viable alternative. Some attribute this shift in mindset to the baby boomer generation, because people are living and remaining active longer both in the workplace and with social and sports activities.

In my practice, I care for the people well in their 80s and 90s who refuse to give in to old age.  At the other end of the spectrum, I also see patients in their 30s and 40s and even occasionally in their 20s who are miserable and elect to have a joint replacement to regain quality of life. In fact, for those aged 45 to 54 who cannot find relief with more conservative treatments, knee replacement surgery alone is projected to increase to nearly one million procedures by 2030 (knee replacement surgery in younger patients).

Because of this shift in demographics, manufacturers have upped their game, attempting to produce more efficient and durable implant designs. For example, all of the major prosthetic hip joint manufacturers now offer a highly crossed linked plastic liner which is proving to wear much better than its predecessor. Before a prosthesis is released to the public, it will be tested with machines that simulate the body forces to which the implant will be subjected. Some manufactures advertise the longevity based on this testing. Other manufactures with similar test results don’t make these claims because of ethics or fear of legal repercussions if the claim proves to be unfounded. We have learned that while lab testing is important, it does not predict the overall performance in human bodies. Many other variables, some not even considered, could arise and negatively affect implant behavior and longevity.

There’s always a cautionary tale to go along with anything “new and improved.” A sad and now familiar example of this is the current, worldwide debacle regarding metal on metal hip replacements and modular neck hip replacements. These implants have caused major problems for people worldwide and the number of revision surgeries being performed to correct problems associated with these types of implants continues to grow.

When patients ask me how long their new hip or knee will last, I tell them honestly there is no magic number. There are so many variables that must be considered when estimating the longevity of a prosthetic joint, including a person’s age, weight, what disease led to the need for a joint replacement, physical activities, and even whether the patient is male or female.

I do share with my patients that there are a number of long-term studies that show that hip and knee replacements, preformed with well designed and time-proven prostheses that are implanted accurately and optimally, have an 85 to 90 percent chance of functioning well after 15 or 20 years. In fact, there are studies of some particular prosthesis, such as the Exeter hip stem, placed 15 to 20 years ago having even better longevity rates.

Below are some of the factors that can that influence the life of a prosthetic hip or knee joint:

• Age: Younger patients, particularly men, not only wear out prosthetic joints faster, but request joint replacement earlier than any other group. I’m hopeful that newly designed prostheses and bearing surfaces will meet the needs of this challenging group. Still, it’s critical that the surgeon doing the primary implantation have a revision plan or strategy, even if it’s 20 or more years down the road. As a surgeon, I ask myself with every prosthesis I implant: what is the next step if it fails? Can I remove the prosthesis and put in another without destroying excessive bone or tissue? What will the next reconstruction look like? It’s critical that the correct components be implanted for your needs, which is an important discussion to have with your surgeon.

• Activity: Some activities simply are not appropriate for patients who have had a hip or knee replacement. But truthfully, we keep rewriting the rules because of patients who are succeeding with remarkably active lifestyles. I allow and even encourage my patients to participate in activities that the surgical community never would have sanctioned in years prior, including singles tennis, downhill skiing and ice hockey. I assess and advise each patient on an individual basis.  My advice to a man in his late 20s or 30s would be different than for a man in his 70s, i.e., a man in his 20s or 30s playing tennis is very different than in his 60s or 70s.  My rule of thumb for everyone is to use common sense and avoid repetitive high-impact sports, such as long-distance running.

• Weight: People who are overweight have a significantly higher rate of hip and especially knee arthritis. For many years, we thought being overweight shortened the longevity of a patient’s prosthesis, as with the body’s natural joints, being overweight will put more stress on an artificial joint. Maintaining a normal body weight has a significant bearing on the longevity of a joint implant. Paradoxically, many who are overweight are not as active so they don’t put the same wear and tear on a prosthetic joint as more active joint recipients. The balance comes from maintaining a proper weight and finding the level of activity that keeps you healthy. Your doctor can suggest appropriate exercises to help sustain a hip or knee replacement and a healthy lifestyle.

• Complications: Some medical conditions and invasive medical procedures, such as dental work, may require antibiotics to keep bacteria from invading a prosthetic joint.  Also, patients with osteoporosis should have proper treatment to avoid a bone fracture near a joint replacement, which could adversely affect functionality.

• Loosening and wearing: Perhaps the most common long-term problem with both artificial knees and hips is loosening of the prosthetic and the wearing out of the joint surface.  We now have much better methods of attaching the implants to the skeleton and longer lasting bearing surfaces. Still, maintaining proper body weight and staying physically fit, while avoiding repetitive high-impact sports such as long distance running, will help preserve joint function and longevity.

• Type of prosthesis used: Some hip and knee prostheses clearly have outperformed others. Each year, manufactures release new prostheses and although the implants are fully FDA approved, most do not have a proven track record.  Unlike computers, artificial joints and the techniques used to implant them need to pass the test of time. It can take 15 to 20 years to learn if implants measure up.  As the need for artificial joints increases, it might seem like a good idea to be implanted with the newest prosthetics or use the newest technique or technology. Newer is not always better. Personally, I’m skeptical of new implants and prefer to wait until a prosthesis has been tested in the field for at least several years. Only then do I consider making a change if there is a real need, not just to try something new. I also feel it is critical that the industry seek input from doctors and scientists when creating new designs.

Be sure to ask your doctor about which prosthetic implant, technique and technology will be used. Have a complete understanding of why your doctor chose a specified procedure for you, and what his or her success rate has been with that surgery. Unfortunately, in our competitive, financially driven world, some prostheses will be released for use without adequate, long-term, follow-up testing. There always will be new technologies and techniques, but often time proves that they are no better than what we already have or in some cases are worse than what we already are using. I think it is very important to have this discussion with your surgeon.

As head of the of the Leone Center for Orthopedic Care, my practice focuses exclusively on solving complex hip and knee problems, including hip and knee replacement surgery and knee arthroscopy.  Over the past 10 years, I have performed more than 5,000 joint replacement surgeries. Studies show that patients who are operated on by surgeons who specialize in performing hip and knee replacements have fewer complications.

As with all surgical procedures, it is imperative to choose a surgeon with a proven track record in this specialty. Get to know and have confidence in your doctor. Feeling comfortable with your surgeon will have a positive impact on your overall surgical experience and the outcome and longevity of your joint replacement.

We thank you for your readership. If you would like a personal consultation, please contact our office at 954-489-4575 or by email at LeoneCenter@Holy-cross.com.