Are Partial Knee Replacements a Viable Procedure? 15 Responses

Orthopedic Sports Medicine

Fifteen orthopedic surgeons discuss partial knee replacements and answer the question: Are partial knee replacements a viable procedure? This roundtable is the second question in a series discussing partial knee replacements. You may also be interested in hearing what the surgeons had to say in response to this question: Are Partial Knee Replacements a Passing Trend of the Future of Knee Care?

Keith Berend, MD, Orthopedic Surgeon, Joint Implant Surgeons, New Albany, Ohio:
I believe that partial knee replacements should be part of every orthopedic surgeon's armamentarium that treats osteoarthritis of the knee. Over time, partial knee replacements have gotten a bad image because of poor implant design, technology and technique, and misunderstanding of the indications. With a true understanding of the biologic and physiologic knee, it can be the best option for patients with osteoarthritis. It is a minimally invasive procedure, which can have benefits for the patients.

Most orthopedic surgeons should see about 30 percent of their patients as candidates for total knee replacements if they really understand the indications for surgery. In my practice, it's over half. I have done more than 2,000 partial knee replacements and have a 96 percent survival rate over seven years. There are some studies that suggest the range of motion is better among patients with partial knee replacements than with the totals, and most interestingly, partial knee replacement shows significantly less pain for the patients than the totals.

If a surgeon doesn't believe in partial knee replacements, they are performing more surgery than is needed for some patients. Across the board, I've found the risk of patients having complications associated with partial knee replacement is one-tenth of what they would have if they received a total knee replacement.

J. Dean Cole, MD, Orthopedic Surgeon, Florida Hospital Fracture Care Center, Orlando: I think partial knee replacements are an important part of my practice because they can help a certain part of my patient population. There is a defined group of patients who are going to do well with unicompartmental knee replacements or osteotomy. Patients with defined compartment cartilage loss and arthritic symptoms, who don't have significant fixed deformity and do have good bone quality are candidates for partial knee replacement.

Recently, I think the use of MAKOplasty and computer navigation technology to go along with the system has been a significant benefit to the patients. I believe that I can optimize the position of the implant to adapt to the patients' kinematics. I was using a free hand technique without jigs prior to the use of the MAKOplasty technology, and it certainly makes me feel better as a surgeon, knowing I'm going to end up with restoration of the patients' kinematics in an optimal manner.

All you can do in this controversial situation is read a lot of the literature. There are some long-term studies showing that unicompartmental knee replacements do hold up in the right patient population, so I think it's important to identify the factors that are indicated and stick with those. If we do that, unicompartmental knee replacement will stand up to scrutiny of evidence-based medicine.

Michael E. Ciminello, MD, Orthopedic Surgeon, Peconic Bay Medical Center, Riverhead, N.Y.: I think partial knee replacements are very good operations, if done by a good surgeon who does a high volume of them, and for the right patient. That is basically true about most surgeries that are good operations. In partial knee replacement, patient selection really is crucial. The patient can't be older or younger than a certain age, can't be overweight, can't have a curve in their knee greater than a certain degree, the ACL has to be intact and they can only have arthritis in one compartment of the knee. It's an operation that's hard to find the right patient for, and I think that's the reason why we see more total knee replacements in this country.

There are some people who say it's a less invasive procedure with a faster recovery period, and that may be partially true, but it isn't less invasive if it fails, and you have to do a total knee replacement. I think both partial and total knee replacements are good options, and at the end of the day, if well done, I think the partial will do as well as the total. There are some people who say you can do more with partial knee replacements, and I think that's variable. I offer partial knee replacements to patients who are candidates for them, and I'm only able to offer the procedure a couple of times per year.

Nicolas Colyvas, MD, Orthopedic Surgeon, El Camino Hospital Orthopaedic, Los Gatos, Calif.: I think the literature right now definitely supports the use of partial knee replacements. The newer type of procedures that are patient specific using computer-generated implants based on the specific patient's anatomy are yet to be fully tested, but it appears to be something that will be more prominent and more widespread as time goes by. Orthopedics is like a lot of professions: there are people who are set in their ways and people who are more open to change. I think the progression of good results and outcomes over time, and the advancement in technology, will steadily help people move more in the direction of performing partial knee replacements for the right patients.

Scott Desman, MD, Orthopedic Surgeon, Martin Memorial Health Systems, Stuart, Fla.: Patient satisfaction levels with the results, as well as the ease of recovery, play a role in surgeons performing more partial knee replacements than in the past. The MAKOplasty technique allows for more precise and predictable implant positioning, which has been shown to be the most important factor in terms of the success, both short and long term, of partial knee replacement. The partial knee replacement allows for a much easier recovery than a total knee replacement, and the 'feel' is much more natural than a total knee replacement. The range of motion is also much better than a total knee replacement. The hospitalization is only one night and there is no blood loss or need for transfusion after the operation.

There are many decisions that need to be made during the course of the MAKOplasty. It requires experience to appreciate the nuances and perform the procedure properly and efficiently. Some surgeons also believe that the results are less predictable than total knee replacement, and prefer to do a total knee replacement for all cases of knee arthritis.  There is also the issue of reimbursement. Most of the patients are Medicare patients, and the partial knee replacement reimburses the surgeon significantly less than a total knee replacement for a work effort that is equal to or in most cases exceeds that for a total knee replacement.

Charles Gatt, Jr., MD, University Orthopaedic Associates, New Brunswick, N.J.:
From the standpoint of my own experience, unicompartmentals have worked out very well. As in all orthopedic procedures, proper patient selection is key and I think that's why there are periods of time where the enthusiasm for the procedure goes up and others when it goes down. They weren't popular for a while and then they became very popular because you could do them as a minimally invasive surgery. When minimally invasive techniques were developed for total knee replacements, the use of unicompartmental knee replacements went down again. Now, there is a debate between the two because if you can do a total knee replacement with the minimally invasive approach, surgeons often decide to do that and not worry about the unicompartmentals.

There is some data showing that total knee replacements are lasting 20-30 years, but that's for older and less active patients. If you can do a unicompartmental knee replacement and get eight to 10 years out of it before a revision needs to take place, it might be a good procedure because there is more bone preservation than with the totals. Based the patient's age and life expectancy, a revision surgery could be likely regardless of the initial procedure.

Henry Finn, MD, Medical Director, Chicago Center for Orthopedics at Weiss Memorial Hospital and Professor of Surgery, University of Chicago:
As an estimate, at any given time, there are 5-10 percent of knee replacements done as partials, and I think that's very telling. There are certain ideal patients for partial knee replacement — where a limited portion of the compartment is affected. Most often, that's the medial compartment. The lateral and patellofemoral compartments have not shown success with partial knee replacements on a regular basis, but it keeps being tried. While the benefits might be intuitive for patients — a limited repair only fixing what is affected — but it may not be the best solution for many patients because the way we anchor the implant to the bone can not be as reliably and successfully accomplished long-term with partial knee replacements.

For patients where the indications are selected very carefully, and they understand it's likely that arthritis will eventually progress in the other compartments, and they conceptualize the durability of a partial device, then the procedure may be appropriate. The patients need to understand that even though they will have less surgery, the procedure may not be as durable and have as long of a survival as a total knee replacement. Generally speaking, although there are exceptions to every rule, a partial knee replacement will not be as good as a conventional total knee replacement.

John Lynch, MD, Orthopedic Surgeon, New Suburban Orthopedic, Malden, Mass.:
Things have evolved a lot over time, and technology now includes computer assistance for knee replacements. Companies are trying to help physicians place implants in the right place. I'm in a community practice, so I do more than just knee replacements, but it's very important to pick the right patient for unicompartmental knee replacements and often they still might not be happy with the procedure. There is a lot of artistry involved. Most physicians who don't like unicompartmental knee replacements see what they can do for the patient in terms of conservative treatment until they are ready for the total knee replacement. I have had situations where we cut out normal bone, joint and tissue ligaments when we didn't have to because we didn't have a good option beyond total knee replacement.

Now, for partial knee replacements I use the patient-specific implants from ConforMIS. The system is attractive to the surgeon because it gives you guidelines that can increase your confidence during implant placement. In my practice, patients have said the partial knee replacements are less painful and more than half of them return home the day after surgery. I've seen a number of patients who are a little bit older and resistant to the idea of knee replacements because they don't want to experience the pain or they don't want to spend a long time in rehab. These patients may decide to undergo a partial knee replacement, if they are a candidate for the procedure. When they are, I've seen a number of patients who have done well.

Michael Mont, MD, Co-Director, Rubin Institute for Advanced Orthopedics, Sinai Hospital: I have done some unicompartmental knee replacements for a selected group of patients with unicompartmental knee arthritis. I am also someone who tries to use biologic solutions and osteotomies — I tend to do more of those. However, considering the limitations of these procedures, I will more often go to the total knee replacements in cases where other surgeons may have used unicompartmental procedures. Unicompartmental knee replacements are still very commonly used.

Some surgeons are combining unicompartmental knee replacements with a patellofemoral arthroplasty instead of performing a total knee replacement. All these surgeons are trying to do the most sparing procedure possible for the patient's knee. The argument for unicompartmental procedures by the surgeons who perform them is that, in many cases, it may be easier to perform, less surgery and it preserves the undamaged part of the knee. The argument against it now is that total knee replacements do pretty well and they can be done reasonably with small incisions. Totals have pretty good function even though the ACL has been removed, and they have a lower revision rate than unicompartmental procedures.

Eric Millstein, MD, Orthopedic Surgeon, DISC, Beverly Hills, Calif.:
Although I don't perform a high volume of partial knee replacements, I believe they have a role with younger patients who have arthritis in a single compartment of the knee. Some surgeons are very optimistic about the longevity of partial knee replacements, while others refuse to perform them. I sit somewhere in the middle. I believe that with careful patient selection and counseling, unicompartmental knee replacements can be very effective. In some instances, the patient understands that this procedure might just buy the patient time before undergoing a total knee replacement, because unicompartmental arthroplasty is not always a permanent solution.

Thomas Schmalzried, MD, Medical Director, Joint Replacement Institute, St. Vincent Medical Center, Los Angeles:
The important principles in the success or failure of partial knee replacement were identified a long time ago. The two factors are patient selection and surgical technique. Given that you have a patient who really is a candidate for partial knee replacement and the operation is done well, the result can be better than that of a total knee replacement in the same patient. However, if the patient has more extensive arthritis, instability or a significant deformity, then the total knee replacement is a better option.

I have not used the robotic systems, but they only solve the second part of the issue: having good surgical technique. If you have good surgical technique, but you do the operation on the wrong patient, you won't get a good result. Having a robot or some type of sophisticated implantation procedure only helps if you are starting off with the right patient.

Milton Smit, MD, OAK Orthopedics, Bradley, Ill.:
There's a high demand for unicompartmental knee replacements, mainly because people perceive it is less surgery. A lot of physicians feel it has a higher function than total knee replacements, and sports medicine physicians generally have a higher interest in performing them than joint replacement surgeons. I've performed partial knee replacements, and I've found them more demanding than total knee replacements, and less forgiving. The alignment needs to be near perfect and it's harder to ensure the fixation is right. As a result, it is my perception that there is a higher failure rate among unicompartmental knee replacements than total knee replacements.

The two procedures fail for different reasons. Total knee replacements fail because of infections or wear while unicompartmental procedures can experience loosening of the components. Approximately 80 percent of unicompartmentals are performed in the medial compartment and if the implant components are attached too tightly, the lateral side is likely to develop some arthritis. Sometimes, physicians say partials are easy to convert into revisions, but we have not found that true all of the time. In some case, there is bone loss and you have to implant long metal stems to make the procedure work. The polyethylene exchange in a total knee replacement is a much easier revision procedure. In my opinion, if you do a total knee, I think they last longer and are easier to revise.

David Payne, MD, Orthopedic Surgeon, Chapman Orthopedic Institute, Orange, Calif.:
It really comes down to surgeon preference. Some surgeons swear by it and some say there isn't any place for it. Surgeons who do perform unicompartmental knee replacements must focus on patient selection. There are several factors, including age, activity level and the patient's anatomy that go into this decision. Typically, surgeons who are experienced in this operation may find a patient with the appropriate indications and discuss the procedure as an option. During that discussion, surgeons must impart to patients the limits of the unicompartmental knee procedure.

One of the big considerations for surgeons and patients before performing a unicompartmental knee replacement is that it will be harder to perform a total knee replacement later on. You want to preserve as much of the patient's own bone as you can. Patients should also be encouraged to get a second opinion before deciding on the best treatment option for them.

Geoffrey Westrich, MD, Director for Research for Joint Replacement, Hospital for Special Surgery, New York City:
We do a high volume of joint replacements, and a fair number of them are partial knee replacements. The reality is that for patients who have isolated arthritis for one compartment of the knee, it happens to be an excellent operation. If you look at the pattern of knee osteoarthritis, it is by far most common in the medial compartment because many people who have arthritis are bow legged. If we find a patient who has isolated arthritis in one part of the knee, we find that they will do well with a partial knee replacement, which often lasts a long time.

The downside to partial knee replacements is that the physician must make sure the diagnosis of the arthritis is truly isolated to one side of the knee. If not, there is progressive cartilage wear in the compartments that have not been replaced, and we have to convert the partial knee replacement to a total knee replacement. If that's 15 years down the line, the partial was still a good operation. But if it's only a few years after the initial surgery, it's a bad procedure and the patient would have done better with a total knee replacement from the get go.

We have a new high resolution MRI that helps us appropriately diagnose whether the patient would be a good candidate for partial knee replacements. In the past, we would do arthroscopy and look into the knee to see if the patient could undergo a partial, but now with the high resolution MRI that includes cartilage sequencing, we get beautiful pictures of the knee's compartments. When patients have osteoarthritis in the medial compartment that could benefit from a partial, I'll order an MRI on the lateral and patellofemoral compartments to see if they show the beginning stages of wear. If so, the patient may not be a good candidate for the partial procedure.

Delwyn Worthington, MD, Orthopedic Surgeon, Arizona Orthopaedic Associates, Phoenix:
For now, I find the partial knee replacements in the medial compartment for the appropriately indicated patients can work very well. The appropriate patients might be people who have a bowed leg or other problems with the anterior medial compartment and are otherwise healthy. I've found the longevity of the procedure for these patients is as good as total knee replacement, and the patients recover quicker. They also have a better range of motion postoperatively and they say it feels more like a normal knee than total knee replacements.

The problem occurs if surgeons don't stick to the right indications or if they cut the ligaments too much perioperatively. The surgeon needs to make sure the ligaments are intact before beginning the procedure and keep them intact throughout surgery.

Related Articles on Knee Surgery:

New in Knee Surgery: Personalized Knee Resurfacing Implants

Developing the Future: Biologic Knee Replacement

The Physician's Role During MAKOplasty: Q&A With Dr. Frank Noyes of Cincinnati SportsMedicine & Orthopaedic Center

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