Knee Replacement for Arthritis
Knee replacement for arthritis has now been around for a little over 40 years. About 600,000 total knee arthroplasties were done in the United States in 2009 with the number increasing with the increasing age of the population. Many used to believe that the knee functioned like a simple hinge. This view has changed after hinge-type joint replacement failed miserably. Resurfacing of the knee joints with low friction components is now the way to go. Over the years, there has been a lot of controversy over the exact shape of the cap that is put over each bone portion that is resurfaced and exactly what alloy the metal is to be. Initially stainless steel was used. Now mostly cobalt chrome alloy variants are utilized. For awhile there were a lot of titanium implants but these have really fallen out of favor because titanium debris causes a reaction in some people and looks terrible inside the knee.
One part of the knee is always surfaced with a metal component (the thigh bone). The other portion is usually metal covered with high-density polyethylene. If the kneecap is resurfaced, it is also covered with high-density polyethylene. There have been substantial improvements in the polyethylene that is available now (namely, the thickness of it) compared to what was used originally. At least two large, prospective, randomized, double-blind studies have been published on the use of a kneecap resurfacing component. The studies have concluded that generally patients do not need or benefit from resurfacing the kneecap, i.e. the patellar component. By avoiding resurfacing the kneecap, over $500 in direct implant costs are saved along with substantial surgical time. There is also less bleeding and it may potentially cause the patient less pain immediately after surgery. Below are some images for a total knee replacement.
|Total Knee Replacement X-Rays
(Front & Side Views)
Joint replacement for arthritis is generally a very good procedure but it is not for all patients. Partial or total knee replacement may be a great option if the person is healthy enough, has good skin condition, can tolerate substantial anesthetic in surgery, and is mentally able and physically able to participate in physical therapy, etc. However, about 2 in 10 people undergoing a knee replacement are not fully satisfied. Just about every one who undergoes a total knee replacement loses knee motion. Only a few people actually gain much motion, so the procedure should be offered to eliminate pain, not specifically to try and improve motion. On the other hand, unicompartmental or partial-knee replacement frequently maintains motion.
Who is a candidate for knee replacement or partial knee replacement?
If a person has pain in the knee usually from arthritis and has good skin (no active ulcer, infection, etc.) and either they can’t tolerate anti-inflammatory medicine (NSAIDs) such as Celebrex, meloxicam and naproxen, ibuprofen, etc. or if those medicines are not giving adequate relief of pain, then knee replacement makes a lot of sense. Degenerative arthritis affecting all surfaces of the knee or rheumatoid arthritis, which invariably does affect the entirety of the knee when the knee is involved, will generally require total knee joint replacement. This includes replacing both the tibia (leg bone side) and the femoral (thigh bone side) of the knee joint.
A unicompartmental knee replacement (arthroplasty) was also introduced about 40 years ago. It's possible the initial results were not good because of a combination of poor patient selection (wrong patient being offered the procedure) and unreliable equipment to put the implants in (hadn't had enough time to evolve). Unfortunately, unicompartmental knee arthroplasty has only gained recognition as a valuable option in the last 10 years. With properly selected patients using the current implants and the fine tools (jigs) to make the procedure reproducible, many people are now benefiting from this procedure. Surgeons doing exclusively knee surgery practice in several parts of the country are estimating that about half of the patients that are undergoing total knee replacement would actually do well with just a unicompartmental knee replacement.
|Unicompartmental knee replacement
for inner knee arthritis.
A person who is a candidate for unicompartmental knee replacement only has substantial arthritis in the inner or the outer side of the knee, usually the inner side. Whatever is going on in the front of the knee (behind the kneecap) or the outer knee (lateral) must be minimal. One implant design, that with a mobile bearing, cannot be used in someone with an ACL deficient knee while the other brands on the market may be suitable for a patient who has developed arthritis in association with an old, untreated ACL injury.
Generally, the same stipulations making a person a candidate for a total knee replacement are there for a unicompartmental knee except that the arthritis has to be limited to just one part of the knee (as seen in the images below). The X-ray to the right is a side view of a unicompartmental knee replacement. Note that the knee cap is preserved.
|Unicompartmental Knee Replacement X-Rays
(Front & Side Views)
The concern in doing the unicompartmental knee replacement is that because arthritis tends to be a progressive illness, a percentage of people having a unicompartmental knee will go on to have further arthritis develop in the other, seemingly uninvolved portion of the knee. The patient may then need additional knee surgery. Unicompartmental knee replacement does not substantially affect future surgery, i.e. it does not make it much harder and it does not compromise the results of a future total knee in necessary.
Advantages of Unicompartmental Knee Replacement
The advantages of the unicompartmental knee is that it can be done as an outpatient, it hurts less, there is less bleeding and the person is unlikely to require a blood transfusion. Range of motion of the knee is generally better. The average person with a total knee replacement only gets back to about 105 degrees of flexion whereas with the unicompartmental knee they maintain the motion they entered the surgery with (up to full motion). Theoretically, a unicompartmental knee implant should cost half as much as a total knee, but this is an example of where logic is overruled by corporate profit. The implant manufacturers claim that the problem relates to the cost of liability insurance, etc. Below are a few images depicting some of the differences between uni and total knee replacement.
Recovery from a unicompartmental knee replacement can be very swift or it can be very slow. Recovery time depends on the person’s pain threshold (how easily they perceive pain), cooperation with an exercise program and follow through with home exercise. This largely relates to a person’s attitude in general. Continuous passive motion (CPM) machines were introduced about 30 years ago to try and improve range of motion in the knee. Within a couple of years it was proven that CPM machines didn’t help obtain motion, but they did help reduce pain while the patient was hospitalized. In the last couple of years it has been proven that prolonged physical therapy beyond a few weeks actually doesn’t benefit the patient in the long run- it is more like a mental massage and a large waste of money.
Return to Activity after Knee Replacement
The majority of people who undergo joint replacement for the knee are over 50 years old and they are not particularly active to begin with. It really wouldn’t matter what sports activity a person gets involved with after knee replacement as long as it doesn’t involve a lot of jumping that could potentially loosen the implant. The same goes for unicompartmental knee replacement.
Obesity in Unicompartmental Knee Replacement
Obesity probably has a lot to do with the development of arthritis in some individuals because the load a person carries is transmitted across the cartilage in the knee. Many more people nowadays are obese and there is a much greater need for knee replacement in obese people. In fact, there has been what is coined an “obesity tsunami” increasing the number of unicompartmental knee replacements dramatically and the projections for even more. A nicely performed study a few years ago showed that with massive weight reduction, about half of massively overweight patients no longer needed surgery. Otherwise said, this supports the value of markedly cutting down one one’s caloric intake to eliminate the load of the arthritic joints.
Support for this concept also is gained from just looking at the value of using a cane. If a cane is properly used in the opposite hand, i.e. the left hand of a patient with right-sided knee problem and vice versa, it reduces the weight across the knee and thus reduces discomfort.
Alternatives to Knee Replacement
Weight reduction, anti-inflammatory medication, and the use of a cane to relieve weight on the arthritic knee is important. Taking anti-inflammatory medication with or without Tylenol is a mainstay. In a person with a unicompartmental, i.e. partial, knee arthritis, there is a possible benefit from what is known as a tibial osteotomy, or sometimes even a femoral (thigh bone) osteotomy. This entails cutting through the bone and realigning the knee joint such that the force is being born on the non-arthritic side. In five years, however, a huge percentage of these people are hurting again, meaning it doesn’t have a good long-term result. Additionally, it is much harder to reoperate to convert to a total knee replacement when the osteotomy fails. This may give the person an odd angulation of the knee. Dr. Ichtertz is not a fan of osteotomy and the procedure would be a distant third choice.
An extremely small subgroup of people with arthritis in their knee have it exclusively between the kneecap in front and the underlying end of the femur bone. This group of patients may be best served by patellofemoral arthroplasty (knee cap replacement).
Click Here for references regarding the unicompartmental knee replacement.