Transcription
Total knee replacement is a surgical procedure performed to replace damaged portions of the surface of the knee joint with an artificial implant. When the cartilage damage from arthritis is so severe, a total knee replacement is performed. Surgery typically lasts between 1 to 3 hours. Some patients return home the same day as their procedure, but it is possible to spend one to two nights in the hospital.
Total knee replacement, also known as TKR, total knee arthroplasty, or TKA, is a surgical procedure performed to replace damaged portions of the surface of the knee joint with an artificial implant. The knee joint is formed by three bones: the femur (thigh bone), the tibia (shin bone), and the patella (kneecap). Meniscus are pieces of cartilage found between the femur and the tibia, while articular cartilage covers the ends of the bones. Together, they work to absorb shock and use friction as the knee moves.
Total knee replacement is performed primarily to relieve pain and stiffness caused by arthritis. Arthritis occurs as the cartilage that cushions the knee wears down, causing the bones to grind against each other. This results in pain and inflammation and can lead to bone deformity and a loss of joint mobility. When the cartilage damage from arthritis is so severe that most cartilage is affected, a total knee replacement is performed. If the cartilage damage is limited to a specific region of the knee, a partial knee replacement may be performed.
There are a wide variety of knee replacement implant options. Typically, they are made of metals such as titanium, chrome cobalt, or zirconium, as well as synthetic materials such as polyethylene (plastics) or ceramics. The implants are usually designed in a way that allows the metal to interact with the synthetic material in order to minimize wear from the movement of the joint. The femoral implant typically is made of metal and is designed to mimic the end of the femur with a groove in the center to allow for movement of the patella. There are a wide variety of options for the tibial implant. Typically, a metal cap is affixed to the tibial surface, or a metal stem is inserted into the tibia, which is then cemented in place or designed to allow bone growth to secure it. Typically, a piece of plastic is secured to the metal surface of the implant to reduce friction with the femoral implant. If the patella needs to be resurfaced, the damaged articular cartilage is removed and replaced with a plastic implant.
There's essentially two ways to provide fixation of a total knee replacement. One way is by cementing the implant into the patient's bone, and that has been the warhorse approach, probably for the past 20 or 30 years. By cementing the implant into the bone, you have immediate mechanical fixation where the patient can get up and start walking and using that implant without any worry about loosening of the implant itself. And we now have decades-long proven survivorship of these implants, and so these cemented trays are have very good workability, and they can last, like I said, decades.
Now, there is a, in recent years, have been more of a push to use cementless implants, or what we call press-fit implants. This does not require the use of any cement. Instead, the implant actually has bone your bone grow into it, and it becomes yours for life. Now, the potential benefit of a cementless implant is because there's no cement grout holding the implant in, theoretically, over time, a cemented implant could potentially wiggle free of the grout and become loose. There's a very low risk of that happening, but over decades and decades of wear and millions and millions of cycles, there is a theoretical risk of that happening. With a press-fit or cementless implant, once the bone has grown into the implant, theoretically, it's yours forever. So, in a younger patient who may want to go 20, 30, 40 years or more on that implant, and someone who has very good bone quality, a cementless or press-fit implant may be a viable option.
Your anesthesiologist will determine whether to use general or regional anesthesia and/or a nerve block. Total knee replacement surgery typically lasts between 1 to 3 hours. Surgical details vary by technique and implant design. Some procedures involve computer-assisted 3D imaging and micro robotic instruments to aid in removing damaged parts of the joint, while other procedures use manual instruments with precision guides.
Your surgeon will make an incision and access the knee joint. Any bone outgrowths, bone spurs along the margins, are removed, as are the meniscus between the femur and tibia, the anterior cruciate ligament, and the posterior cruciate ligament. In procedures where the PCL is not spared, the damaged portions of the femur and tibia are removed. Your surgeon will insert the femoral and tibial implants into the bone and secure them in place. The bearing surface is affixed to the tibial plate to complete the reconstruction. It also may be necessary to remove the damaged underside of the patella and replace it with an artificial implant.
Potential risks associated with total knee replacement may include infection, blood clots, nerve or blood vessel damage, joint instability, and stiff and loosening or wearing down of the implant over time.
So, what can a patient do before knee replacement surgery to ensure they have a successful outcome? You know, we've looked at this from a number of different ways. There are preoperative modifiable comorbidities that we can change before surgery. And so, modifiable risk factors are such, weight loss, getting yourself to a safe range. Modifiable risk factors include if you're diabetes, if it's uncontrolled, getting it more controlled. Smoking, stopping smoking. We know nicotine, everyone looks at nicotine and they say, oh, it's just my lungs, oh, it just hurts my lungs, but nicotine constricts the blood vessels, which decreases the nutrients and the food that may go, or you, I call it food, but the nutrients and the white blood cells and all the different good stuff from going to the knee after the replacement. So, nicotine is really bad for the outcomes of surgery. Proper diet and nutrition. We know malnutrition plays a role in increasing the risk of problems. And so, while we don't test for that always, we can look at, you know, albumin or your vitamin E, vitamin D levels, and if those are low, you may have more poor nutrition and you have an increased risk of problems.
Another way we've looked at making you a better candidate for hip or knee replacement, or knee replacement, is prehabilitation. Everyone has heard of rehabilitation and getting yourself fixed up after surgery, but certainly making yourself a better candidate before surgery in regards to muscle strength or mobility plays a role. We ask simple questions like, can you walk a city block without getting short of breath? Can you go up one flight of stairs without getting short of breath? And so, preoperative modifiable factors are now at the forefront of what we're doing to make sure you're safe for surgery.
Some patients return home the same day as their procedure, but it is possible to spend one to two nights in the hospital. Following TKR, you will be able to walk with crutches, a cane, or walker.
So, let's talk about physical therapy after knee replacement. You know, if you look at my hip replacement patients and my knee replacement patients, the knee replacement patients are going to have a tougher time. It is a little bit tougher recovery for a knee replacement, and therapy is much more important with a knee replacement. In regards to the amount of work that you put into this, is the amount that you'll get out of it. We all want to obviously be pain-free, and that's a low goal with a knee replacement, you're going to get there. I can step over that goal pretty easily in terms of being satisfied with your knee replacement. Range of motion goes into that, stability goes into that, and we know that the harder you work with physical therapy after your replacement, the more you're going to get out of it. Knee replacement, we want to get a 0 to 120 or 130 degree bend. And if you don't get zero, you're not going to stand up straight. And if you don't bend back to 120, you can't sit on these small airplane seats we have now or on the bus. And so, we want you to work really hard in the first three months to get that range of motion because those first three months set the stage for the rest of your life. And so, I tell patients that you're going to work really, really, really hard with therapy these first three months so that you're happy with my knee replacement for the rest of your life.
So, will a patient do more damage if they hold off on having their knee replaced? I think the answer is technically yes. And if you take the pessimistic view, the day we're born is the day we start dying. And and and so, I don't believe though that most patients as they continue to wait are going to wear out their joint to such a point where it's going to make my job harder or their recovery harder. Yes, there are cases where things progress very rapidly, but overall, you want to make sure that you need this surgery before you jump into it. Causing more damage is not really going to be the case.
There are some considerations where I tell a patient, listen, we ought to start thinking about doing this. Ultimately, I let the patient make the decision. I say, when the bad days outnumber the good days, when this knee or this hip keeps you from doing what you want to do, what you need to do, or you pay for it after you do something, and when you've tried non-operative therapy and it has no longer worked, or you've decided, I'm tired of doing this, that's when we start to broach the subject of having surgery. But there's a couple of considerations that you need to keep in mind of when you really need to push yourself. And so, we know preoperative motion predicts postoperative motion. Now, what that means is, if you bring me a knee that won't bend anymore at all, it's going to be tough for me to bend that knee all the way back and to give you that motion back. So, certainly, that's a consideration. My other considerations are not that you're wearing out the knee too much or you're wearing out the hip too much, but that you're keeping your heart and your lungs from being healthy by limiting your activity. And as you become decompensated because you don't want to do anything because of this hip or this knee, you should be talking yourself into something to get you back out there and to stay active. I know my role as a joint replacement surgeon is to get you a better quality of life, get you out of pain, but also to keep your heart and your lungs healthy so that you can stay with us longer. So, I don't really buy into you're doing more damage and you're going to make my job harder. And while there's rare cases that that can happen, for the most part, we just need to look at these other factors that should talk you into having surgery.
Visit understandortho.com to watch medical animations and physician interviews about a wide range of orthopedic conditions, treatments, and surgery.