It’s 2024. We’re in a technologically driven world where everything we do has been touched and affected by technology and hip and knee replacement should be no different. If we’re doing things the same way we were doing 30 years ago, then we’re not trying to evolve or change. I want to highlight newer technology for hip and knee replacements.
New Hip Replacement Technology
The Impact of the Approach in Hip Replacement
Hip replacement is arguably the most successful surgery in modern medicine at restoring patients’ quality of life and functional outcomes. Much of the focus to this point has been on surgical approach: direct anterior, posterior, and a variety of approaches in between. However, long term, a well-done hip replacement is a well-done hip replacement. There is evidence to suggest that a direct anterior approach will speed up the recovery timeline, reducing the time spent on the walker by up to a week. To the doctor, a week doesn’t seem like a very long time. But when you’re the patient and in pain, a week is a long time. Therefore, I think surgical approach is important.
The Importance of New Hip Stems
Even with the direct anterior approach, we have newer techniques that are pushing the recovery timeline even faster. In the early days of direct anterior hip replacements, we were taking hip stems (the part that goes into the leg bone) that were designed to be put in from a posterior approach and we were trying to put them in from the front. The anatomy and the geometry of those two are very different. It’s like taking a square peg and trying to put it in a round hole, which resulted in some higher complication rates with direct anterior hip replacements. One complication early on was fracture, or breaking the bone at the time of surgery. Another complication was putting in stems that were undersized, which had higher failure rates long term. One way to avoid those complications is by stripping more soft tissue and cutting more things off the proximal femur. However, when doing that you are increasing the likelihood of instability and increasing the amount of post-operative pain.
In about 2018, the first true major direct anterior-friendly hip stem and related implant became available. The modern hip stems are shorter and are shaped to be able to go in easily from the front without having to strip much soft tissue to put them in. The new hip stems allow surgeries to be much more minimally invasive, which speeds up the recovery process. In 2024 it’s very common for patients to be off a walker in less than a week after a primary direct anterior hip replacement, because the instrumentation has improved.
New Knee Replacement Technology
If the hip replacement has been a home run, knee replacement has been much tougher at bat. Between 5% and 20% of patients don’t love their knee replacement, and the number has been steady for the past 20 or 30 years. While there have been improvements, fundamentally we’ve been doing knee replacement the same way for the past 30 years too.
In traditional knee replacement, all processes are based on averages. We take a rod and put it up the femoral canal and use it to take a preset amount of bone. The amount of bone and the angle are the same for everybody based off an average. We make four cuts, taking the same amount of bone for everybody. We move to the tibia and again take a preset amount of bone and cut it. At that point, we’ve made all of our bone cuts and we’ve done nothing that was customized to that knee. Sometimes, you then need to start doing releases and cut soft tissues because the knee doesn’t have the needed balance.
Compare that process to a modern robotic system knee replacement, using the Mako robot. With the Mako, the patient receives a CT scan ahead of time so the surgeon has a three-dimensional image of the bones. We know exactly where those bones are in space, what they look like, any bone spurs they have, and any bone defects they have. We know the size of the implant before we go into the operating room.
We can use all that information and take it into account during the surgery as well because we have a CT scan. Some other robotic systems aren’t CT-based, but the CT scan provides three-dimensional accuracy. Due to the sub-millimeter accuracy of the scan, we can assess the ligaments in the knee before cuts are made to maximize the position of the implants and to minimize the soft tissue release needed after the cuts. You can still have a great knee replacement done in the traditional method, but the discrepancy on outcomes is going to be broader because those are based on averages.
A traditional knee replacement compared with a knee replacement with a Mako is like a road trip in 2005 versus today. In 2005, you had a flip phone. You may have printed out MapQuest directions, or maybe you pulled out the map of the United States, found point A and point B, and started driving. You didn’t know where traffic was, where roads were closed due to construction, or where there was an accident up ahead. You would have a general sense of when you would arrive.
Compare that road trip to a road trip today. You have your smartphone and tell your map app where you’re going. It tells you exactly how long it will take, the fastest way to go and exactly when you will arrive. It tells you where there’s construction or delays and avoids them in real time while you’re driving. If there’s an accident causing a major slowdown, it will redirect you. That’s what Mako does for knee replacement: it gives us real-time data as we perform the replacement. As a surgeon, you need to know how to use the data to incorporate it, but it allows us to do a better knee replacement in a more soft-tissue-friendly manner that’s specific to the patient.
A knee replacement is a knee replacement. We still have to move muscles out of the way and cut bone. It will hurt. However, by using modern technologies like Mako, we can do a better job, be more soft tissue friendly and do these surgeries in a way that will minimize your pain, expedite your recovery and most important, give you a great long-term knee.
Frequently asked questions
How do you know when it is time for a replacement?
First, you’ll need to have bone-on-bone arthritis before you have a replacement. You also need to have either pain all day, every day that’s really bothering you or have pain that is affecting your quality of life because it’s preventing you from doing the things you want to do. If you are a golfer and you’re dreading the thought of playing 18 holes because your knee hurts so much, it’s time to consider knee replacement. If you’re a hiker and you can’t take the thought of a five-mile hike, it’s time to consider replacement. If you’re a pickleball player or a tennis player and you can’t do the things you love because of joint pain, we can fix that. We can’t make you 18 again, but we can reduce the pain and get you back to being active. It doesn’t have to be 24/7, around-the-clock pain. It has to be pain that’s preventing you from having the quality of life that you want to have.
What is the recovery time after a hip replacement or after a knee replacement?
Generally, hip replacement patients go home the same day and will use a walker for a week or two. Over 90% of my patients attend their two-week follow-up visit with no cane and no walker, walking quite well. Many of them tell me they’re off the walker three to five days after surgery. You’re sore, but it’s a slow, steady improvement through the first six weeks. You need to get your strength and endurance back, but the pain goes away relatively quickly after a hip replacement.
Again, most knee replacement patients go home the same day. The first two weeks are tough. After the first two weeks, most patients are using a walker outside their home but have stopped using it while at home. By week six, most of my patients hurt less than before the surgery.
Long-term recovery is an individualized process. If your goal is to be back on the tennis courts, that is going to take longer than someone whose goal is to walk around the neighborhood.
How long does a replacement last?
For modern hip replacements, the lifespan is over 30 years. The older types of plastic wore out and limited the life of the hip replacement. Modern plastics came out a little before 2010, but wear studies in the lab suggest that we’re not seeing the wear problems that the older plastics had so we think these current implants should last 30 years.
From all reasons, including infection, dislocation, etc., the failure rate for hip replacements is about 1% per year. Twenty-five years after surgery, 75% of the hip replacements will still be in.
For knee replacements, the plastic also used to fail and we think we have solved that. The newer technology available in knee replacements includes press-fit technology, where the bone will grow into the metal. The Mako system helps us with the press-fit implants because it allows the perfect cuts needed. Not every patient is a candidate for a press-fit knee replacement, but patients who are able to receive it have good outcomes.
Which should come first, a knee replacement or a hip replacement?
I generally recommend the hip replacement first. Hip arthritis is often more debilitating to patients and affects their quality of life more than knee arthritis. However, if the knee is more severe than the hip, the knee may be done first. The overall recommendation is whichever bothers the patient more should be done first.
Is it better to replace both knees at the same time or to do them individually?
Most studies suggest that doing both knees at the same time leads to more complications, including issues like blood clots, infection, and stiffness. I recommend not doing them at the same time, but I’m willing to if it’s really important to the patient and the patient is otherwise optimized. If you’re a less healthy patient, I won’t offer you the option to have both knees done at once because the evidence says you have a better chance of something bad happening to you.
How long after a replacement before you can drive yourself?
There is no hard and fast answer, and there’s no legal definition of when a patient can return to drive. It’s up to the patient and their comfort level. Do you honestly feel that you can step on the brake in adequate time to prevent an accident?
If you’re using opioids, you should not be driving.
Many hip replacement patients start driving 4 to 6 weeks after surgery. I recommend knee replacement patients don’t drive in the first six weeks after surgery, and possibly longer depending on your comfort level.
If somebody lives alone, will they need a friend or family member to stay with them after surgery?
I think patients are surprised by how functional they are right away, especially after hip replacement. How much support you need depends on your preoperative functional status, as patients who are less mobile before the surgery will probably need more help after the surgery. You don’t need 24/7 support in the house, but it’s nice to have someone who can stay overnight the first couple of nights.
You won’t be leaving the facility after your surgery until you can get from the bed to the bathroom. Before you leave, you’ll also practice stairs and getting out of the car. You’ll be sore, but you can manage.
If someone has bone-on-bone arthritis in their knee, but the pain is tolerable, are they causing more damage by not getting it taken care of?
Once you have bone-on-bone arthritis, it’s severe and it’s as bad as it is going to get, pain-wise. You will not make your surgeon’s job harder by waiting. If your pain isn’t bad enough that it’s impairing your quality of life, don’t have the surgery yet.