Robotic Assistance Improves Knee Replacements

Orthopedics

By: Kendal Gapinski

Published: 9/3/2020

Share:

Perfect cuts and precise implant placement can take your total joints program to the next level.


What if your surgeons had the ability to perform the perfect knee replacement, limiting against soft tissue damage and ensuring they had the right bone cut every time? That’s the hope of the latest robotic systems that increasing numbers of orthopedic surgeons are using for total and partial knee replacements. Surgeons who rely on robotic assistance love to share why they love the technology, and how patients and facilities are benefiting from it.

“A knee can be replaced without a robot, but the technology prevents outliers,” says Brian Patrick Flanagan, MD, an orthopedic surgeon at Northwestern Medicine Huntley (Ill.) Hospital. “Those rare cases where ligaments are too tight or implants aren’t aligned, or a muscle gets injured because the saw slips out of the bone — that’s all prevented with the robot.”

More manufacturers are creating robotic orthopedic systems, and each have different capabilities and work with different implants, says Yair D. Kissin, MD, FAAOS, vice chairman of the department of orthopedic surgery at Hackensack (N.J.) University Medical Center. Haptic systems, which were the first robots available to orthopedic surgeons for knee replacement procedures, use 3D models of patients’ specific joint anatomy that are created from pre-op CT scans. The systems feature a robotic arm with an attached saw that provides feedback to surgeons as they cut, ensuring the saw doesn’t leave the intended path.

Dr. Flanagan says his haptic robotic system ensures he’s getting the right cut and placement of the implant each time, allowing him to shift the implant placement a tenth of a millimeter at a time, or rotate the implant placement just a degree or two for the perfect fit. The system can be used for both partial and total knee replacements.

One of the key benefits of a haptic system is that the robot has boundaries that prevent you from sawing outside of the bone area, points out Dr. Flanagan. “Even if you try to push it into a ligament or soft tissue, it will stop it,” he says.

While haptic systems still require surgeons to do some of the manual labor, a new robotic system removes them entirely from the cutting process. These systems still use a 3D model created by pre-op scans of the patient’s joint, but instead of the surgeon operating the robotic arm, the active robotic system makes the cuts to the bone while the surgeon stands by with a hand-held controller, says Dr. Kissin. Because the technology is so new, this robot can currently be used only for total knee replacements.

“The main difference is that you’re removing the potential for human error,” says Dr. Kissin, who was the first in the nation to perform surgery with the robot this year. “Surgeons still set up cases similar to how they would with a haptic system. However, when it’s time to cut, the robot will go in and do it.”

Better cuts for more patients

SPOT CHECK Robotic assistance lets surgeons place implants within millimeters of pre-op measurements and confirm the joint is properly aligned.   |  Northern Westchester Hospital

The benefits of the robotic assistance are clear — increased accuracy could lead to higher patient satisfaction with knee replacement outcomes. Some reports suggest up to 20% of patients are dissatisfied with their knee replacements, and robotic assistance could help reduce that number. Though robotic assistance is so new that there isn’t yet a significant amount of data to back up claims of improved outcomes, Dr. Kissin notes that it makes sense that a technology ensuring accurate cuts and placement of implants would enhance outcomes. He notes that a study conducted at his hospital showed patients who received robotically replaced knees had implants placed within two millimeters of the pre-op surgical plan.

Plus, some experts theorize robots could move more cases to same-day settings, because it’s believed the technology results in shorter recovery times and happier patients.

“At the end of the surgery, we can extend the knee and the robot will tell us how many degrees the implant might be off, which helps us to make adjustments,” says Dr. Flanagan. “If a fully straight leg is zero degrees, but the robot is telling us that it’s actually at minus-five degrees, then we know the joint might be misaligned. A matter of a few degrees isn’t something you can see with the human eye, but the robot lets us double-check our work.”

The robot also lets surgeons attempt more complicated knee replacement methods. Dr. Flanagan notes that robotic assistance has allowed surgeons to perform more press-fit knees, which are performed without bone cement or glue. This is another potential way to boost patient outcomes. “The theory is that by doing press-fit knees, the bone will attach itself to the metal implant components and fuse as one piece, which may make the implant less likely to loosen over time,” he says. “They’re easier to put in when you have a robotically cut knee. Essentially, the implants haven’t changed, but how we put them in is better.”

With the guarantee that the cuts and placement will be almost perfect, it’s hard to imagine a patient who wouldn’t benefit from a robotic knee replacement. Typically, it depends on the joint itself. “Someone who has a severe deformity that causes it to be out of the parameters set by the robot’s boundaries may not be the best candidate,” says Dr. Flanagan. “I’d say, though, that one out of every 100 isn’t a good candidate. It doesn’t mean the person can’t get a knee replacement, but on some people, the robot won’t be able to account for the deformity.”

While that’s the case in some complex cases, Dr. Kissin notes that he’s found the robot useful in traditionally hard-to-perform surgeries. In his facility’s study on the active robot, he notes there was one patient who presented with a lot of bone loss in the knee. They were able to use the robot to perform the replacement, and he’s now a patient Dr. Kissin cites when touting the robot’s advantages.

“What was interesting in that case is that robotic surgery might have been better because the bone loss would not allow usual tools to sit how they’re supposed to and could have introduced error,” says Dr. Kissin. “Some of the worst knees might make for better candidates as this technology continues to grow.”

Overcoming obstacles

ARM FOR A LEG Robots give surgeons the confidence to attempt complex knee replacement techniques, which could improve outcomes.   |  Stefan Kreuzer, MD

While the benefits of robotic surgery are plenty, there are a few things to consider before you add the technology. First, make sure you understand which implants work with what system. Dr. Kissin notes that his robot is able to use a variety of implants from different companies, which made it an attractive investment because surgeons don’t have to change their preferred brand of implant.

Speaking of investment, be prepared for a high price tag with this technology. Northwestern Medicine says its robot cost $1.2 million, and Dr. Flanagan notes that there’s also a slight increase in the cost of disposables for each case. “Part of the handle and saws are changed out every case, so that’s an added cost per case,” he says. “However, having some cases completed more quickly and lowering the chance of revision surgery helps to make up for some of that cost difference.”

There’s also a learning curve to using robotic technology. “You have to get certified to use a new system, so even if surgeons have already performed a lot of knee replacements, they don’t automatically know how to use it,” says Dr. Flanagan.

Depending on the case, robotic assistance also can add some time to the procedure — Dr. Flanagan says it can tack on about five to 10 minutes to get the platform set up — but during more challenging cases, the robot actually helps to shorten case times. “We’re able to cut some of our complex procedures from two hours to one hour,” he says.

Dr. Kissin notes that his active technology robot typically adds about a half-hour per case, plus some additional time as the surgeon first gets comfortable with using the system. “When you perform robotic surgery, it looks and feels differently, so there’s definitely a learning curve,” he says. “But after about five cases, and certainly after the first 10, there is an improvement in the surgeon’s time and comfort level in using the technology. The ultimate goal for us is to get it to time-neutral.”

Despite these challenges, the surgeons say the robot adds a level of reassurance that both their facility and patients appreciate. “I’m a believer,” says Dr. Kissin. “Hopefully, we will be seeing research soon that shows that robotic assistance is truly a benefit to patients. A lot of technology has come and gone, but I think this is going to be a part of the future of knee replacements.” OSM

Related Articles