In the operating room, a robot that could improve knee replacement outcomes

Vail-Summit Orthopaedics is excited to be working with the Zimmer Biomet Robotic Surgical Assistant (ROSA) at Vail Health

By Lauren Glendenning Brought to you by Vail-Summit Orthopaedics and Neurosurgery

There’s an app for recovery
Zimmer Biomet, the maker of ROSA, has partnered with Apple to develop a recovery App called MyMobility. The app offers tools such as direct communication and remote monitoring, education, exercises and a to-do list.
Combining both the ROSA and MyMobility technologies with modern rapid recovery protocols, will help patients get back on their feet faster. It also can potentially help minimize the risk of chronic pain after total knee replacements, and has potential to improve the longevity of knee replacements.

For more details, visit

Historically in the U.S., total knee replacement surgery carries a 20 percent risk of lingering chronic pain, but Vail-Summit Orthopaedics and Neurosurgery is using a new technology that surgeons hope will reduce that risk.

“ROSA, which stands for Robotic Surgical Assistant, is a very exciting opportunity to better influence outcomes of total knee replacement,” said Dr. Nathan Cafferky, a total joint and reconstruction surgeon at Vail-Summit Orthopaedics and Neurosurgery.

Innovation in total knee replacement surgery isn’t new — Dr. Cafferky said there have been many technologies over the years that have tried to improve outcomes. What makes ROSA different is that it’s combining all of these other technologies into one platform while operating as a surgical assistant.

“ROSA truly is a surgical assistant, and not a robot that is doing the surgery,” Dr. Cafferky said. “As the surgeon, we are still in control the situation, utilizing preoperative X-rays and intraoperative findings to restore a lot of important biomechanical aspects of the knee.”

How it works
ROSA allows surgeons to make bony cuts more pure, gives a scientific data on balancing ligament tension, allows for scientific restoration of limb alignment, and improves the opportunity for patella tracking and knee range of motion. Dr. Cafferky said all of this information together has the potential to improve total knee replacements.

The first step is a preoperative imaging study. Dr. Cafferky said other robotic systems are using either MRI or CT scan for this, but ROSA uses preoperative X-rays. MRIs and CT scans create increased costs for insurance companies and patients. They are rarely required to diagnosis or treat arthritis. MRI and CT scans are studies looking for potential soft tissue athletic related injuries or bony fractures.

“Also, increased radiation exposure for patients is also a concern from my standpoint. Avoiding CT scans, when possible, as a way to help minimize radiation exposure,” Dr. Cafferky said. “With ROSA, we use our standard X-ray series, and through some high-end engineering this X-ray gets converted to a 3-dimensional computer representation of the patient’s knee, ultimately allowing us to map out the patient’s anatomy before we even go to the OR. This gives me the opportunity to customize everyone’s knee replacement individually, even before we go to surgery. ROSA really provides the surgeon with objective scientific data to allow us to better restore the biomechanics of the patient’s knee, utilizing artificial technologies.”

At the time of surgery, sensors were placed on the tibia (shin) and femur (thigh bone) and the robot will be able to navigate the knee based off the sensors placed. The robot than verifies that the pre-operative x-ray model matches the anatomy that the ROSA is seeing during surgery. The robot goes into 2 different modes: one called collaborative mode, where the surgeon is positioning the robotic arm close to the body, and the other is automatic mode, where the robotic arm is positioning the cutting guides to within 5-6 cm of the body.

The safety mechanisms will not allow the arm to actually touch the body without the surgeon guiding the robotic arm to the final position, Dr. Cafferky said.

“ROSA allows the surgeon to stay in control, making the final decision on every boney cut made, and ultimately the surgeon is still the ‘captain of the ship,’” Dr. Cafferky said. “As the surgeon, I personally do not like the idea of robot ‘doing the surgery,’ but with ROSA, it really is a surgical assistant that allows robotic navigation to better influence the surgical outcome. It’s like going from paper maps to GPS.”

Improving outcomes
ROSA gives surgeons the ability to restore appropriate tension on the ligaments, which Dr. Cafferky said is really the first-of-its-kind technology.
“A total knee replacement isn’t just a bony surgery, but rather a soft tissue balancing surgery. Using the robot, I can then evaluate the patient’s range of motion at time of surgery, and also simultaneously assess the ligament tension throughout the knees arc of range of motion,” he said. “Attention on the soft tissues and ligaments is really what is most important to give you a knee that is functionally stable and allowed to get back to activities.”
Surgeons now have concrete data — during surgery — telling them if the patient’s knee is balanced with appropriate ligament tension.

“Historically, Historically, ligament tension, or balancing as surgeons call it, has been known as the ‘art’ of total joint surgery. But with this newer technology, we will have more scientific understanding of what appropriate ligament tension is meant to feel like,” Dr. Cafferky said. “With this information, surgeons will have a better chance of dialing in your exact biomechanics to meet your needs.”

Because ROSA makes bony cuts more pure, implant positioning more precise, and ligament balancing more objectively evaluated, Dr. Cafferky thinks ROSA has the potential to improve a patient’s satisfaction and long-term outcome.

America’s aging population wants to maintain an active lifestyle, which is why total knee replacement surgeries are becoming more prevalent. Dr. Cafferky said there is about a 1 percent risk of failure per year over the lifespan of a total knee replacement.Thus, there is an 80 percent chance a knee replacement done today, with traditional techniques, will last 20 years. That also means there is a 20 percent risk of joint failure within the first 20 years of a knee replacement. Revisions are challenging both for patients and surgeons, which is also very costly to the overall health care system. Implants today are better than they have ever been, but failures still occur. Companies and surgeons are now looking at how to improve surgical outcomes and also improve implant longevity.

“With ROSA, we have the opportunity to improve implant position, improve patient satisfaction, improve ligament balance/tension, and thus potentially improve the longevity of a knee replacement and hopefully minimize risk of revisions in the future, as well. However, these are long-term goals, and only time and research will tell,” he said. “This is really cutting edge technology and total joint replacement. I am thrilled to be able to partner with Zimmer Biomet to bring this amazing technology to our mountain communities.”

Support Local Journalism

Support Local Journalism

As a Summit Daily News reader, you make our work possible.

Summit Daily is embarking on a multiyear project to digitize its archives going back to 1989 and make them available to the public in partnership with the Colorado Historic Newspapers Collection. The full project is expected to cost about $165,000. All donations made in 2023 will go directly toward this project.

Every contribution, no matter the size, will make a difference.