Augmented Reality Makes a Difference in TKA

By Matt Phillion

A new software offers a different view on total knee arthroplasty procedures. Removing nearly all operating room footprint, STELLAR Knee from POLARIS AR offers a mixed reality surgical navigation software, using a mixed reality headset to display patient-specific anatomic data and digitizing that data into holographic displays. The intent is to enable surgeons to make quick assessments and micro-adjustments to their surgical plan, removing the need for the imprecision of traditional instrumentation with more control than robotics.

“You’d be surprised how many procedures are manual, either measuring or manually performing tasks—and that’s particularly true in total knee implants,” says Paul Mikus, CEO of PolarisAR. “A lot of procedures involve the surgeons not only taking measurements mentally, but also compiling that measurement information in their heads. It’s really a feat of mental energy focusing on that measurement matching the plane where you’re going to make the cut.”

A place where STELLAR comes into play is this measurement component: taking the measurements digitally and then doing the computation so the surgeon can focus on that they do best, understanding and assessing what’s going on in the OR rather than doing rote mathematics.

“Think of AI doing the rote tasks and then allowing people to use their higher thinking—saving that thinking for analysis,” says Mikus.

Mikus worked previously with organizations enabling technology for bone cutting, and robotics organizations trying to marry these concepts to create a very precise, fully automated procedure.

“The problem with robotics is that they are more limited than you’d imagine. They’re limited with freedom of degrees of movement. A robotic arm is jointed with gears and mechanisms, and there are only so many ways they can move,” he says.

Augmented reality allows the human aspect of surgery to remain, Mikus explains.

“When I first saw augmented reality I thought, ‘We could do a lot of those calculations and that guidance and just use the surgeon’s hands,’” he says. “The limitation of a surgeon’s hands is not really the problem: they are very precise. The question is the information and guidance for what needs to be done and the distribution of that information. We can address that with a mixed reality format.”

The wow versus the reality

Augmented reality comes with a bit of pop culture baggage that can get in the way of explaining just how functional and useful it can be, Mikus explains.

“Augmented reality has this amazing wow factor to it. When it was first introduced, everyone focused on holographic images, the floating three-dimensional image in space, but I think that wow factor actually hurt the technology,” he says. “Everyone was reliant on it not understanding what its usefulness could be.”

He thinks what STELLAR can make an impact is the capacity to be a computing tool: mapping the surgeon’s field of view and three-dimensionally assessing that space, calculating what needs to be done there and then presenting the data back to the surgeon.

“The use of these devices as really precise measurement tools are starting to gain a foothold. They’re meant to be used where precision and data exchange matter,” says Mikus.

Initial response

The company received FDA clearance in November and the response thus far has been positive.

“It’s interesting because when you go into the room, nobody wants to be the first person to put the headset on, because they don’t want to look foolish or not know what to do,” he says. “But once they put the headset on, it’s hard to get it off.”

Rather than the more traditional wow factor of AR for recreational use, the big advantage for surgeons is seeing the data that normally isn’t right in front of them while doing a total knee procedure is now there, being measured and tracked with sub-millimeter accuracy and end to end specifications.

“This information being there is eye opening the first time you experience it,” says Mikus. “The clinical value and utility come through right away. The technology is incredibly intuitive. One surgeon I spoke to said he can’t see why surgery would be done any other way.”

Mikus notes that it’s beneficial to have augmented reality following a decade or more of robotics. There’s more of a cultural and intellectual understanding of the use and limitations of robotics now so there’s a baseline with which to compare it.

“What’s happening now is because robotics has come in and stalled a bit. It’s very expensive and complicated with a big footprint in the OR,” says Mikus. “It’s proven the value or precision but hasn’t been able to democratize that value. What AR does is provides equivalency of that with lower cost and a smaller footprint.”

The utility is drawing users in.

“The utility is what is delivering in a clinical way. It’s not, ‘Wow, I can see the knee in three dimensions.’ That is less clinically useful than the data we’re capturing, and then providing guidance for,” says Mikus.

Trust in the surgeon

The aim is to really relieve the surgeon of the mental burden of calculation and also provide the ability to check things as you go to provide improved safety.

“You’re about to make a cut into a bone, and you want to make sure that cut is made right,” says Mikus. “Not only does it measure and calculate, but it also validates where you’re going to cut. It provides constant checks and relieves the surgeon of that mental burden.”

From the patient side of things, augmented reality helps offer that most desired quality in a surgery: precise, repeatable, reproduceable process so you know what outcomes to expect.

Currently, about 85% of total knee replacement surgeries are non-robotics. With a smaller operating room footprint and easier-to-access technology, Mikus hopes surgeons and organizations will see value in this new software.

“We really want to make this precise, digital approach a standard of care,” he says.

The organization is focusing now completely on total knee replacement, but as their success grows, they envision expanding into other areas where augmented reality tools would be immediately helpful, like spine, hip, and shoulder surgery or trauma applications as well as other total joint surgeries.

It comes back to empowering surgeons to do what they’re best at by removing the mental burden of menial—but important—tasks in the moment.

“Having control is the way we think of it,” says Mikus. “The cost of precision in using robotics is you give up some of your control. You get precision but lose that control. What we think we’re delivering is a similar amount of precision, if not better, but without giving up that control, enabling surgeons to use their own hands and retaining more control. It’s better for the patient, better for the surgeon.”

It removes a barrier between patient and surgeon as well.

“Surgeons are never really comfortable offloading cuts to something, or offloading where the saw will be placed. The idea is that they’re in control but with the precise amount of guidance that a robot has, but giving that control to the surgeon,” says Mikus. “We think augmented reality has an amazingly bright future. We’re on the tip of the spear of this, and I think because of that, surgeons, hospitals, and patients will benefit from this technology.”

Matt Phillion is a freelance writer covering healthcare, cybersecurity, and more. He can be reached at