tech notes
tech notes

Smart knee surgeries can also collect data

Michele Meyer

Table of Contents


“We’ve seen the impact remote patient monitoring can have on patient care,” says Liane Teplitsky, president of global robotics and technology and data solutions at MedTech orthopedics firm Zimmer Biomet. “Orthopedics definitely has been behind in this.

So the Warsaw, Indiana, company joined Canary Medical, a Carlsbad, California, medical data firm, to develop “smart knees.” Formally known as Persona IQ, these artificial knees have built-in sensors to track patients’ post-op recovery.

The U.S. Food and Drug Administration approved the implants in the fall of 2021, and the first were used that October.

Now physicians can remotely monitor medical issues before implant patients report them. They also can have hard numbers versus recipients’ sometimes hazy memories to determine whether recovery is on target— or of concern.

The device measures gait, walking speed, distance, stride length, average steps per minute, number of steps and range of motion—all of which can reveal whether a patient is limping or moving too slowly for their expected stage of post-op recovery, given their age and gender.

“Those are important parameters to know how well someone is doing,” says Yair Kissin, M.D., orthopedic surgeon and interim chairperson of orthopedic surgery at Hackensack University Medical Center in New Jersey. “It takes knee replacements to the next level.”

Persona IQ smart knees serve as an early warning system, influencing the frequency of physical therapy, lab tests and in-office or telemedical visits, and raising flags for surgical revisions.

“People come from long distances away to my practice,” says Fred Cushner, M.D., an orthopedic surgeon and associate professor at New York’s Hospital for Special Surgery. “I’m more comfortable stretching time between in-office visits if their recovery is on target. And if they’re not doing well, we can intervene earlier than was scheduled.”

Not only is knowledge power, but it also leads to greater patient satisfaction, says Cushner, who’s a Canary Medical founding member and chief surgical officer. “The saying is that the reaction to hip replacements is ‘wow’ and to knee replacements is ‘ow.’ One of our goals is to get more ‘wows.’”

With the Agency for Healthcare Research and Quality reporting as many as 634,000 knee replacement surgeries yearly — equal to the entire population of Portland, Oregon — the move from “ow” to “wow” could be dramatic.

Many people have used wearable remote monitors, such as watches or braces with sensors. But studies have found that up to half of them aren’t wearing the tools correctly — or at all, Kissin says. “With the smart knee, they can’t leave home without it. It’s 100 percent more reliable.”

How it works

The Persona IQ’s tibial extension, which is named “canturio te,” is as long and wide as an AA battery, Cushner says. Within are an antenna and radio system akin to that in a pacemaker. Sensors use electronics, accelerometers and gyroscopes to track movement, and most data is collected every 20 seconds.

“We measure activity and function to see whether the joint is firmly in place and moving appropriately,” Cushner says.

The information downloads nightly into a bedside base that’s barely larger than a smartphone. It’s also stored in the cloud, where physicians can locate and interpret it.

The Persona IQ also can reassure— and motivate—patients, Cushner says. Zimmer Biomet’s related mymobility patient app enables users to see how they’re doing compared to others of the same age, gender and time since surgery.

“Humans are inherently competitive,” he says. “If they fall behind, they may become more diligent, and if their numbers improve, that’s positive reinforcement.”

The future

Soon, the tibial extension will shrink to the size of an AAA battery, Cushner says.

But the impact of such monitors should grow. Smart hip and shoulder replacements received FDA breakthrough status in mid-2022.

“The more data we collect, the more we can learn,” he says. “Our holy grail would be to diagnose infections or scar tissue.” Other goals are to detect blood clots (DVTs), contracture (arthrofibrosis) and whether a knee implant is properly anchored to the bone.

Yet the first months of monitoring progress post-op are not the end game, Kissin says.

Even years later, a physician may notice that a patient has stopped being active. The physician then can phone the patient between yearly check-ups and learn if they have redness, swelling or fever.

“Thanks to the smart knee, we may detect that a patient is doing poorly before the patient realizes it’s important for us to know,” he says. “We also may catch an infection early. That’s huge.” •



Michele Meyer

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