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By Mario Aguilar Nov. 1, 2021
Last month, surgeons implanted the first of a new, souped-up knee implant, developed by Zimmer Biomet as a way to passively collect data about recovery after one of medicine’s priciest and most common procedures.
Zimmer Biomet, which pulls in $7 billion a year selling implants and other musculoskeletal care products and services, is unsurprisingly bullish on the new device, called Persona IQ, which gives the century-old company the sheen of a Silicon Valley tech innovator. The implant — cleared by the Food and Drug Administration in August for use in a small subset of knee replacements — contains sensors, a wireless transmitter, and a pacemaker-like battery that could paint a far clearer picture of the recovery process and problems that arise. The company has called it “groundbreaking” and claims it will “help write the future of orthopedic technology.”
But the surgeons who will need to embrace the implant caution that while the device has potential, insights are likely far off — if the data turns out to be useful at all.
“Technology has to be proven that it’s going to improve outcomes in order to be used,” Calin Moucha, the chief joint replacement surgeon at the Mount Sinai health system in New York said. “So, you know, even though this sounds like a cool idea … this isn’t going to improve our outcomes.”
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In the world of joint replacement, novel technology usually isn’t favored over established implants with years of positive results. And the benefits to early adopters of the Persona IQ will be limited: Surgical teams will be able to look at metrics and infer that a patient is doing well, or perhaps that they need attention. That kind of data from many patients could help “improve our understanding of joint replacements” as well as “improve our understanding of what patients are doing post-operatively,” said Moucha.
In addition to walking speed, steps, and other familiar metrics, the implant captures the knee’s range of motion, which can’t be collected with a traditional fitness tracker. And because the sensors are implanted in people’s bodies, they will continue to collect and transmit data uninterrupted, as long as the modem-like base station in a patient’s house is connected to the internet.
The new implant’s data feeds into Zimmer Biomet’s existing ecosystem, and, it claims, supercharges it. Zimmer Biomet, based in Warsaw, Ind., holds an arsenal of surgical robots and other high-tech products, and since 2018, the company has worked with Apple to incorporate iPhone and Apple Watch data into its mymobility app, which transmits health and activity data to physicians for remote monitoring of recovery. The app also provides guidance and support to patients during recovery, and the company recently issued a press release about research showing that the platform showed “noninferiority” to standard care when measuring 90-day readmissions and visits to emergency departments and urgent care.
As an early target, knee replacement surgery is a potentially fruitful area of focus. While many people walk away from surgery with better mobility and less pain, a commonly cited figure suggests 20% of patients walk away dissatisfied. That number is staggering, given that some 700,000 surgeries are performed in the United States every year, each at a cost of $30,000 for an inpatient procedure.
What constitutes dissatisfaction, however, is elusive, Liane Teplitsky, Zimmer Biomet’s worldwide vice president and general manager of technology and data solutions, told STAT.
“Does that mean they’re in pain?” she said. “Does that mean they didn’t meet their expectations? Does that mean, you know, that something didn’t work quite right with the implant? Or … is it just that they expected to be able to go for a 6-mile run at three weeks out, and they couldn’t, so they’re angry?”
It’s a set of questions Zimmer is hoping the implant could help answer, and one researchers have been trying to address for years by using data to track the quality of implants and to improve patient outcomes. That process has been faltering, though, as technology and clinical habits stumble into the future. Regulators, insurers, and surgical centers have been slow to require more systematic records in the United States. Patient-reported outcome measures, or PROMs, the ideal standard measures for pain and function after surgery, are captured for just a fraction of procedures.
Even if they were collected consistently, the measures have proven challenging to make sense of, because what patients report doesn’t always line up with what a clinician would expect to hear based on X-rays and physical exams. Mobility data might help fill in the gap between provider perspectives and patient experiences.
Bill Hunter, CEO of Canary Medical, the company that developed the sensor technology used by Zimmer Biomet, told STAT if the company can do something as simple as helping clinicians identify the patients who are likely dissatisfied, “that would add significant value to the medical system,” by identifying who needs additional attention.
A flood of new data holds even more promise to flag the most complicated cases and, potentially, help researchers design ways to intervene.
“We believe that we’ll be able to develop algorithms through machine learning and identify the patterns [and] the differences between normal recovery and someone who is developing an infection or somebody who is developing a contracture,” said Hunter. “And if we are able to provide advance warning of that, then I think our technology will be really impactful. For most of the major complications of orthopedic surgery, the sooner you know, the more likely you are able to treat that patient without having to replace the joint or without having to do surgery.”
Today, when a patient and clinicians are considering joint replacement surgery, many health systems use tools that plot patient characteristics like weight, age, and reported pain against historical outcomes to help determine whether surgery is likely to improve a patient’s condition — and if there are any risks from comorbidities like obesity that might factor into a treatment plan. That data also provide a baseline of activity and pain for comparison if a patient does undergo surgery.
Statistics from national and statewide registries also help track the quality of implants by measuring how many need to be replaced. As implant failures have declined, the focus has increasingly moved to the more complex understanding of patient outcomes, Patricia Franklin, a professor at Northwestern’s Feinberg School of Medicine who leads a large effort to capture and study PROMs in orthopedics, told STAT.
“Now that generally the design and the implantation in the surgical approaches are more uniform and more defined, there’s a lot of work on saying, how do we make sure we optimize the symptom relief that patients seek?” she said.
Zimmer Biomet has marketed Persona IQ as a “talking implant” that can objectively measure outcomes that tell a more complete story than PROMs. But some experts say that misses the point.
“Some would call [PROMs] subjective because they’re based on patient responses,” said Kevin Bozic, chair of the department of surgery at the University of Texas at Austin’s Dell Medical School. “But ultimately, the only reason we do this surgery is to try to reduce pain and improve quality of life. So that’s the most important measure is pain, function, [and] quality of life before surgery and then after surgery at different time intervals.”
Brian Larkin, a surgeon and chief medical officer of Orthopedic Centers of Colorado, which has been working hard to implement systematic tracking of patient outcomes, told STAT that combined with data from Persona IQ the effort might lead to insights that help patients more often meet their goals and expectations from surgery. “If the technology gives us a way to do that at a better percentage — great,” he said. “If it identifies problem people that maybe need a different type of something — I’m not sure what it is yet — great.”
Finding that something will be the next challenge.
Zimmer Biomet warns that the kinematic data from the implant are “not intended to support clinical decision-making and have not been shown to provide any clinical benefit.” And right now the company will only go so far as to say the data enables patients to be “more actively engaged in their recovery.” Hunter said that this labeling reflects the fact that so far, Canary and Zimmer Biomet have only illustrated that the device can be safely implanted and can reliably capture the data as promised.
Zimmer Biomet is candid that the research on mobility data remains in its early days.
Some surgeons agree with Hunter that such information might one day help identify patients whose implants had loosened or who were in need of attention that couldn’t be detected with routine X-rays or changes in symptoms — such tools would need to be supported by clinical trials and would likely need review by FDA.
Cleveland Clinic orthopedic surgeon and researcher Nicolas Piuzzi, told STAT that data captured by technology like Persona IQ could help improve the practice of surgery by helping “determine which patient would benefit from which approach,” and with the help of other tools, could allow researchers to one day develop personalized protocols. (Cleveland Clinic and Zimmer Biomet have partnered on research in the past.)
But he and other surgeons still have concerns about the utility of the data Zimmer Biomet is collecting as it goes to market with the technology. Bozic agrees that mobility data is “interesting from a biomedical science standpoint and understanding the function of these implants,” but is adamant that it’s no substitute for hearing from a patient. He cites research at his university comparing Fitbit data to PROMs as evidence.
“The bottom line is there’s not a strong correlation,” he said. “You could be out moving more, and your pain poorly controlled and your function [and] quality of life is not improving. Or you could be fairly sedentary and have less pain and you feel like function is improving.”
And Zimmer Biomet’s own data shows the connection, if any, isn’t yet clear. A study presented at the American Academy of Orthopaedic Surgeons annual meeting this summer failed to find a correlation between patient-reported outcome measures and the passively collected measures. However, “there were associations between PCOMs and PROMs about pain, walking, standing and activity levels,” the company wrote in a release. The passively collected metrics and PROMs “assess entirely different metrics and complement one another to provide a more holistic and objective view of how a patient is recovering after surgery,” Zimmer Biomet said in a statement.
It’s impossible to know now if the mobility data will in fact be useful, but there’s a consensus, at least, that it’s a commendable effort.
“I admire them for doing that,” said Franklin. “That they’re in many ways raising the bar — that they’re trying to evaluate the impact of their implants beyond the minimum standard of not failing to a higher level of really serving patients’ quality of life.”
Surgeons raised concerns about the design of Persona IQ, which, while based on Zimmer Biomet’s popular Persona implant, is only indicated for patients who need a certain type of knee replacement surgery that requires what’s known as a stem extension, which extends into the tibia and helps stabilize the implant. Stem extensions are frequently used in revision surgeries or cases when there are bone issues, but surgeons prefer not to use them when possible because it’s more invasive. Stems are optional with the conventional Persona implant, but with Persona IQ, a long stem is needed to hold the sensors and electronics. Practices differ and surgeons were mixed on the importance of adding this additional length to the stem.
Mount Sinai’s Moucha said he doesn’t always use the approach and noted that “if you have to take it out, it’s going to be an absolute nightmare.”
Larkin said that while it’s not a deal-breaker, it would certainly be better if the extension didn’t have to be inserted so deeply into the bone. He added that company representatives have seemed optimistic about future developments in his conversations with them.
“The goal is to get this smaller, to get it as part of the actual implant instead of an addition to the implant,” Larkin said. “All those things are, quote unquote, being worked on. But this is, and I think Zimmer acknowledges this is, different than what I would implant today. And, I think that that merits disclosure to patients.”
Zimmer Biomet said in a statement that it’s up to surgeons to “use the clinical judgement they’d use for a similar-sized stem when deciding whether this device is appropriate for a particular patient.”
Piuzzi also cautioned that for now, patients should be told upfront that their implant is a just a sensor and is generating data that hasn’t yet proven useful.
“Patients need to be counseled, and to get accurate information, and marketing,” he said “I think they need to understand that they’re just getting the same implant another patient is getting and how they will do is probably going to be the same.”
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