Orthopedic surgeon at Mercy Medical Center, Marc Hungerford, MD talks about knee replacement.
Interview conducted by Ivanhoe Broadcast News in 2023.
A Holter monitor, is this more of an advanced technology because that is constantly transmitting?
Hungerford: A Holter monitor is a little bit different because you wear an appliance on your skin and then it records intermittently, but it also does a burst transmission of the EKG traces. This is more like a pacemaker. It’s implanted, and it has a battery that can last technically up to 20 years. It doesn’t have a huge amount of battery reserve or battery power, but it doesn’t need it because it only comes on once a day and transmits the sensor information, and it records sensor information twice a day so the usage per day is very small, and therefore it can run for years a lot like a pacemaker, and it’s a pacemaker battery.
What is it about this particular device, since you only chose for a year, that attracted your attention in terms of usefulness?
Hungerford: This is a model of a knee replacement right here. These pieces, this is the femur, this is the tibia. This is the polyethylene or the plastic that goes between the two parts of the joint. That basic technology has been around since the ’60s. It has been gradually improved over that period. Not radically, but gradually. The results now are good. The question is, what needs to happen to make that next leap in results where the percentage of people who are extremely happy with their knees goes up? Second of all, where the function of the artificial implant is more similar to a normal knee. There’s a lot of effort on that front. There are technologies to place the implants with more precision, like say robotics for example. There are sensor technologies to balance the ligaments more precisely during surgery. This technology is a reporting piece where we see outcomes in real-time. We see how the knee is functioning in the patient and can use that information to improve the quality of the implants, the design of the implants, the way the rehab is done, identify people who are not meeting expected milestones, and get people to hopefully, overall a better level of outcome so that’s the idea.
In terms of compliance for people, and here’s the deal about that. I don’t want to look at that as a negative, but people sometimes have the idea that they’re doing more than they are walking 10 miles a day when walking 10 feet a day. What you’re getting from the patients currently is what they’re telling you?
Hungerford: This is more objective. We’ve had some semblance of this before. For example, there are programs where you can wear an Apple watch and it can tell you how many steps a day. It can give you messages like, do this, do that, or you’ve been sitting too long. But this is in the implant itself, so it can tell you how much the knee bends, and what the angle of the tibia is when the heel strikes the ground. It’s another potentially rich source of objective outcomes data that we can use to improve outcomes. That’s what outcomes research is all about. You do something and you see how it went and then you make a change, and you see if it helped. That’s how the outcomes research process works.
I don’t know if you’re referencing this with that terminology, outcomes research, but real-time information so that you’re adapting so quickly to it. It’s amazing.
Hungerford: Yeah, a lot of times with research in this field is say the minimum number of patients that you need to follow is say, 100. You’ve got to follow at least a year. Well, that means it’s going to be three years until you have any new data. It takes you year to enroll the patients, a year to do it, a year to follow up, that’s three years. With this, you’re getting it as you go, which is potentially quicker, we’ll see. I don’t know if it’ll be quicker or not, but you have more information in real-time than you’ve been able to have before.
Tell me if the patient has had knee surgery and they’re sitting at home watching what’s transmitting from their knee in terms of information. Where is it going so that they understand what’s going to be done with the information?
Hungerford: This is a sensor. It’s not a tracker. It does not have any GPS information and doesn’t know where you are or anything. It has an accelerometer from your phone that measures your step count, for example. What the accelerometer can transmit is angular information. In other words, how is this thing moving in space? Also, frequency information. If the leg is going up, hitting the floor 1,000 times a day, because you’ve done 1,000 steps, you’ll see 1,000 bounces in that motion trace. What this does is it takes two time periods during the day when patients are most likely to be active, say 10 in the morning and four in the afternoon. It records for some time. Then at night when the patient is most likely to be home and inactive, say two in the morning, this is next to their bedside and the sensor will wake up and transmit that motion information to the base station, and that goes into the cloud database. Now the patient has access to their information so you can go on. This is called Persona IQ. And you have an account in the portal, and you can see your progress over time. As the surgeon, I can see all my patients. I can see here’s everybody we did last week. Mr. Jones is doing great. His recovery curve looks like this. Mrs. Smith is doing great. Mr. Smith, however, is not progressing appropriately. Maybe it’s time to give them a call and see what’s going on. Is he having a problem with swelling? Is he having a problem with pain? What kind of problems? Is there anything that we can do to improve his recovery curve in the short term?
This is great for you guys and it’s great for the patient. Let’s focus on them, since most of these are patient-driven and tell them what this is going to do. It’s going to give you incredibly valuable information. What’s it going to do for them?
Hungerford: Also give them the information, so they can see in real time, on a day-to-day basis, what they’ve done as far as not just step count, but also a range of motion of their knee and are they progressing? Also, they have comparatives. How am I doing compared to people my age? How am I doing compared to people who are weak after surgery and see whether they’re on track or whether they’re a little behind or maybe they get a gold star because they’re a little bit ahead? It’s a little bit motivational too. It’s all the things that why people love the health app on their phones. You have the activity rings, and this is that extrapolated to knee replacement. It’s a personal sensing device that will show you how you’re using your knee how much you’re using it and how much you’re bending, and you can see that in the software.
Then who takes ownership of all of the data that you accumulate, that the company accumulates going into a massive database?
Hungerford: Yes, there’s personal data and then there’s de-identified data. The de-identified data means nobody knows what your name is, what your data is, where you live, what your social security is. They might know this is a 55-year-old male and that’s it. The reason that that data is critical, that this is all federally regulated, so they can’t use it in any way that’s not approved. It’s in terms of what they call PHI, personal health information. Any information that’s shared with any medical facility and any corporate sponsor of any study or whatever is very strictly regulated what can and cannot be shared. The only things that can be shared, are things that essentially can’t be traced back to you or me, they’re just generic. The reason that it’s important though is you’re not going to know what to do with this data on an individual basis. You’re only going to know what to do with it based on hundreds of thousands of inputs. This happened in cardiology decades ago when they first came out with EKGs, they didn’t know what to do with all the individual traces and leads. It was just through a process of following thousands of them that they knew that if you get a spike here, that means trouble. If you get one over here, it’s no big deal. We intend to use this data in the same way. That is, what does it mean when somebody is slow to recover? Can they recover? What can we do? Which interventions are effective? What does it mean when we make a design change to the implant? Does that make things better? In what way? How does it compare to normal? And you need a lot of data for that, but it’s not personal data.
When you’re describing this to the patients and they’re in your office talking to you about it pre-surgery, what are some of their concerns or questions that they’re hitting you with?
Hungerford: The biggest concern is patients want to know if it is new. Is this experimental? The fact is that this implant has been around for approximately 10 years. The actual knee replacement, what’s going on your knee and what you’re walking with and climbing up and downstairs, that’s not new. The only new thing is the sensor on the bottom and that is in the bone. It does not move, and it doesn’t have any effect on function. You cement it into place, and it just sits there. Anything that affects how your knee performs is tried and true, it’s not new or experimental in any way. The two other concerns that patients have, is a phobia of computer technology dealing with your Wi-Fi network and whatever. The good news there is, somebody sets this up for you. We don’t just give it to you and say, go into your computer and punch in these 4010-digit codes. We have somebody set it up. The third thing is whenever you’re talking about sensor technology, some people are suspicious that this can track you in some way. It does not have a GPS tracker; it doesn’t know where you are. It doesn’t matter if you’re at Walmart on vacation, sick leave, or anything. All it knows is how much is your knee bending and how many steps are you taking. However, I would say if somebody were very concerned about that, don’t get it. I cement this into your knee, I cannot get it out.
Next question, can you explain that too?
Hungerford: It’s permanently cemented in and it’s in for the life of the implant. You can’t get it out without taking the implant out. It’s not something that’s a temporary or easily removable piece.
What have you heard back from the patients who have that sensor in their knee about how happy they are with it, on how their recovery is improving because of the data that you’re getting?
Hungerford: We’re early in the process. I’ve done less than 10 of these so far. I haven’t done it for everybody that I’ve done knee replacements on. It’s been people who I thought this person will appreciate this and they want it and they’ll do well with it. They all have. The people that we’ve done this on have been happy with it. The process has gone smoothly, and we haven’t had a problem. Where it gets more interesting is when you roll it out to everybody, you are you going to get a group of people, let’s say I have my knee replaced and for some reason, I’m not happy with it, am I going to think oh, it’s because of this sensor? There might be some patients like that. I haven’t seen it so far, but that’s a concern because like I said, you can’t easily remove it. It doesn’t cause any issues with the knee bending or straightening because it’s not in the joint, it’s in the bone.
Cost and also whether or not insurance covers it now or will?
Hungerford: It’s not a separate charge, it’s part of the implant charge and the implant charge is covered over the overall hospitalization. When you have a knee replacement, you don’t pay separately for the parts, for the recovery room, for the stay, it’s like one fee. For the patient, there’s no extra charge.
Will insurance cover it eventually?
Hungerford: Insurance covers it under the lump sum. They don’t give you anything extra for it. They’re covered under the lump sum. Insurance pays a lump sum for a knee replacement to the hospital, and the hospital must cover all the expenses for that knee replacement out of that lump sum payment.
Is there anything that the sensor does to impact the reliability or the operational technique of that particular knee plant?
Hungerford: No. the sensor is just sitting there. Just like if I took the sensor off. The sensor in this part is a sensor, see this is just a model so I can’t remove it. But if I took this sensor off, there would still be this part of the implant called a keel. The reason that this part is here is that let’s say you have poor bone quality, or this is like the second or third implant, you would put a stem on here where the sensor is, it’s already made to have a piece attached to it. That, that keel even if I don’t use the sensor, that keel is the same as the sensor is. It doesn’t get removed. There is already a piece in the bone that’s part of the normal design. This is just a slight elongation of that same piece.
Have you found that they’re more compliant with this because you got to be aware somebody’s watching?
Hungerford: Yes, but we’ve also picked the people that we thought we were going to participate. Where it gets interesting is when you have the people that tend noncompliance. If we can motivate them to work harder on their recovery and have a better outcome. I tell all my knee replacement patients; this is 50 percent me and 50 percent you. I can do a perfect knee replacement, but if you sit on the couch for six weeks and you don’t do anything, it’s not going to go well. It’s rehab-dependent. I think patients overall are very willing to work on their own recovery. I wouldn’t say patients are generally noncompliant or anything like that. I think most people are very willing. Where this will help is, some patients, they’re having a problem, and they don’t say anything. We can avoid those gaps in care where, for whatever reason, maybe it was a holiday weekend or maybe the patient went out of town or went out of state. Those are critical days, so the beginning is the most critical part.
What do you advise them in terms of several steps daily compared to the average Joe between two and 10,000 steps a day?
Hungerford: Well, what we want to see is, we want to see progress. We get people in all states of health. We have people who are young and very healthy and they’re doing two to 3,000 steps from day one. We have other people who’ve been debilitated on a walker, even in a wheelchair. We don’t have the same expectations for everyone, but what we want to see is we want to see progress. If it’s going nowhere, that’s a problem.
Also, in addition to the number of steps, you want to see movement. You want to see them doing it with the need.
Hungerford: We want to see it bend and straighten, and we want to see steps.
Is there anything in that, that I’ve left out that you wanted to tell us about?
Hungerford: No. I think it’s a technology that hopefully has some legs and that will give us some valuable information to move the science of knee replacement forward along with other technologies is not the only one, but we’re excited about it. I’m just interested to see what we can do with the data, and what we can do to improve patient outcomes.
People all over the country will see those. What can they do actively later, to get involved?
Hungerford: It’s on Zimmer’s website. It’s called Persona IQ. And they have a list of centers that are using it. People who are participating. I think It’s not too hard to find. The company Zimmer with a Z. The product is called Persona IQ.
END OF INTERVIEW
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