Lew Schon, MD, Director of Orthopedic Innovation at Mercy Medical Center, faculty at the Institute for Foot and Ankle Reconstruction (IFAR), talks about a new system for ankle replacement.
What are some options for people who feel like they have gotten to the end of their rope and continue to have ankle pain?
SCHON: People who have ankle pain may have it from several causes like arthritis, a tendon or ligament problem, or even an alignment issue. Any of those problems could mean reconstruction and realignment might get them better. If it is pain that is due to arthritis based on the lack of cartilage space between the bones that causes stiffness, swelling and sometimes deformity, those cases would be seeking more advice as to what to do for their ankle regarding fusion or replacement. They usually come in after things like therapy, medications, injections, and braces haven’t worked, and we will then discuss both options of fusion and replacement.
When you say fusion, what are you doing and what is the end goal?
SCHON: Every time you move the joint that’s in pain, it sounds like a squeaky door with a rusty hinge. To stop that squeaking, a fusion is a great procedure. However, something has to compensate for the lack of ankle motion. There are other joints around the foot and ankle that will give us some of that motion. So, it could be a good choice for some patients because of the magnitude of their problem, their disease state, sometimes their size, medical conditions, medications they take, or even the severity of deformity. We may say to them, you need the fusion. You need to get rid of that joint, stop the motion and stop the pain. If we realign it, that’s going to be good for them.
What do they lose with the fusion?
SCHON: With fusion, you lose the up and down movement. So, the ankle moves in what we call Dorsey flexion and planar flexion. There is side-to-side motion that a lot of people attribute to the ankle, but it’s really the subtalar joint that’s responsible for that. Now, if they have that side-to-side motion and it’s not painful, that gives them a little wiggle waggle which allows them to compensate. Over time, that compensation, which is not physiologic, will start to become more problematic. We know after a fusion, the adjacent joints take a beating. It may be as quickly as three years, or as long as 30 years, but those other joints will start to become arthritic. When that happens, now we have an ankle that’s fused, and we’ve got to fuse the joint below that. When you fuse the joint below that, you have a stiff foot. The replacement on the other hand says, ok, we got a bad hinge and want to keep the hinge going because we like going in and out of the door. So, the ankle replacement allows us to remove the diseased cartilage and bone, realign the ankle, and replace the surfaces with metal and plastic. Then, you maintain that up and down movement. Now, if you’re stiff before surgery and your ligaments, tendons and soft tissue around the ankles is rigid, when you replace that ankle, the hinge will move well but the tissues don’t always give you the freedom. The stiffer patients are when they come in, they tend to be a little bit stiffer than the other patients with great range of motion but the arthritis. We do preserve range of motion and sometimes, even if you have a little motion versus that fusion, it dissipates stresses and the hind foot joint. In other words, that wiggle waggle joint doesn’t have to overwork and therefore doesn’t become arthritic.
Who are the best patients for a replacement over a fusion?
SCHON: Historically, the metal and plastic components we used to replace the arthritic surfaces were ok. Well, they have gone from being good to being very good. I’m a co-creator/inventor of the Zimmer total ankle replacement. When we brought the product to Zimmer about 20 years ago, they were the champions of joint replacements throughout the body but had not entertained an ankle. However, just like an IndyCar racer, the company says we want our car to be the best. They put maybe 34 engineers on the project, and we designed the best replacement. We’re the only ankle with tantalum. That is a very special metal that inspires bone to grow into it. We have a highly cross-link plastic, called Prolong poly, that’s been used in knees and hips and other joints, so it has a very good durability. We have a system to put in the replacement that allows us to take the least amount of bone, preserving as much of the natural tissues as possible, and to put it in in a very stable fashion. We have a technique which we designed for doing realignment of the foot and ankle in a frame in the OR, and we lock it into alignment, then mill away the surfaces. By doing that, we create a perfect geometric space and slide in the implants to fill that space. Intrinsically, there’s a lot of stability, and that has helped expand the indications for the prosthesis. Initially, I started doing them seven and a half years ago. We were hoping that, at two years, we weren’t going to see any problems because other companies do have some problems that start to be exposed by two years. I didn’t want to see loosening and cysts, plastic wear, or plastic fractures. And at two years, we didn’t! So, now we’ve had 50 patients with five years and more follow-up, and I’ve done about 320 or more cases. We’ve done thousands of cases worldwide. The metal is indeed bonding with the bone beautifully and the plastic is withstanding the stresses with no signs of wear. Now, we are going to get wear, but because of these changes preserving more bone, having good fixation, being able to correct a deformity, and putting in metal and plastic that is up to the physiologic load, I have expanded my indications. Other people have done that with other replacements worldwide. I’m not the only one pushing the boundaries. But I have seen nice results with pushing the boundaries, even in people who are obese, people who are not the healthiest patients, people who are maybe younger than your traditional cases, and people who are maybe older than the traditional cases. So for me now, I would say to most of the patients that don’t have a history of infection or some horrible bone disease which would cause the bones to just fall apart, everyone’s a candidate for the replacement. We just first see what’s going to be best for their lifestyle and for their demands.
Like other replacement parts, sometimes they have a limited shelf life. Where do we stand with the Zimmer ankle? How long would it last and can you replace the part once it goes bad?
SCHON: The first thing is we really don’t know, in humans, how long the plastic’s going to last. We have robotic testing that gives us the sense that we’re going to be out 15 years before the plastic needs to be changed. In the other designs, the plastic has gone faster. We compared our plastic with other plastic in a study we published in Foot and Ankle International, and we had five times better wear properties than the conventional plastic. So, we’re hoping we’re 15, or even 20 years out, but we’re not seeing at this point with seven and a half years any problems. In terms of the metal-bone bond, that bond is really good, and we have seen great incorporation. We do a special technique called metal artifact reduction, or MRI. It’s a special MRI technology that has been designed locally here. I’ve worked with the people who have made that imaging technique, and we’ve looked at the interface and find excellent metal-to-bone bonding. As such, if the plastic wears, we could just change the plastic. As long as that bone and metal are bonded, we don’t have to revise the metal. Some of the other replacements had cysts all around the metal and you’d have to take out the worn plastic and change the metal, which created a need for revision systems and then other revisions of the revisions. So, that’s a slippery slope. Right now, I’m not anticipating metal changes. We will probably have those cases, but right now it’s not looking like it based on the cases I know worldwide and by my own cases.
If you have metal that’s bonding to the bone, which is great for stability, and must replace it, what does that do to the replacement since you’ve got that bond?
SCHON: The main reason we would be changing the metal is if the metal got loose. I had one case of some other doctors who did it and never got the implant to bond well to the bone. I revised it and just took it out, milled two more millimeters of bone, and put in a new component. I haven’t had to do that in any of my patients, but I imagine if that happened, that’s what it would be because that one case showed me that.
Does that extend the metal and lifespan of the age of the patient? And, if you can go in and just change that little plastic part, does that mean it’s an option for younger patients?
SCHON: Yes. I feel that way, but we don’t have the science to back it up. We are following my patients and being very cautious while discussing and analyzing. We have whatever science is available to help us predict that. So, I feel safe talking with my patients. If we do a younger patient, I let them know if this fails, we have a bigger hole in your bone and the conventional ankle replacements, but we’re not expecting that. If it did happen, then we would take out the metal and put in a graft. With those strategies in my back pocket, I have done it on younger people. Sharing the risk with the patients, they understand what the upside and the downside is, and I feel in my heart and in my brain, as best as I could visualize the future, that we will be changing the plastic on those patients in 15, maybe 20 years. However, we won’t be doing the metal, so we can have an easier revision without a bigger operation, and therefore, extend the timeframe that we could give people ankle movement versus fusion.
If you could, walk us through how you perform the implant?
SCHON: They’re all done from the side. It’s a unique feature of the implant which pretty much allows me to do all the changes. Everybody typically goes in from the front. But, by going in from the front, you have some limitations as to what you can do. Your creativity is limited. By going in from the side, I could really change more elements of the deformity. I could address the tendons and ligaments and realign the bones better. I can mill away a curved surface which is better, in my opinion, than a flat surface. I’m sweeping a radial arc, and that just removes the surface. By doing so, I preserve more bone and we could get better correction. So, all of my cases are a lateral approach. We cut the outer bone, position it, get everything properly aligned, and correct the deformity.
Are there any restrictions for patients with these?
SCHON: It’s the usual restrictions we have for arthroplasties. In general, I’m very strong about not letting people run or jump. The reason is that metal and plastic is the gift and we don’t want to break it, stress it, or overuse it. If they’re running, they’re getting seven times the bodyweight, and that plastic will wear faster. That’s an issue with the younger patients because they want to run and jump. We have people playing doubles tennis if they’ve played before and if they are comfortable doing it. Some people are not fully comfortable because they have other things going on in their foot. When you have a bad fracture, it’s not just the ankle. I don’t like snowboarding, but we have some snowboarders. I don’t like it because it’s a little bit too much bump. We have a skateboarder or two, which I don’t like either. So, I don’t encourage that at all. I think walking, hiking, swimming, biking are the standard things. Many of the patients who are in that healthy category can do those.
Is there anything else you really want to make sure people know?
SCHON: Yes. The other precautions are if you have a replacement, you’re still subjected to other things that happen in your body that can affect the ankle. For example, if you had an infection somewhere in your body, it could go through your bloodstream and into your ankle. Same thing with a prosthetic knee, hip or shoulder. So, we must be careful. If you have an infection going on, get it taken care of and make sure your doctor knows that your implant is vulnerable in case you need to be on antibiotics. If it’s a chronic thing, not so good. So, I think the no running, no jumping, and be careful of infections in your body are the biggest things that we worry about.
You have an interesting hobby… Tell us about that and maybe tell us about Fenway Park and how that crossed over.
SCHON: Yes, of course. So, most doctors are regular people! And, a lot of regular people have hobbies and passions outside of their work. I’ve always enjoyed music. I came from a musical family and always liked arts and crafts and music. I’m probably a mediocre arts and crafts and musician guy, but I have good passion. So, I’ve practiced and kept up my skills. We formed an orthopedic rock and roll band called, The Stimulators. That was a good use of time, energy, and enhanced the other side of my brain. I take care of musicians and dancers and performing artists. My patients and I will sometimes become friends and in a certain situation, I was taking care of a front man for a famous rock group and he had asked me to check him out before a concert. I missed the concert which was at Fenway Park because we were flying in from California. So, I checked him out and he said, why don’t you stay tomorrow and perform with us? He insisted. Anyway, I went for it. I did “Seven Nation Army” by the White Stripes, Jack White song. I think people were a little bit surprised to see, at a grunge rock and roll concert, some dude with a bow tie and curly hair and glasses come out and do “Seven Nation Army.” So, it went viral and it was a lot of fun.
What instrument do you play?
SCHON: I’m a keyboardist and I sing backup. Dave, the performer liked the song a lot and I was happy to do it with the Foo Fighters. It was a lot of fun. He and I have stayed in touch before that and after that. It’s good to bond with your patients. It’s good to have some connection. It was beautiful that he could share that with me, and I can’t say I ever dreamed of being on stage in front of 35,000 people. It wasn’t on my bucket list, but certainly it was a great thing to do!
Interview conducted by Ivanhoe Broadcast News.
END OF INTERVIEW
This information is intended for additional research purposes only. It is not to be used as a prescription or advice from Ivanhoe Broadcast News, Inc. or any medical professional interviewed. Ivanhoe Broadcast News, Inc. assumes no responsibility for the depth or accuracy of physician statements. Procedures or medicines apply to different people and medical factors; always consult your physician on medical matters.
If you would like more information, please contact:
Dan Collins
Mercy Medical Center
410-332-9714
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