Latest / AHF Podcast / Part I: Decoding Hip Resurfacing with Professor Justin Cobb

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Part I: Decoding Hip Resurfacing with Professor Justin Cobb · AHF Podcast

• 0:24
  Joseph M. Schwab: Hello everybody and welcome to the AHF podcast.
• 0:27
  Joseph M. Schwab: I'm your host, Joe Schwab.
• 0:30
  Joseph M. Schwab: Few topics in modern hip surgery seem to strike up as much controversy as hip resurfacing.
• 0:36
  Joseph M. Schwab: Hip surgeons have been trying to solve this since, at least as far back as the 1920s, with both Marius Nygard Smith Peterson in the US and Ernest Haygrove in the uk, independently reporting on work they had been doing to restore function to arthritic hips, using things like glass and ivory.
• 0:54
  Joseph M. Schwab: We've seen mold arthroplasty, cup arthroplasty, double cup arthroplasty, and more using.
• 1:00
  Joseph M. Schwab: Materials from acrylic to Teflon to stainless steel and cobalt chrome.
• 1:05
  Joseph M. Schwab: With the introduction of more modern metal on metal implants like the Birmingham hip resurfacing or the Conserve Plus, starting in the mid 1990s, hip resurfacing seemed to undergo not only a renaissance, but a considerable spike in popularity, thanks to the purported advantages of bone preservation, anatomic restoration of joint mechanics, and a very stable head to shell ratio.
• 1:28
  Joseph M. Schwab: With renewed interest, however, came some renewed scrutiny and with a growing number of designs in the marketplace, it was clear that small design differences were associated with substantially different results.
• 1:41
  Joseph M. Schwab: Some designs like the A SR we're seeing 10 year revision rates nearing 50% failures associated with the bearing surface.
• 1:49
  Joseph M. Schwab: Materials seem to be a common theme though to be fair.
• 1:52
  Joseph M. Schwab: Not all designs exhibited the same problems.
• 1:56
  Joseph M. Schwab: So why do we come back to this concept year after year, decade after decade?
• 2:02
  Joseph M. Schwab: That's the question for my guest today.
• 2:04
  Joseph M. Schwab: Professor Justin Cobb is an orthopedic surgeon and chair of orthopedics at Imperial College London.
• 2:10
  Joseph M. Schwab: Not to mention the fact he's been orthopedic surgeon to Queen Elizabeth II, as well as King Charles III.
• 2:16
  Joseph M. Schwab: But most important to our discussion today is that he's been working to develop the H1 ceramic on ceramic hip resurfacing.
• 2:24
  Joseph M. Schwab: And with that, he hopes to be the surgeon who finally cracks the code for a reliable, reproducible and durable hip resurfacing implant.
• 2:34
  Joseph M. Schwab: Professor Cobb, welcome to the AHF podcast.
• 2:38
  Justin Cobb: You are very kind, delighted to.
• 2:41
  Joseph M. Schwab: So depending on who you talk to.
• 2:44
  Joseph M. Schwab: Hip resurfacing is either potentially the pinnacle of all hip surgery, or it's an unmitigated disaster.
• 2:52
  Joseph M. Schwab: Could you put hip resurfacing in a context that seems reasonable for the rest of us?
• 3:00
  Justin Cobb: Yeah.
• 3:00
  Justin Cobb: So.
• 3:01
  Justin Cobb: Um, I really got, um, convinced about, um, hip resurfacing when measuring function in our gait lab.
• 3:12
  Justin Cobb: And we looked at, I was, I got, it was very keen on resurfacing from, I guess around about 2000.
• 3:18
  Justin Cobb: It felt like a more conservative procedure and, but as you pointed out, many surgeons never really got on with it.
• 3:27
  Justin Cobb: And one of my friends who's a very good hip surgeon, thought it was the invention of the du and we really had parallel practices, same patient groups.
• 3:35
  Justin Cobb: I was resurfacing, he was replacing.
• 3:38
  Justin Cobb: And then the, and we, I got a, a grant paid for a, um, a, a instrumented treadmill so we could see how people walked, how they went faster and faster.
• 3:47
  Justin Cobb: And we weren't the, I think I can safely say nothing I've done has ever been the first in its field, but we showed what other people have shown, which is that healthy, normal people have got this fantastic continuously variable transmission gearbox in their brain.
• 4:04
  Justin Cobb: And when you put your foot on the gas and walk faster and faster, your stride length and your cadence smoothly increase until you start to run.
• 4:14
  Justin Cobb: And what we find with healthy adults is that's what happens in their thirties, forties, fifties, sixties, seventies, eighties even.
• 4:21
  Justin Cobb: That's what happens if you've got a stem in your femur that doesn't happen.
• 4:27
  Justin Cobb: Strolling is great on the catwalk.
• 4:31
  Justin Cobb: Nobody can tell.
• 4:33
  Justin Cobb: But if you wanna push, put your foot on the gas, the person with a hip replacement with a stem in their femur, and I'm, I don't think it's really, I'd love to say it's just because of the anterior posterior approach, it does seem to be the stem in the femur.
• 4:47
  Justin Cobb: I think, um, with a stem in your femur, once you start to stress the elasticity of the femur, um, it doesn't feel, people don't report pain.
• 4:58
  Justin Cobb: They just don't do it.
• 5:00
  Justin Cobb: So they don't push off so hard with the stem in their femur.
• 5:02
  Justin Cobb: But the resurfacings, huge posterior approach taking down gmax tendon, huge approach.
• 5:09
  Justin Cobb: A year later, they're walking very, very close to normal people in a way that no one's ever published a total hit that can do that.
• 5:18
  Justin Cobb: So that was, that was data.
• 5:20
  Justin Cobb: I was, and I, this was in the early two thousands and it was really exciting, the stuff.
• 5:26
  Justin Cobb: But as you pointed out, the metal or metal debacle.
• 5:30
  Justin Cobb: Um, meant that all of these patients, um, who were doing great, if you did it accurately, um, they were okay, but there was a growing feeling across the whole world that metal irons were bad.
• 5:47
  Justin Cobb: And so it was increasingly difficult to persuade people to have a, a procedure.
• 5:53
  Justin Cobb: And certainly in Britain there was an advisory.
• 5:55
  Justin Cobb: You had to have a metal land level test every year implying that you had a pros, a prosthesis that was about to explode.
• 6:03
  Justin Cobb: And so the metal work, it was, it was never going to be widely adopted around the world as, as you found out.
• 6:10
  Justin Cobb: But functionally, and the total hip industry has done a, I mean, as you know, in the anterior hip foundation, I'm a huge fan of the insult to the patient for anterior hip surgery is minimal.
• 6:26
  Justin Cobb: But in the end it's a hip replacement.
• 6:28
  Justin Cobb: And if you cut out someone's calcar, which is the strongest bit of the whole femur and you de power that calcar, you don't let the femoral head take all the force coming from your flexors and abductors.
• 6:44
  Justin Cobb: If you de power that, then you are, you are changing the biomechanics irreversibly.
• 6:48
  Justin Cobb: Whereas if you just resurface the hip, um, you can allow that femur to perform like a normal femur.
• 6:55
  Justin Cobb: And I think that's the difference.
• 6:57
  Joseph M. Schwab: So, so this is interesting'cause when I look online at discussions, for instance, every once in a while you'll see a, a post on LinkedIn where somebody puts up, um, an x-ray of an arthritic hip and says, should they get a total hip?
• 7:10
  Joseph M. Schwab: Should they get a hip resurfacing?
• 7:12
  Joseph M. Schwab: And the discussion always comes down to recovery with many surgeons feeling like the recovery is simply easier with a hip replacement than it is with a hip resurfacing.
• 7:22
  Joseph M. Schwab: But it sounds like you're talking more long-term functional recovery with people going back to normal, as opposed to what happens in the short term.
• 7:31
  Joseph M. Schwab: Is that right?
• 7:33
  Justin Cobb: Um, I was until, um, uh, a couple of years ago, I would've said what you said is absolutely right, that with an anterior approach, total hip, you are up and going very, very fast and with, with a resurfacing your, you are a bit slower off the, off, off.
• 7:52
  Justin Cobb: You're not, you, you probably are a slower.
• 7:56
  Justin Cobb: I don't think there's a significant, I think if anything resurfacing are a bit quicker.
• 8:01
  Joseph M. Schwab: Well, and that, that actually brings up the other part of the discussion that I usually see is when somebody talks about a resurfacing, it's almost placed as an anterior approach, and hip resurfacing are at odds with each other.
• 8:14
  Joseph M. Schwab: They're competing products, so to speak.
• 8:16
  Joseph M. Schwab: But I mean, really what you're talking about is doing the surgical approach of an anterior approach to put in a, a bone conserving, hip resurfacing implant.
• 8:26
  Joseph M. Schwab: Is that correct?
• 8:28
  Justin Cobb: That's right.
• 8:29
  Joseph M. Schwab: Yeah.
• 8:30
  Joseph M. Schwab: So how do you think we should approach that discussion with those surgeons, you know, online about, uh, anterior approach, sort of versus hip resurfacing?
• 8:41
  Justin Cobb: so you and I, as surgeons, we know we really can only sell the shoes in our shop.
• 8:47
  Justin Cobb: And if, if you can't do an operation, you brief against it pretty vigorously.
• 8:53
  Joseph M. Schwab: Yeah,
• 8:54
  Justin Cobb: If you are a key opinion leader for a total hip arthroplasty, you better not promote something that the company that is paying you big bucks doesn't even have in their arsenal.
• 9:07
  Justin Cobb: So I think the online chat is, some of it is, I mean, some of it is real truth if you like people talking from their own personal experience and some of it is industry based noise slash testosterone fueled egos
• 9:27
  Joseph M. Schwab: That brings me to the H1 specifically.
• 9:29
  Joseph M. Schwab: 'cause uh, you know, one of the, uh, one of the things that you've been working on is the development of this, uh, product.
• 9:37
  Joseph M. Schwab: And can you, first of all, can you tell our listeners, um, a little bit about the product and a little bit maybe about the release schedule for it?
• 9:47
  Joseph M. Schwab: 'cause it's not available everywhere at this point, is that correct?
• 9:50
  Justin Cobb: It is not available anywhere at this point, unfortunately.
• 9:53
  Justin Cobb: I mean, so Derek McMinn, who's a, um, uh, obviously very senior and August, but nevertheless, dear friend, um, Derek, when he was developing the Birmingham in I think six years, went through five major changes, cementing, uncementing, uh, different designs.
• 10:12
  Justin Cobb: These days, so we, we started with H1 in earnest with Ceramtec in 2013
• 10:19
  Joseph M. Schwab: Yeah.
• 10:20
  Justin Cobb: and really working very hard to get it into people.
• 10:24
  Justin Cobb: We got our first patients of the summer of 2017, and we got a CE mark, um, September of last year, and we expect it will be released in, I, we hope, six different European countries, including Switzerland.
• 10:43
  Justin Cobb: Um, this autumn.
• 10:45
  Justin Cobb: So the, the, the program of, um, regulation is just brutal.
• 10:52
  Justin Cobb: It's absolutely brutal.
• 10:54
  Justin Cobb: And I'm very sorry.
• 10:55
  Justin Cobb: The, the FDA, when we last spoke to them, they'd all just had a letter of Elon Musk saying, what are you doing every day?
• 11:02
  Justin Cobb: And,
• 11:03
  Joseph M. Schwab: yeah.
• 11:03
  Justin Cobb: and we were speaking English and they were speaking American.
• 11:06
  Justin Cobb: And it was a very uncomfortable experience.
• 11:08
  Justin Cobb: I mean, I really, I've never had that experience before.
• 11:10
  Justin Cobb: Very uncomfortable.
• 11:11
  Joseph M. Schwab: So, uh, let's talk a little bit about the, the H1 itself, because like you said, you partnered with Ceramtec and so the, the prosthesis itself, the bearing surface is the Biolox delta, right?
• 11:24
  Justin Cobb: the, the device is monolithic Biolox Delta, which I've been using actually.
• 11:29
  Justin Cobb: I used, I was very happy with Forte before Delta came along and, but Delta now we've got, I think there's 13 or 14 years of experience and, and tens of millions of people with Biolox Delta in their bodies.
• 11:44
  Justin Cobb: So it seems like it's quite a safe material.
• 11:48
  Justin Cobb: Um, and so we felt very comfortable, um, going to them.
• 11:53
  Justin Cobb: So they.
• 11:55
  Justin Cobb: The device, it's then coated in Medicoat.
• 11:59
  Justin Cobb: Medicoat was set up in just outside Zurich to coat, actually it was set up by, um, Haki, um, Gruner to, to coat the furlong ha coated, um, uh, hip back in the eighties.
• 12:14
  Justin Cobb: And his son Philip, runs the company now and they, they've been coating Titan Tanium for a very long time and coating directly onto green machined ceramic that is new, but it seems to be, um, it seems to be, you know, if you do the testing, you can rip it off, you can shear it off, and the forces needed to, to take it off are a bit greater.
• 12:41
  Justin Cobb: Well, there's equivalent order of magnitude to ripping off, uh, plasma per titanium from titanium or cobo creme.
• 12:47
  Justin Cobb: It's a very, very strong bond.
• 12:49
  Justin Cobb: Um.
• 12:51
  Justin Cobb: But adhe, the, if you, I don't wanna talk about adhesion science.
• 12:54
  Justin Cobb: It's very, very niche.
• 12:55
  Justin Cobb: It's way outside.
• 12:56
  Justin Cobb: Orthopedic surgeons pay grades,
• 12:59
  Joseph M. Schwab: But, um, suffice it to say you can, you're putting these in without the use of cement, correct?
• 13:04
  Justin Cobb: so both sides.
• 13:05
  Justin Cobb: So I had good experience with Cementless, um, metal and metal resurfacing, and Paul Beaule in, in Ottawa, who's a real giant in this world.
• 13:15
  Justin Cobb: He, he's got, again, very good experience with the Conserve plus Cementless.
• 13:20
  Justin Cobb: Um, Tom Gross with, uh, cementless Recap in South Carolina.
• 13:25
  Justin Cobb: Um, KDA met in, in Gent has had, I think he's done all three of those, um, cementless.
• 13:30
  Justin Cobb: And it seems to, it seems as though the Cementless feral component, it's a safe construct.
• 13:36
  Justin Cobb: And so we have the experiment of plasma spray titanium on ceramic on both sides.
• 13:43
  Justin Cobb: So a single experiment, whereas.
• 13:46
  Justin Cobb: We felt that going cemented.
• 13:49
  Justin Cobb: That would be an experiment too.
• 13:50
  Justin Cobb: No one had ever got a device cement onto ceramic.
• 13:53
  Justin Cobb: That would be a new one too.
• 13:54
  Joseph M. Schwab: Why ceramic as the bearing surface?
• 13:57
  Joseph M. Schwab: I mean, you have, I presumably there are a number of different options you could have considered.
• 14:01
  Joseph M. Schwab: Why did you choose ceramic?
• 14:04
  Justin Cobb: yeah, so obviously initially, honestly the first thing that came along was the contour.
• 14:11
  Justin Cobb: So in the old days, in fact in the current resurfacings and with total hips, two groin pain is a thing in hip arthroplasty and it's between sort of three and five times as common.
• 14:23
  Justin Cobb: Sorry, commoner in, in resurfacing arthroplasty.
• 14:27
  Justin Cobb: Um, and that's partly, it looks like it's mainly the acetabular rim.
• 14:32
  Justin Cobb: You know, it looks like if someone sort of growing pain, you probably didn't get that anterior rim inside the pelvis enough.
• 14:40
  Justin Cobb: Um, and we.
• 14:41
  Justin Cobb: Back in 2007, well done, actually one of my PhD students, um, and I, we looked at the contour and we realized it was quite a mathematical contour.
• 14:52
  Justin Cobb: And so we, we, we patented that in 2007 and I wanted to do it with metal on metal, but as we were doing, it was obvious metal, metal was going nowhere, and so a contour metal on metal was never gonna run.
• 15:05
  Justin Cobb: So we then looked the different materials.
• 15:10
  Justin Cobb: As I'm sure you know, the poly motion is in use in North America right now.
• 15:13
  Justin Cobb: There's an IDE going on in North America, which is a metal on highly cross think poly, um, but what we, in our preclinical testing, um, it, one of the things about the, the group of people who want really benefit from resurfacing are the young, very active men with cams, all of whom have quite shallow sockets.
• 15:35
  Justin Cobb: And the young, very active women who, some have got cams, but quite a lot haven't.
• 15:39
  Justin Cobb: They've just got a bit of dysplasia, quite a shallow socket and leaving.
• 15:45
  Justin Cobb: So you have to have the opportunity to leave some substantial amount of uncovered bone uncovered prosthesis laterally to give them the good articulation and that unsupported polyethylene, um, the preclinical testing, it just fails it.
• 16:02
  Justin Cobb: So we unsupported, metal backed, it doesn't fail it, but without, um.
• 16:08
  Justin Cobb: Metal backing.
• 16:09
  Justin Cobb: We couldn't get polyethylene to to, to succeed.
• 16:12
  Justin Cobb: So we had to go to hard on hard.
• 16:14
  Justin Cobb: And in Europe, I think in every country in Europe, ceramic and ceramic is a well established, um, bearing couple.
• 16:22
  Justin Cobb: It's only really in North America that doesn't, doesn't accept that as a regular thing.
• 16:26
  Justin Cobb: Um, in Europe, um, we've all got really good experiences, I think of, of, of c ceramic bearings.
• 16:34
  Justin Cobb: And so we went to that and, and in fact the un unsupported, um, rim, it's a really, you've gotta have the ability to have a cup that is unsupported in mild or even moderate dysplasia that is not gonna fail.
• 16:52
  Joseph M. Schwab: So do you think the reason, um, the, the, is the primary reason that the cups were sort of exposed anteriorly or groin pain was occurring anteriorly more common in resurfacings because of the material, because of the shape of the device or because of the size of acetabular prosthesis relative to a more conventional total hip or a combination of those
• 17:16
  Justin Cobb: Combination.
• 17:17
  Justin Cobb: Combination.
• 17:18
  Justin Cobb: So, um, I wanted, I'll send you a last picture showing the, um, uh, of an acetabular component of a metal, metal one and our contour.
• 17:29
  Justin Cobb: And the fact is, if you haven't got a cutout for the oop pubic recess anteriorly, where the S comes and the ichi, it's much more gradual recess posteriorly.
• 17:42
  Justin Cobb: If you haven't got those cutouts, you've gotta put the socket a long way further in to avoid, avoid, um, conflict.
• 17:50
  Justin Cobb: And we can, we can leave the center much more where it wants to be with the contours.
• 17:58
  Justin Cobb: Um, so, so I think it really makes a substantial difference to the surgeon trying to get the socket in the right place because it doesn't have to overhang except to give you back your, your where whale scar was.
• 18:12
  Justin Cobb: You've now got a lovely big, um, peninsula there, but you haven't got overhang for sos um, anteriorly.
• 18:19
  Joseph M. Schwab: Interesting.
• 18:20
  Joseph M. Schwab: So you, you briefly mentioned indications and, and let's, let's talk about this because, um, indications over time for hip resurfacing kind of shrank substantially, uh, from everybody can get it to, you know, maybe males with a larger bone size and their, you know, who are very active in their, you know, fifties to sixties, forties to sixties.
• 18:44
  Joseph M. Schwab: It's different depending on the literature you look at.
• 18:47
  Joseph M. Schwab: But certainly over the last 20 years, the relative indications for a traditional hip resurfacing contracted.
• 18:53
  Joseph M. Schwab: From your perspective and with the development of the H1, does it address some of the reasons for those, uh, changes in indications and what are your
• 19:04
  Justin Cobb: so so the, it, it wasn't so much the indication, I think it was the, as the truth of the matter, the problem was edge loading of the wear scar in a metal or metal bearing.
• 19:14
  Justin Cobb: That was the problem.
• 19:15
  Justin Cobb: That was the only problem.
• 19:17
  Justin Cobb: And to get a, and I've got several very, um, prominent female athletes and dancers and so on who are 10 and 15 years after every resurfacing, doing just great.
• 19:29
  Justin Cobb: But you had to get the socket orientated, right?
• 19:33
  Justin Cobb: You didn't get it right.
• 19:34
  Justin Cobb: They got, um, um, high Medline levels and Tom Gross has published on this, and he is a real master of this.
• 19:42
  Justin Cobb: Um.
• 19:43
  Justin Cobb: So the indication in women is very strong.
• 19:46
  Justin Cobb: If there isn't a contraindication, the contraindication of a, um, a uniform thickness metal bearing couple means you've just got this very small surface area on the smaller sizes.
• 19:58
  Justin Cobb: With ceramic, ceramic, the rules are completely different with literally, I think I don't, with millions of ceramic and ceramic bearings with decades in humans, the case report of edge loading of runaway wear has yet to be published.
• 20:13
  Justin Cobb: And because we all love bad news, you know, we all love bad news.
• 20:18
  Justin Cobb: If there was bad news, the ceramic and ceramic haters would be putting up pictures of edge loading of runaway wear on every talk they gave.
• 20:26
  Justin Cobb: But it seems to be a, a, a a more, a much, much more benign tribal environment.
• 20:33
  Justin Cobb: Um, so the worry about edge loading of runaway wear doesn't seem to be there.
• 20:39
  Justin Cobb: And so for women.
• 20:43
  Justin Cobb: Um, resurfacing is a great option for women.
• 20:45
  Justin Cobb: It really is.
• 20:46
  Justin Cobb: It's fantastic.
• 20:47
  Justin Cobb: And unlike the sporting, um, we, uh, athletic man, women live forever.
• 20:55
  Justin Cobb: Okay?
• 20:56
  Justin Cobb: They're never gonna die.
• 20:58
  Justin Cobb: And, and to cut large bits out of them, um, unnecessarily, it seems like a big mistake.
• 21:05
  Justin Cobb: So, so our indications are adequate bone mass.
• 21:10
  Justin Cobb: And the one thing that gives me the heebie-jeebies is bisphosphonates someone who's had bisphosphonates preoperatively.
• 21:19
  Justin Cobb: I think that's a.
• 21:21
  Justin Cobb: I, I don't that, that's a difficult, I, I think it's just too scary for us right now.
• 21:27
  Justin Cobb: Um, but if someone's got a, if they're a healthy adult, that means that we know Wolf's law carries on working in your nineties and hundreds.
• 21:35
  Justin Cobb: You know, if you are active, you keep your bones active.
• 21:38
  Justin Cobb: So, so, um, in our trial we had 70 as the upper age limit.
• 21:44
  Justin Cobb: Um, and I, I had one, um, built muscular Californian man who literally sent money trying to Bri he was 72 trying to bribe his way onto the study.
• 21:59
  Justin Cobb: Um, and so since the trial, I mean, people in their seventies, as you know, there are lots of really good people in their seventies.
• 22:05
  Justin Cobb: And to say to them, no, you've gotta have your femoral head and neck cut out and someone bang a big bit of metal into their fma, well, you know, you don't have to have that, I don't think.
• 22:16
  Joseph M. Schwab: I suppose how, how about things like, um, certain types of pediatric hip deformity.
• 22:21
  Joseph M. Schwab: So you said adequate bone stock, is that just dealing with osteoporosis or things like perthes, advanced Perthes and,
• 22:29
  Justin Cobb: So the planning, I mean the, the we've done a really difficult per is is really difficult.
• 22:35
  Justin Cobb: It's really hard.
• 22:37
  Justin Cobb: Um, of course it is.
• 22:39
  Justin Cobb: And so there's some things that are just too difficult and you can't do very much with people's.
• 22:45
  Justin Cobb: Um, you know, you can't do what you can do with an estro with resurfacing, of course you can't.
• 22:51
  Justin Cobb: But I have, um, done corrective osteotomies and resurfacing, um, simultaneously with fractures of the proximal femur.
• 23:00
  Justin Cobb: I think that's something you can do, um, and just resurface the feral head.
• 23:05
  Justin Cobb: Um, but I think in bad path, I mean, and bad av n too, of course you can't use it for those things.
• 23:12
  Joseph M. Schwab: So do you look at version of the femur?
• 23:15
  Joseph M. Schwab: Um, for instance, before you're, when you're planning for a, a hip resurfacing, would you correct a femoral version?
• 23:21
  Joseph M. Schwab: Or obviously you're not gonna do that through the prosthesis, um, but or do you just prefer to put them where they anatomically came from?
• 23:29
  Justin Cobb: So it's a great question, and in, in really bad DDH with huge, um, femoral inversion in my old days of metal on metal, um, I, on a couple of occasions did a rotational osteotomy of the femur the same time as, um, during the resurfacing.
• 23:48
  Justin Cobb: I haven't seen, you know, it's a, it's a real question, but I just haven't seen that for a while.
• 23:55
  Justin Cobb: Um, and I, but I think the rules are the same in all arthroplasty.
• 23:59
  Justin Cobb: You've got to give somebody a biomechanically sound, um, reconstruction, which may require corrective osteotomy,
• 24:09
  Joseph M. Schwab: I think, um, the, the kinematic alignment total knee folks are challenging our conventional wisdom as to what, uh, biomechanical soundness is.
• 24:17
  Joseph M. Schwab: And, uh, I, I, I find that interesting as well from a total hip
• 24:21
  Justin Cobb: for the, from the femur, you know, the, I I hope we're gonna publish quite soon, some more work on, on the, the elasticity of the femur and, um, and the, the, the impact of e femoral stem on that, on the biomechanical properties of the femur.
• 24:40
  Justin Cobb: Um, and if you've, if you can save the compression trabecula from the car, car going up onto the femoral head, if you can save those, then your hip flexes are just driving straight up them.
• 24:55
  Justin Cobb: If you cut them off, they've gotta go down into the.
• 25:00
  Justin Cobb: Um, shaft to bond onto the metalwork and then go back up.
• 25:04
  Justin Cobb: It's just, it's a tortuous route for the forces to be delivered.
• 25:07
  Joseph M. Schwab: you've mentioned briefly your detractors, uh, well, you said sort of jokingly, you know, if, if detractors were finding these problems, of course they'd be bringing'em up online.
• 25:15
  Joseph M. Schwab: I.
• 25:16
  Joseph M. Schwab: I'm certain you must have run into some detractors in during this development period for some reason or another.
• 25:23
  Joseph M. Schwab: What are they saying and has their message changed over time or has it gotten louder or quieter?
• 25:28
  Joseph M. Schwab: What would you say?
• 25:31
  Justin Cobb: um, I think I got, I've gotta be, um, gotta be polite.
• 25:40
  Justin Cobb: It's DA data.
• 25:41
  Justin Cobb: You know, there are big hip groups that publish huge amounts of stuff that have never published any outcome data.
• 25:50
  Justin Cobb: Not not revision rates, but actually outcome.
• 25:55
  Justin Cobb: And if you look at the Swedish registry, and the Swedes have, have done a pretty, a very good job of looking at how their patient's doing, not just revision rate, but everything else in their registry.
• 26:07
  Justin Cobb: Um, the, uh, cemented stem isn't that great, you know, functionally in terms of outcome studies.
• 26:15
  Justin Cobb: They're not that great and cement less stems seem to be better, but not as good as resurfacings in functional terms.
• 26:24
  Justin Cobb: Now, of course, there's selection bias and all that.
• 26:28
  Justin Cobb: Of course there is, but no one's ever done the other way around.
• 26:32
  Justin Cobb: No one's ever shown, um, that the, the resurfacings do really badly, um, functionally.
• 26:40
  Justin Cobb: Um, and so to say, I insist on cutting out your femoral head and, and fossilizing the inside of your proximal femur.
• 26:49
  Justin Cobb: So the big arguments in Britain, honestly, it's about cemented stems.
• 26:52
  Justin Cobb: Can you believe that?
• 26:54
  Justin Cobb: Um, it's amazing.
• 26:57
  Justin Cobb: They really are devoted to that.
• 27:00
  Joseph M. Schwab: Is there, um, do you have any thoughts or plans on, um, uh, turning the H1 into, uh, sort of a smart implant or something that has some built in sensors so you can understand, um, maybe a little bit more in depth what the interface with the bone is like, what the load transfers are like, or any other, um, uh, any other changes to the
• 27:24
  Justin Cobb: So, I mean, it's a really interesting, it's a really interesting question.
• 27:27
  Justin Cobb: I, I feel the, um, because you are just putting a coating on the, on that femoral head, um.
• 27:36
  Justin Cobb: It behaves, it behaves very like a normal femur.
• 27:39
  Justin Cobb: It really does.
• 27:40
  Justin Cobb: Um, and I think it's a, I think the, I mean the thought of going through ethics and the, all the development pathway to get the strain gauges into something in the femoral head, I'm not up for that yet.
• 27:55
  Justin Cobb: I think when we've got, you know, we've only got seven and a half year results so
• 28:01
  Joseph M. Schwab: Yeah.
• 28:01
  Justin Cobb: and
• 28:01
  Joseph M. Schwab: Yeah.
• 28:02
  Justin Cobb: nobody thinks that's long term.
• 28:05
  Justin Cobb: I think if we absolutely know what the 10 and 15 year results are like, then I wouldn't feel bad about asking someone to do that.
• 28:12
  Justin Cobb: But for the moment, I think we, we, I wouldn't ask someone to have that done.
• 28:19
  Joseph M. Schwab: Thank you for joining me for this episode of the AHF Podcast.
• 28:23
  Joseph M. Schwab: Be sure to join me next week for part two of my conversation with Professor Justin Cobb.
• 28:29
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• 28:32
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• 28:37
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• 28:45
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• 29:00
  Joseph M. Schwab: New episodes of the AHF Podcast come out on Fridays.
• 29:05
  Joseph M. Schwab: I'm your host, Joe Schwab, reminding you to keep those hips happy and healthy.