BoneChat #66 - David KIRWAN introduced a simple solution to total hip dislocation.

Foreign.

So welcome to bone chat discussion 66 with David Kerwin, a retired orthopedic surgeon who's got two stars brewing. Dave and I met on LinkedIn and I immediately loved his original thinking, his entrepreneurial thinking. We talked live and then he pitched me on his new novel solution for total hip dislocation or to prevent it. And so I thought he'd be great on Bone Chat. And this may be more of a clinical discussion than a startup discussion, but I, I know everybody's going to enjoy it, so. And we got a bunch of MDs on, so the mic is yours, David.

Well, thanks tiger. Thanks so much for reaching out and I'm really honored to be invited on here because I've always enjoyed your posts. So this is a big day and I'm sorry for those of you who are not clinical or engineers or vice versa or marketing. I'm kind of a master of none of them, but I've done a lot of surgery, so I hope you like this. I wouldn't be bold enough to suggest we're going to completely eliminate dislocation, but if we can cut it down a lot, reduce the risk of it, that's what we're after. So is everyone hearing loud and clear and seeing loud and clear? Correct. So complications and revisions, they happen and impingement is one of them. And it's many sequelae which I don't have time to go through. But you know, neck notching, metal debris, plastic debris loosening, failure of poly, etc where and instability, dislocation instability and late periprosthetic fracture. So they're all very different complications. They all occur. But I believe we have a, a solution that will address all of those. But we'll see. So we've got assistive, assistive technologies out there that you've, I'm sure all heard about and mostly they're about modifying cup position or, or idealizing optimizing cup position. But you get down the bottom of that list and you've got navigation, which is great and all these things help a little bit and probably have reduced complications. But robots haven't fixed dislocation. They, they haven't fixed that list of complications I mentioned before. And that's actually very topical at the moment. So they haven't fixed it and neither will the former governor of California, I don't think. But we'll see. And if he doesn't, and it is controversial, maybe ZB's competitors will cop the assistance of a retired president or something to up their marketing ante a little bit but anyway, robots haven't fixed these complications. They all help component placement but none of them have improved the implants. Now this only got printed last night. If you see it literally came through last night or today your time. Doug Dennis. I'm sorry, Doug Padgett. And these guys have looked at robots in hip replacement. Now they're retrieval studies. They actually found that in good hands, surgeons did better than robots. How about that? I mean that is so contemporary. It was only published yesterday. Surgeons did better than robots or robotic arm assisted total hip replacement. So when you consider the investment that's gone into hip replacement. I'm sorry, into robotics. It's time to pause now. Robots and Tog and I you and I discussed this. Robots have been great. The mako was great for unis, no one can argue with that. But then that got kind of cross pollinated over the total knee replacements. Massive investment, enormously successful marketing campaign around the world. So the, the competitor companies all invested their billions to develop their robots as well. But that's, I'm talking knee replacement. No benefit has been shown with robots in total knee replacement in the hands of high volume surgeons. That's a fact. Definitely have. They confer a benefit in the hands of low volume surgeons. So they're very good trainer wheels for rookies but they don't actually help busy surgeons. And for hip replacement here apparently in this study anyway, really respected study, journal of Arthropasty published only yesterday actually no worse than no benefit. So spinal pelvic mechanics now some of the same. Doug Dennis here and Jim Pierpont and the Ops Coron Ops and they're best in class. They looked at it and wanted to see if cut position which is optimized with their software affects prosthetic position. Prosthetic or bone impingement after hip replacement. And they found that in good hands that improved from 61% down to 9%. That's prosthetic impingement. So it still occurs 10 called 10%. So 10 hip replacements still get prosthetic impingement in the hands of really good surgeons. And bone impingement, which is a different thing and you should expect it. Cup position does not affect it. There is no benefit. You put the cup in upside down, it will not change bony impingement because bony impingement occurs outside of the joint anyway. So spinal pelvic mechanics helps. It's very sophisticated, very clever. There's some super clever guys involved with it, but it is not the entire solution. So currently we can't make all hips impingement Free or stable, can we change the implants to improve the range of motion, to impingement and the intrinsic stability of every hip that we replace and in any position of that leg, affected leg, or for that matter, the spine, can we do that? Maybe we should try. So I'm going to assert that if we restore hip sovereignty, I believe we can do all those things. And if so, that's a holy grail. Now, 60 years or more now of progress since Charlie. We've tweaked and we've modified, we changed colors, coatings, you know, different heads, bearings, monoblock, etc, but ultimately those prostheses. And don't get me wrong, the actus insignia, I think is a beautiful stem. It's a great stem, but geometrically they haven't changed. They're identical. They're still not side specific. So impingement and stability have changed very little with all of that progress, with all that development, investment and improvement. So to restore sovereignty, we need more than another tweak to hip design. We need a substantive design change. I don't know if you guys have all seen that movie about Michael Jordan. I saw it about a year ago. Wonderful movie about his mum stepped in and said, no, I'm not going to accept $300,000. I want a slice of the action. I think he's received $42 billion in royalties since there's a great quote in that movie. The designer of the shoe says, the Air Jordan shoes says that human beings have been wearing footwear or shoes for 3,000 years. And in that time there's only ever been one substantive change in footwear design. And that was when they invented a different shoe for the left foot compared to the right. Great quote. I just jumped out of my chair and yeah, it's just so relevant to what I'm talking about today, as you'll see. So with a Karai type stem, it's a low osteotomy. You cut most of the neck off so that retro tilts compared to normal. It kind of lines up mostly with the shaft of the femur rather than the neck. And so you lose anterior femoral offset. With a neck retaining stem, you retain the neck and the native anti tilt, so you retain that anterior offset. So those two green lines there kind of represent the difference. And anterior stems, like the actor sits somewhere in between those two. The innovus optimus stem, type A, where you retain the neck, it's the same stem, but they're two very, very different operations. It retains the neck, therefore it retains the native anti Tilt of the proximal femur at type B, it weighs sandy tilt completely and it's no better than a karai. Prosthetic impingement will be no, no different as we'll see. So one normal anterior offset, the other one loses anterior offset. Now, anterior offset, we can get it by either rotating in the transverse plane or the sagittal plane. So you can either tilt the prosthesis forward or we can rotate it forward. But either way that's how we obtain that dimension. Anterior offset. There's two problems I'd ask you to consider, please. And I think they're the only real primary problems we need to look at because everything else stems from it and that is anterior bony impingement, bones impinging at the front of the hip, outside the hip and posterior prosthetic impingement. Now they occur opposite sides of the hip and different distances. Obviously this is not a replaced hip. But the posterior prosthetic impingement, that's as far from the centre of rotation that can occur. If you've got a 28 or a 32 millimeter bearing, it's even closer to the center of rotation that that problem occurs. So it might occur on the rim of the cup with the neck or it might occur on the liner. But all non side specific stems induce both of those problems. That's really important message. I can't prove that to you, but I think common sense will show you. So here's a look at the back of a right hip from above and you can see where the anterior bony impingement's occurring. Intertrochanteric line of femur abutting against the anterior inferior iliac spine of the pelvis outside of the joint. And there's a gap between the neck and the prosthesis there where anterior prosthetic impingement doesn't occur because bony impingement occurs first. And remember, anterior offset, sorry, increased anterior offset will mitigate anterior bone impeachment. So if you rotate that component forward or you tilt it forward, you'll bring the head forward, push the femur back and that'll enable the patient to get more flexion before ABI occurs. Posterior prosthetic impingement, as I said earlier, where the X is as far away as it may be, but it can be even close to the center of rotation. But the native femoral head is not centered or concentric with the neck. There is posterior offset of the head on the neck in most patients. So posterior prosthetic impingement causes component harm because it's so close to the joint. It just can't cause enough displacement, so it doesn't cause instability. It reduced by the posterior offset of the head on the neck. And it's increased by what is ubiquitous, posterior cup overhang with hemispherical cups. That's what all hip replacements do. We just accept that as normal because it's kind of prevents dislocation. So we say well it's a good thing. So anti offset, it's produced by anti tilt or anteversion. But anteversion causes posterior prosthetic impingement and anti tilt does not. And that's a key feature, anterior bony impingement. It can occur in three places. So A, B and C. Terrible good. And the best inter trochanteric line of the femur on the inferior spine. That's what causes dislocation. A little bit further out, proximal third of femur on the iliac wing. Physiological. No problem. It's protective. And best of all, if your knee hits your ribs, well, you're not going to dislocate your hip. But that will only occur, can only occur for lumbar spina is flexed. So if it's lordosed extended, it won't occur. And whichever happens first, one, two or three will present will win. It prevents the others happening. And hyperlordosis, the lumbar spine, it prevents the good one happening and it absolutely facilitates the bad one. And that's probably when a lot of dislocations occur. So just a schematic way of looking at it. Now there's two ways to restore anterior offsetting and the correct position, the center of rotation for the femur. Now if you look down the bottom right hand corner there, that's the leicest canter. And anti tilt, which is normal plus neutral version, no version will obtain it. The alternative, which is what we often do with hip replacement, especially a carotid, we lose our tilt, but we make up for it with extra anteversion, non physiological anteversion. That's what the Karai and the Exeter do. But it works and the success rate's fantastic. So why change it? This is why. If you put a cup there and that arrow, that curved arrow is there to represent posterior prosthetic impingement from a cup, it will impinge, it will occur. Occurs in 9% Doug Dennis says of all hips in good hands, even with OPS planning. So femoral anteversion induces a posterior prosthetic impingement risk. No question about it. So breaking news. Anteversion is a 60 year old mistake. If your Stem resides in the shaft, it obeys the shaft. If you like, you have to rotate antivert it to replicate the center of position. But if it resides in the neck, it will normally anti tilt with no need to rotate. So anterior bone impingement, posterior prosthetic impingement, big differences. And it's worth just running down the list. ABI occurs in flexion at the front of the joint. It's remote from the joint. It's an abutment phenomenon which causes displacement posterior instability. And if it happens aggressively, such as in a fall, it can cause periprosthetic fracture. That is actually what causes the most common hip fracture in the unreplaced elderly parotic population. They fall in the kitchen or the bathroom and they whack their femur with the inferior spine and cause an inter trochanteric fracture, the most common pattern. I believe that's the same mechanism for replaced hips. Why would it, why would it differ? And it's harmless to the components. It doesn't hurt them, but it can separate them. And it's caused by loss of anterior offset. It's obviously mitigated by a big posterior wall on an excessive cup version too. And this is the dilemma because posterior prosthetic impingement occurs at the back of the hip in extension, but it's within the joint, close to center rotation. It's intensely frictional because the hip only has two jobs, it can weight bear with the other. The only other thing it can do is rotate. So when impingement occurs there, it's frictional and it causes severe component damage, doesn't cause instability. Posterior prosthetic impingement is common. Doug Dennis said, In 10% of hips, how many anterior dislocations of the hip you see maybe one in your life as a surgeon. So it posterior prosthetic impingement does not cause anterior instability full stop. It's reduced by the posterior offset of the head on the neck, which is anatomical. And it's caused by stem and cup anteversion. So those two and that Doug Padgett paper doesn't really differentiate between those two. So people get in the habit of saying, oh, impingement causes instability. Well, wait a minute, bony impingement does. Prosthetic impingement does it. So it's important distinction. So proposed solution. And this is just one example, but I'm proposing a a neck residing stem, neck retaining stem side specific. So you've got to have left and right anterior offset of the native neck is retained. The posterior offset of the head on the neck is retained because we actually retro tilt the neck and that both anterior bony and posterior prosthetic impingement are reduced. And it's got a landing plate. Don't like the word collar because it's not a collar, it's a landing plate or a landing pad. Collars are what priests and dogs wear. It's a landing pad. And in this case our landing pad, which prevents subsidence and helps with stability, is also side specific. You don't want it hanging out the front like it does with an actus, because you can get impingement of your psoas complex and psoas tendon on that. So just schematically you can see how it resides in the neck and the very top of the femur. That retrotile on the neck allows more or replicates posterior offset of head on neck and it allows more extension to occur before PPI can occur. And the old ABG II which anti tilted and antiverted the neck, which is a great idea, it was a size specific hip or stem which failed for other reasons. But it would have induced posterior prosthetic impingement early. As soon as you extend hard or extend and externally rotate, you would have got PPI more with that than you would say a karai, et cetera. So this novel short stem, compared to other short stems, reduces ABI PPI taper problems, which I haven't really got time to go into, but it does subsidence periprosthetic fractures, it avoids diaphyseal fixation and proximal stress shielding and it's easy revision. And perhaps another thing that's worth throwing in there, I'd be happy to put that hip, that stem into an 80 year old osteoporotic female. There's no other stem I'm really happy to do that with. I mean an actus is okay, but cemented stems tend to go into elderly parotic ladies with type C bone. But I'd put that in there any day of the week. I wouldn't put many other stems. So that's kind of what it looks like. And with our CT modelling range of motion to impingement modelling, we got a total of extra 20 degrees range of movement before impingement occurred front and back. And that's what the stem looks like, obviously the right to mirror image of it. But 20 degrees range of movement, that's for me that's getting up there with the holy grail. Now just going back to that other picture, there's a gap between, that occurs between the front of the neck and the Cup When ABI occurs we can exploit that gap. We can modify neck shape so that as soon as API anterior prosthetic impingement occurs, it doesn't occur because the bone stops it happening. The bones get in the way. So we can reduce. We can exploit that gap. And we should. A dry hip will move 223 degrees. We can. If we make it side specific we don't get any extra movement. We just alter the arc of movement so we can balance those two arcs. Because remember, bones get in the way so that we can use it to exploit that gap. And down the bottom there just shows you a standard hip, a karai or an exeter, how it impinges. The chamfers on the neck are actually quite useless. But if you see this elliptical neck that's modified and rifled, et cetera, we can actually reduce the impingement. Even if it does occur, it's less aggressive. So we can reduce posterior prosthetic impingement as well. This stem or these stems is a family of will do both. So we get an extra 20 degrees range of movement. Remember that schematic they're just. The corri and the Exeter are a high risk of PPI actus. Not as bad as those two but in between. So side specific stems increase both flex and extension before impingement occurs will reduce multiple risks. And the extra 20 degrees range of motion enlarges the Leuvenix safe zone. Thank you.

Wow, that was a lot. I noticed you didn't even talk about offset or leg length, let's say irrelevant I guess.

Correct. You probably saw Tiger. There was a study just released. They looked at, I think it was 12 and a half thousand hips. They used AI to model them all and they looked at 12 different parameters and two of them were length and offset. And they found didn't affect dislocation. Trouble with. And it's. This is. It's a custom I suppose it's just a habit we're all into. Everyone ignores anterior offset. If that study they'd actually looked and there's not enough radiologists to do that with 12 and a half thousand x rays. But if they looked at anterior offset they would have shown an enormous correlation of strong negative correlation with dislocation. So yeah, they just looked at the wrong things. And a lot of the so called enabling technology ignores it as well. They'll look at length offset and anti version. They but you're looking at two apples and an orange when in fact there should be three apples and three oranges. There should be displacement and rotation in three independent planes, X, Y and Z. None of this fancy stuff looks at it and I think the engineers who work for those companies realize it. And they realize anterior offset is so bad with most stems we don't look at it. And it is with our models we see sort of sometimes you might only lose 5 mils of anterior offset, which is not going to matter. But other cases, 14 mils, that's a lot. So yeah, anterior offset is absolutely. It's a smaller dimension than the other two, but it's equally important.

So the industry has lost its way trying to reduce inventory. It sounds like nobody wants rights and lefts.

They started that way and I guess it's customary. And like everything, they're a bit like sheep, the big companies. You know, Stryker gets a robot for Total knee, so the others have all got to get a robot for Total Knee. Well, they copy each other. I mean everyone has an Exeter, everyone had a Karai. Now everyone. And this fascinates me that the actors and the insignia, I can't tell the difference between the two. So presumably there's no IP protection or else someone's licensed it to all the companies, I don't know. But it's not, it's not unique. And everyone's got a mid length stem. Now they've all gone. No one was ever really game to go to the short stems like the, the Optimus or the current mini hip. So they went halfway there, they went from Karai halfway to a short stem with a mid length stem, which is what we have with the Actus. It's customary though. It started with Charlie. Probably it was cost constraint back then. It's just been a custom ever since. And you know, they'll spend millions of dollars developing a new hip, but it'll start out right at the start of the project. No left and right because we got to save money.

Yeah, go ahead, Kyle.

Yeah, so I think there was a stem that Depew had back in the day maybe called the replica, that I think tried to do something a little bit like this. And one other thing I want to add is that your point about the navigation software, the Velos hip navigation doesn't even have a lateral view. It's like length and offset. And you are looking at pre op, post op or intra op, operative side or operative compared to contralateral. And there is no lateral view involved at all. So you wouldn't even be able to appreciate anything anterior offset if you wanted to. Now in the updated version of that software, the cuptomized thing is where the spinal Pelvic tilt comes into play then. Now they're looking at laterals as well, but they're just looking at the pelvis and whether that moves and it tries to give the AI and that tries to. Gives you an optimized cup position just based on how much mobility you get from the lumbar spine. So there's a lot you said there that fits in line with your skepticism that the rest of the industry is even paying attention to this.

That's great, Kyle, thank you. With all due respect, I mean, the HSS guys who started that, they're clever guys and they've done a lot of really good work and we've got some good, good points out of it. Like all these things, they've made a contribution. But I think it's probably barking up the wrong tree. If you restore the sovereignty of the hip itself, it's like changing a gearbox in a car. You change the gearbox, you change the gearbox. Whether the roof's high or low doesn't matter. Now, first of all, the spine, great example. You look at the spine on an AP picture of a patient, it's dead straight. You look at it on the sideline view, it's got lordosis and kyphosis everywhere. It's the squiggliest lie in the world. So an AP and lateral give you very, very different information. To not even look at the lateral when you've got a robot, for heaven's sake, the software to program a robot. That sounds dangerous. If your software doesn't look at the lateral view, your software is deficient. And you know the saying computers, they say crap in, crap out. Well, I'm afraid the robot's going to get. It's going to do its job beautifully. It'll do a really perfect job of a bad operation. And there's a wonderful old saying, surgery goes back over 100 years. It's better to do the right operation badly than the wrong operation. Well, and that's so true, because human beings can, you know, they have the capacity to heal up. But if you're planning it wrong because you're not even looking at the lateral, then doesn't matter how well your robot does it, it's still wrong. So if they don't look at all three dimensions, I'm afraid they're barking up the wrong tree. And spinal pelvic mechanics, by pelvic analysis, you got to see that for what it is. It is the art of compromising cut position to make up for a deficient stem. I mean, I think, yes, we've Learned that a hyperlordotic spine can throw the anterior inferior ilic spine down onto the, onto the proximal femur when you get out, usually when a female gets out of the chair. And that'll induce dislocation. And we've, we've learned from it that a fixed posterior rotation of pelvis if the hip, only if the hip can hyperextend, will cause posterior prosthetic impingement. But I think we're barking up the wrong tree by fiddling around with cup position, compromising cup position because the spine has got a curve in it or it's mobile or it's stiff or whatever. Yes. We've also learned that a stiff spine or a fused spine will make a hip dislocate that didn't before. And that's only because the hip becomes, it becomes forced to be hypermobile. Patients can't cope. They can't get out of a chair if they can't bend their spine without hyper mobilizing their hip. So that can induce a dislocation. But yeah, and thanks for your questions. Great. I mean they're good points.

I've got a question from Dr. Udi Purvel in Philadelphia. What does prep look like for the stem? How do you broach while maintaining anti tilt and not removing lots of bone along the way?

Well, it's a tapered stem for a start. And if you look at the trabecular pattern of the bone and the femur, it, it absolutely, it's the opposite to the cortical pattern. In other words, the cortex is thin in the head, thin, thin in the neck and gets thicker all the way down to the diaphysis. Well, the trabecular pattern is the absolute opposite of that. So the bony trabecularly in the head are very strong. Proximal neck, very strong. And the further you get down the neck, the weaker they become and you end up being in jelly. So you've just got marrow fat in the, at the metadiaphysical junction. It's only marrow fat. There's no trabecularly down that far. So it's a piece of cake. It's just if it was straight or curved, it would make no difference. So you start off with a, I use a rat tail file type as a starting oil. And you must, these things must be put in varus. Can't. They're designed in varus. They've got to be in varus if you, if the surgeon doesn't put them. Same with the mini hip and the innovis one, the optimus if the surgeon doesn't put these short stems in varus, guess what? Give them five minutes and the patient will. So they must sit in varus. So they sort of lay over and lay on the calca, which is good compressive load, the calca. And the tip of the stem just engages just to butts the lateral post lateral endocortex, the femur. So there is no difficulty rasping because the bone just gets softer, even in strong young men. The proximal femoral neck, trabecularly really strong. The distal femoral neck, it's already thinning out. Inferiorly, it's strong, but actually it's already out to jelly.

Any. Well, everybody's head spinning.

Well, look, it's. It's different. I mean, it's disruptive. And I wouldn't be here talking to experts from all over the world if I didn't believe in it. But, yeah, I think it's. It's disruptive and it's. After 65 years of convention and it's all paying great homage to Sir John Charnley to suddenly say, okay, well, we've been doing it, not doing it wrong, but we can do it better. Yeah, it's pretty disruptive. It's a bit. It's different.

Let's talk about your company. You obviously have a prototype design. Do you have. Have you done any cases? Are you looking for funding?

It's a huge question. We need about all day. But I've got license agreements with Signature Authority. Declan Brazil. A lot of you guys would know. And Declan's engineers have done a lot of the drawings for me. We've done. They've done some prototypes, we've done some 3D printing. We actually got some cases to do and got government authority to put it in, believe it or not. The last minute the hospital wet themselves and said, oh, no, you can't do that. It's new. And I said, well, that's why we've got government approval. It's new so that our federal government approved it. The hospital said, yeah, but you haven't done it before. And we said, no, that's why we got it. Anyway, they wouldn't let us do it, so we sort of have to change it. And what we're doing at the moment on this one is some cadaver stuff and we'll kind of model it up a bit and go back. And I've got a group of fantastic surgeons. Really, really clever, high profile, busy guys, super competent. They're all surgeons. I'd be happy to replace my hip if I Need it and they're interested. They want to start the clinical trial for us, but the regulatory stuff's just holding that up at the moment. So that's with Signature. There's several products, and I mean, we can do what we like. I don't know. Main company, I just work for myself. This is just research I do. And. But the manufacturing. Signature does it for us, but we could license it to other companies, sell it to other companies. I mean, I think it's disruptive enough that the traditional way of bringing things to market, where you just make a little tweak and you make a little trial and you run a few numbers, and then eventually, if it's really good, a big company buys it in a way that's. It would be sad because I think all hip replacements that are done should have this technology in it. In 10 years from now, people say, why on earth? What were we doing? What were we thinking? So once people are actually putting right and left hips in that work and get rid of all these or substantially get rid of all of those risks that we mentioned before, it will make sense. Well, it would be sad if those, those benefits were only provided to, say, Zimmer's patients, but not depews, et cetera. So I think it should be widely used and I hope it's disruptive enough that some smart people in those companies will say, hey, we want to talk. And I mean, I'm more interested in the science than the commercialization of it. I mean, I want it to be commercialized, but I'm more interested in the science and the human benefit than I am in the making a buck. You know what I mean?

Yeah, I'm sure it will be in Australia.

Yes, definitely. Yeah.

And, and do you. How many cases, what's. How big is the series to kind of prove the dislocation rates lower?

Oh, look, I don't know the answer to that. I mean, the, the computer modeling is probably more powerful because it's safe. I mean, we did, we took 10, 10 patients. We put four different hip stems into all of those patients. Now we, we did that on the computer. Now, if you do that in the lab, you can't even do the same operation on the same patient, but we did four different operations on each patient because we did it on the computer. Now, I know that's not real, but it's fantastic information because you could actually compare stems in one patient rather than 100 stems in 100 different patients. So that's the first thing. Computer modeling is very powerful, and the messages the message it gives us is just mind blowing. It's just so compelling that 20 degrees, about 12 degrees at the back and 10 at the front, or it depends how you, you can tweak it different ways. But in a regulatory sense, if we get 250 cases in here and all we have to do is have a lower, equal to or lower revision rate than comparable stems or other stems, then it will be allowed and then the companies that make it can get funding to do it. But the first 250 have to be put in for free. So it's kind of like a minimum size and mostly people go for 300 anyway just to exceed it. So if you've got 300 cases and the company has to provide it for nothing and that's a big deal, that's a big investment and the revision rate is lower than anything else, then it'll kick off. And then from there you've got to look at doing it in other countries. And there is another country that's very interesting doing a trial and if we got slowed up too much more with the regulatory hurdles in Australia, we'd probably go there and they'd put them in. Yeah, that happily put them in. But it's harder for me to control that. And we want to, you know, CT scan and plan all of them pre and post op. So we really want to run it as a proper trial. You don't want to just let people go and come back and say oh we tried it, didn't work or we tried it, it's great but it's not valid. It's got to be valid research, you know, verifiable.

Right, right. Seems like bilateral study would, would be interesting. Size specific on one side and generic on the other side.

Okay, well I, I did a lot of current mini hips years ago and I've used the Innovis, the Optimus when this with the previous company had it forget their name now before they, before Anova took it over and I used one of the Braun ones as well. So I've played around with quite a few different ones and these things subside. Short stems didn't take over the world and probably the reason the Actus model was embraced and they didn't go all the way to a neck neck only neck preserving stem is subsidence was a problem and you had to be really careful. One thing I found is if you did bilateral simultaneous the patients just can't protect and they need four weeks of protection post op otherwise they knock them around. They just got have enough boning. Growth, early boning, growth to occur to stabilize them. Otherwise there's this cyclic loading, inflection, extension, and there's abrasive destruction of bone from the porous coating, et cetera, and they'll subside, they'll sink, and that's a bad complication. So subsidence occurs if you do bilaterals because no one's got the upper limb strength to protect both hips, unless I want to sit in a wheelchair for four weeks, which they don't. So, yeah, bilateral is a bad thing to do. But this I probably would do bilateral because of the, the landing plate and the column, because the shape of the stability, et cetera. And the anova, which I showed those pictures of Professor Kushner's. The type A where you put it in the can you still, still see my screen?

Yes, yes.

Okay. The type A, which is this one where, where you retain the neck, you can only do that in a young patient with good bone. If you try doing that, it's got a quadrilateral cross section. You do that in an old person, it'll just cut out straight away. So that's for good bone in young people only. This stem, the TRC stem, the size specific one, I'd put that in an 80 year old female. No worries at all. No problem.

So Carl says Medacta is looking at this. Let me see if I can share or. Kel, why don't you share the screen? Can you do that?

It's probably the easiest for you to do it.

I'll do it.

I'll do it.

Hang on.

I think Dr. Cravel commented that this Minimax thing has been available.

Just.

I know there's, there's some other stems that have drifted into the space of doing something different proximally. I don't know that I've seen anybody doing anything different with the neck geometry itself, but it sounds like this Medacta device may be in the marketplace. It's got some anterior curvature to it in the proximal shape. Just, just wanted to throw it out there, in case you weren't aware, because understanding what you know, you know the game of this, right? Understanding what other people have tried and failed at can sometimes guide you. I cannot find the Depew ty replica stem. I think that was the one I found. It's 510k, but it doesn't have a link to it because it just. They didn't do that back in those days. It's a 510k from 2003. So that stem was doing Something again with the proximal geometry, but nothing. It still had the regular neck. Neck shape at the same reduced AP profile like you talked about. You called it a chamfer. That. That was in the. In the solution. Aml. That led into other stems. They had a whole family of stems that all had the same exact neck geometry. The replica one did as well. But that one, I think, is the one that had the slightly curved proximal geometry, so it would have a left and right.

Okay, well, I've seen the Mini Max, and I like it. It's not maybe as aggressive in terms of its adapting to normal anatomy side specificity, but, yeah, it's a good standard to start. He's just. Can you see.

See this natural fit on the screen?

Let's try to look at the other angle. Yeah, we can see it. We can see it.

Yeah, you gotta.

You gotta get. There you go. You gotta get down into the other angles. That lateral.

Yeah.

Okay.

I'm not seeing Carl's picture. Carl's just coming up with a name. No, no picture.

Oh, he's got. He's on a phone and. And a laptop. But you can't see my screen. It's a white.

We can see your screen. Yep.

Okay.

You can see. You can see target, but not Kyle.

Oh, that's weird. Here, I'm gonna set. I'm gonna. I'm gonna send this to you.

It's in the chat too.

Yeah. Oh, yeah, go to the chat. Can you find the chat button at the bottom?

Yeah, stop the share.

So go to Kyle's. Dacta may be trying something similar. And there's a link.

Huh? Yeah.

While you're pulling that up. While you're pulling that up, you also mentioned with the posterior impingement that the prominent cup is ubiquitous, which is 100% right. However, I have seen a couple of designs floating around out there where they have a notch, like a relief notch on one side of the cup. Maybe Surface might have been doing that, which somebody just picked up. Depew has licensing from them.

Just Justin Cobb's ceramic cups got the cutouts, the notches, and they're a great idea. The surf is the same as the adept. They're both adept. Okay. And they're. They're. They don't have cutouts, but they're subhemispherical. I think they're 163 or maybe 168° instead of 180. So they're not hemispherical cups. They're subhemispherical, which gives it a Bit of a relief as well. But all hip plans, I mean I did hundreds of OPS cases and every one of those plans came through with the engineers producing big posterior overhang. And prior to that with all the different ones with the. I've done anterior approach since 2012 but before that I was doing posterior approach and posterior overhanging is just normal. You just think, oh that's what happens. We accept it. It's a bit like accepting that a left sided hip, a left karai will go into a right hip, you know what I mean? Because they're the same. We just accept it because it's normal. But the cutouts In Justin Cobb's H1, I think it is his ceramic on ceramic cup and the subhypnospheric. Yeah, they're going to help it. They'll definitely help it.

Everybody's quiet. So how, how do we help Dr. Kirwan get this thing, you know, proven and out there are the, you, do you hold the patents?

Yeah, yeah, definitely.

Okay, so, but, so anybody could license the patents for, you know, for the.

Right agreement if, if anyone in the audience is really involved with high end people in the big companies, those people should talk. Like I'm happy to talk to them. They should talk to signature as well. Because I think if they wait until this gets proved up and then someone goes and buys an exclusive, they'll miss out. I think everyone should be taking an interest otherwise they'll be left behind. It's, it's going to. Well, I totally believe in it. It's going to make a difference. I mean I've just seen these problems 30 years in clinical, in private practice, clinical practice. I've seen the problems over and over again and believe this is the solution. And it's just, it blows your mind when you look at big companies, massive companies, billion dollar companies, developing navigation suites, developing software suites, now even robots and they're ignoring this stuff. I mean and the robotic platforms now have got. The striker one I know has impingement software in it, which is a great idea. What that will do is prove that impingement will occur and they'll say oh well you know, if you, if you patient mustn't flex over 130 degrees otherwise they'll impinge. Well you don't want that and you can't, you can't impose those things on patients. So sadly I think for the surgeons the software will also prove that oh you know, we planned 4021 and you did 3923. Therefore it's surgeon error. So I think the surgical planning on a lot of that software will protect the companies and expose the surgeon like pilot error. And that's a shame because it's not really the surgeon's fault. It's the, it's not the company's either, but it's a, it's a deficiency in our design. It's, it's out of date. It's over 60 years old, that design. So yes, it's a deficiency in our current implants. We need not robot, not AI. Not AI telling us how to spell orthopaedics either. Tiger.

Sorry about that.

No, it was good. It was good. But AI doesn't fix it. Robots don't fix it. We need an implant based solution to an implant induced problem. And one of the reasons it's happened for so long, a total hip proposal, is such a good operation. It's such a forgiving operation. There's so much wiggle room and the head to neck diameter ratio is what's protected us from prosthetic impingement. It doesn't make any difference for bony impingement, of course, but. So the head to neck diameter ratio doesn't give us stability, but it protects the hip from wrecking itself. And if you think about it, the first dual mobility hip, do you know what I reckon it was? The Charlie cemented hip was the first dm. What happened was that the stem hit the cup commonly, not in all of them because some of them luckily were put in beautifully beautiful position. But the stem hit the cup and eventually made it loose because we used to get taught that a charming stem would loosen after 20 years and the cup would loosen after eight years. Well, the reason for that is prosthetic impingement. Eventually push that cup to be loose, then the cup would move around inside the pelvis. So you had a dual mobility construct. The inner bearing was head inside poly and the outer bearing was ceramic coated poly inside bone wasn't very good. But guess what? They didn't dislocate. Really fascinating. They didn't dislocate. It was a DM construct.

Unintentional.

Yes. Yeah. Serendipitous maybe. No, they weren't good. I mean, they got, you know, they got terrible osteolysis and they sunk into the pelvis. They had big reconstruction problems. So I wouldn't call it serendipitous, but it was a phenomenon that we saw and probably didn't understand. So a Charney stem that's solid with a mobile cup, loose cup, with lots of osteolysis around it where the cement was grinding pelvic bone. That's a DM construct, not a very good one. We can see you now, Kyle.

So I have a quick little story that the surgeons on the call will probably appreciate about robotics and AI. So my daughter is an equestrian. She rides horses. And if you know anything about horses, like they have one of the greatest senses of what humans are feeling and, and whatever a human feels will project back through that horse. So anyway, my daughter's horse was kept right next to the head of surgery. And he, he would. And. And he was telling me about the residents. Sorry, he was telling me about the residents that he trained and had met. And all the years he had been doing this as the head of surgery in this major hospital, that he always knew that the surgeons who had ridden horses, because they exceeded the expectation and they were far more accurate surgeons than those who didn't. And he said it was. He really believed it was because by horseback riding all those years, they had a better sense and a feel of what was happening during surgery. That is one thing that AI cannot do and robotics can't do. They can put all the sensors in the world, but they can. It cannot feel. So it's one of these talents as we look at the evolution of AI that I think about this head of surgery and the residents program often, because how do you replace what you guys bring to the table at that other level? You can't.

That's great comment, Colleen. Thank you so much. And I totally agree, not just with the horse thing, but you think about a robot. The robots have been used to as marketing tools. They're marketing their bling, their sales tricks. Robot can't even examine a patient, let alone put them on the table, position them, adjust things and know how to position them for surgery. They can't prep and drape, they can't make the incision, they can't do the dissection. All they do is bring this thing in to tap the cup into place and say, oh, that's accurate. And then how that goes and someone else, people have got to sew it up and get the patient off the table, look after them post op. So if you look at the robot's contribution to that whole event, it is minuscule, it's trivial, but it's been pumped up as a marketing trick to influence referral patterns. And hospitals are using it to say we've got the best surgeons because they're robotic. It is total bs. And as a surgeon, I'm, I feel really strongly about it. I'm sure your friend, your colleague who sensed that the surgeons had done a lot of horseback riding, had a different sensitivity that other guys didn't have. That's really important. That's called acumen. It's judgment and robots don't have it. And AI doesn't have acumen and judgment either. I mean it's brilliant. Don't get me wrong. AI is brilliant, but I can't see AI ever. It'll be just like the robot. AI can tell the robot how to plan the surgery, how to put it in there, and it still won't be any good if the implant isn't improved. So AI is not the answer. Robot's not the answer.

Goes back to the implant. Yeah. So Yuri's got a comment and then em and all. Oh, Yuri just dropped off.

Thanks Colleen, that was great.

I was just gonna on the comment about robotics. Tiger. So my company has a genetic test that can identify patients who are predisposed to cobalt chrome hypersensitivity. And we've just exited a contract, just contacted Smith and Nephew and exited a contract with them. Been working with them for a couple of years and they've had trouble, you know, being able to identify patients and say to a surgeon, you know, this is the sort of patient who should get, you know, a particular implant. And the idea was, you know, companion diagnostic, etc. And they've just gone 100% with backing robotics, trying to get robotics in, trying to get consumables in and just seem to have totally moved away from the idea of how do you identify the patient that's appropriate for, you know, a non cobalt chroma or a non titanium based implant. It's just been fascinating to watch the new CEO just throw his entire weight behind the robotics elements and the consumables element and just, you know, not worry about other patient factors.

Which company was that was that was Smith and Nephew, was it? Yeah. They lost so much market share to Stryker. Stryker did a great job with, with Mako with Total Knee. I'm not saying they did it better. They just got surgeons to put 2030 year old designed knee replacements in. They didn't do any improvement to the prosthesis, but they did a great job in marketing. They had hospitals telling communities they had primary care practitioners were told that robots are better. So if Smith and Nephew don't do a robot, they lose. ZB did it or they lose. J and J Depew did it or they lose. So yeah, it's a massive game and it's so, it's profound. The implications of it. It's such a shame. You've got, you've got a test there that could prevent people having revisions or really painful uncomfortable knee. And yeah, in some cases multiple revisions, multiple procedures for chasing infection that doesn't exist. I mean it's a nightmare, you know, and we can test for that.

We can test for that now. It's, it's a no brainer. Yeah, it's crazy. So, so Yudi asked a question in the text. So does this design put an end to all spinal pelvic planning? That is the rage right now, yes. Does it become a question of matching patients native anatomy of both cup and stem side with this kind of implant? And does anything change with the spine pathology?

Great question and the answer is yes and no. I think they're barking up the wrong tree. Look at the hip, get the sovereignty of the hip. Correct. If you're a 4020 man or I think, look, they've made a good contribution, but it's not the answer. So the spinal pelvic analysis isn't necessary if you get the prosthesis right. So if 4020 is correct, maybe it's 4015, then the stems will match it in any hip, in any patient in any position. Position of the femur, in any position of the spine. If you think about it, if you lengthen the femoral shaft or you shorten the femoral shaft, say by 150 mil 6 inches, what difference does that make to the hip? None. Okay, so if you then do that osteotomy where you're either lengthening or shortening the femur instead, just rotate it, rotate it 90 degrees if you like, so the foot's pointing sideways, inwards or outwards, I don't mind. What difference does that make to the hip? None. So we have all this rubbish about. And by the way, normal version is supposed to be minus 19 to plus 33 degrees. Rubbish, it's not. You're describing variation of human anatomy with respect to one, the obliquity of the joint line, the knee, because the knee joint line is the, say 10 degrees oblique, then the retrocondylar line of the femur is 10 degrees tilted as well. So if it's various, then it's going to be internally rotated, et cetera. So of that so called normal variation of hip version, it's not hip version at all. 10 degrees of it comes from the knee and that's 10 degrees either way. So let's call that 20 degrees. The other thing, there's this variation in Terms of the spine spiral deformity of the rifling of the femoral shaft and most of that variation, that minus 19 to plus 33 degrees, that 50 degree range of hip version, it's not true. There's a 50 degree range of variation below the Lesser Tricander, all outside the hip. And none of that matters to the hip. Restore the sovereignty of the hip. So by the same argument, I don't care what the spine looks like, it can rotate 180 degrees, it's not going to affect the hip. It's wrong. It's wrong. Now it's made a contribution. The science has made a contribution. There's some super clever guys and some of the calculations are actually helpful for standard non site specific stems. But if you go for a size specific stem, you don't need any of that stuff. And quite frankly I find it too difficult to understand. I mean it's just so complex and, and it's clever. Don't get me wrong. It's clever. It's helped people do bad hip stems better, no doubt about that. But if you improve the stem, you don't need it.

It's fascinating. Well, this is. Yeah, people are dropping off at the end of the hour. This is great, David, I really appreciate it. I think, I think we all got CME credits today too. We usually talk about startups and we're talking deep clinical. It makes so much sense. So we're pulling for you. Does your company, do you have a company name?

No, we just go through Signature Orthopedics. They're licensed to do it all. I'm just a designer and I work for them. I just license the technology to them and we kind of co develop stuff.

Okay, well we're pulling.

I'm the mouthpiece.

Makes. I love you. You're you.

You've.

You're saying the emperor has no clothes and it makes sense.

I hadn't thought of it that way, but yeah, it's. It's disruptive.

Yeah, it's disruptive. I'm just worried the big companies have too much inventory out there to, to, you know, obsolete their products. But it'll take time.

The one, the one who gets the first mover advantage will make the others all. Sorry. They worried about the inventory. I mean and we're talking about maybe changing, in some cases changing the implants, but not even changing the instruments. So I don't, I mean, let's face it, they've all got right and left sided knee replacement components. So what's the big deal about having them in the. In the stem of the hip. You don't even need it in the cup. So it's. It's a. It's flawed logic to say, oh, we've got to save money or we've got inventory or we can't change. Because as soon as one of it does it, one of them does it. The others will all get scared and run right behind them and chase them.

And do it as well, like they're sheep. Like you said, they'll follow. Well, thanks.

20 degrees range of movement will make a difference. Yeah.

Yeah, it sounds like it. Thanks. Thanks a lot. This has been terrific. Yeah.

Thank you, everybody, for.

Really interesting.

Thank you all. Thank you. Thanks, Carly. Good day.