Dr. Derek Fox, DVM, PhD, DACVS joins Dr. Andy Roark to talk all things angular limb deformities and why they’re about so much more than crooked-legged Bassets. In this episode, Dr. Fox shares how limb malalignment is often the root of conditions like patellar luxation and elbow dysplasia, what general practitioners should be watching for in growing puppies, and how to set realistic expectations with pet owners when surgery might be needed. From practical recheck tips to why simple photos can make all the difference, this one’s packed with orthopedic gems. Gang, let’s get into this episode.
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ABOUT OUR GUEST
Derek B. Fox, DVM, PhD, DACVS
Dr. Fox is a Professor of Small Animal Orthopedic Surgery and Chief of the Small Animal Surgery Service at the University of Missouri’s Veterinary Health Center. He graduated veterinary school from Michigan State University in 1998, after which he completed an internship, surgical residency and PhD at the University of Missouri, eventually becoming faculty in 2004. He teaches courses and lectures on a variety of topics regarding small animal orthopedic surgery both nationally and internationally. Dr. Fox’s special research interest is in limb alignment and deformity correction. He has authored or co-authored 50 peer reviewed papers, 8 text book chapters and numerous abstracts. He pioneered the adaptation and use of the Center of Rotation of Angulation methodology for the quantification and pre-surgical planning of angular limb deformities in dogs. He is a member of the American College of Veterinary Surgeons, Veterinary Orthopedic Society and AO.
EPISODE TRANSCRIPT
Dr. Andy Roark: Welcome everybody to the Cone of Shame Veterinary Podcast. I am your host. Dr. Andy Roark I am here today with a legend. Dr Derek Fox he’s talking about his passion, which is angular limb deformities, and I know people are like Andy I’m not sawing bone. It’s like, trust me. This stuff is fascinating and we talked a lot about What is general practitioner gonna be doing with this?
What do I need to do to set expectations for pet owners? How do I need to be monitoring and following up on cases that I think might need corrective surgery or that have gotten corrective surgery. Anyway, we get into all of that stuff. It’s just absolutely jam packed with pearls. This is a really interesting episode and it’s on a subject that I just, most of us don’t hear a lot about, but we see these dogs with feet on sideways coming in the door, I want to make sure I’m doing what I can to take care of these pets when I see them. So anyway, that’s what we’re doing today. It’s really good. Let’s get into this episode.
Kelsey Beth Carpenter: This is your show. We’re glad you’re here. We want to help you in your veterinary career. Welcome to the Cone of Shame with Dr. Andy Roark.
Dr. Andy Roark: Welcome to the podcast, Dr. Derek Fox. How are you?
Dr. Derek Fox: I’m very well. Thank you so much for having me. It’s a real honor.
Dr. Andy Roark: Oh man, it’s so funny to hear you say that. I’m like you sir, are above this podcast. I have to say, I appreciate you making time for it.
Dr. Derek Fox: Absolutely.
Dr. Andy Roark: You, for those who don’t know you, you are professor of small animal orthopedic surgery and chief of the small animal surgery service at the University of Missouri’s VA Veterinary Health Center. You are one of the absolute leaders in angular limb deformity and malalignment and an orthopedic surgeon by training. I I’m thrilled to have you on today because I want to talk to you , about sort of your passion as I have heard it in limb malalignment.
And so when we first started to talk about, about limb malalignment you said to me that, we don’t tend to think about things like patellar luxation in terms of being a malalignment or potentially hip dysplasia or some types of hip dysplasia as malalignment issues. And I think that’s very true.
And so when I think about you know, limb deformities or malalignment, I think about the Bassett Hounds that have their feet, turned around and twisted out to the side. And so let me just start at the, at the, at the top here and say, high level overview, talk to me a little bit about, limb malalignment and what it looks like in clinical practice.
Dr. Derek Fox: That’s a great question. And when I started, you know, when I was doing my residency, you know, many, many years ago, that’s what we thought of when we, when you would hear the term angular limb deformity, you thought of the basset hound that has his feet on quote unquote sideways. And I literally have had patients referred to me, where the referring veterinarian will call and they’ll say, Doc, I’m not lying to you. This dog’s got his feet on backwards and, and the dog will show up. And certainly, you know, it’s pretty, it’s pretty maligned. But as I have studied this topic over the years, what I have learned is there are so many different orthopedic conditions that at their roots can also be attributed to diseases of malalignment of the limb.
And as you just mentioned, patella luxation is a great example. And, you know, when I was a young resident in 99, in 2000, you know, we thought the patella was the problem with the, I mean, just by the name, that’s a patella must be the problem. And what we’ve learned now over the past 20 years is The patella is never the problem.
The problem is the femur is malaligned or the tibia , may be malaligned, and most of our correction strategies are aimed at realigning the femur in the tibia. Another great example that has been investigated now in great depth is elbow dysplasia and a very specific kind of elbow dysplasia, which is coronary disease, and there’s a subcategory of that can be called medial compartment syndrome.
Where the dogs will develop severe osteoarthritis in the medial compartment of their elbow, where overlying the medial coronoid. And there are many investigators now who think that this may be as a result of malalignment of the humerus to the radius and the ulna, which can put excessive force and pressure on that.
So, the topic of limb alignment really goes beyond the classic deformity, okay, of the Bassett. And it really does apply now to all of orthopedics. And we are now looking at, old conditions through new eyes and studying their limb alignment to find out if that is the, is it the root source of that secondary disease entity.
Dr. Andy Roark: Okay. Help me to be a better doctor what should be causing me to start thinking about limb alignment abnormalities , that I’m not thinking about it now. Like what is walking through my door that I’m looking at that I’m laying hands on and limb alignment abnormality is not popping into my mind. Help me to spot this earlier.
Dr. Derek Fox: I think it probably is beneficial to kind of maybe lump them into different categories, right? Because let’s, let’s just take the basset, right? You know, you got a dog that’s coming, maybe it’s a year old bass that they seem to be the classic and they’re just starting to develop a lameness.
And sure enough, there’s a symmetry between the left and the right forelimb and that right forelimb is really, really, really angulated. That’s a classic, you know, pretty quick. observation that, wow, I think this dog’s got, you know, severe limb malalignment of its forelimb. This is attributable probably to growth disturbance at the level of its growth plates, and there are a lot of reasons why Bassets get these specifically.
And that’s one kind of category. But I think just as we’ve spoken about, you know, there are other categories of diseases that we didn’t use to classically think of as malalignment. Again, think about the patella laxation. Say you’ve got, you know, a year and a half old Yorkshire Terrier and he is, you know, walking, extremely bow-legged , in the rear limbs, and he is struggling.
He’s struggling to, you know, jump up on things. He’s, he is struggling to have any jumping ability. And you palpate that and you’re like, wow, these patellas are, out and I’m unable to put them back in. So that’s what we call a grade four patellar luxation. And I can guarantee you grade three and four patellar luxations, those dogs have some kind of malalignment of their femur and their tibia.
And so that’s not probably, especially if you’re in general practice and you feel pretty comfortable, correcting patella luxations as many general practitioners are and they do a great job. A grade four patella luxation is not the same as a grade two patella luxation, meaning that it’s going to require something above and beyond maybe more simple or straightforward surgical corrections that we’ve all learned in vet school, like a wedge recession or a tibial tuberosity transposition.
A grade four patella luxation is probably going to need some kind of realignment of its, femur or tibia that it goes above and beyond. And if we don’t address that malalignment, the recurrence of that patella luxation, that risk gets much, much higher.
Dr. Andy Roark: When we start talking about, these types of conditions, I gotta be honest with you, Derek, like, intervention seems It’s scary to me. You know what I mean? Like, this is not a, this is, even a soft tissue surgery, you go, okay, I can get my hands in there, I can do that.
We’re really talking about orthopedic intervention in a significant way, especially if we’re talking about a young dog, and so I’m talking to the pet owner, I’m going, well, this is kind of what we’re looking at, and I’m worried that we’re progressing in this direction.
Dr. Derek Fox: Right.
Dr. Andy Roark: And, the intervention is for me to cut the bone and, you know, and reposition it and put it back. How do you start to look at these cases? So I’m gonna, I’m gonna go all the way around to kind of how to elegantly sort of balance these things out. But one, do in your mind, do you feel like intervention is a pretty significant step? And then how do you start to think about us? I don’t want to say how do you start to think about categorizing these patients as, this is a dog that I would strongly recommend intervention.
This is a dog where we might see an issue, but I don’t know. Help me to balance those
Dr. Derek Fox: Yeah. That’s a really good question. And obviously so many of or the conditions that involve malalignment, they’re starting as juveniles, right? Because the puppies are, you know, there’s some maybe growth disturbance of the physis and so the, you know, the limb is starting to become out of line and it’s getting more severe as the animal matures.
And this is one of the, it’s a really great question because this is one of the trickiest aspects of dealing with any of these as like, okay, when do I intervene? How do I intervene? And it really is so dependent on the condition that is that the animals presenting with and its severity.
Okay. And how much and what is the age of the patient? Many dogs that present with a malalignment, say, at 8 or 9 months of age. We may just say, Hey, let’s wait and watch. Okay. Because the dog, most of the dogs longitudinal bone growth is going to be done by 10 or 10 and a half months of age.
So we’re just going to tap the brakes and we’re going to reassess, you know, and in some dogs that present, you know, very young at four or five months, and I can think of a classic example or some Great Danes that, you know, will present to me what their forelimbs and they’re starting to develop some distal and the owner’s very concerned. The referring veterinarian may be very concerned because it definitely seems to be beyond what we would consider just normal variance and alignment. know, there are different strategies. One might say, Hey, let’s intervene right now.
Let’s do something right now. But I’ve seen many of those dogs outgrow it. And so. It really is on a case by case basis. It depends kind of on which bone is affected, what is the age of the dog, and what is the severity, because a Great Dane that is very symmetrical and both of its forelimbs are starting to develop a little bit of valgus at say four, four and a half, five months of age, I’m probably going to sit and watch and wait and recheck them monthly.
If it’s a four, let’s say it’s a five month old Border Collie who’s very straight in the left forelimb, but now is really valgus on the right side. I’m probably going to pursue something like we probably have premature closure of one of the distal feces of the radius of the ulna. Let’s get rads.
And if it’s drifting that bad at this young of age, I’m probably going to intervene to some degree. Yeah.
Dr. Andy Roark: Are you going to, are you going to sort of wait for growth plates and stuff to close before you start to intervene? So I always feel like when I see this four month old dog and I’m seeing this abnormality, I I don’t know if I picked this up. I don’t know if I just imagined this, but I immediately feel this ticking clock of we need to intervene on this as early, you know, early as this development is happening.
And what I’m hearing from you is it doesn’t sound like, like racing to do something is as valuable maybe as I thought it was.
Dr. Derek Fox: Well, you know, we all have that urge, right? And it’s especially bad in surgeons too much. So is that we think that, Oh, I’m going to be this animal’s best friend because I’m going to get in there and cut it and, and intervene. And, you know, one of the things I’ve learned over the many years of doing this is sometimes it is best to wait and watch.
And it, and so when would you know, when would that, situation arise for me. It would really depend again on the severity of it. And some dogs you just see at four or five months of age and they’ve got, so let’s stay on the topic of the anabrachium. They’ve got so much carpal valgus that it’s like, okay, there’s no way this is going to auto correct.
I think we might need to intervene. And one of the things that we’ll do is obviously just, you know, simply take radiographs and look and radiographically, do I still see a physis that has got some degree of opening to it? Or is it already shut down? Do I see no, you know, radio lucency in that physis, meaning that physis is shut down and there’s no opportunity to pull this out of the nosedive, in which case I’m going to intervene.
But like that Great Dane example I gave you, it’s a dog. Great Dane comes in about that age. He’s bilaterally kind of symmetrical. He’s just going a little bit valgus. If I take radiographs and his physis are still wide open, I might give that, I might tap the brakes and give that dog an opportunity to see if he can’t correct on his own.
Dr. Andy Roark: When you talk about seeing , these dogs come in and you say, you know, I might wait and I’ll, I’ll just sort of recheck them. how are you rechecking this? Are you monitoring degrees rotation? What does that look like when you say, I’m going to see this dog back I want to see if it’s getting worse.
How do you know?
Dr. Derek Fox: Great question. So how does one, you know, wait and watch on any kind of, you know, developing anger deformity? There are several ways is the first most basic is just through gross examination. And it’s it can be as simple as taking a goniometer and just laying it on. Let’s say we’re dealing with antebrachium.
How much is the meta? How much are the metacarpals valgus with respect to the antebrachium? We can measure that grossly, you know, in, in inexpensively with a goniometer, just laying a goniometer down one arm of the goniometer down the radius and the only the other down the metacarpals measuring that angle.
Recording it in our, recording it in the medical record, checking that monthly. And if we really want to see, you know, radiographically how the physis are looking, are they staying open or are they shutting down that? Yeah, just taking radiographs. And for some of these guys, I’ll radiograph them monthly.
Dr. Andy Roark: When you were looking at these dogs and you’re kind of deciding what you’re going to how you’re going to intervene. How has your approach evolved over the last, or 15 years? What, what are you looking at differently? What are you, how are you approaching these differently than you did kind of earlier in your career when you were, when you were less experienced or when we knew sort of less, less about the conditions?
Dr. Derek Fox: Well, I was definitely more aggressive surgically as a younger surgeon because that’s how I was trained and taught. So if you saw, a dog that had developing radial valgus the kind of the classic premature closure of the distal ulnar physis that all your listeners will, you know, be, you know, well, well educated and, man, we would, I would fire in and do an ulnar ostectomy to try to release that tension on the ulna, the bowstring effect and like, oh, that radius will now auto correct.
And so we did a lot of those. What I’ve learned over the years is yeah, those ulnar ostectomies. They don’t really, they’re not quite as effective as we once thought they were. We see relatively few, it may prevent it from getting worse, but relatively few radius then go ahead and auto correct. There is a, there is definitely a need for that in improving elbow congruity, so that’s a whole other topic.
But I have, over the years, I have become a little bit more conservative and less aggressive surgically early on. All right. But I’ve also just become, I think, better at making that call of, wow, this is so severe at such a young age. If we don’t intervene, we’re going to lose, we’re going to lose the carpus or the elbow would get dramatically worse.
And then instead of just trying to accomplish anything through an ulnar ostectomy, I’ll go in and do a correction. And, and so many, a puppy has come in with a severely angulated forelimb that is developing already. And it’s, you know, it’s quite asymmetric and I’ll radiograph it and the physis are shutting down already by five months of age.
Okay. And ulnar osteotomy is not going to cut it. So it’s kind of the go big or go home. If you’re going to go in and do something, let’s, let’s get it right. And so for an animal like that, what we would do is put on a hinged external fixator or an ilizarov frame and then gradually pull it back around.
Yeah and retrain that, forelimb.
Dr. Andy Roark: When you look at these and you think oh man, that’s we’re gonna have to do something that that’s going to be unacceptable. Does there does that just come with experience or there’s certain flags that you see waving where you go when I see these things that’s when I that’s when I really get motivated immediately.
Dr. Derek Fox: There are certain flags, some of it is subjective to be sure some of it is experience because I’ve been doing this for so long, but there are other things if I see radiographically and I would always radiograph a dog if they’ve got left to right asymmetry, meaning, you know, one of these is really starting to drift.
That’s the first marker. This isn’t just the dog’s confirmation. It’s not just a great dane that, you know, maybe a little turned out in the feet. So if I see asymmetry, that to me automatically is a warning bell, like, okay, the physis on, on, on the right side or the left side, something has happened there.
Let’s get radiographs. Another big flag for me is if I’m losing elbow congruity, if the ulna is not matching up with the radius and the elbow, we need to intervene and do something. We need to try to save that elbow by optimizing the congruity. That is a red flag for, yeah, we surgically, we need to do something.
And then the severity of the lameness and the angulation. And this is where it gets a little subjective. But if owners are telling me, yeah, he’s consistently lame on this, he’s only a 5, 6 month old dog, but he’s really lame. And if that asymmetry, you know, is pretty pronounced. If you walk in the room and say, wow, I can just across the room, I can see a difference between the left and the right.
That’s going to be something and he’s concurrently lame. That’s probably gonna prompt me to want to do something. And the last red flag I can think of is if I take an x ray in that patient and the physis is shut down, either the distal ulna or part of the distal radial physis growth. But there’s not, there’s no growth that’s going to overcome that.
It’s spot welded itself down. We probably need to intervene.
Dr. Andy Roark: Yeah, that makes sense if you could huddle together the general practitioners of the world and say all right guys when you see these coming in this is what I think This is the small thing the first step that I would love to see GP’s doing more of in general practice, right? I’m not asking you to become an orthopedic surgeon but when you see this, this is something that I think would benefit the patients.
I think it would benefit you know, the orthopedists you refer to. What is this, like, the fairly subtle ask of, Hey, just maybe make sure you do this.
Dr. Derek Fox: Excellent question. So the first thing, and some of these things are so, you know, easily done is photograph the animal, you know from stray and and and again, it’s different for different limbs and different conditions, right? But let’s stick with the forelimb and you’ve got a puppy that you think has got a developing angulation malalignment of its forelimb the classic right photograph it have you know, the dog sit there and get a, you know, straight cranial to caudal or front to back, you know, just photograph a bow and get both forelimbs in that photograph at the same time.
It’s a great thing to put into your medical records so that you can visually watch this animal over time. It’s objective. Okay. And it’s a snapshot in time and you can do that again in three weeks or four weeks. Puppies change so quickly. So just getting a photograph is. is fantastic. And then the next thing I would say is that orthogonal radiographs of the antebrachium, okay, including both the carpus and the elbow, because it’s, not just the malalignment of the radius that we’re worried about.
We’re really worried about what is happening in the joints, right? What is happening in that carpus? And then maybe more importantly, what is helping in that or what is going on in that elbow? Does he have incongruity along with this deformity or is the elbow really, you know, look great? Because that is a major deciding factor if I’m going to intervene very young or if I’m going to just tap the brakes and wait and see how he develops.
Because if we got a lot of elbow incongruity at five months, we need to get in there and do something. If the elbow is fine but he’s starting to develop a little valgance. We’re probably safe to wait and watch that month by month and maybe pull the trigger later on. But that, so again, taking a photograph of that animal so that we can get in a, you know, a really nice visual between the left and the right.
That’s something you could put in your own medical record. And then the orthogonal radiographs, including both the carpus and the
Dr. Andy Roark: elbow.
Yeah, that that’s that sounds fantastic. This is easy to do. It totally makes sense. Yeah, I like that a lot. What expectations should I be setting in pet owners minds when they come in and they’ve got their let’s say they’ve got the six to eight, 10 month old, you know, young dog and I’m seeing pretty significant limb abnormality and there’s there’s some it’s affecting the gate and I say, Look, I think we have to do something about this and they’re going to say to me, What does that mean, Dr. Roark, what are the healthy expectations to put into their mind about? One is just outcome long term. What is the prognosis if they take action? And then just general recovery time. And I don’t know. It just, I don’t want to say cost necessarily, an idea of like, what are they getting into and how do I communicate that to them?
Dr. Derek Fox: Yeah, these are all just the perfect questions and the questions that I answer day in and day out for my own clientele you know, what they’re getting, it was one of the first most basic questions that I get from, you know, any client is, Hey, is there a brace? Is there something I can do? Is there a medicine that I can do to revive these growth plates and correct this?
And unfortunately there’s not, you know, the, the only thing that we can really do is some kind of surgical intervention. And with that surgical intervention, that is, you know, it’s pretty invasive, unfortunately, for most of these cases, you know, straightening a metal line bone means corrective osteotomies, and it can be more than one corrective osteotomy, especially when you look at the chondrostrophic bone.
reads to answer, to address a further an earlier question, they get a very specific kind of deformity in which they actually have multiple deformities, not just a single deformity. So these can be quite invasive procedures that, you know, require an invasive, you know, operation to get in there and make corrective osteotomies.
And either through external fixation or internal fixation with a bone plate and screws, you know, we’re going to be straightening the bone, realigning the joints. Then the next thing that they’re going to have to expect is the aftercare can be sometimes quite challenging. So they’re looking at any young dog two to three months post op.
No running, no jumping, no playing of stairs. The dog may be in a splint for six to eight weeks afterwards, depending if we do internal fixation, lots of rechecks, you know, at the vet to have those bandages changed and in longterm, you know, we’ve yet to do really good longterm evaluation, objective outcome measures to learn how much return of function they get.
We know we improve them significantly, but I am, Very comfortable saying none of these dogs we get back to 100 percent normal. Okay, there’s always a ramification of having a malaligned limb as a young animal. And usually that comes from loss of range of motion in the carpus and or some osteoarthritis in the carpus or the elbow.
And that is frequently what the rate limiting
Dr. Andy Roark: No, that, that totally makes sense. I was going to ask you about that and sort of say, you know, if the owner says to me, okay, well, he might not run the same, but he’s going to be comfortable, right? You kind of have to prep him and say, you know, there could be osteoarthritis here. You know, it, it, it might not be completely pain free, but we’re going to do our best.
Okay.
Dr. Derek Fox: Yeah. And, and in nearly all the cases that I deal with with that have severe distal radial ulnar malalignment from a premature closure of the distal ulnar physis, they lose a lot of range of motion in their carpus. And we don’t yet know what the full ramifications are of that long term. Like, Hey, how much is this really, you know, limiting them?
But to, you know, to preserve pet level function and comfort, it is quite amazing. I have clients who’s 13 years post op will send me video of their dog and the dogs are running and having a great time. And you know, we know that we, this is, you know, one of the orthopedic procedures we do where we can dramatically improve the quality of life of an animal just through, you know, limb alignment, reestablishing
Dr. Andy Roark: If you’ve got somebody who’s fascinated by this, and they, they, I think these cases are so interesting, you know, I’ve, I’ve always, I’ve always thought angular limb abnormalities were just really, really interesting. Do you have a favorite resource for people to go to? So short of going to a residency, what do you like for people who really geek out about this?
Dr. Derek Fox: Yeah, great question. So obviously we’ve we’ve written a lot of papers on this topic over the years and anyone if they really want to nerd out on this can hit PubMed and and you could search my name and and you’re going to find a lot of papers. We’ve written several textbook chapters about this.
We’re kind of in the planning phase of writing an entire dedicated textbook on this topic. It’s a massive undertaking. But we also teach courses in limb alignment correction, and I’m teaching, I think three courses this, this year through AO, also through ACVS. The ACVS course will be in June and Fort Collins.
We’re teaching an AO course on this topic in Glendale, Arizona in October. I’m also going to Italy to teach this internationally in March. and these courses are dedicated to the forelimb or to the rear limb. So if you have, of the cases that you’re seeing them are pelvic limb, you know, we’ve got a pelvic limb, a three day course in that.
So there are lots of opportunities to learn more about this for sure.
Dr. Andy Roark: That’s fantastic. I’ll put some links in the show notes for people who are interested in learning more. Dr. Derek Fox, thank you so much for being here. I really appreciate your time. Thanks for sharing. Guys, thanks for tuning in to listen, everybody. Take care of yourselves.
And that’s what I got. Guys, thanks for being here. Thanks to Dr. Derek Fox for being here and sharing his years of knowledge and experience.
Gang, I hope you took something away from this. I know I did. It’s just stuff like this just makes me, it makes me want to do better. I’m going to be taking pictures of my patients when I start to say hey We need to document this foot is starting to turn out in a way I don’t like and I’m hoping it’s going to come back but let’s go ahead and get some good photos of this and again, I’ve had a couple episodes recently.
I talked to Dr. Fox I talked to Dr. Donnell Hanson the dentist recently and they’re both just like hey take photos of what you’re seeing. And I just go, man, I think a lot of us really need to step their game up. I need to step my game up with photos and putting them into the records.
I take photos of my patients and keep them on my cell phone, which is not. Not the medical standard that it should be. And so anyway just great advice. It’s a practical stuff that I’m pledging here right now to, to do better and start capturing that stuff and really putting in the records and being intentional about it.
So I’m making that pledge to you guys right now today. Anyway, gang, take care of yourselves. Be well, I’ll talk to you later on.
