I'm Claire Moran. I'm a small animal, soft tissue surgeon. But like I said, we are going to be talking a little bit today about more of an orthocentric topic. It's probably my favorite orthocentric topic and that is juvenile bone disease, primarily canine. You know, I am kind of a crazy cat lady, so I did have to sprinkle just a little bit of cat in at the end, but primarily we're going to be focusing on what we see in juvenile dogs today. So we'll go ahead and get started. 

Our first disease process that we're going to talk about is kind of what I think of as the number one, the like, the most classic juvenile disease, juvenile bone disease and that is panosteitis. So panosteitis is a disease process that we tend to see most commonly in large and giant breed dogs. You know, German Shepherds are kind of the poster child, but we see it in, other large and giant breed dogs as well. Generally, it presents as a chronic shifting leg lameness. And the reason for that shifting leg lameness is because, as the name would imply, pan means all, and so multiple limbs are frequently affected for these guys. And so usually what the owner will come in with is they'll bring the dog and they'll say, yeah, you know, the past few weeks I've noticed sometimes he seems to be limping and sometimes it seems like it's a forelimb, sometimes it seems like it's a hindlimb. It maybe left, it maybe right. And so often the history is kind of, changing a little bit, because, again, multiple limbs can be affected. When you evaluate the dog, usually what you'll find is that they are a happy, bouncy, pretty normal puppy, maybe a little bit lame on one or more limbs and often when you start kind of getting in there doing your orthopedic exam, if you're pressing along the diaphysis of long bones, the affected long bones, they'll often be a little bit tender on that palpation. The severity can vary. You know, usually puppy orthopedic exams are kind of challenging to evaluate, you know, are they really paying for this just being a wiggly puppy? But usually they are, you know, consistently at least a little bit reactive to long bone palpation. So that's generally the most significant thing that we'll find on our physical exam. We don't know exactly why this disease process occurs. You know, the fact that there are some breed predispositions suggests that there might be some underlying hereditary effects. But potentially there could also be dietary effects. You know, we just don't entirely know. But the best theory that we have right now is that, these animals, for whatever reason, develop, essentially an intra osseous compartment syndrome. So the pressures within their bones, are higher than they should be, and that can cause an ischemic necrosis of the normal bone marrow inhabitants. So that's what we think is, you know, going on we don't know exactly what kicks it off, but that's our theory as to why they are presenting, with this pain and this lameness. Essentially parts of their bone marrow, are starting to die off and so are becoming necrotic. There's inflammation. They're painful because of that. 

This is an excellent NAVLE® disease process to know about because it has very classic radiographic findings. So if you look at the image over on the right there, those yellow areas are pointing out the lesions that we see in panosteitis. Essentially we would describe them as multifocal to coalescing regions of mineral opacity within the medullary canal. Remember that the medullary canal should normally look like this area. You know, it has a lot of that component. And so normally it should be, relatively lucent in comparison to the, much denser cortices. And so what we'll see in panosteitis is that they have these relatively discreet mineral opaque lesions present, usually in multiple locations along their diaphysis. These are usually centered around the nutrient foramen, which for most long bones is going to be kind of towards the center of the bone. The ulna and I do have a picture of pano in an ulna coming up. And the ulna remember the nutrient foramen comes in quite a bit more proximal in the bone and so don't be thrown off by that. It is a little bit of a different appearance. But for the most part, we'll see these, these thumbprint lesions or fingerprint lesions, they're often called, within the kind of mid diaphyseal region of the bone. It is important to note that the radiographic changes do lag behind clinical signs a little bit. And so if you have an owner who brings in the dog, you know, early in the disease process, you may take a radiograph and see nothing because these changes, like I said don't show up right away. And so generally in those cases, you know, if we have a young limping large breed dog whose painful on diaphyseal palpation, even if my radiographs are pretty normal, I'm probably just going to treat presumptively for panosteitis. But if you're, you know, unsure or you're looking to kind of check off that final question, you can get the owner back in in a couple of weeks and re-radiograph and likely at that point, assuming that it is panosteitis, you'll be able to identify those fingerprint lesions at that point. 

The good news is that treatment is pretty easy. It's, you know, this is a self-limiting disease process. And so even if we did absolutely nothing, eventually the dog would get better on its own. So, so that's really nice. However, we can make things more comfortable for them in the meantime, they are usually a little bit painful, a little bit lame. And so usually what we'll do is we'll start them on an analgesic. I often will use an NSAID, as long as they don't have any other contraindications for it. And then we'll recommend that they maybe take it easy for a few weeks. You know, generally these guys are not going to be able to make anything worse by being active, but if they're pounding around doing crazy puppy things on bones that are already a little painful, you know, that can kind of exacerbate their discomfort. And so usually we'll say, you know, keep them a little quiet for a few weeks, give them some carprofen or whatever your NSAID of choice is and generally they will improve nicely with that. This is a disease process that has a very good prognosis. You know, most of these animals, like I said, are fairly feeling fairly good when they come in. They're just a little bit ouchy. And so if we can get their pain under control, most of them, like I said, are going to be just fine and the disease process will resolve on its own. It is good to warn owners that this is something that, we can see recurrent episodes, especially if they're relatively young, when they have their first flare up. So it is something where they might need to come back and get a couple courses of, you know, that NSAID along the way. But for the most part, they tend to, do very well. And generally, once they reach skeletal maturity, they'll stop having these recurrent episodes. The one exception to that rule is German Shepherds. If you haven't already figured it out, when in doubt, if there's an orthopedic question asking you about a a breed predisposition, put German Shepherd. They do tend to get recurrent episodes of panosteitis into skeletal maturity, sometimes as late as five years has been reported. So if you do see a German shepherd with this disease process, maybe give the owners a heads up that it could be something we're dealing with a little bit longer than normal. And then like I mentioned, the ulna, the, the nutrient foramen comes in a little more proximal in that bone. And so this image over here on the right, does show what panosteitis looks like in the ulna. So it's a little bit closer to the elbow. And but again, same thing. You can see these, these thumbprint lesions present within the diaphysis of the bone. 

So we'll go ahead and move on now to hypertrophic osteodystrophy. I think of hypertrophic osteodystrophy as like the sister syndrome to panosteitis, because it tends to affect the same group of dogs. Again, it's going to be most common in our large and giant breed dogs. Weimaraners are the poster child for this disease process. But again, we can see it in, you know, Great Danes, in Labradors, in any of those large and giant breed dogs. The presentation is a little bit different. We mentioned that panosteitis tends to cause mid-diaphyseal pain on palpation. When these guys come in, they tend to be more painful around the metaphysis of affected bones. So a little bit closer to the joints, they'll often have discomfort swelling around that area. And it could be pretty severe. You know, I mentioned that most of the pano dogs come in and they're bouncing off the walls and they're being, you know, silly little puppies. And they generally feel pretty good. They're just a little bit sore on, you know, limb palpation. A lot of times the HOD dog's hypertrophic osteodystrophy dogs, they tend to be more acutely ill, more severely painful. And so these guys are more, more likely to be presented fairly acutely in the disease process rather than the pano dogs where the owner says, yeah, you know, the past few weeks I've noticed that he's been a little bit lame. So they can be quite severely painful in this case. And then we also much more likely in HOD than in panosteitis we see that the bony changes are also accompanied by signs of systemic illness. So there's a lot of inflammation associated with the bony lesions in these cases. And so that can sometimes manifest as systemic illness. These guys are not wanting to eat or drink. They can get dehydrated. They can also commonly, be having diarrhea. They're lethargic. Sometimes they're febrile. And so those things are much more common to see with HOD than with panosteitis. Sometimes these changes can be so severe and the inflammation, from these, these lesions in their bones are so, associated with so much inflammation that this can actually result in, the development of SIRS in a severe inflammatory, systemic inflammatory response. And that can actually be life threatening in some of these patients, certainly not in all of them. You know, those patients are by far the minority. But it is important to recognize that sometimes these animals can be quite severely ill, even, you know, even though that is atypical for most of our juvenile bone diseases. Once again, the etiology is uncertain. There's been a lot of proposed mechanisms for why these lesions develop. But we're unfortunately not entirely sure at this point, why these animals develop these bony changes. 

Which specific bony changes we see. Once again, we've got some very classic radiographic findings. So again, really good, options for, for board style questions. Again, we have this sort of very classic radiographic finding of the double physis sign. So if you look at the image, to the left here, this femur is a really nice example. You can see this animals normal physis making the sort of V right here, this relatively lucent region. Dividing the metaphysis from the epiphysis. This is the animal's actual lysis and then adjacent to that located in the metaphysis, you can see that there is this, kind of poorly defined area of lysis surrounded by slightly more sclerotic, slightly denser bone. And so that's running parallel to this physis. And so I guess to some people it kind of looks like a second additional physis. And so hence the name double physis sign. Obviously it looks quite different from the actual physis, no one would mistake that for the animal's true physis, but it is implying that there is an area of lucency adjacent to the true physis. Alright? You can see the same changes down here on the tibia. Once again, we've got the normal tibial physis present, kind of where I'm outlining with my mouse. And then down below that we can see these, lytic region, present within the metaphysis. So this is often what we will see in an acute case. We can see, however, that this is another situation where these animals may have recurrent episodes or sometimes these guys come in with a little bit more of a chronic history, usually the ones who are less severely affected. And in those guys, in addition to the lytic change in the metaphysis, we can also see periostial new bone formation. And so over here on the right sided image, you can see these arrows are indicating these regions of periosteal new bone formation. This animal still certainly has the double physis sign as well. You can see it. I'm tracing it here adjacent to the normal tibial physis. But this has clearly been going on, you know, long enough, for the animal to also develop these signs of periosteal reaction. Once again, radiographic signs can lag a little bit behind clinical signs. So if you are unable to confirm your your suspected diagnosis on the initial presentation, you can consider re-radiograph at a later date. 

Once again, treatment is primarily supportive. This is also a self-limiting disease process. But remember that these animals are often more acutely ill than the panosteitis dogs. The pano dogs are generally good to go home, take their NSAID, and go home. The HOD dogs are more likely if they are, you know, vomiting, not eating, having diarrhea, you know, febrile, they are more likely to need more intensive supportive care. You know, these are young puppies very often. And so if they're not eating, having diarrhea, they can very easily get dehydrated, they can become hypoglycemic, they can get quite a bit sicker. And so, you know, if they are, systemically ill, they might need to be hospitalized, require I.V. fluid therapy. They can also be quite significantly painful. And so they, you know, not be might not be enough just an anti-inflammatory. They might need opioid administration, you know, other injectable pain medications, they might need nutritional support if they're persistently not eating, support for their blood glucose. We do generally give these guys anti-inflammatories, and there's some data that suggests that steroids may actually be more effective than NSAIDs. But one thing I do want to mention that in these, you know, severely sick and ill, you know, puppies, one of the big differentials that we have for something that causes lytic change to the bone like this is a hematogenous osteomyelitis.  Fortunately, that's quite rare in small animal patients, but it is something that can look similar radiographically and so the idea of giving a steroid to an animal who, who it could but you know, who is certainly acting septic, who is certainly, you know, very ill. And these signs could be related to an underlying infectious process rather than just an inflammatory, process is a little bit scary. So generally in those cases, if we are going to treat with steroids, we would probably pair it with antibiotics to be on the safe side, as well as aspirating the lesion and getting a culture of the bone just in case this is not an HOD and is instead a hematogenous osteomyelitis. For the animals who are less severely ill, alternatively, you could consider NSAIDs. Again, you do just want to be careful, in those animals that are having a lot of, vomiting, diarrhea that are at risk for becoming dehydrated, giving those guys an NSAID could be an additional insult to their kidneys. So these cases can be a little bit more of a balancing act than most of the panosteitis cases are. 

That said, you know, I don't want to scare anyone too much. Most of these dogs do great. This is something where the prognosis is generally good. Most animals respond nicely to their supportive care. It's really just those ones that are truly, strongly, systemically ill, where we worry about them having a poorer prognosis. And believe it or not, you know, I have seen some animals actually go into multi-organ failure or die or need to be euthanized as a result of HOD. So the ones that are really sick can be really sick. But again, those are not the majority by any means. Most of these guys are going to have a good prognosis. Once again, we can see recurrence. I mentioned that before that this is something that can come back, especially if they're quite young at the time that they have their first flare up. Recurrence, recurrent episodes are expected to resolve as they reach skeletal maturity. We don't expect to see it anymore after that. But like I mentioned, some of these animals will have periosteal new bone formation that develops, as part of some of these, these lesions. And in some cases, especially if they're having like episode after episode after episode, that periosteal reaction can actually bridge the physis, so it can go all the way across from the metaphysis all the way over to the epiphysis. And if that happens, that can result in growth disturbance or angular limb deformities. That's what we're seeing in this picture here. This dog has an angular deformity of its antebrachium. And so in some cases if that has occurred that could be something that the animal needs surgery for once it reaches skeletal maturity to correct that angulation.

So like I said, I think of pano and HOD as being sister syndromes. I kind of mentally like put them together because they affect the same group of dogs, those young, large breed dogs. But they do have some differences with their physical exam findings and with their radiographic findings, of course. And so, I do think that it's helpful just to lay out the differences in a little chart. So I did that here for you guys. Alright.