Well, hi, I'm Doctor Megan Williams. I'm an associate professor of equine surgery at Oklahoma State University. I've been here, for about 8 years now, coming from a few years in private practise in our residency before that at, at Michigan State University.
And today, I'm gonna talk about, case selection specifically for palmar digital neurectomy. And, and how we can maybe better serve our patients by, by more carefully selecting what horses are and are not good candidates for this procedure. So, first of all, I'll do an overview of why, traditionally, palmar digital neurectomy has been performed in the horse, the commonly used methods for performing the surgery, what the reported success rates are, how long it tends to last, and then I'll talk about The potential things that can go wrong, so short and long-term complications, and then the ways that we can improve, our case selection to hopefully avoid at least the more severe complications, and then I have some case examples that I'll run through at the end.
So before we perform palmar digital neurectomy, these are kind of the steps that have usually or hopefully been at least discussed with the client, hopefully performed at least the majority of these things. So, we diagnose our horse with heel pain based on a lameness examination, diagnostic blocking, and, imaging thereafter. And then we talk about What we can do to treat the horse.
So generally, my approach, for most clinical cases, at least lameness related cases, is to start with less and then gradually you know, move towards more aggressive options depending on the goals and, and timeline of the, of the client, of course, and the diagnosis of the horse. But for navicular cases, you know, the least aggressive thing that we could do, for a horse that's blocked just with heel pain, generally speaking, is rest. Just give them some time off, plus or minus some pain medications.
So a lot of times that's gonna be non-steroidal anti-inflammatory drugs, butbanamine, maybe ferrocoxib. Something like that. A lot of times, if it hasn't been tried already, we'll talk about some therapeutic shoeing, and trimming.
So many of these horses have long toes and low heels. Maybe we trim their toes, pull that breakover point back, get them in a, a shoe with a, a rolled toe to further pull that breakover back, maybe some pads, things like that, potentially a wedge if their hoof pasture and angle is, is really inappropriate. That might be something we try as well.
And then, we can talk about injections after that, it'll be a little bit more invasive. So a lot of times we'll start with a coffin joint injection. A lot of times there's a component of coffin joint arthritis, and or we know that those injections will diffuse to the bursa, and it's a less, invasive injection or treatment than, than going for the navicular bursa right off the start.
So, usually, I would do cough and joints first and then maybe bursa if that's not, sufficiently effective. And for either of those, injections, we might put corticosteroid in, plus or minus some hyaluronic acid or an alternative, for injections that's, that's becoming more and more, the way that a lot of veterinarians want to go for injections in general would be some type of regenerative therapy, which is a whole separate topic, entirely. And then, In some cases, depending on how the workup goes and how the horse blocks, we also could do those same types of injections in the, in the digital flexor tendon sheath.
So, could put corticosteroid, HA or, or regenerative therapies in the tendon sheath as well with the thought process that maybe we've diagnosed, some deep flexor tendon pathology within the sheath, but, but in the distal limb region and the horse might benefit from treatment there. So that would be a, a potential treatment option as well. We may opt for some bisphosphonates and these navicular, navicular pain horses.
Sometimes we'll do shock wave therapy over the navicular region, certainly provides some, some analgesic benefit. If nothing else. And then for, for select cases, at least, navicular burstoscopy is still, a viable treatment option.
So, specifically, that would be helpful for horses that have deep digital flexor tendon lesions that we can debride, maybe break down adhesions and the Smith and Wright 2012 paper, reported that 61% of those horses would return to work sound, with 42% of them going back at their previous level of work. So that might be an alternative that we would discuss with our clients also, depending on their goals and their budget. Palmar digital neurectomy, has been performed in the horse since the late 1700s.
We've been doing it for a long time. The most common indication is navicular disease, heel or heel pain. Generally speaking, that's not responsive to medical therapies and shoeing changes.
So other indications, maybe just for select cases, might be a horse that's got Side bone, that, that is blocking out to that specific sign to the palmar digital nerve, degenerative joint disease of the coffin joint is gonna be less, likely to respond at least fully to palmar digital neurectomy because, unless you're doing a really high neurectomy, which we really should not do, you're, you're not gonna get all of the coffin joint, desensitised with a PD neurectomy, but maybe in select cases, that might help. Improved quality of life at least. And then soft tissue injuries within the hoof capsule potentially, would be an indication for penine neurectomy as well.
It's important to recognise that this is a palliative treatment. So we are not treating the disease itself, we're treating the symptom of the disease, which is the lameness. It can be effective for as little as 1 year or even less in some cases and as long as 5 years, but it's not a permanent solution.
And I think it's important that clients understand that if, if this is the route that they're going to go. So, techniques for performing PD neurectomy, chemical or physical irritant injection, ethyl alcohol has been used for this, formaldehyde as well, some other alternatives. Most traditionally, it would be a surgical neurectomy, so sharp surgical transsection via the guillotine technique where we Move a segment, a section of the nerve, and that can either be done via a single incision, or we can do two incisions with a pull-through technique.
So one more proximally placed, one more distally placed, and then pulling that section of nerve, through the distal incision. And then we can also do sharp transection of the nerve, but follow that up with additional treatment of the nerve stumps. So the idea behind those treatments would be to reduce the likelihood of, of the horse developing a painful neuroma post-surgery, which can happen in some cases, and these are just some of the ways that that's been pursued in the past.
So capping those cut ends of the nerve, electro coagulation of them, freezing them with liquid nitrogen. Injecting neurotoxin, around those stumps as well, have all been tried with variable rates of success. Procedurally, before surgery, it's gonna be really important that the horse has had a thorough lameness examination with substantial improvement with a palmar digital nerve block.
So, obviously, if the horse doesn't respond favourably to a palmar digital nerve block, it makes little sense to cut the palmar digital nerve, as a treatment for the horse. So we want to make sure that they respond well to that. And then, it's always a point of interest to me, at least.
Does the, does the lameness swap to the opposite forelimbs? So when you block out, say, a left front lameness to a PD nerve block, does the horse become right front lame? So horses with disease of the navicular bones specifically, that, that tends to fairly commonly be a, a bilateral disease, whereas if you just think about the odds if a horse is, is severely lame and doesn't swap, it makes me More concerned that the horse has a soft tissue lesion in the foot rather than navicular bone degenerate.
Disease process just because they're less likely, though not impossible to tear tendons, for example, in both foot, but, there are certainly exceptions to every rule, so that's just kind of something that pops into my head when I'm looking at those horses and they don't swap as well, maybe this horse has a tendon lesion, we should look at that a little closer. So, not always. I prefer to give them at least 7 days between the time that I do my diagnostic blocking and the time that I perform the surgery, and that is simply because you do get a bit of an inflammatory response in the tissues from, your lidocaine or carbocaine that you use for the block, and I wanna do everything I can to reduce the likelihood that my horse is gonna get.
A neuroma after the surgery. So I would see the horse, do the lameness exam, block the horse, do my additional diagnostics, but then wait at least a week, if neurectomy is what we elect to actually do the procedure. And then if the horse blocks, I'm gonna want to get some radiographs of those feet, especially if neurectomy is a possibility for the horse.
So I want to look at the navicular bone itself and see what kind of changes are present, within the bone itself and then kind of characterise those as mild, moderate, or severe. And then I'm definitely radiographically looking out for any mineralization in the soft tissues. Specifically, we will, we will recognise mineralization in the area of the deep digital flexor tendon that might indicate a prior, and now more chronic in nature, but, significant tear of the deep digital flexor tendon.
So those are things that we would want to do prior to surgery. After surgery, it's important to keep compressive bandages over the surgical sites for a good 6 weeks is my preference. And again, this is all aimed at reducing, Likelihood of developing a neuroma and then Along with that stall rest with controlled hand walking for 6 weeks as well and just for the same reason, not even so much for incisional healing, as to just keep that area quiet while everything heals up.
When it comes to the radiographs that we're going to take pre-op, positioning and preparation of the foot are critical for accurate assessment, so, to take quality radiographs, ideally, we would remove the shoes, clean up the sole of that foot. Some people like to pack the foot, some people don't. But if you, if you clean up the foot, get all the dirt and debris off and out of the foot, because depending on where you live, there may be more or less mineral in the soil, but that can affect the quality of radiographs that you get.
So clean them up really nicely and then The standard views that gonna, we're gonna want to get, you could always get additional obliques and things, but the standard views are gonna be a standing lateral, a standing DP, a dorsal proximal to palmarro distal oblique, and then a palmeral 45 proximal to palmarro distal oblique, which we would call the navicular skyline. So this, there's a, there's a really nice article by Sue Dyson, from about 2008. So it's a little bit older paper now, but it has a really nice description of all the different radiographic abnormalities that we can recognise just with X-rays, on the navicular bone of the horse.
So I've highlighted the things that she points out in the videos with some, some radiographs from case examples. Of some of the things that we're looking for when we're trying to characterise navicular disease radiographically. So we'll see irregularities or, or radiolucencies along the distal border of our navicular bone.
So this top example is going to have maybe less severe changes than the one over here to the right, but both of these horses have some radiolucencies and irregularities along the distal border of the navicular bone. So those we see fairly commonly. Generally, the larger the number and maybe the larger the lesions, the more likely they are to be clinically significant.
In some cases, we'll recognise distal border fragments like the one highlighted here. This particular image is from that paper. These can be a little bit harder to detect, in some cases without an MRI, but we can see them radiographically.
These are going to be more commonly seen in lame horses versus sound, so like less likely to be an incidental finding, more likely to be a legitimate cause of clinical disease. And those can be related to mineralization of that distal seismoid and impar ligament. It can be a proper fracture of the distal border of the bone.
And that's gonna be if there's a radial lucency that corresponds to it at the medial or lateral angle, like in this case, there's a little bit of a, like you can see where, where the fragment came from, that would be more suggestive of a fragment versus just mineralization, or sometimes it it would be a manifestation of enthusiapay at the origin of that distal sasmoidian impar ligament. If we see cyst-like lesions like the one, in this image, those are always, clinically significant. Something that I, I, I hadn't in previous years paid a lot of attention to that I think this paper nicely points out is, abnormalities and flexor cortex thickness that we see on the lateral radiographic view.
So the cortex on this horse is thicker than, it should normally be. And then distal or proximal extension of that flexor cortex. So when they have this kind of little hook on the distal aspect of the navicular bone, that would be considered abnormal as well.
Then some other things, pretty classically, we'll talk about changes in corticomedullary definitions. So, the way I explain it to clients and vet students is you, you want there to be a nice crisp outer cortical border to the navicular bone, a nice crisp white line on this navicular skyline view, particularly. and then the marrow medullary cavity in the middle should be, more radiolucent, with, with kind of a crisp border in between.
So horses that have degenerative change of the navicular bone, that starts to, that line starts to kind of fuzz over time. And in this horse, it's, it's basically absent. The bone is so sclerotic, that there's really no, virtually no definition between the cortical bone and the medullary bone.
We'll sometimes see enthesophytes, so where the collateral smoidian ligament of the navicular bone inserts on the navicular bone, they'll get kind of little horns or hooks, that you can see on your navicular DP view and on your standing DP view. On the corners of, of your navicular bone, and sometimes we see those in, in pre-purchase exams, for example, in horses that aren't even clinically lame, and, and you can question the clinical significance of them, but certainly larger ones, are more likely to be associated with clinical lameness. Flexor cortex lucencies, usually we'll see on that navicular skyline view at the sagittal ridge.
So this one's, sorry, this one's a sagittal ridge lesion or just kind of add axial to it. Those are indicative of erosion of the fibrocartilage and potentially deep flexor tendon adhesions. You have to be a little careful to not overinterpret packing artefact, or gas, opacities in the frog of your foot for, a true flexor cortex lucency.
So a lot of times if I see those, I'll unpack, repack the foot, and, and take another image just to try to verify that it's real. But certainly those can have clinical significance as well. And then in rare cases, we'll diagnose a proper navicular bone fracture.
Usually, those are parasagittal in nature. So those are some of the things that she highlights from that paper, and I think it's really helpful to kind of review, to think about how much information we can glean just from radiographs of our patients. But, there's some other things that we can do that I think help us to better characterise whether or not a horse is a good candidate for palmar digital neurectomy once we've done all those other things.
So, you know, in an ideal ivory tower world, we would do our, our lameness workup, our radiographs, and we would ultrasound the poster and navicular region. And we would get an MRI to really get a good look at the soft tissue, structures of the foot. CT is an alternative option if you, if you don't have access to MRI that I'll talk about just briefly, as well.
But again, in a perfect world, we would be able to do all of these things before we, before we did a palmar digital neurectomy on a horse. If all of our other treatments that I've talked about up to this point. Are not effective for the patient.
So, ultrasound-wise, you could scan the palm or pastern region, that's gonna be really helpful, especially in horses that block maybe partially to a PD and then the rest of the way, to an a axial nerve block or, have tendon sheath effusion or maybe in some cases, I've actually blocked those horses to the tendon sheath. In select cases, that, that area can be imaged with a linear probe. And you can get some pretty good images.
Now, ultrasounding the navicular bursa and the deep digital flexor tendon, I would say when we're starting to try to look deeper, into the heel bulb and, kind of down into the hoof capsule region around the navicular bursa, that is a difficult thing to do well. I think it's, it's just more technological or more technically, sorry, advanced. And requires some practise.
You also need a microconvex probe to get a really good look just cause you can't get good contact in that region, with a traditional linear probe. And it does help to have the limb held up and flexed. So, a difficult thing to do well, but it is possible to get, to ultrasound that region of the horse, and get some useful information.
So this is another paper that I think can be helpful if that's something that you wanna practise more. Just a tutorial of how to ultrasound. That region of the horse, and diagnose injuries to the deep flexor tendon, and associated areas.
So you can identify thickening of your, of your tendon lobes, changes to the dorsal aspect of the tendon, potentially tearing, mineralization, and, and potentially adhesions as well, or at least increase your index of suspicion that the horse has got adhesions in that region. And then we can also identify, injuries to a thickening of the distal digital annular ligament via this ultrasound technique. MRI is gonna be.
Kind of the standard for diagnosing soft tissue lesions in the hoof capsule. So if I could MRI every horse that I see for foot pain, I'd be a very happy person just because I think it gives us so much more information about what's really going on in that hoof capsule because oftentimes, it's not just navicular bone changes, there are other things going on as well. And these are some of the potential things that we can see if we're able to do an MRI of that horse's foot.
So, pathology of the deep digital flexor tendon is gonna be the most common one. So, in this image, we can see, there's fluid signal here in the tendon where the horse has got a dorsal margin tear, of the lobe of the deep digital flexor tendon. So that would be a fairly classic example.
MRI is also particularly useful for identifying navicular bone edoema. So sometimes horses that don't have a lot of bony changes radiographically, you'll put them through the MRI and And they've got more change in that bone than you realise radiographically, and that manifests in the form of, of edoema that we see on our MRI. Also, other things outside of, of navicular regions.
So, injuries to the soft tissue structures around it. So the collateral sesamoid and ligament that we talked about, maybe recognising anesthesophytes associated with that radiographically, but in, in more acute stages, we might recognise injury to or thickening of that ligament. They can injure their impar ligament, distal border fragments of the navicular bone that maybe were too subtle to detect radiographically.
We might see on our MRI. Collateral ligament injuries of the coffin joint can be diagnosed, potentially on ultrasound, but definitely, on, on MRI as well. And then a, a better look at those distal digital annular ligament injuries than maybe what we can, detect on ultrasound.
And then I did mention, I touched a little bit on CT. So for us, at OSU we've, we've got a niceCT machine. We, we're not able to MRI horses, with the MRI machine that we have for the small animals.
So, you know, what's the potential application of CT? The other benefit maybe to CT is that it's less expensive, not inexpensive, but less expensive, and it's a faster scan. So some potential benefits there.
And certainly, we can get some good information. On it, maybe not, quite as sensitive in diagnosing soft tissue, injuries within the hoof capsule as our MRI is gonna be, but still potentially a helpful diag diagnostic tool. So there's a couple of papers more in more recent years that have looked at, CT or contrast enhanced CT in this case, to evaluate the deep flexor tendon in the foot and then compare that, postmortem, to macroscopic and histologic findings.
So in this case, they looked at 23 limbs and horses that had foot lameness. They did plain CT and then contrast enhanced CT and then all these horses had postmortems with histopath to compare that to what they found on CT. They had a 93% sensitivity of contrast enhanced CT for diagnosing the flexor tendon lesions in the foot, so not too bad.
They did have 3 false negatives and 3 false positives, and certainly the location of the lesions, the position of that lesion within the tendon, and the extent of the lesions, were consistent with previous reports for lesions seen on MRI. So it was, they noted, the least accurate or less accurate at least, when the lesions were right adjacent to the navicular bone, than when they were more distant from that. Location.
So this is one, these images are all from that paper and that's one particular horse looking at pre and post-contrast, highlighting this deep flexor lesion that then you can see on the gross postmortem images and histologic images as well. So certainly, you know, some potential application there. This is just a case report where they used CT to diagnose bilateral forelimb tendon pathology in a horse that was only unilaterally lame.
So radiographically, this particular horse had just some mild pastoral way and a little enthesophyte on the proximal aspect of the navicular bone. Pre-contrast, they were able to identify these little dorsal border deep flexor lesions. As well as some thickening of, of that collateral sesamoid ligament of the navicular bone.
And then on their contrast enhanced CT, they found that the horse also had deep flexor tendon lesions, that enhanced with contrast on the right. So they, they also appreciated some distal seismoid and impar ligament desmitis near the insertion. So, All that to say, just to highlight that we can actually diagnose even, even soft tissue lesions on CT, in, in some cases.
So, I think my preference ultimately would still be MRI, especially for a pre-neurectomy horse, just so that I can detect, especially around the area of the navicular bone where maybe that's a weakness for this diagnostic technique, some more subtle lesions, but maybe in a case where MRI is not an option for the client either financially or, You know, access wise, geographically, then, then this might be a good way to go. So, we've kind of talked through all the diagnostic and treatment approaches for heel pain, horses, horses that block to the foot in general. We talked a little bit about the different ways to perform neurectomy on a horse.
This is just the way that I the way that I was taught in my residency and the way that I still do them. So instead of the, I do a guillotine technique, I don't do any capping, or treatment of the nerve stumps after cutting. I just do a guillotine technique and I do the single incision.
Rather than the double incision. This is an image from the equine surgery textbook of the traditional single incision approach. The only thing that I do differently is I make my incision at, at a diagonal rather than right parallel with the neurovascular bundle, and that's just to improve my visibility of vein, artery, nerve there together.
. Make sure that I'm, I'm confident that I'm cutting the, the correct structure or not. It's, it's a common mistake is to cut the ligament of the errogate which looks and feels very much like the palmar digital nerve. Will not hurt the horse to remove the ligament of the ergot, but it certainly won't desensitise the foot, so.
That's something to look out for. And then once I make my incision, I'm gonna just bluntly dissect, vertically, so parallel with the neurovascular bundle to isolate that nerve, stretch it out of the incision, and then I'm gonna transect proximally, stretch and then transect, distally and remove that segment of nerve. Oh.
At the end. So, and then this is just post-op with a couple of skin, skin sutures in my incisions. Complications?
No surgical procedure is without complications. So short-term complications of neurectomy, the most common one, you've probably figured out by now, is, is gonna be a painful neuroma. So inflammation of the cut nerve stumps, where you performed the procedure, and those horses can be so painful from neuromas that they are more, more lame than they were before you did the surgery in some cases.
And a lot of times they'll be pressure sensitive just palpation-wise, to that region, where you did the neurectomy. So, we usually tend to see those pretty early on after the procedure, days to weeks after, the neurectomy procedure. That it is a treatable complication, usually, rest, anti-inflammatory, sometimes we'll inject some steroid in the region, and bandaging, and a lot of the time, they will recover from that.
If they don't, then the alternative would be to go in and remove a little bit more, section of nerve. Another potential short-term complication would be remaining heel sensation that could occur because, not every horse reads the same anatomy textbook and they may just have aberrant, aberrant branches. So skin sensation doesn't necessarily correlate to foot sensation.
So just because they do still have some skin sensation on the heel doesn't mean, that the lameness won't improve, or resolved in some cases. But that could be a potential complication. The other reason for that might be, that you didn't, you didn't, cut the right structure.
So, human error would be, I suppose, another potential explanation for that complication. And then as with any surgical procedure, incisional complications, it's a, it's a small incision, a quick procedure, so those tend to be pretty relatively rare, but incisional complications can occur, anytime that we do a surgical procedure on a horse. And then the biggest focus really of this entire talk is more relative to long term, longer term or more severe complications.
So, like I've, I've touched on towards the beginning of this talk, this is not a permanent solution, so reinnervation or regeneration of the nerve is a long-term complication. I, I guess you, you could term it a complication. You also could just term, term it, I, I guess an expected occurrence because eventually, whether that takes 6 months or 6 years, they're, they're probably going to, regenerate enough of that nerve to, to have some sensation in the foot again.
And if you've not resolved the problem that was causing the pain, then they're gonna be lame again. So certainly that will happen in the long term. The scarier things are gonna be rupture of the deep digital flexor tendon, fracture of the navicular bone, sub subluxation or as in this image, luxation of the coffin joint, or all three of those things together.
Those complications, any one of those really, but especially all three together would result in a, a life-ending complication that would, would necessitate euthanasia of the horse. And then another thing you should also warn your clients about, is that if we've done our job correctly, the horse can no longer feel the heels or sole of the foot, which means that if they step on a big rock or a nail or things like that, Have some kind of injury to the heels or sole of the foot, they may not, or they are unlikely to feel that, so it may take you longer to diagnose it. So we recommend, if you have a horse that's had a neurectomy, that you make sure and evaluate that horse just the bottom of their foot every day, pick their foot up, clean their foot out.
And just make sure that there's, you know, no injuries have occurred, cause the horse isn't necessarily gonna be able to tell you, at least in short order if something like that has happened. And then in rare cases, sloughing of the hoof wall could be a potential longer term complication. So outcome of neurectomy, there's a bunch of papers, most of these are pretty old, but there's kind of a similar theme that look at the outcome following PD neurectomy.
So, this first paper, 2018, they looked at guillotine versus pull through. 20% of the guillotine and 33% of the pull through cases had lameness recurrence within one year, so a third of cases, not ideal. This older 1993 study by Jackman, 20% of their cases recurred within a year, 74% were found one year after surgery, but only 63% sound two years after surgery.
Really old study from 1965, 68% of theirs were found a year after surgery. 59% at 2 years, 57% at 3 years, Maher 2007, 12% of their cases had a lameness recurrence within a year. Oh, sorry, did it again.
1968 study, 81% sound after a year, and then this last 1, 67% sound one year after, but only 40% sound two years after. So all of that, I think pretty solidly reinforces that while there's some variation in, in how long they stay sound or how quickly they lose the effects of that neurectomy, the percentage of horses that are able to perform post-surgery will decrease over time. And the individual patient response is gonna be pretty variable, and it's just, you know, important that the client understands that this is not a permanent solution.
It's not a, it's not a long-term solution for the horse. It's kind of a short-term fix. And while you can redo a neurectomy on a horse a few years later, you can only do that so many times, and with each time that you try, it's gonna be more and more difficult.
There's gonna be scar tissue, things like that. This is just a kind of a general overview. Again, it's an older paper, but just looking at overall, how these horses did, 57 cases, 50 with a long term follow up over 18 months.
And they had complications in 34% of those horses, but they considered recurrence of heel pain to be a complication. So that was 14 of the 17, which I would just consider that an expected occurrence. And then 3 of those horses got neuromas, .
They did radiographs after their limb was examined only 53 of the 57 horses that they nerved, 85% of them had navicular changes radiographically, that were graded mild, moderate, or severe, and the distribution is fairly even between that. They noted no association between severity of radiographic changes and degree of lameness, and their degree of lameness and severity of radiographic findings were not correlated with outcome, which highlights, I think, this, that the difficulty in case selection, at least when you're only using lameness examination and radiographs to diagnose your cases. But if you look at when this paper, when this was performed and think about the advances that have occurred since then in our ability to diagnose soft tissue lesions within the hoof capsule and things like that.
I think you can probably kind of surmise from this that the reason for those findings is because there was probably a lot more going on in a lot of these horses than simply degenerative changes in the, of the navicular bones, specifically soft tissue lesions that might have influenced the outcome. For those horses. So, what makes it good and what makes a poor candidate for a neurectomy?
Good candidates are gonna be horses whose primary pathology involves the navicular bone only, but is not severe, and horses that have minimal findings on MRI or, and or CT and or ultrasound. At least that findings that are not going to indicate to us that that horse is maybe what, what we would term structurally unsound or, or compromised where we worry about the severe complications such as deep flexor tendon rupture, coffin joint luxation or subluxation, and navicular bone fracture post-op. So those are the things I'm looking for when I think about is this horse a good candidate for neurectomy or not, is how likely are those things to happen.
So, poor candidates, a horse that has flexor cortex erosive lesions radiographically, moderate to severe deep flexor tendon lesions that we diagnose, Ultra sonographically, radiographically with tendon mineralization or on advanced imaging. Young horses, it's, this is, I guess, maybe more of a soapbox issue, but it's my personal preference not to be doing neurectomies on young horses because again, it's a temporary solution to the problem and those horses have a lot of life left to live. So, especially, you know, if you're, if somebody brings you a 3 year old horse and wants to do a neurectomy, I think we need to have a serious conversation about the long-term outlook for that horse and maybe, trying to get to the bottom of Of what's going on and, and, and what that horse's long-term prognosis is before we consider that type of treatment.
Severe lameness that does not swap over after blocking and has minimal findings on radiographs. The, the lights go off in my head, immediately that I, you know, I'm really worried about a severe soft tissue lesion and at the very least, I'd like some more advanced imaging on that horse. .
Before I'd consider a neurectomy, and if the client's unable to do that, then I would, I would strongly encourage just prolonged rest for that horse, if, if at all possible. And then horses that compete in high intensity or speed events, particularly when it's a child riding the horse, I think again, You know, just ethically, you have to think long and hard about whether or not you want to remove the foot sensation in a horse that, that does that for a living, more for, more for rider and horse safety than, than anything else. So this is from a paper that looked at, outcome of neurectomy in horses with foot pain that did have MRI imaging.
So they looked at 50 cases. This is a little bit more recent. All of those horses had lameness evaluation, blocking, radiographs, and a low field MRI performed before surgery.
And then they had palmar digital neurectomy with the guillotine technique. This was, because it's a retrospective, so they went across 4 hospitals, combined their efforts, and so that's why you'll see kind of depending on which hospital, was reporting the results, maybe they see kind of different types of populations of horses, so kind of a nice distribution. Quite a few low level show jumpers, that was 60% of them, and then the other 40% was low level dressage, trail, eventing, fox hunting, and western pleasure.
Oh so they found age, sex, breed, athletic use were not associated with the horse's likelihood of being lame post-op. 52% had bilateral forelimb lameness, 44% unilateral forelimb lameness, and just a few, unilateral hind limb lameness, which would be much less common. Uni versus bilateral pre-op lameness did not, associate with post-op lameness.
85% of these horses got better with just a PD block pre-op, . And then 52 in 52% of them, the lameness was completely resolved. So, not surprisingly, if they didn't completely block out with a PD block that was associated with increased rate of post-op lameness, versus those who were sound after just the PD block.
On the radiographs on these horses, 54% had radiographic lesions in the foot that included navicular bone pathology like enlarged vascular channels, sclerosis, or loss of that corticomedullary definition, focal ralucent areas, cysts in two, and then elongation of that distal, palmar navicular bone. In a couple. Collateral cartilage ossification or side bone in 2, poster and arthritis in 1, and then in some cases, they had no radiographic abnormalities, but on MRI 84% of those horses had soft tissue lesions detected.
So, the, the majority of horses had something soft tissue-wise on their MR, and 32 of those 50 horses had deep flexor pathology, super common. Navicular bursitis and then some altered intensity in the navicular bone, so like navicular bone edoema detected on your MRI. So as far as how those horses did, their median length of soundness was 20 months, so 92% sound post-op, 80% returned to their previous level of work at 15 months, 80% of those back at previous work, so 80% of the 80% were still sound, and then at 30 months, only 70%.
We're still sound. 6 horses had a repeat MRI anywhere from 5 to 24 months after surgery. And one of those horses, their deep flexor tendon lesion that was previously diagnosed was worse.
I would say that's not super surprising if you, if you have a horse that already has a lesion and then you take away the sensation of the foot. That's one of our concerns is that those tendon lesions are going to propagate and worsen. One had worsening of a collateral ligament lesion of the coffin joint, and one had worsening of an impar ligament lesion.
. And then 2 of those 3 horses listed above now had navicular bone trauma or contusions that they didn't see before surgery. So, they did find kind of take home message, a difference in foot pain, and the timeline for recurrence of lameness if the horses had deep flexor tendon lesions prior to surgery. So basically they're more likely to have a lameness recurrence if they had a deep flexor tendon lesion.
And horses that had core lesions were more likely to get lamer earlier than horses that had just dorsal border fraying or no tendon lesion. So, all that to say, if you are fortunate enough to MR a horse before, before doing a neurectomy, you need to be mindful of the fact that if the MRI diagnoses a core deep flexor tendon lesion, that horse is not a good candidate for a neurectomy because it is likely to progress that disease over time. Once they return to work and, and come up lame rela in relatively short order, after that procedure is performed.
OK, so now I'm just gonna run through some different cases. The first is a 22 year old Quarter Horace Gelon. He was donated to us at the university for euthanasia, due to chronic severe lameness, and he was just losing body condition, getting thin.
On presentation to us, he was lame at a walk, grade 4 out of 5 on his left front. We did a Palmar digital nerve block for teaching purposes as much as anything for our students, and he did swap over, so he became a grade 3, strong grade 3 to to grade 4, lame on his right front after our left front PD block. We took some radiographs again just for teaching purposes.
This was a donation case, but here's on his lateral views you can see on this horse's left front and right front. He does have a little bit of that distal extension of the navicular bone on the lateral view, but he also has mineralization, on the dorsal aspect of his deep flexor tendons, so deep flexors right here running down the foot. And you can see mineralization here and here.
So he has evidence, of a previous, pretty, pretty severe deep flexor tendon tear, in the navicular region or just proximal to in both front feet. So, it makes sense that his lameness would swap over, both from the tendon lesion aspect and, you know, his navicular bones radiographically are abnormal as well. So on his navicular DP views, he's got some distal border irregularities, not, not terrible.
This, the, exposure on this image is a little bit different, just technique wise, so I apologise for that, but same, same thing, just a little bit irregular, but not. Not terrible on this view. He does have some flexor cortex erosive lesions on both the left and the right, and loss of corticomedullary definition.
He doesn't have that nice crisp cortex, versus medullary cavity definition that we'd like to see. So certainly, he has evidence of deep flexor tendon lesions, erosive lesions, on that sagittal ridge, which can correlate to adhesions and or deep flexor pathology. .
Which, which certainly we have evidence of on the lateral view as well. And then again, the bony changes, degenerative changes of the, of the navicular bone. So, multiple reasons to be severely bilaterally lame.
We also went ahead and, Did an ultrasound just for, for teaching purposes as well. This, the left pictures of the left front, the right pictures of the right front, they're taken at different levels of the pastern. So the left image is more distal pastern and hopefully you can appreciate just some irregularity and fibre pattern of the dorsal aspect, kind of dorsal section of that deep flexor.
And then on the right, I think it's less obvious, but this particular lobe's got some change here dorsally as well. And then postmortem, of course, this horse was again donated for euthanasia, so we did put this horse down, and then, performed a bursoscopy with our residents for teaching purposes just of the left front. So this is, I usually do those from a, a transthecal approach.
So I go into the, digital flexor tendon sheath and then I drive down and cut into the navicular bursa from the tendon sheath. So this is on our way into the bursa. You can see this horse does have, some adhesions.
And then this is after we've kind of cleaned up those adhesions. So this is dorsal aspect of deep flexor tendon as we're driving down into the bursa, so. So all that to say this horse, for all the reasons described on the previous slides, would not have been a good candidate for neurectomy, right?
So he's got severe degenerative changes of his navicular bones radiographically. He's got evidence of prior, pretty significant deep flexor tendon tears radiographically and ultrasonographically. So this is A horse that doesn't even need advanced imaging, for me to tell you, that if the owners had not elected to donate the horse, he really would not have been a good candidate, for a neurectomy, and I would have, I would have strongly discouraged, going forward with that procedure in this particular horse because structurally, the horse's tissues were not healthy enough to withstand that procedure.
Essentially, he would be likely to rupture tendons and or fracture navicular bones post-op. OK. Next case, is an 8-year-old quarter horse mare.
She presented for a 3 out of 5 left forelimb lameness of 18 months' duration, started after she pulled a shoe. She does block to a palmar digital nerve block pretty convincingly and does not swap over to a right forelimb lameness. Radiographically, she had very mild navicular bone changes, but those X-rays were otherwise unremarkable.
Her owners have tried. Injections, showing changes, without sustained improvement, so she didn't improve with coffin joint injections, at least, . And they would like to pursue a palmar digital neurectomy.
Now, this horse is relatively young, so, I would be less inclined, to do a neurectomy, and certainly without more information. But this is what the horse looks like, on a lunge to the left, so pretty severe, 3 out of 5 left, 4 limb lame. She's plenty of lane, and she does not swap to a right front.
So right away, I get, I get worried about, soft tissue lesions, specifically deep flexor, in the foot. These clients were, on board to pursue an MRI prior to surgery, which is great. So, bear with me.
I'm not a radiologist, but I can point out the big things to you. So, on, the stir image sequence on her, these are sagittal views of her left front and her right front, so her normal limb. Is on the right.
Her abnormal limb is on the left, and what the arrow is pointing to is this is the area of the collateral sesamoidian ligament of the navicular bone. And hopefully you can appreciate the difference. It's very thick on the left in comparison to the right, but if we look at the deep flexor tendon, which is.
The block structure drawn down here, to attach, on, on P3. We don't see fluid signal on this particular scan that would show up as bright white. It's suggestive of a tear in the deep flexor tendon, so I'm happy with that, on this sequence at least.
And then in on these transverse scans, the, the arrows highlighting the same thing. So that collateral semoidan ligament is quite thick on the left, not on the right. But you know, this is just one image and hundreds of images on her MRI.
But, but her scans didn't indicate really anything else in the way of pathology. I think there was a little bit of fluid signal in her navicular bone, but the, but the predominant finding was just that, collateral sesamoid and ligament injury, which in the grand scheme of things compared to deep flexor tendon lesions, collateral ligament lesions, things like that. It's not so bad.
So, for this particular horse, we, deemed based on the ultra or the MRI that she was a, a structurally appropriate candidate for the aneurectomy. So if that is what the client wanted to pursue, then that would, that would be an acceptable treatment, for this horse. OK.
This next case is a tough one. So this is a 20 year old quarter horse gelding. He was a teaching horse for us and a really good one for a number of years.
He was donated for chronic lameness, chronic bilateral forelimb lameness. So he's taught a lot of vet students over a lot of years, on lameness evaluation and doing Palmer Palmer digital nerve blocks, things like that. But unfortunately, The severity of his lameness, unsurprisingly got a little worse and a little worse over time, to the point where the horse is now painful at a walk.
So we were faced with a decision just to humane treatment of a, of a really, a good teaching horse that had been good to us, you know, the alternative, you know, alternative was either, euthanasia, humane euthanasia, or, Or palmar digital neurectomy because he was not responding to other conservative treatment options at that point, trimming, injections, things like that. So, here's his radiographs way back in 2017. So even back then you can see, we talk about navicular bone sclerosis.
This horse has no corticomedullary definition, that's his left, that's his right, it's all very sclerotic, a lot of, of navicular bone remodelling on his lateral radiographic views. He's got, he's got lots of things, but on his left, he's got, Mineralization in the area of his deep flexor tendon just proximal to the navicular. You can see even back then, well, this one, sorry, is from 2018, but even then, shape of his navicular bones pretty irregular, even on the lateral view, you can see how sclerotic the bone is, you can't even recognise the flexor cortex.
He's got some change in his coffin joint, so some osteophytosis here and even remodelling on that dorsal P2, more so on the right than the left, but suggestive of arthritis of the coffin joint, and he's got side bone on both. So lots of reasons to be laying in the foot region. On these DP views, he's got some kind of lytic areas in his navicular bone on the left and especially on the right.
He's got kind of a cyst-like lesion in that one. He's got some enthusiaathy at the corners from that collateral, smoidan ligament, particularly on the right, but even on the left as well. And then, of course, his side bone is, is pretty substantial on both, on both feet.
This is, OK, so this is one day prior to surgery, so you can see that his cough and joint arthritis has certainly progressed. His mineralization in his deep flexor tendon on that left foot has gotten worse. The, the shape, the contour of his navicular bones, got worse as well.
And I think, yeah, I've got navicular skyline views as well, where you can appreciate, now he's got even some lysis on the flexor cortex on this right one, severe navicular change. So, were this a client owned animal, I would absolutely not perform a neurectomy on this horse under any circumstances. He's, he's not a good candidate for the procedure.
We went ahead and did it in this case, for right or wrong, purely to preserve the horse's comfort level as a pasture ornament. He, he was not intended to do anything else, certainly nothing athletically, just basically stand there and, and let that students do physical exams on him and things like that. But we wanted to do everything we could to give him potential, to have a little bit longer life, as a teaching horse.
So against my better judgement, we went ahead and did. A pedoneurectomy on this horse under general anaesthesia via the, the technique I've described to you already. We kept him in hospital for the full 6 weeks post-op with distal limb bandages.
He was unsurprisingly, dramatically improved in his comfort level post-surgery, and he was discharged on pasture turnout at that point. On a recheck, more formal recheck evaluation a couple months later, he was still getting around well, but did look uncomfortable when he had been walking just the past couple of days. And so this is a video of that horse, and if you look really closely, you'll see, especially on the right front, he's got, I'll play it again, he's got a toe flip, and he kind of lands heel to toe.
And he flips that toe up when he walks, which should make you worry about the integrity of his deep flexor tendons. He does it on both, but more, more apparently in this video, at least on the right. And then if you just look at this, image on the right, it's just a picture, but if you look at the way the horse stands, the angle of his coffin joint doesn't look quite right.
So he just looks more, almost, almost. Almost like his hoof pastern ankle is broken back, but he's got some, some edoema and effusion around his coronary veins as well. So we were concerned based on that exam that he had ruptured his tendons, and in fact he had, on both four limbs.
So these are, some ultrasound images. I apologise for the glare. .
On these particular pictures, but in his pastern region, so that's a transverse image, and you can see his deep flexor tendon just kind of looks like Swiss cheese, total loss of normal fibre pattern alignment, proper clefts, with fluid, you know, indicating tearing. On the longitudinal view, you can see that basically the deep flexor is just absent in this particular region. .
Versus and then on this view as well, so that should be distalsmoid and ligament and then kind of Swiss cheese deep flexor over top. So ruptured tendons bilaterally. We did take radiographs for teaching purposes, and, and noted subluxation of both his left and right coffin joints.
And this horse, was a trifecta. He also managed to fracture both of his navicular bones as well. So, severe, damage slash rupture to deep flexor tendons, fracture of navicular bones, and subluxation of, of coffin joints.
Postmortem, we ran him through the MRI again just for teaching purposes. So, on these, transverse images, it really nicely highlights his navicular fractures. And then there's fluid signal in the area where his deep flexor tendon essentially ruptured.
So that's his left front, this is his right front. He's a match, so these are different scans, but just ones that I picked out that highlighted, the total loss of, of tendon architecture. And then again on his right front, deep flexor tendon rupture, navicular fractures are evident.
So, and then after, his postmortem MRI we also just dissected out that tendon, and I think, this also just really brings home the, the bruising in the tendon and just almost, almost necrotic appearance to the tendon more distally. You can see the fractures of his navicular bones. And then when we pull the tendon out of the horse, you can see where he's ruptured.
He's got a big old hole in it, on the right. We did publish, you know, although this is a, a known complication, potential complication, we were able to publish a case report for this horse and one other for horses that did this, post neurectomy just cause I think it's really important. To emphasise that in, in a horse with this severe of changes prior to surgery, even, even if your only goal is to make the horse, comfortable to stand in a pasture, even then it's, it's not something that we should probably pursue, and this is why, because the horse can, can end up with this severe life-ending complication as a result if they're not structurally sound, Either in, in the navicular bone itself, the soft tissue structures of the foot or both, to have this procedure performed.
So, and then this is just an interesting case report that I found, of a different cause for deep flexor tendon rupture. So this was a younger horse, a 10 year old jumper that presented for an acute severe lameness, and he ended up having a, a parasagittal fracture of his navicular bone and a tendon rupture. A deep flexor tendon rupture on ultrasound, but what happened with this horse did not have a neurectomy.
What had happened was the horse was lame. He had had repeated intrabursal injections of corticosteroids, specifically triamcinolone. 4 times over 4 months, which to me is an excessive amount.
That, that's a, that's a pretty aggressive number of times and, and, and frequency, like in terms of duration between treatments, to inject a navicular bursa, but the horse, they were trying to keep the horse sound, I gather, and the horse remained in training throughout. And wound up fracturing that bone and rupturing the tendon, and the discussion in this paper talks about there's, there's multiple reports in, in human literature of corticosteroid, either intra tendon or peritendinous injection of corticosteroid, making tendons more likely to rupture because of the adverse effects that it has on the collagen structure of the tendon. So, just a, a, an interesting case and another example of, of when things can go wrong, unfortunately.
This one is a 13-year-old quarter horse gelding that was 3 out of 5 lame right front, 6 months previously. He had a lameness exam performed by the home vet who blocked the horse to a palmar digital nerve block. The horse did not swap to the opposite forelimb.
And then the horse received a coffin joint injection with corticosteroids and hyaluronic acid, so not an uncommon, course of events. Horse responded well to injection. He continued in work until he came up severely 4 to 5 out of 5 lame on his right front, 2 weeks before he presented to us.
So the day that we saw him, he was weightbearing, but certainly lame at a walk, 4 out of 5 lame right front. Not responsive to hoof testers. We did not re-block him just because of how severely lame he was, but elected to image him based off of the fact that he had blocked to a palmar digital nerve block, several months prior.
So that combined with our physical exam, we went ahead and radiographed the foot, and, you know, on, on the navicular DP view, he's got enthusiahytes on the corners of that navicular bone, a little bit of irregularity of the distal border, but on his skyline view, it doesn't look terrible, you know, for a middle aged quarter horse, he's got some corticomedullary definition, maybe some mild navicular changes, but nothing just awful, . He does have a little bit of remodelling to the back of his of his P2 and the dorsal aspect of his P2, but not a whole lot to write home about. On the standing views, the standing lateral and, and DP views.
So, on the ultrasound images of his pastern region, you can see deep flexor tendon. These are all, going to be transverse views, but you can see he has a pretty obvious tearing of his deep digital flexor tendons. You can see the cleft in the tendon there, the enlargement, on this side, on this lobe, and then loss of normal, fibre pattern.
And same thing on, on these other views, you know, not normal fibre pattern alignment, pretty severe tear. It looks like this, dorsal border is, is a tear and maybe like a tendinous granuloma, associated, with the, with the tearing of the tendon. So this horse also really doesn't need an MRI for me to tell him that, neurectomy, you know, if the horse isn't responding well to injection, that he's still not gonna be a good candidate for a neurectomy cause he's got a really severe tendon tear.
So then this is a longitudinal image where you can see some loss of normal fibre pattern and even absence of, of, of any normal tendon architecture at least on that particular lobe of the deep flexor tendon. So, Ideally, we could still MRI the right front foot of this horse just to get more prognostic information for the client. We could potentially do a navicular burstoscopy to debride the dorsal, aspect of the tendon lesions, clean that up, maybe improve the horse's long-term prognosis, although I would say, To be honest, probably with that severe of a tear that the long-term prognosis is, is for performance at least is not good for this horse regardless, but, maybe to improve his long-term comfort level.
We talked a little bit about, orthobiologics, maybe an intralesional or intendon sheath. Injection of PRP to help, with the healing of the tendon tear, regardless, corrective shoeing, shorten the toes to pull his breakover back, wedge the feet to take some tension off of that tendon as it heals, and then strict stall confinement with hand walking, for 3 to 6 months. No forced exercise for, for 6 to even 12 months, for that horse, but certainly not a neurectomy.
So, the take-home points, are appropriate case selection, particularly without advanced imaging, can be challenging in this case, in these cases. Like in the last case, you know, we were able to identify that tendon lesion, pretty easily because of its severity and its location, but the more distal end of the hoof capsule those tendon lesions get, the harder they are, to identify. Without advanced imaging.
So that can be, that can be really tough in some of those cases. And just to know that neurectomy, while, while It, you know, it's not that you should never do it. There are certainly horses where a neurectomy is an appropriate, treatment strategy.
It's not something that should be taken lightly. It should not be considered a long-term solution. I think it's important that clients are really well informed, you know, of, of what this procedure can do and what it can't, how long it's likely to last, and the potential complications, that can go with it.
So, choose your cases carefully and that'll give you, better outcomes. That's all, that I have, and I'm, I'm happy to answer questions, if people want to reach out to me about them.
