So hi, my name's Andrew Wood, I'm a surgical resident at the Liu Eine Hospital in Surrey, and over the next hour I'm going to discuss the diagnosis and treatment of digital flexor tendon sheath pathology. And during the webinar, I'll discuss the different methods of diagnosing and treating digital flexor tendency pathology, and hopefully give you some hints and tips on how to get the most out of your diagnostic workup, and we'll hopefully cover a varied range of conditions as well. So the learning objectives, first thing is the relevant anatomy of the digital flexor tendon sheath, how to approach a swollen digital flexor tendon sheath.
We'll touch on ultrasound of the digital flexor tendon sheath, which I think is quite important, when you're working out these cases. We'll look at some other diagnostic techniques to assist your diagnosis and then importantly at the end we'll look at the prognosis for different common conditions that we're gonna find. So the first anatomy, and I think anatomy is really important, can't sort of overstate that enough, and if you ever did get the chance to just get a sort of cadaver limb and dissect it, it definitely helps you get an understanding of the 3D anatomy of the digital flexor tendon sheath and the structures that's contained within it.
In principle, this digital flexor tendency extends from the junction of the middle and distal 1/3 of the cannon bone to the level of the middle phalanx. And at this area it terminates as a T ligament, and this is the structure that separates the digital flexor tendon sheath from the navicular bursa and the distal interphalangeal joint. Within the digital flexor tendon sheath, there's the superficial and the deep digital flexor tendon and their associated structures.
And at the level of the proximal sesamoid bones, palmer or planter to the fetlock joint, the tendons pass through the fetlock canal, and this is created by the angular ligament palmerle, the proximal sesamoid bones laterally and medially, and the intercesmoidean ligament dorsally. So as you can see from this sort of contrast tinogram on the right hand side of the slide, that just nicely delineates where the tendon sheath runs to and from. So the first structure that we're going to talk about is the superficial digital flexor tendon sheet tendon, and within the proximal aspect of the digital flexor tendon sheath, the SDFT forms a smooth ring around the deep digital flexor tendon, and this is the structure known as the the manic flexoria.
The manic flexoria has a free distal border, and its proximal margin is continuous with the digital flexor tendon sheath wall. You can see it on the left hand side of the image here, the free margin at the bottom of the image, and the proximal extent of the manica flexor, the the top arrow on the left-hand image. Within the proximal sheath, the SDFT also has a meatinon which reflects off the palmer or planter axial surface of the SDFT to the sheath wall from the proximal level of the digital flexor tendon sheath to the level of the fetlock canal.
Distally, and the sheath wall reflects from the entire surface of the SDFT. The SDFT bifurcates to the mid aspect of the proximal phalanx, and here it bra the branches into two branches which are connected by a thin ismus. At the site of bifurcation, the SDFT forms a digital manic flexoria, which wraps around the dorsal DDFT as it does in the proximal sheath.
And the SDFT branches insert on the middle phalanx. So on the right hand side of the image here, this is looking distally within the digital flexor tendon sheath. You can see the SDFT and the DDFT and wrapping around the dorsal aspect of the DDFT is the digital manic flexoria.
It's a site that's uncommonly, pathologic. So next up is the deep digital flexor tendon tendon, and the proximal DDFT is attached to the sheath wall medially and laterally by mesottenons, which arrives just proximal to the maniaca flexoria. So these sit within the manic flexoria, and that can be seen on the left hand ultrasound image originating from the DDFT.
These provide the blood supply to the tendons within the tendon sheath, as they lack a paratenon. So they have an epienon and these mussotinons are what supply the blood to the tendons. In the distal digital flexor tendon sheath, the DDDFT has further mesottenons, or these are sometimes called vericulate, which attach the DDFT to the dorsal sheath wall just distal to the digital maniflexoria that we just touched on.
And they can be seen on the right hand side of the image of these small strands. So the DDFT becomes bilobed in the pasttern and continues past the digital flexor tendency to insert on the distal phalanx, which obviously lies within the navicular bursa. Then probably the last important structure that we're gonna talk about in the digital flexor tendon sheath is the aneurlar ligaments.
Now obviously the most well known aneur ligament is the palmer or planter annelar ligament which attaches to the abaxial borders of the proximal sesamoid bones and forms a palmer or planter aspect of the fetlock canal. And this acts to hold the SDFT and DDFT within the fetlock canal and supports the proximal sesamoid bones during movement. And that can be seen on the right hand side of the image here, the palmer or planter and your ligament.
For the distally at the level of the proximal phalanx, we've got the proximal digital aneur ligament, which is more of an hourglass shaped ligament. The proximal borders attached near the proximal tubercles of the proximal phalanx, and the distal borders near the distal tubercles of the proximal phalanx. And this ligament in this area is closely adhered to the to the main body of the SDFT and where the SDFT bifurcates in the mid-pastern region, it's closely adherent to the SDFT connecting branch or Emuth that I talked about in the last slide.
The function of this ligament is cos when the fetlock joint overextends during weight bearing, the flexor tendons are tensed against this this ligament, and it resists the plumer or planter loading forces of the tendons, so stops them bowing in the pastton region. That can be seen in the middle of the image here, you can see that hourglass shape and structure which is closely adherent to the SDFT where it bifurcates in the mid Pastern region. And the last annular ligament is the distal digital annular ligament.
And this originates at the medial and lateral borders of the distal proximal phalanx, so near where the proximal digital aur ligament inserts. And this forms a sling that supports the distal extent of the DDFT to its insertion to the distal phalanx. Now this is mainly within the hoof capsule, as you can see here, the dissection is continued into the digital cushion.
And so this would be uncommonly diagnosed via conventional diagnostic imaging techniques. Other associated structures just to have a little think about that form the dorsal boundaries of the digital flexor tendon sheath and so may result in signs consistent with digital flexor tendon sheath pathology, would be the straight and oblique distal sesamoidium ligaments and of course the proximal scuum as well, which I think is sometimes forgotten. So what clinical signs are we going to see in horses that are presenting potentially with a digital flexor tendon sheath issue?
So your lameness grade may vary and it often improves with rest, so you might get an acute non-weight bearing lameness which quickly improves with rest. But some of these can be more chronic insidious onset lamenesses. Horses may be reluctant to fully load the heels, and distal inflexion can exacerbate the signs.
When you palpate the limb, you usually can feel an effusion of the digital flexor tennis sheath, but as as in cases on the left-hand side of the screen and heavily feathered sort of thick skin breeds such as cobs, it can be really quite hard to sort of palpate and differentiate the different structures and what is swollen. And so in these cases I would really suggest clipping the feathers off the legs, if you suspect a tendon sheath issue. And to be honest with you, in, in most cobs, that present for lameness, I would be wanting to clip the legs off because tendon sheath pathology is very, very common in these horses, even if the owners might, resent that slightly.
There's one school of thought that that believes that if fusion will be maximal with pathologists, this might help guide your later diagnostics. And there may be thickening of the annual ligament which presents as either a bulge or a convex surface, concave surface rather, where the annual ligament is constricting in the digital flexor tendon sheath at the level of the proximal sesamoid bones. It's important to note that the ergot can sometimes draw you quite distally in the sheath to think that that's where the sesamoid bones bones lie, but they actually lie a bit more proximal than that.
And also, you know, as, as is the case with with many tendons and ligament lesions, you may get pain or palpation of the different structures within the within the digital flexor 10 sheath and of course on the annual ligament itself. So this is a, you know, quite a common thing that you would be presented with, you know, a reasonably lame horse. But as you can see, you know, they're covered in mud, they've got massive big feathers, and so actually trying to work out where this lameness is coming from is, is, is really gonna be quite tricky, actually.
When you, when you go to your horse, you know, and you, you see what breed it is and what type of horse it is, what, what activity it does, this can really guide you in terms of what lesions you should be thinking of that you're going to find within the digital flexor tendon sheet. So one of the most commonly reported conditions would be manicfixorial lesions or tears, and these are gonna be really seen in your cobs and ponies. More commonly seen in hind limbs and medial tears do tend to be more common.
Deep digital flexor tendon tears, these are gonna be in your sort of in your warm bloods, your thoroughbreds and your draught horses. Show jumpers tend to quite commonly get this, especially in the forelimbs, and they tend to be lateral border tears, and in in the show jumpers it's thought that when, when they're jumping over a jump, if it was in the hind limb, the hind limb can compensate for that increased load by flexing the hop, whereas that composition is not possible with the way that the forelimb flexes with the carpet and the forelimb and so you get a lot of pressure, you know, through the structures within the digital flexor tendon sheath. And there's a thought again that when these horses jump over a jump, the inward rotation of the foot towards the end of the stance phase when they increase the load on the DDFT is what which means is why you get the sort of lateral border tears predominating.
And one study did show that they're more common in the right for them as well, which might just indicate the the way these horses are going when they're competing. Lesions of the annual ligaments, and palmer or planter annual ligaments specifically, these are gonna be more commonly seen in your cobs and small ponies, equally actually distributed between the hind limbs and forelimbs, there has been some have been some studies that have shown that the hind limbs are more commonly, affected, but actually recent studies have shown that there's an equal share between hind limbs and forelimbs. One of the things we've got to remember with aneur ligament pathology, it's a really common diagnosis to get and actually sometimes it can indeed be primary, but if, if I've got a case where I'm suspecting a ligament pathology, I really want to be looking to see if there is any, you know, secondary pathology, cos it definitely is common in association with other lesions such as manic flexoria tears.
The reasons for cobs is, is kind of unknown as to why they're sort of, they've got a a performance for annual ligament lesions, but it's likely the confirmation, you know, has a role. And these horses tend to be sort of middle aged, you know, median age of sort of 12 years old in one study, and that's likely, you know, due to the fact that you get a loss of elasticity of the ligament as these horses get a bit older. SDFT lesions, again more common in your cob type horses, and this kind of fits nicely with the fact that they are quite commonly seen in conjunction with manic flexoria lesions or annular ligament constriction and this.
It's probably because where the annular ligament runs over the SDFT you get quite commonly get lesions here where it's constricting against the SDFT and also obviously the maniacal flexoria sites of attachment are on the SDFT. So sometimes quite often, if we get tearing of the maniaca flexoria border, it will extend into the SDFT. And again, like the aneligament lesions, doesn't tend to be more common in either the forelimbs or the hind limbs.
So the next step in your workup is gonna be determining if the litmus is indeed coming from the digital flexor tendency. Obviously in some cases you're gonna get an acute digital flexor tendency of fusion, for example, in a really fine, fine warm blood horse, and lameness, you know, and the diagnosis is obvious, you know, cos you're gonna have lameness, you're gonna have the tendency to fusion. But in many, you will get sort of, you know, some horses can have one goal sort of type swellings, and so diagnostic analgesia will, will be, indicated.
The approach in terms of diagnostic analgesia is very, you know, one clinician dependent, case dependent, and also can depend on what pathology you think is, is gonna be present. Remember, if there's no obvious digital flexor tendency diffusion present then then do block the foot first as you definitely can sometimes get local anaesthetic diffusion and inadvertently block foot pathology if you're blocking into the tendon sheath itself. A low 4 point nerve block should definitely abolish all lameness originating from or making a significant improvement to the lameness that is originating from the digital flexor 10 and sheath or its associated structures.
But actually if you just block the two planter nerves between the suspensory ligament and the DDFT in the canon region, then that in theory should block out all those palmer or planter structures which include the digital flexor tendon sheet . As well. Certainly if you're unsure of what to do in these cases, you know, in terms of whether you block the sheath first or whether you don't, a low 4 point would be a really good place to start, as you can, as you can block it to here, and if the horse improves, then you can go back to the individual blocks separately after.
So, as I said, low point abolish all lameness, if you want to be a bit more specific, then intrathecal analgesia will definitely be indicated, so putting some local anaesthetic into these digital flexive tendencies. In terms of the structures that are going to improve to this, so it's been shown that deep digital flexor tendon tears, if they're present, they're much, much more likely to improve the intrathecal analgesia than the other lesions you could find. A study that looked into my flexoriatis found that only 75% of these improved after intratheal analgesia.
It's a bit unknown as to why this happens, you know, considering the structure is within the tendon sheath, whether they have, you know, other sites of pain, for example, the annual ligament as well might be, might be a reason. But these h. Horses certainly usually have a all horses tend to have a partial improvement to this block, so a significant improvement whether you want to call that sort of 50% improvement in in structures.
With the annual ligament, recent studies showed that sort of 100% again of these are going to block to low 4, obviously, you know, the low 4 point blocks everything distal to this. And digital effects tendency 93%, so pretty good improvement, you know, I see there's a significant improvement. The horse might not be sound after this, but certainly they'll be significantly improved.
This is probably why, because the annual ligament is extrathecal in its location, and so you are, you know, getting a little bit of diffusion from the sheath into into this, this region. And as I kind of briefly touched on earlier, you know, what else could we be blocking when we're blocking the tendon sheath, when we're putting local anaesthetic directly into the digital flexor tendon sheath. Now one study showed that if you block it in the proximal pouch, which we'll go on to in the next slide, then you can get lots of heel box sensation from inadvertent blocking of the palmer or the planter nerves.
But then in contrast to this, another study showed that anaesthesia of the digital fix tendencies did not alter lameness associated with the distal interphalangeal joint, navicular bursa, or the sole. What I would recommend in light of this is, you know, always combine your findings of diagnostic analgesia with the clinical exam. So for example, a horse that's not really got a massive digital flex a tendon sheath of fusion, it might just have a slightly puffy tendon sheath that's not sort of hard, you know, totally effused, then you know, think about blocking other structures first for and the main one I would say is the foot, to be honest with you, because certainly I would worry in some cases.
That local anaesthetic leakage or diffusion could block out structures within the foot, which could lead to a wrong diagnosis and potentially lead the horse to having an incorrect surgery. So where are we gonna If, if, you know, low 4. Nerve but reasonably simple, but digital fix tendon sheath, where, where are we going to inject this sheet?
Now hopefully these diagrams, you know, make it reasonably clear as to the different sites to inject, but there are essentially 4 standard ways to inject the digital fixer tendon sheet, and I would commonly use a 19 gauge to 20 gauge 1.5 inch needle for for this, for all these techniques. So the first one and the one I would commonly go to is the distal approach, and this is where the needle is inserted in the distal out pouching of the digital flex attendant sheath in the gap created by the digital and your ligaments.
And with this technique, I insert the needle at kind of 45 degrees with the devil facing towards the tendons. This might not seem important, but certainly for me, it makes sure that there's more of the needle within the digital flexor tendon sheath, and the more the needle's more stable when you're injecting. The skin in some horses in this area can be really quite thin, and so you can sometimes get inadvertent subcutaneous injection here.
And also if you wanted to try and get fluid from this sheath, it's most important that your needle is as far in as possible. Without obviously damaging the underlying tendons. The basic sesamoid technique, which is the next needle up, coming from left to right, and this is done in the space between the proximal and the digital distal digital and your ligaments and the Palmer annual ligaments.
So this is the second dot up you can see there, and this is quite a nice, easy to feel out pouching, you know. And it can be good to get some fluid out of there. Axial sesamoid, which is the next one up on both them, both diagrams, and this is where you go through the angular ligament and you aim your needle between the proximal sesamoid bone and the flexor tendons.
And with this technique, I would definitely flex the leg, so for all these techniques apart from the proximal, I do these non-weight bearing. You can get an assistant to hold the leg if you want. For the axial sesamoid, I would definitely flex the leg a bit more than the rest, and this is so you can feel that axial border of the sesamoid bone which can help guide your needle in, cos certainly in some especially thick skinned horses, it's really, really difficult to feel where that sesamoid bone is.
And obviously the last technique is in the proximal out pouching of the digital flexor tendon sheath where there's this you usually get a palpable fusion. This is my least, you know, favourite one to go to. I find it's quite inconsistent in terms of how much fluid you get from this site.
And also there's a lot of synoium up there and also, you know, that you do worry about, subcutaneous leakage. So as I said, each of these has a pro pros and cons, and they have been studied. As I say, I would do, you know, mostly all but the proximal one, non-weight bearing, and again for the actual sesamoid, just to remind you, definitely flex that leg.
So in terms of what one's better, you know, obviously a lot has to be said for experience and where you're used to injecting these horses, but certainly it's good to have a knowledge of all these techniques and where you can do them, cos obviously, you know, not related to a aseptic digital effects tendon sheath diffusion, but say for example, if you have a wound near the tendon sheath, you definitely want to see where else you could inject this sheath to see if it's contaminated. In terms of successful injection, Patern approaches an axial sysmoid is definitely the best one, The proximal approach has its flaws in terms of subcutaneous injection, you can sometimes inadvertently go into the fetlock and also as I said, anaesthetizing the palmar or planter nerves. If you want to get some fluid out, the basic sesamoid approach has been shown to be the most successful.
So diagnostic analgesia next, we'll just touch on all these points. Ultrasound's obviously the mainstay, but obviously in thick skinned breeds such as this horse here, it's gonna be really quite difficult, . I'll just know if you can't get an image, I'd certainly wrap the leg with a soap bandage for one hour, and this is just gonna moisten all that skin up and make it slightly more penetrable by the ultrasound probe.
Certainly if you are scanning these legs, whether it's a thick leg or a thin leg, really be patient. It does sometimes take a little bit of time for the ultrasound gel to soak into the skin and for you to get a good diagnostic image. So don't just take 2 seconds running up and down.
In these six skins cobs legs, you know, you're not going to be getting. Images that would, you know, you'd be able to put in a paper, for example, so certainly turn your frequency down and turn your gain up and you are gonna get an appreciation of some of the important structures in there. Sometimes you won't get to see all structures, but you will get an indication of stuff like that on your ligament, etc.
We'll touch on non-weight bearing techniques as well, and this is a really good technique to to master, and it allows a wider contact surface with the probe and it decreases the flexion. The tension on the flexor tendons and so structures like the manica flexoria for example, are much more easy to identify. Also in thick skin breeds, for example, cobs, it allows us to use a much more proximal ultrasound window and this is where the skin is a bit thinner than lower down the leg.
Use your basic principles, look at each structure separately, so it's very easy, you know, we get people all the time that just focus on the manica flexoria straight away. Try and look at all the structures independently before you get sort of guided down a path of just trying to look at one. In the stop sharing screen.
Sorry about that, hopefully we'll pick up. OK, it's back on now. Great.
So yeah, I'll just go into detail of the most common lesions you're likely to be faced with when you're diagnosing with ultrasound. The annual ligament, can be observed at the level of the fetlock canal, as can be seen in this image with, with the proximal sesamoids forming that characteristic appearance at the dorsal aspect of the image. So you can measure the annular ligament on the midline, especially in cases where it's hard to discern from the surrounding soft tissues, or it can be measured at the insertion of the proximal sesamoid bone, as being seen on the right hand side of the image.
If in these sort of thick skin breeds you can't discern the annual ligament from the surrounding structures, one thing that you can do is just measure the skin to SDFT distance. The SDFT is always easy to find and so is obviously the skin. And this has been shown to correlate actually quite well with annual ligament thickness, so I would certainly use this in my thick skin co breeds, for example.
And this includes the measurement of the para ligament or fibrosis, which can definitely cause constriction of these tendon sheaths. So the annular ligament, a normal horse, we are usually looking at thickness, obviously you can get sort of anechoic lesions within it if you've got disruption of this, but usually, you know, these cases are a bit more chronic, so we're looking at thickness. In a normal horse, we should have an annular ligament that's sort of less than 2 millimetres thick.
And the skin to SDFT distance should be less than 5 millimetres thick. And you know, whilst annual ligament pathology can occur in isolation, as I said before, it usually occurs in conjunction with another injury. In a recent paper, it was shown to occur, in around 68% of cases with another injury.
And so every effort should be then made to thoroughly examine the remainder of the tendency if you can. Sometimes in your thick cob skin breeds when you've got the, you know, you've got your frequency right down, your gain right up, sometimes this is all you'll see, but it certainly gives you an indication that there might be either just this going on by itself or another lesion within the tendon sheath. So lesions in the manicca flexoria, for example, can be found with ultrasound.
And the weight bearing scan provides really good detail, but non-weight bearing scans and non-weight bearing dynamic scans, which I'll touch on as well, has really improved our ability to detect these manic flexoria lesions. For example, the weight bearing scan, not a great sensitivity, 3 to 64% sensitivity, but pretty good specificity, here, so I'mlikely to get a lot of false positives. Images here show the normal maniflexo and a longitudinal on the left hand side, which is sort of you get this little V inserted dorsal to the DDFT and in a transverse scan as well.
Other things to note on this ultrasound scan on the right hand side of the image at the palmer or plantar border of the SDFT is the mesotenon, and this can appear thickened in some cases, . It's unknown whether this cor correlates with pathology, but you know, our certain experience at at Liook would suggest that this is not correlated with pathology but more potentially an indication that you've got some constriction within the sheath. Really note though how well opposed that manica flexoria is to the DDFT and you can, you can see in how a thick skin breed that'd be really hard to determine if that was manicca flexoria for one, and if it was torn for two.
And this is because, you know, the tendons are under tension and it's really, really hard, to, to work out what's what. And this is where the sort of non-weight bearing ultrasound scans have come in. The static non-weight bearing scan is the first thing I would do, and with this, I would have the foot flex, so you can have an assistant flex it, or you can just rest the toe on the ground.
Personally, I like to hold the foot in a foot block. I just think it gives you a bit, little bit better flexion and a bit more manipulation of the limb. Obviously some horses won't like standing like this, so sedation is definitely, probably required when you're doing this.
And things we're looking for is an asymmetric or heterogeneous appearance of the manic flexoria, an unattached margin of the the manic flexoria margin, or thick irregular edges of the maniacal flexoria. So these images here, you know, these are torn maniflexoria in a, in a non-weight bearing scan. So you can see here that on the left hand side and between the left hand side and the right hand side of the images is the same horse, that you've got an asymmetric appearance to the manic flexoria.
It certainly seems more thickened on the left hand side, the lateral side of the of the tendon sheath compared to the medial side. You can also get the impression where the SDFT and the manica flexoria insert that there's an unattached margin here, and as I said, it's thickened in appearance. Whereas on the right hand side of the image, at the the medial border, the manica flexoria seems to be intact and well opposed to the DDFT.
So this would give me an indication that this was torn. But obviously, you know, even with the non-weight bearing scan, these can be, you know, hard, hard to pick up. So this is where the dynamic examination came in, and this was only recently described and it really, you know, personally for me it's really helped me, you know, try and detect these manic flexorial lesions with a bit more accuracy.
And what we're looking for here is floating maniflexoria fibres, displacement of the SDFT in a lateral or medial direction relative to the to the DDFT and I'll show you that in an image in a minute, which hopefully will shed a bit more light into it. You can get a gap between the SDFT and the DDFT at the level of the manica flexoria, and also recoiling of the manica flexoria in more severe cases. So to perform this, the limb is held in a non-weight bearing position and sometimes it is good for an assistant to hold this, this can get a bit fiddly, to be honest with you.
And you apply pressure to the back of the tendon sheath, I usually hold my hand over the back of the tendon sheath and squeeze it with my thumb and and first finger. And you just pulse the tendon sheath here to create turbulence, and this will hopefully identify a tear and the location of the manicca flexoria tear. Sometimes you can just hold pressure on, which again pushes the the more fluid, distilling in the sheath and hopefully just gives you a bit more manoeuvrability between your tendons, which hopefully will allow you to identify some tears of this structure.
So the non-weight bearing dynamic compared to the the weight bearing, as you can see, sensitivity and specificity massively, massively increased and actually this is, you know, a reason why a lot of clinicians now won't bother with other diagnostic techniques because this is really, really sensitive and really, really specific for maniclexorial lesions. So what can we see here in these images? So we've got recoiling of the maniacal flexoria and you've got displacement of the SDFT lateral to the DDFT on the left hand side image.
That manicca flexor looks really quite thick, it looks unattached at that lateral border, and you've got a real big gap between the SDFT and DDFT. And when the manica flexoria, you know, one of the functions of the manica flexor is to guide the the DDFT down and the tendon sheath and keep it nicely opposed to the SDFT. And so if this is broken, then this is why you get this gap.
So in a normal non-pathologic tenden sheath, you certainly should not get a gap between the manic offioria, sorry, between the DDFT rather, and the SDFT. So you can see the two arrows here show sort of, you know, recoiling of the manicleoria, it definitely doesn't seem attached, on, onboard there. These next images should hopefully, you know, they're a bit more severe, and this is an interesting longitudinal scanner actually, which, which isn't commonly done really in the non-weight bearing technique, but I quite like it.
And you can see here this manic flexoria is just, you know, flapping around, it's, it's certainly torn, it's not nicely opposed to that DDFT, . In the middle here you can see there's sort of medial displacement of that SDFT compared to the GDFT, the red asterisk DDFT and the yellow asterisks, the SDFT. Don't confuse the structure on the left hand side of the GDFT for the maniclexoria, that is the mesotenon that we talked about earlier.
And as you can see, this horse is a complete tear of that that border of the maniccalexoria. There's absolutely no structure there that looks like the manic flexoria. And the, as I say, the SDFT is displaced immediately to the DDFT.
And if you imagine in your mind if the lateral border in this case, for example, is torn, then the only thing holding that is the the medial border and so the SDFT is gonna be pulled that way, or vice versa. You can see on the right the right image here you've just got sort of a really sort of ragged edge, a regular edge of the mania flexoria here, with some recalled material laterally. Looking a bit more recall, and this is a really severe case here, you can see the SDFT GDFT, slightly oblique ultrasound scan this, but you can really nicely see the sort of maniacal flexoria looping round, and it's recall laterally.
The the asterisk here actually marks probably what is the previous medial attachment of this mania flexoria. So this horse had a medial mania flexor tear. But you know, these images are a few select cases you quite often don't get images as, as, as nice as this.
DDFT, so don't get, as I said, don't get fixated on your manic flexoria. If you've got a show jumper, 4 limb lame, 10 inch sheet of fusion, think DDFT. Not a great sensitivity.
Specificity's not too bad, you know, 54 to 63 sensitivity, 74 to 92% specificity. They can definitely, definitely be much, much harder to identify and sometimes horses that you scope will have a massive DDFT tear that you haven't even been able to see, on scan. Useful to remind yourself that most tears occur within the proximal digital flex tend she under the man of flexoria, so be useful to look at this area.
Look at the lateral margin, most importantly in these horses, is that's where it's most likely to occur. Oblique images can be really useful to look at these, these as well. So that's a bit of a subtle tear here on the left hand image, right hand is the other side of the tendon, which is normal, bit more severe GDFT lesion here, so that's a bit more obvious to pick up.
The SDFT can also be really quite hard to identify, to be honest with you. 66% sensitivity, 94% specificity. So the good thing with a lot of these is there's not a lot of false positives, but there's certainly a lot of false negatives.
I quite often find it hard to differentiate these between from an inflamed on your ligament. And as I said before, they can also be seen at the sites of attachment of the maniacallioria, and so you get a sort of poor definition of the maniacalfioria and the SDFT. But certainly this case here, in hindsight, we know it had a SDFT tear cause we, did tenoscopy on it.
But certainly you can appreciate the sort of rough and irregular margin of it and also the tendon looks a bit, thickened in this area. So evidence of, a tendinitis here as well. So contrast tonography, you know, again, really, really good diagnostic technique, was brought into play mainly due to the sort of lack of sensitivity of, ultrasound from Malioria tears, especially in these big thick cob skin breeds.
You know, the images I've shown were from cobs. In cobs, it's really hard sometimes to get any image of the tendon sheath, especially in thick skinned ones. So how, how, how do we do these, how do we do this?
So I do them at the same time as local analgesia, which is really good, so you're only putting one needle into the tendon sheath, and I would inject 57 mLs of contrast ihexo, which is omnipe, and 10 mLs of mepivacaine. Usually into the distal pouch, which is what's a scribed, you can use other techniques, you know, this, this, picture here, I think the basic sesamoid technique's been used. You walk them around the room for 4 to 5 strides, then you grab a lamedal radiograph and slight obliquity doesn't tend to affect, your interpretation, of, of, of these.
Another reason I like these and is, is you're descending the sheath with quite a lot of fluid and actually, especially in a thick skin breed, it makes your ultrasound a lot easier afterwards and also separates your tendons during the normal weight brain scan cos you can get a really nice image of that. So just to point out some anatomy, again, as I said, these were brought in mainly for manic flexoria tears. You can see the maniacaflexoria here is this tapering structure down onto the DDFT which is on the right hand side here, and it should taper down nicely to the top of the proximal cessamoid bones where that distal free border is.
You can sometimes get contrast leakage, where you inject it. Don't worry too much about this, but you know, you certainly can get it. And the nice other thing in the, you know, for contrast tonography is that you definitely know you have injected this tendon sheath.
It's very, very easy and much easier than you think sometimes to inject around the tendon sheath, especially with a big needle and a thick skinned leg. You can't just be subcutaneous and injecting it into what you think is the tendon sheath, and this provides some clarity on that. So maniafflexoria, what we, what we're looking at, so it's been shown to have a really good sensitivity for the detection of mania a flexoria tears.
So what are we looking for? So this is from the Kent paper, you know, it's a really, really nice diagrams and I would encourage people to look at this paper. So first thing we're looking for, as I said before, are the two parallel lines delineating the manaclexoria and the end of the proximal sysmoid bones.
If yes, then you've got an intact manica. If not, then you don't, and as you can see on the right-hand image here, we don't have that, that nice tapering structure, there's two parallel lines delineating the manica, so certainly you can say in this case, yes, we've got a manica footorate here. The next one, does the dorsal border of the of the of the of the parallel lines extend distally to the proximal sesamoid bones, and if it doesn't, if it's too sort of proximal, then this can be an indication of a tear as well, .
It's because when you get a tear, you get sort of proximal displacement of of of the tendon. Of the manica, sorry. And then the last one, is there an isolated area of contrast overlying the dorsal board of the of the GDFT at the level of the manic flexoria, as in the left hand image here again shows that there is potentially a manic flexoria tear.
And if we look even further into this, this paper showed nicely that having two parallel lines is the most specific indicator of a manic flexoria being present or not. Displacement of the distal end of the manic flexoria is the most sensitive, as if you've got complete disruption, as I said, you're going to get proximal displacement of the maniaflexoria. The isolated area of contrast is the least sensitive and specific, and so you know, that potentially the least helpful in terms of diagnosing manic a tear.
Tear through the deep digital flexor tendon, so you're looking for a thin line of contrast extending proximately and obliquely from the out pouching of the distal digital flex attendant she distal to the proximal sesamoid bones coursing within the outline of the GDFT. This is actually proximal to the sesamoid bones here, this is the the sender paper, which again is another great paper to look at, and you can see this sort of line of contrast, faint line of contrast within the DDFT in this image. It's got a moderate ability to detect the DFT tears sensitivity of 54 to 72% depending on what paper you look at, specificity 53 to 73%, which certainly can be helpful, but sometimes can be quite hard to pick out these lesions, to be honest with you.
And the last thing you want to look at is a ligament constriction, this can definitely be seen on contrast tonography, and there's been a few papers, the Kent paper, and another recent publication that looked into a ligament constriction that do report these and have some nice diagrams in them. So what you're looking for here, and I'll just go through the images, really, the image on the left, so you've got an irregular contour, a soft tissue contour at the planter aspect of the limb, at the level of the proximal sesamoid bones, and this is consistent with mild annual ligament constrictions, so you can see there's a real sort of concave contour to the limb here at the level of the angular ligament. On the right hand side of the image, you've got an irregular soft kick tissue contour again where you see the arrow.
At the level of the proximal sesamoid bones, and importantly you've got an unequal distribution of contrast in the proximal and distal aspects of the digital flexor tendon sheath, proximal and distal to the sesamoid bones. And I think this is really important, you know, on the left image you've got reasonable distribution, on the right image you can certainly see that there is less contrast in the top of the sheath in the bottom. And this is probably an indication that that sheath has been really tight and constricted.
Again, moderate ability to detect these tears, that these lesions. And lastly, I'll just quickly touch on this, you can use advanced imaging modalities, but they're really invariably expensive compared to tenoscopy, which would be the gold standard. Standing CT and MRI are now available in most institutions, but to get good diagnostic quality images of the digital flexo tenancy, GAS tend to be required.
Standing CT may be helpful, but it's still in the infancy of its, of this technique. So the top paper showed how CT can be useful to diagnose lesions in the digital flex tendon sheath, including manica tears, DDFT lesions, and also on your ligament constriction. Standing CTE, yeah, that's also been used as well, and, and it showing promise in the diagnosis pathology, and obviously you don't need the GE, but you know, there has to be some discussion as to whether these are needed when tonoscopy could be performed.
So as I said, tenoscopy remains the gold standard for the diagnostic diagnosis of digital effects tendency pathology and also allows you to have, you know, therapeutic purposes in there as well. So, you know, obviously some horses might not never end up having tenoscopy, but you know, certainly if you want a gold standard diagnosis, then this is, this is the way forward. So if we go into treatment of these conditions now.
So in the initial period, symptomatic treatment can be started and I would usually consist of some, you know, rest, box rest probably, and some anti-inflammatories. After this acute phase, you're kind of faced with a decision on whether you treat this tendon sheath medically or you offer tenoscopy. Now, a lot of this is gonna be based on your diagnostic image imaging, to be honest with you.
But obviously, you know, as I've just described, there are some failings of diagnostic imaging, but you know, if there were some circumstances such that medical treatment was sought, you know, whether that be finances, whether that be the horse's body condition score, you know, got to remember that a lot of these horses getting, especially manicots and stuff can be very overweight and so their suitability as an anaesthetic candidate really, really needs to be considered. And we've certainly seen some horses that have suffered from post-anesthetic myopathies and even having to be put to sleep because of them when they've only had a simple tenoscopy just due to their, their, their weight. But certainly, you know, if you've got a com a combination of all these techniques, you know, contrast tonography, ultrasonography.
To look and diagnose these tendencies, and there's no lesions you can see there, then certainly medical treatment could, could be, could be used, but obviously you can't 100% say to the client that this isn't gonna have, for example, a DDFT tear. Medical treatment would usually consist of steroids into the digital fix tendencies, but other or biologic agents could be used, but that's a bit beyond the scope of this talk. And Lehman and signs may improve with treatment, but certainly if they recur, then I, I, I would, you know, urge you not to just keep treating these tendon sheaths, you know, if they're recurring, it's for a reason and they probably need some sort of surgical debridement.
As I said, simple tuna synovitis cases may just simply resolve, but more cases, especially if you've repeatedly medicated them, can sometimes result in more extensive damage and form adhesions to tissues which can make them really, really difficult to treat surgically and therefore alter the prognosis. There was a paper by Arnsberg at all, in 2011, that looked to DDFT tears, and this interestingly actually, despite what I've just said, showed that, following the outcome following tenoscopic debridement of these tears was no different in horses that had it straight away before 5 weeks or after 5 weeks from clinical signs. And 55% of these horses that were treated after 5 weeks had intrathecal or systemic anti-inflammatory medications.
And so, you know, there is a theory that, you know, certainly you can medicate these once, but I wouldn't urge doing it more, more, more than that. So certainly, you know, if there's still a concern of these sheaths after you've medicated them tenoscopy definitely indicated. There's some evidence to show that hyaluronic acid might be beneficial in these cases, and reducing adhesions, and this can also be the case postoperatively if you operate on these horses, and certainly I would add this into a treatment regime and the 10 she.
So I would initially rest these for 2 weeks and then make a decision. If it's still really quite lame, I would always go for tennoscopy first. There's no papers really that look at conservative management of digital flex or 10 and sheath lesions.
The only paper that looks at these conservative outcomes was a paper that looked at the treatment of a ligament desmopathy. 38% of the horses in this study were treated 38% they were treated conservatively, returned to their previous levels of work. But you know, given that no imaging modality is 100% sensitive or specific, these cases would have had varied intrathecal pathologies present, as I said before, you know, quite often cases of annual ligament sits, dysmopathy, whatever you want to call it, will have another lesion within that tendon sheath.
And so the outcome for each individual condition within the tendencies kind of remains unknown because we don't know exactly what's going on in there. And so therefore, it's hard to prognosticate how these horses would do medically. As I said, experience would suggest that if you do, if it doesn't become sound following a period of rest and potentially some intrathecal medication, then there's an injury in there that probably requires surgical intervention.
As I mentioned previously, and I just want to reiterate it as well, often people will say, you know, the horse needs an anneligament demotomy, or it has aurligament desmitis, and whilst this is true in a lot of cases, they will have primary lesions of this ligament. You know, it's not always the only lesion within the tendon sheath. As I said before, you know, papers have shown that there's commonly other lesions within the tendon sheath, and the only thing I would mention about conservative treatment is, you know, in the future with all these advanced diagnostic imaging modalities coming through, is that there might be a time whereby we can diagnose these conditions definitively with a 100% sensitivity and specificity or near.
Enough to there, we're never gonna get 100%. And so that might prompt some clinicians to trial medical treatment of certain conditions, and that might provide, you know, additional information in the literature as to how these do medically. But certainly at the moment, unfortunately, lack of evidence, in this area.
So inevitably, you know, tennoscopy is the gold standard for diagnosis and actually the treatment of digital effects of tendency pathology. So as you can see there's a varied range of prognoses for each of these conditions. So, you know, manica flexoria tears, the treatment for this, if they've got a partial tear, you can debride them in my experience, and certainly the hospital's experience, I think just resection of the manicca flexoria is, is probably indicated in most of these cases and certainly ones with complete tears or more, more or less complete tears, resection of the mania flexoria is definitely indicated.
79% of these horses will return to the previous level of excise, which is reasonably good. Deep digital flexor tendon tear is not as great an outcome, to be honest with you, 37 to 42% returned to the previous levels. There is one paper that suggested that longer tears have a worse prognosis, so potentially if you had a short tear, you could prognosticate slightly better, but still not great and treatment's gonna involve debridement of that tendon which can again expose quite a lot of free sort of tendon fibres.
Mechanical resection definitely better than, complation. Coblation has actually been shown to negatively affect the outcome, even though you get a nice postoperative picture. The SDFT slightly in between, 61% of these are going to return to the previous level of exercise.
As, as I said before, you know, you get these at the sites of manica flexoria attachment quite commonly, and these again are just debrided after reception of manaflexoria, or if they're there by themselves, they are just simply debrided with the receptor. Anne ligament constriction, although this is not a a disease pathology within the tendon sheath, obviously the anal ligament is constricting the tendon sheath, and so areas where you are struggling to pass the scope through the tendon sheath or you've got thickening of the annual ligament, certainly this ligament should be cut by an annual ligament desmotomy, closed technique always better than the open technique in terms of post-op sin of sepsis. And 71% of horses with primary constrictions, so as in don't have any other pathologies within the digital flex attendance sheet, will return to the previous level of exercise.
And the differences between these outcomes is, is probably because injuries to the weight bearing tendons, so particularly the DDFT is a more serious injury than one to the non-weight bearing structures such as her mania flexoria or the aneurligament. So, as discussed, if medical management is pursued, I would do a gradually sending exercise programme, after, medication, for example, 2 weeks of walking exercise with reassessment and 4 weeks post-medication to guide further rehabilitation. As I said, if lameness persists at this stage, then I would definitely be sort of prompt, you know, urging the client to do tenoscopy.
Obviously that's not always possible in all cases. And following tenoscopy, the rehab period will be very clinician dependent and lesion dependent as well. But in cases of, you know, angular ligament or manic flexor pathology, you know, they usually require a shorter period period of convalescence and injuries to the deep digital fixed tendon or the SDFT which require a bit longer time because you're wanting a tendon tendon to heal, rather than you, you've simply, you know, removed the manicus, you just want the, the tea synovitis to to resolve.
So for example, cases of a ligament constriction may only require 4 weeks in the box, whereas a DDFT lesion might require longer. Many clinicians, and I certainly would advocate for this as well, would advocate gentle walking exercise after surgery and usually after suture removal, just to try and prevent the formation of adhesions and. These cases sometimes, especially in called thick skin breeds can be prone to sort of infection and so certainly I would, you know, quite often leave this until after suture suture removal.
And I always urge reexamination at each stage to guide a return to exercise or a guide a return to the next stage of, of the process. And many of these cases will need digital fix, tendon sheath medication post-op. Quite often it's easy to think that, you know, it's gone in for surgery, I've treated it, but some of these do require ongoing maintenance management of that tendon sheath, and so that's certainly should be considered, especially after surgery if you've got a lame horse and you've, you know, it's still coming from the tendon sheath, certainly medication of that sheath with, you know, an orthobiologic agent or some steroids definitely, definitely indicated, as the sort of levels of exercise, increase.
So expected time to return to exercise. It's quite hard to sort of pry this apart, to be honest with you, . Horses with intrathecal, you know, SDFT or GDFT tears tend to take longer, so in one paper, the Smith and Wright paper, take longer and so around 7.4 months to return to work compared to the horses, for example, that would have angular ligament pathology which take a mean of 3 months.
And again this goes back to the whole weight bearing versus non-weight bearing structures and also the fact that the angular ligament doesn't need to necessarily heal, you've cut it and you're gonna reduce the tension on there. And actually only 42% of mostly warm blood horses used for leisure activities, treated for a variety of digital flexor tendency pathologies. This is a sender paper, achieve soundness in less than 6 months following surgery, with a further, you know, 17% taking more than more than 12 months.
And you know, again, as I said, the shorter convalescence period for annual ligament is just the difference in the severity of the annual ligament ligament constriction versus these other lesions. So lastly, I just wanted to touch on, you know, that's the main common conditions you're gonna be faced with, but never forget there are other structures in the tenden sheath that can or surrounding the tendon sheath that can be affected, and certainly these structures can give you digital flexor tendency, the fusion and lameness and, you know, block to the tendon sheath certainly. So the first one will be the distal sesamoidian ligaments, that's can be seen here.
So the, the, the black asterisk shows the straight distal semordian ligament, and the yellow asterisk shows the oblique distal cesamodal ligament, obviously, of which there are lateral and medial. You can see the GDFT has been resected here, but you can see how close those ligaments are to the tendon sheath, essentially. So distal systemsmoidal ligament injuries, there was a nice paper by Hawkins, recently that showed that 78% of these will be positive or partially positive to digital flexitten she analgesia.
Interestingly, with these lesions, ultrasound can be as good as MRI to diagnose them, so certainly, you know, concentrate your ability again, not really within the scope of this talk, but cer certainly concentrate your you know your your ultrasound scan to this region as well when you're scanning digital flexor tendance sheaths. So certainly don't forget the pathogen region. An outcome of these, you know, these are a condition that probably initially you want to manage conservatively, unlike most of the other tendency pathologies.
So not a great prognosis, but around sort of 51% with conservative treatment will return to previous levels of exercise, and this is just rest really. If you do additional treatments, shock wave, you know, medication, for example, then 64% will return to their previous levels. There are the odd case in the with these ligament injuries that you can do tonoscopy onto the bride, certainly you can sometimes get torn extruded fibres into the tendon sheath.
And 80% of these horses that are debrided returned to their previous level of exercise, but there was only a small number, in, in the study, so you can't really draw any conclusions from that, to be honest with you. And I thought this was just interesting as well, really, really uncommon to see. But when you're doing your your sort of contrast tinogram, don't forget about other structures.
Sometimes you can get an accumulation of contrast like this, for example. This was a case that had a proximal sputum tear actually diagnosed, definitively during tinoscopy. But just don't forget, if you see a bit of contrast in a weird area, again, links back to the first slide of the anatomy, think back to what anatomy is there and what could be torn.
If there's contrast going into something, it usually means that it's torn. And finally, distal, sorry, digital aneur ligament disease, this would be proximal or distal digital aneur ligament. Proximal digital aneur ligaments could be easier to diagnose, could say within the past and region, as I explained earlier.
Really, really not a common pathology to find, but we certainly have seen quite a few cases at the hospital recently. Definitely more common in cobs and ponies. Cases definitely can block to the digital flexor tendon sheath, but the main thing in these are they have palpable thickening of the distal digital flex tendon sheaths.
So again, don't forget to palpate the distal aspect of the tendon sheath when you're palpating these forces. Ultrasound is the mainstay of diagnosis, as you can see here on the left image. So at this at this site, the SDFT is already bifurcated, but you can see just how thick that pump, the digital proximal digital and your ligament is in this area, and you know it should be around again 21 to 2 millimetres thick, and you know, it's massively thicken this region, you know, up to about 1 centimetre thick.
So it certainly shows that that's, that's pathologic in nature. Medical treatment in these cases in our experience invariably fails due to mark constriction. But surgery can definitely be effective, and we've seen really good results, of, dysmotomy of this and your ligament, to get horses back to their previous level of exercise, albeit most of these horses are only doing low level exercise.
And finally, synoviaces sometimes you'll see a weird structure like this and you'll think wow, is it a foreign body, synoviaces, you know, they, they can occur and they concur in conjunction with other lesions, you know, you can get them in conjunction with a ligament constriction and manic flexoria tears. They're usually found proximal to the PL but we've certainly seen similar structures within the aural ligament. They're firm to palpate, sort of firm sort of nodular swelling to palpate.
And the reason these cause lameness is because you get a sort of one way valve that increases pressure. And this causes irritation to the surrounding neurovascular structures, and neurovascular bundle, which again is gonna irritate that and cause some lameness. But these again have good a good outcome with surgical intervention, whereby it's resected either extrathecally or via the digital flexor tendon sheath.
So yeah, that's, that's everything covered in the talk really, so hopefully that was all helpful, and if anyone got if anyone's got any questions you can feel free to reach out to me anytime. Thank you.
