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Soles…

Sole Failure, is it the same as Retracted Sole?

When I got Walker (an OTTB) the soles of all four of his feet were slate grey. He never had any retained sole, or chalky sole flaking off; they were always hard and grey. Much like hard plastic. This persisted for the first two to three years.

When I first started scrubbing feet and taking photos.

At year 4.5 we were having a nice snowy winter. It was time to trim him and when I picked up the first snow scrubbed foot I was taken aback. Where he’d had only slate grey before, he had a large patch of cream colored sole, with a border of grey. This on his near fore.

As I checked the rest of his feet, I found his other front also had some cream colored sole with a boarder of grey, though not as much as on his other front. His hinds were still slate grey and hard.

I took slivers of the grey sole material to look at through my stereo microscope. When top lit (light shining on them from the top), they looked as grey as they do to the naked eye. But when I looked at them bottom lit (a light below them shining up through them) it became clear that they were a ruddy color, with more definition to be seen between parts. The ruddy color looks distinctly like dried blood.

It’s my studied opinion that at least on dark colored feet, grey sole is sole that has experienced catastrophic failure, and the grey is the sole tubules, laid over past their optimal angle, devoid of the creamy, inter-tubular matrix, which is present in soles where the tubules of live corium have not been laid over or squeezed shut.

The sole tubules (sensitive and insensitive) lack the stiffness inherent in the capsule tubules. It’s the capsule that provides structural support for the sole tubules. Like how a glass drinking straw holder provides structural support for straws. When capsules go long in the toe and heel buttresses are either folded/laid forward or nonexistent due to having been rasped away, the sole tubules, which lack the stiffness of the capsule tubules, are pressed forward and laid down by ground forces.

Pollitt in his book The Horse’s Hoof has a paragraph on the sole wherein he shared that the vasculature of the sensitive tubules of the sole are arranged in each tubule as a corkscrew. From a fluid dynamics perspective, this reveals each tubule of the sensitive sole corium has the design of a small spring.

It’s reasonable to postulate that as the capsule is born of sensitive papillae that give rise to tubules that are surrounded/encompassed in an inter-tubular matrix , that the sole too is born of it’s sensitive papillae that give rise to sole tubules surrounded by/encompassed in an inter-tubular matrix. The live papillae feed all aspects of the sole including that part which exudes the white waxy substance that makes up healthy, cream colored sole.

When sole papillae are squeezed (when capsules contract), or lay over (when capsules grow or are trimmed below an angle sustainable by the non-ridged tubules, the ability to exude the inter-tubular sole is compromised. When these springs, lacking the required angle of support of the capsule, get laid over, the waxy inter-tubular matrix, lacking the structure provided by the tubules or no longer being created any more by those tubules, ends up wearing away from the sole, leaving it to be replaced by an inter-tubular substance made up of possibly a mixture of blood and lymph, or the same substance that serves as the inter-tubular horn of the capsule.

It’s this waxy inter-tubular sole horn that when present, gives soles their depth.

Laid over sole tubules bound by blood, lymph, or inter-tubular horn of the capsule, have no means of growing depth.

This way of thinking about what is going on in some soles sheds new light on Cheryl Henderson’s ‘beetle experiment’. Cheryl put some cadaver feet in with beetles so they could eat the flesh from the feet, and in some of the hooves she found that not all of the soles of some of the feet were eaten. Some had expanses of harder material left on the sole plane. She postulated that this uneaten sole was actually bar, as the beetles would not eat bar/capsule. But what the beetles would not eat was not bar, but sole that had experienced failure and had inter-tubular sole wax replaced by blood and lymph (or perhaps, by the same substance that binds the capsule tubules together) It seems to me that the beetles liked the waxy sole, but were disinclined to eat the failed sole.

I believe it’s a catastrophic laying over of sole tubules that causes the phenomenon of ‘retracted sole’. The tubules lay down from the back to the front of the hoof, and when that laying down reaches the capsule wall the tubules stack up against it, creating the characteristic ramp to the distal/ground edge of the capsule. And when soles have spots of black/grey, that is from the live sole corium being squeezed forward by circumstances (trimming or keep) that cause the capsule to shrink forward.

I’ve reason to believe that the hard sole that develops in failed sole is fortified by the same, or some of the same substance that glues the outer pigmented capsule tubules together. In dark footed horses, a failed sole is grey, and in light soled horses I’ve seen it to be almost orange. So it seems as if this harder glue is in part pigmented by the same substance that pigments the outer capsule. Thus far, the only truly waxy sole I’ve seen is cream colored.

One last thing I noticed was that when I first started the process of bringing back Walker’s toes when his soles were grey, and I rasped into sole at the toe, this grey sole seemed to have moisture in it, again, I wonder about lymph.

The non- structures.

In hooves there are three void spaces that tell us as much about the feet and their state of health as the physical structures do.

The central sulcus is the space between the two legs of the frog. An optimal central sulcus is situated at the caudal half of the frog and opens out of the end of the foot in the shape of a triangular wedge.

The collateral grooves are the spaces between each side of the frog and the bar lateral to it. In an optimal foot both the sides of the frog and the bar will be straight, and the caudal end of the collateral groove will be occluded by the frog curtain.

Lamina. Sensitive and insensitive.

These are the thin fingers that inter-digitate between the internal hoof and outer capsule. The internal hoof is sensitive, having nerve cells. The outer capsule, while still ‘live’, while aligned with and being fed by the inner hoof, is insensitive, not having nerve cells.

Inter-tubular horn of the wall. Laminar serum. Waxy sole substrate.

What even are they and where are they each borne from?

“What are they?” is a very technical question. I want also to know the molecular makeup of each.

“Where are they borne from?” is equally technical. Do they all exude from the coriums, tubules…? I’m guessing that the laminar serum exudes from the laminae, most likely the terminal laminae that grow from the lowest point of each sensitive lamina, creating the ‘white’ line.

Cheryl Henderson, creator of the ABC trim examines sole material by taking a very thin sliver and folding it. She maintains that if the sliver after having been folded, springs back open, then it is bar material. If the sliver after having been folded, retains a crease, it is sole material. A trimmer friend had mentioned Cheryl’s “beetle experiments” to me during a conversation on soles. So I went to the ABC page on Facebook and searched for them. Her photos show hoof capsules that were left in containers of flesh eating beetles that she uses to clean bones. The beetles, she maintaine, would eat sole but not wall. Some of the capsules had slabs of uneaten material over varying parts of the sole plane. While I found the studies interesting, and can see how one might come to the conclusion that what was left on the sole was migrated bar, I’m still not convinced.

Yesterday I took some slivers from the hard grey sole on my geldings feet. When I folded them they sprang back open in just the way, as it’s said by Cheryl, that run forward bar does. When I look at them under the microscope top lit, they appear gray. When I look at them bottom lit, they are not gray but ruddy/brown/amber with brighter flecks of blood in spots. The tubules in these sections also seem to be very shallow in angle.

It’s my theory that healthy sole grows at the same angle as healthy capsule, and when it is at this angle. And when sole grows at an optimal angle, there is an inter-tubular wax exuded from some part of the sole corium/papilae. And when the sole tubules are forced into a more shallow angle of growth, they cannot function the same. And due to being much less stiff than wall tubules, they lay over due to compressive forces and at this sub optimal angle the corium/papillae can no longer exude the waxy substrate. It’s at this point, in the absence of that substrate that something else get exuded in it’s place, or maybe not, maybe this hard, (at least sometimes) grey sole is just what happens in the absence of waxy substrate. It may be blood or blood filled lymph, or that orange serum that sometimes presents on some soles when unhealthy.

I’m trying to find a lab that will do some histology on samples in order to further my understanding. The white sole sliver I took off my horse when folded, holds it’s crease. The grey sole when folded springs open. But I’m not ready to believe that it is bar material that is run forward. On these same feet, when I trim bar to sole level I can see very clearly the white line and the evidence in the laminar serum of the bond of laminar serum and insensitive laminae. And there is no evidence in this white line of bar tubules crossing over it.

But bear in mind, this is just the first flush of my looking at all this. I wouldn’t be surprise if there’s not more to see that’s I’ve not seen yet.

Somethings going on, I just don’t know what, yet…

Retained Sole

The idea that the hoof holds onto or grows anything because it has a mindful preference for that thing has always baffled me. If we really believe that, why trim at all? If we believe that, every horse has exaclty the foot it wants, even the corkscrewed ones.

This false sole is there for a reason, for sure. But it’s not because the hoof or horse wants it there. It is there because this hoof has been trimmed in a way that created a situation where dead sole could not naturally slough off.

Hooves are devices that run on proprioceptive input and responses to ground forces. They are machines, of sorts, running on a program, and responding to their environments. They are programmed to grow and respond, at a biological level. They are not at all thinking structures with opinions. They run on input of information and output of growth. And their ability to run according to their programming can be hampered by how they are maintained by ground forces or humans. The more parallel the walls of a foot, the easier it is for dead sole to remain trapped and tamped solid by ground forces, especially as the wall grows beyond live sole, especially if the wall is heavy and strong or held tight by a shoe.

Bars Follow Buttresses

Except when they no longer can.

When heel buttresses are laid forward, bars are going to lay down on the sole.

It is possible for a hoof capsule to be so compromised that the wall corium from which the buttress grows no longer produces a full buttress.* The back end of the hoof is made of soft tissues. These soft tissues can and will compress when the capsule is trimmed incorrectly. When this happens, the bar is no longer truly attached to the buttress. I’ve seen more than a few hooves where the bar is butted up against wall, as opposed to there being a robust buttress connecting wall and bar. A true and robust buttress provides support the bar attached to it. One job of a buttress is to support the bar structures in maintaining their optimal angle. Optimal bars grow straight from and with a strong attachment to the buttress. From the buttress they grow straight to their natural termination approximately half way down the frog.

When the bar does not have a true attachment to the buttress, it has nothing to hold it vertical. An unattached bar is totally and completely subject to ground forces. The relative integrity of the hoof in front of/under unattached bars may keep them in place to an extent and for a time. This, though, is dependent on how the rest of the hoof capsule is being maintained.

*Similar to what happens to grass if you lay something it, the grass will not grow.

Another thing that just came to me regarding bars…

I’ve seen many hooves that have the tell tale cracks at the natural terminus of the bar. I’ve seen some too, that don’t have it. It occurred to me yesterday that that cracking very likely corresponds to the flex point in the foot that is determined by the caudal end of the coffin bone. The inner sensitive hoof has the coffin bone for structure in the front half (and half is used loosely here), and the back/caudal half of the foot is made up of tough yet flexible structures. So when a horse lands on it’s heels, and then transfers it’s weight forward during locomotion, there’s a bend point that happens between the front and back parts of the foot.

When the hoof is of optimal size, and the corium that grows the bars is as long as is intended by DNA, the flex point falls at the natural terminus of the bars and cracking is visible. When a hoof is foreshortened and the corium that grows the bars is pushed forward into the capsule and under the coffin bone, the natural terminus of the bars is pushed forward as well. When the natural terminus of bar is forward of this flex point that leaves solid bar over the flex point, and solid bar is much less likely to crack due to it’s very design.

Proprioception

proprioceptionprō″prē-ō-sĕp′shən

noun

The unconscious perception of movement and spatial orientation arising from stimuli within the body itself.
The sense of the position of parts of the body, relative to other neighbouring parts of the body.
the ability to sense the position and location and orientation and movement of the body and its parts

There’s so much to say.

The hoof is structure that works on feedback between it’s receptors and ground forces.

Hooves that run forward and grow toe and long under-run bars quickly, are doing so because the proprioceptive receptors are not getting pressed in such a way that growth is signaled that it can slow.

I’ll add more on this when I’ve time.

Time Walker

This horse came to me with flat frogs that had only a hint central sulcus. As his feet have restored his frogs have gone through cyclic changes with the central sulcus going back and forth between somewhat open to pinched. In April of 2021 I saw indication on this frog that this cycle was coming to an end* on this foot, with the hope of his feet being restored to full size and balance a real possibility. They’re not there yet. But stay tuned.

*May 2025 edit: The cycle was, as it turns out, just ramping up. They’re still not fully restored, but they’re so very much better. Better looking to me, and better feeling, as per the gentleman himself.

This is where this foot started, or at least…where it was when he came to me just coming six.

His soles were hard and dark grey, and very thin. His frogs were hard and dark grey as well. He was walking on his perioples and hairlines at the caudal ends of his feet were all on the ground. He was uncomfortable on all but soft pasture. His hamstrings were rock hard, and his stance was camped under. I’d noticed too that when he walked, he would not extend his hind legs past vertical, always walking under himself in back.

I’d been taking pics on and off for a few years, but these snow scrubbed feet re-piqued my interest and hope. And holy skew, Batman.

That spot in the crack at the back of his ‘heel bulbs’ was so odd. It looked very much like what is sometimes found being held onto by oysters.

The periople turns white when waterlogged. The dots follow the growth lines of the periople and highlight how the back of the foot had been pulled down and under from where it should be. The skew in the foot is almost all worked out.

More waterlogged periople. And awkward growth at the fissure between the ‘heel bulbs’.

The fact that periople turns white when waterlogged is very helpful in seeing better what is going on with these feet. You can see how it is unfolding out of the back of this foot.

When I uploaded and edited this pic, and saw the ‘marker’ that is traced in yellow dots I got SO. very. excited. At this point I’d been training my eye to see the movement in the structures of the foot as regrowth occurs and this contiguous line told me that we were finally, maybe, in the home stretch of waiting for the soft structures of the caudal foot to grow back out from where they’d been pulled under.

This central sulcus was deeper than it looked. I could get my thumb in there half way up my nail when treating for thrush.

A bulge? You do you, boo.
You can trace the growth lines in the periople around the back of the foot up around the front of that false central sulcus. It’s not totally unlike watching a hot air balloon unfurl.

Another thing that changes is the amount of ‘flesh’ within the periople. Eight months earlier that area was much thinner, less ‘full’ looking. The skew is back a bit on the lateral (right) side again.

All the while his frogs have been sub par, to say the least. When I first got him they were hard grey/black, unforgiving, unfriendly wedges of nothing-that-seemed-alive or vital.

Every time I look at this pic that pattern of grow out there in the central sulcus reminds me of crab mandibles. And look at the space building along that center line between the bulbs. Also, that bit between the periople and the ground surface, that’s frog curtain. It’s not all it is meant to be, but another unexpected, delight-inducing realization.

See those two flaps there in the crevasse of the central sulcus? I’ve seen those on so many feet. I’d opened up the central sulcus to more easily be able to treat for thrush. And because I was curious what was going on under there.
This was the last time I trimmed anything away from the central sulcus. I wanted to watch to see how it would change without intervention.

It boggles my mind just how much movement, growth and change can happen in a foot in just a few weeks. Look how deep in that CS is. And how much more plump the bulbs are than in the previous pic.

Look at that central sulcus opening up. And at that frog stay growing in, back, and up.

I put this in as the shadow fleshes out a bit more the depth of the thing. That there is the frog stay. It will continue to grow in and move up to it’s rightful place between the heel bulbs at/in the hairline. There’s so much here that still has yet to unfurl.

I heard once that pigs grow bone then flesh then bone then flesh. I’ve since seen similar patterns in other things. In the past week, it looks as if these heel bulbs there at the periople have plumped out. And just look at how wide the area proximal to the frog stay is. And much thanks to a rainy day for highlighting exactly where the periople is. Notice how it is no longer shooting up between the buttresses.

The heel bulb/periople area is nowhere as thick as a few months ago. We’re coming into new coat season, and I’m thinking that between the minerals that demands from the body, combined with the growth that’s going on in all four of his feet (his hinds hoof walls have lost quite a bit of color over the past few months) I’ve decided to go get a bucket of Frank Lampley’s minerals, as it’s a stellar product and he’ll eat it straight if he needs it.

At this point he’s had three days of the Frank Lampley’s. I write that as a ‘let the record show’ as I’m not keeping track anywhere else. I’m always a bit bummed when my pics are not clear, but it’s still clear that there is some plumping going on in his caudal hoof there under the stretch of periople. The clefts around that protrusion don’t seem as deep and there’s more room between it and the hairline.
He’s got these back-of-central-sulcus-clefts going on on all his feet at this point. His hinds are bringing up the rear, with his off hind furthest from good, but it’s both interesting and heartening progress.
It’s alarming to think just how small some horses are having their feet trimmed.

Periople has thinned out considerably since this past September. Central sulcus has deepend and thinned, both from the caudal foot at the hairline growing out.

The staining and frog changes here are due to it being “stand around the hay manger in urine soaked hay and poo” season. I’m glad it’s coming to an end. There seems to be chuncks of heel and bar growing in there on his lateral (left of pic). Tubules newly uncovered often first regrow with less pigment at first, and darken up later.

Heels look long, maybe true, but given how drawn forward the caudal
hoof is, as indicated by the shape of the frog, heels are growing down
from where the heel quarter would be in a fully expanded foot. Dropping
these heels would strain the bony column and the system of softer fascia
supporting it.

Quite a crack there on the lateral heel/heel quarter…

Of interest to see how much has fleshed out there were the central sulcus/frog spine is regenerating. Interesting too how the periople gives way when grown out of (at the lateral heel).

Not sure what insult took that medial heel out. Pics like these that make my eye twitch, and have me out addressing balance the next day.

More growth at center caudal… Still has that crumbling medial heel buttress. Check out the fold in the periople where the heel buttress comes through.

And now…expansion there at the back. And if you zoom in on that white bit of buttress growing down from the lateral periople, you’ll see that it’s new growth.
New growth wall often first comes in with little to no pigment. See too how when the periople (on the lateral) thins out during this phase of regrowth that it leaves the heels looking even more high. Granted, this is pre trim, so they are a bit high…on the lateral, anyway.

Poochin out at the central sulcus again. And low the bit of new (unpigmented) buttress continuing to grow down on the lateral.

So clean…

It’s fun too, to watch the hairline change…

Still with the lateral heel buttress growing in un-pigmented.

I feel like that there is a whisper of a naturally open central sulcus…

Still more unpigmented sole there on the lateral. And check out the change in trajectory mid way down the buttress.

There’s a lot more creamy sole coming in…

Wondering here if we’re not about at the end of what has yet to grow out at the central sulcus…

Well, I guess the answer to my wondering is “Not quite yet.” But again, check out the flap there along the inside of the central sulcus. That’s looking like a natural terminus to me. Again, love the water soaked periople shots for added clarity. And appreciate again, in water logged clarity, how much more creamy sole is growing back in.

Bonus sole shot. Again, look at those triangular flaps at the central sulcus. Those aren’t cut out. Those grew that way. I’m pleased as punch with the improvements in these feet. Everything’s improved. Not 100%. I’m not sure if 100% is achievable given how early he was shod and how bad his feet were. Time will tell…

Buttress~Heel~Switchback

A Buttress by any other name…
https://www.thoughtco.com/what-is-a-flying-buttress-4049089

The hoof as a whole is an amazing mechanism that is perfectly suited to it’s purpose. Everything on this earth that grows naturally has been engineered to it’s current form by the forces around it, and so, can be thought of using the terms of engineering. https://simplicable.com/new/material-strength

The buttress (and bar) structures serve as the lynch pin of the hoof.

Turns out, ‘lynchpin’ is very similar in meaning as ‘buttress’. Who knew…

This is not yet an optimal buttress, but it’s getting there. Note the laminar line is still a bit pointed. Note the increase in bulk.

Picture a hoof capsule without a buttress. It wouldn’t work. It doesn’t work.
When buttresses are compromised, the hoof is compromised. Full stop. Compromised being less than optimal.

And optimal buttress is more than the sum of it’s parts. Literally.

Buttress mass = Wall mass + Bar mass + (X)

But it’s more than just that. This fortified structures hold their respective heel walls and bars at a specific angle to one another. From each buttress, the bars point back into toward the center of the capsule, to the toe quarter on the side opposite. The buttress is pointed at its outside, posterior end and the yellow laminar line makes a graceful arch around it’s interior edge.

But here’s the thing . . . It’s not always easy to see when a hoof has a compromised buttress. But, there are some tell tale signs specific to buttresses not yet being all they can be, and that there may be an issue, bearing in mind that each foot distorts in ways specific and peculiar to their own internal weaknesses and external conditions:

Thin bars ~ Thin bars can happen when the hoof is run forward from behind.

Laid over bars/bars that wont ‘stand up’ ~ Bars stand up only by virtue of their solid attachment to the buttress structure, so if they’re not solidly attached, or if the buttress structure is no longer there, the bars by virtue of the horses weight and ground forces, can only lay over.

Cracks where bar ‘joins’ buttress ~ But when there’s a crack, that’s a sign that the bar is no longer joined to the buttress. This show up as a buttress is getting trimmed out of the foot, or as the foot is being rehabbed.

Bar abutting buttress further up the wall ~ This is the next step after a bar crack. First there’s a small dis-attachment between the bar and buttress. Then, in some feet, as the frog structures get pulled forward, the bars get pushed along forward in front of it.

Curves ~ Curved bars are a sign that the back of the foot will expand when trimmed in a way that will allow for this.

Kinks at the buttress end of bars ~ Kinks at the buttress end of bars are what happens mid way between curved bars and a dis-attached bar that is heading up the solar surface of the foot.

*Some examples below were found on the internet, not sure whom to credit.

Thin, curved bar. An optimal bar will be a bit more robust than this.

Kinks where bars become buttress. Bars look thin as well.

Bar kinks at buttress. Crack between bar and buttress. Bar also looks of different material than buttress where the bar currently butts up against the buttress-yellow arrow. Notice how the bar is grey and the wall a dun color. If you were to push the bar down along the wall to where the red dots would run in a straight line, the grey of the bar would match up with the grey of the caudal end of the wall there.

Buttress on left is scant in size with crack. Crack at bar/buttress meeting on right.

Distinct kink where bar and buttress meet. Crack started too. Bars curve before they kink when the back of the foot is being drawn down and forward.

Bar migrating up the inside of the wall. Bar outlined in red dots. Wall outlined in blue.

The Hoof As A Pump~Does the horse really have four hearts?

Do the hooves really serve as additional hearts? Is the frog a pump?

I’ve read recently in Pollitt’s book, that the veins in the horses hoof do not have valves to stop back flow as other veins do. If this is really the case, it highlights just how important movement is to the health of the horse. It is movement that unloads and loads the foot, and it is this loading and unloading that serves as the dynamic pumping action of the foot. Without movement, there is risk of stagnation.

I’ve read more than once the frog described as a pump. The importance of a beefy frog with ground contact upon weight bearing being the hallmark of desirable, which to me meant that others were thinking of the frog as a push pump. What I understand of biology is in line with the concept of the foot serving as a pump. But what I know about engineering showed me that it’s not that the frog is a ‘push pump’ so much as it is the whole mechanism of the hoof that works as a bellows pump, and the frog serves as the bellows proper.

A perfect Bellows Mechanism.
White-Bars, Aqua-frog wall, Blue-Central Sulcus Wall

Moving from the left to the right: the bar, outside frog wall, central sulcus wall x 2, outside frog wall, and bar wall all work together to form the bellows.

The wall, serves as the spring mechanism upon which the expansion and contractions of the foot acts, and that returns the expanded bellows to it’s un-expanded state, when pressure is released. When the foot is weighted, both the bellows and the wall expand. When the foot is unweighted, both the bellows and the wall contract. The degree of movement is nil at the toe, directly opposite the caudal foot, and increases in amount to where it is is largest, across the heel end of the frog.

Comme ca.
Don’t @ me. Desperate times call for desperate mock-ups.
1&8-wall/spring mechanism, 2&7-bar, 3&6-frog wall, 4&5-central sulcus wall

As you ponder these things, imagine what goes on inside a foot when a static shoe is nailed on to the expansion spring while the mechanism is non weight bearing, and so, contracted. Then imagine what happens to the forces put on that now fixed structure when is is weighted.