Flare induced sheared heels. WARNING - PIC HEAVY

Blue Flame · Flare induced sheared heels. *WARNING - PIC HEAVY*

The subject of sheared heels and lateral flares came up in Alva's thread on Rosie's feet. In this thread I'd like to put forth a hypothesis concerning how a flare might induce a hoof deformation resulting in sheared heels. I've put it into a seperate thread so as not to confuse Alva's thread as my hypothesis does not take into account any existing conformation issues - it merely works through a process in which a flared quarter might (or might not) induce hoof deformation and flared heels.

If nothing else, it might just get our minds looking from another perspective and will hopefully lead someone to think about things in a new way. I'd just like to put it up for discussion/critique etc. in the hope that it might lead to something useful to us.

I make no claims as to the correctness of the theory as it is only that - just a theory. Also, I must state up front that I did not follow the theory through to actually lowering the medial heel as suggested. In the end all we did was to keep the inside heel and wall down at the sole plane and keep the inside heel platform as far back as we could while not invading live sole.

So, now that the disclaimers are out of the way - Here goes:

Beginning with a normal hoof capsule diagram (black lines) as viewed from the rear of a right hand side foot, we see the beginning of a lateral flare (red). We are assuming in this case that the hoof and pastern axis are in perfect alignment. The second assumption made is that the flare is able to pull through the wall whiteline, sole and bar whiteline such that it causes the bar on the same side to flare outwards as well. Since the bars initially were the same length, the newly flared angle of the bar caused the heel to swing with it into a vertically shorter and more forward position - that is, the heel is pulled outwards and forwards towards the flare. So now we have a heel imbalance caused by flare forces in which the heel is unweighted.

In the second diagram, since the lateral heel has been unweighted, more load and hence wear is transfered to the lateral wall. This extra load wears the lateral wall down more or causes it to flare more (red area) and causes the hoof to tilt over to the lateral side as it wears down or flares it outwards. As it wears down, a new ground line is established in relation to the hoof and it becomes low on the lateral side. This new wear pattern has the effect of unweighting the medial wall and transfering some of the weight to the medial heel and bar (see green shaded area). Looking at the forces acting on the hoof, a number of things come to light:
1. On the lateral side, we have the ground pushing the quarter wall upwards and at the same time we have the weight of the horse pushing the unsupported (by the ground) lateral heel/bar structure downward. These two forces create a couple or torque which acts to rotate the lateral wall and heel/bar anticlockwise relative to eachother. This couple or torque will not be balanced until both lateral wall and heel/bar are both being supported by the ground either through wear or distortion of the structure. If these forces do not balance and stabilise, the outward flaring will continue.
2. On the medial side, we have the opposite thing happening with the wall/heel/bar structure. The tilt of the hoof away from the medial side has unweighted the wall and transfered load to the heel/bar (green area). We have the ground pushing the heel/bar upwards and the weight of the horse pushing the wall downwards. Again, this sets up a couple or torque on the wall/heel/bar structure which acts to distort the medial wall and medial heel/bar in an anticlockwise direction relative to eachother. As with the lateral side, this couple or torque will only be balanced when the wall and heel/bar have even loading with the ground - whether by wearing down the heel/bar/sole to the level of the wall or by overgrowing the wall/sole to fill in the green area. If these forces do not balance or stabilise, the medial wall/heel/bar structure will become more upright or even flare "inwards".
3. Since the hoof as a whole has rotated clockwise, the hoof axis is now out of alignment with the pastern axis - or the limb if you prefer. Assuming that misaligment of a loaded joint under load is less comfortable and causes more fatigue, we might expect the horse to try to realign the coffin joint. In order to do this with the right side hoof, the horse could place the hoof further to the left, which will cause the limb axis to lean over to the right to match the hoof axis. If the horse had a mirror image situation happening on the left side hoof, then he would tend to stand with the hooves closer together so as to minimise the angle through the joints. Unfortunately, when the horse does this, it tranfers more weight to the lateral wall and medial heel and further unloads the lateral heel and medial wall - so worsens the situation as far as forces acting on the hoof in an effort to reduce stress through the joints. Also note that the feet can only move medially until they begin to interfere with eachother.

So we finally end up with a hoof that ends up looking like the one above and a horse that stands with the feet close together. Below is the hoof that started me on this theory while trying to work out what to do for him (not long unshod at the time - they look much better now). You can see the upright-pulled in medial wall, the flared lateral wall, the upright medial bar, the flared lateral bar, the pushed up medial heel bulb and the more foward lateral heel.

So here is the conclusion that I came to at the time - again, I must re-iterate that this was not the option we used in the end. This is just an extension of the theory above and was formulated when I knew much less about the internal structures than I do now (which is not so much, but still way more than back then).

I was thinking about this and did a bit of analysis which I've marked up in the attached pic to see how lowering the inside heel might pan out.

In red is the effects of lowering the inside heel and how the wall angles would change in relation to ground level. The hoof would lean over to the left. This would seem to make the wall angles worse but it changes the way forces are applied to the walls in ways not obvious.

In green is the effects of the horse standing wider if lowering the inside heels makes him more comfortable. The significant thing that happens if he stands wider is the pastern leaning over to the left in relation to the hoof. This changes the forces applied to the base of the hoof wall.

In crimson, this shows how the forces have changed that act on the base of the hoof walls. Because the horse stands wider, his weight comes down through the hoof and more to the right. The reaction force at the ground comes up through the hoof and more to the left to balance it. The crimson arrows show the "to the left" part of this force which should help to spread the upright inside wall and heel and gather the flared outside wall and heel.

There is so much more to the forces acting on the hoof when moving. The major weakness of the above as I see it is that it really only considers the stationary hoof and doesn't take into account how the hoof might land, or the twisting action on the hoof that might be present at breakover as it was in the real hoof above. We'll leave that for the discussion . . . . if anyone's up for it . . . . .

Newfman

Very well done. I will have to read it ten more times to fully encompass everything

Just kidding.

I like it. I pose this question though. If I understand this correctly, you are effectively suggesting that, ultimately the presentation is such that the medial heel is properly situated and the lateral heel is effectively....extended (for lack of a better term)? I only ask because I was under the impression that the medial heel is effectively driven upward, and the supportive internal heel bulb structure has evectively, 'caved in'. Therefore, the pastern angle changes towards leaning in on the medial side, like a car with a flat tire. In other words, your (very excellent) diagram (3), the topline on the medial side (this is a left foot by the way , correct?) dips down, when I would have thought of it being elevated.

As far as the photos and trims go, there is obviously a good hoof in there needing to get out. You look to be giving it good guidance. That was my point with Rosies feet (Alva's mare) At some point, someone needs to perform a proper trim, then re-evaluate what you have.

Great job! By the way, I may be wrong.

Blue Flame

It's a right side foot in the drawings and right hind in the pics. So the flare causes the opposite heel to be driven up at the same time as the adjacent heel is pulled outwards and forwards. The medial side is driven up and also twisted anticlockwise to make it more upright- making the medial heel,bar and wall more upright. The lateral heel is pulled laterally and so the lateral heel, bar and wall lays over and flares as a unit. You can see this reflected in the solar pics - look at the angles of the bars and line of heel/bar turning point to bulbs. See how the lateral flare is pulling the lateral heel outwards and forwards. Also see how there is a wider expanse of sole on the lateral side.

It could just as easily be a left foot but for the purposes of the explanation and the use of the terms 'medial' and 'lateral' it is a right foot.

One basic premise of this is that if long toes can pull a hoof and heels fowards, then why not a flare pulling things sideways? Imagine looking at the sole of the foot as if trimming and that the foot is made of flexible rubber. Imagine then bending the quarters outwards - would that not pull the heel on the same side outwards and forwards. So in the scenario described above, at the same time the medial heel and bar is becoming more upright or vertical, the lateral heel and bar is becoming less upright and more horizontal - it's a double whammy where the medial side becomes taller at the same time as the lateral side becomes lower.

Newfman

I mis-read, I just went back and read it again. Don't know how I got turned around but yes, I see it now, and I think you have a very good explanation. I, personally, don't think of long toes "pulling" the heels forward, as much as interfering with the rollment/unrollment of the hoof in such a way as to keep a horse on its heels in an unnatural manner, basically pounding the heels forward, just like you are describing with pounding a heel into submission, creating a collapse hence, shered heels.

The same kind of effect. That is why I think taking the heels out of play for awhile and giving them time to change direction of growth could be helpful in the healing process.

Very impressive diagrams, have I said that yet?

Flare induced sheared heels. *WARNING - PIC HEAVY*

Flare induced sheared heels. WARNING - PIC HEAVY