An important hoof parameter that has probably never been considered before - pt. II
Updated: Nov 26, 2022
What happens when DCA is out of range - 6 hoof types
In the previous article we have explained what DCA is, how to measure it and why it is important. We mentioned that specific angle range values go hand in hand with certain characteristic features of the hoof. Before we describe each type, we need to pre-introduce one more parameter that will help define what type of hoof we may be dealing with.
This parameter is the angle between the coronary band and the medial and lateral wall of the hoof in the front view (we’ve named it QCA - Quarter wall - Coronary band Angle). The guidelines on how to take photos and measurements as well as the normal ranges have not yet been defined and need more investigation - so we will only outline the topic in general.
These angles are important, because they are likely to tell you about how much load the hoof is bearing, how the load is being distributed over the hoof capsule and how well the hoof capsule is dealing with it. Unless the walls are flared or deformed, it goes hand in hand with the angles the side walls are creating with the ground - that may be easier to measure. Specific ranges of values may be difficult to assess due to genetic differences in coffin bone shapes, but what we should look at is whether these angles are similar on both sides of the hoof and in a pair of limbs.
when medial and lateral QCAs are similar within the hoof capsule but there is a significant difference in their values between the limbs, it indicates that the leg with wider QCAs is being overloaded and/or the leg with narrow QCA is being unloaded
when QCAs are not symmetrical within the hoof capsule it indicates that the center of pressure is probably shifted to the steeper side (the side where the QCA is narrower)
the bigger the difference, the bigger the disbalance
HOOVES WITH TOO WIDE DCA
We have distinguished 3 types of hooves with too wide DCA (above 108-110 degrees).
Migrated forward Flat and collapsed Coronary band dropped in front
TYPE I - MIGRATED FORWARD
The first type of wide DCA hooves are the ones that have migrated forward from heel to toe – where literally each tubule is migrated forward. Therefore, they may even have tight white line (which often temporarily deteriorates during the rehabilitation process) and sufficient sole thickness but often struggle to build true concavity under the edge of the coffin bone – as the sole tubules grow forward instead of downward.
When viewed from the front, the QCAs are usually normal to narrow.
The heels are long and at a similar angle to the dorsal hoof wall (not underrun), but a hoof angle is often too low.
Broken back hoof pastern axis that tends to break rapidly at the coffin joint and mildly at the pastern joint. The third case has been diagnosed with some kind of ddft degeneration.
They often have very long migrated frogs with the apex pulled even to the area of the edge of the coffin bone – thus this hoof type may be hard to map for an inexperienced person. Bars can be very long and grow forward, so they may seem to end even around the frog apex. Sometimes it looks like they ‘choke’ the frog so it becomes narrow in the middle and takes this characteristic shape .
Oblong sole shape, long thin frog, long bars, base of support far in front - all are very typical in migrated hooves.
Those hooves often retain sole (sole and bar tubules sometimes 'stick' together with the frog tubules and grow forward) or form a characteristic little ridge of sole in front of that stretched frog apex.
Oftentimes, to maintain proper dorsal hoof wall angle, those hooves need to have really long heels – sometimes even close to the length of the dorsal wall. This causes the collateral groves to be very deep (especially in relation to the front part of the sole) and that sometimes goes along with weak underdeveloped digital cushions and frogs. Shortening/pulling the heels back causes the palmar angle (PA) to become too low, the hoof pastern axis (HPA) to be broken back and most times actually exacerbates the problem. The toes may seem long even when there is little material to shorten them.
When you ‘pull the heels back’ on those hooves (no matter how underrun they are), you only exacerbate the problem.
With those hooves you have to decide whether to prioritize the concavity and sole thickness, heel length/height, position of the base of support or PA/dorsal wall angle. Because of the migration, the structures within the hoof are not aligned properly with each other and it’s not possible to get all of the parameters correct. You have to (by design temporarily) sacrifice at least one of them to get the others correct. We are going to talk about in details in the article about how these hooves can be improved but below we've outlined the problem in general:
1. Leaving sole depth, partially compromising the hoof angle (too low) and the heel length (too long). Base of support is far forward.
2. Prioritizing hoof angle, sacrificing sole depth (too little concavity) and heel length (too long). Base of support is far forward.
3. Prioritizing heel length and moving the base of support to the back (‘backing up the hoof’), severely compromising hoof angle (too low). Notice the angle of the heels to the ground – except for being ‘pulled back’ (when looking from the sole plane), they are now at much shallower angle to the ground, thus more susceptible to become underrun. The horse has to raise the fetlock to adjust to the lower PA, which is going to make the hoof capsule migrate forward even more.
Those hooves may be called ‘long’, but unlike often taught, with this type of hoof, it's neither the long toe that is the problem, nor is it the heels that run forward. Often the heel tubules grow at a similar angle as the dorsal wall does. It's the whole hoof capsule that has run forward.
An illustration showing a simple analogy how the tubules migrating forward make the hoof look long and may make them seem narrow – which usually is only an illusion.
As hooves of this type may have quite an oval and long shape, some people also tend to find them narrow. They don’t need widening though, but moving all the tubules back. As they do, the long shape of the sole becomes more round.
Sometimes the capsule can move back really quickly, sometimes it takes months. Photos of the same hooves prior trim, 6 weeks apart. This type of hoof may occur uni- or bilaterally and is typical in horses that stand with raised fetlocks. Those hooves, if they don’t start improving quickly after first adjustments (2-3 cycles), can be one of the hardest to rehabilitate.
An example how DCA can change in this type of hoof, which we'll talk about in details in the following articles. TYPE II - FLAT AND COLLAPSED Another type of hooves with too high DCA are the flat, low hooves with very little sole thickness and concavity, weak, collapsed, splayed heels, weak white line and wide QCAs.
They tend to flare all around, bulge in the quarters and are unable to grow in height, instead they mostly grow in circumference. Unlike the migrated type, they usually have very little depth in the collateral groves, bars that grow at a shallow angle and thin, flat soles all over the sole plane. Frogs are usually quite wide but super thin as the solar and frog corium are being compressed. They literally lack mass and height and probably won't improve unless you get a new tighter growth from the coronary band.
Underrun heels, low hoof capsule that tends to grow only in circumference and not in height. The horses either put the leg in front or a little back under the body and raise the fetlock. Usually the other leg is a club foot.
Broken back hoof pastern axis – unlike in the migrated type, usually the hyperextension of coffin and pastern joints is similar, there is no rapid break at the coffin joint. The sole will be flat and thin and collateral groves shallow.
Wide, round shape of the sole, stretched white line and flares all around, heels and bars splayed to the sides.
Flat, thin soles, very little depth in front and in the back. Bars seem to be laying on the sole – they literally have no space to grow down.
On the DP view these hooves will be wide and low. You may see the flares, stretched white line, low PA (narrow joint space in the coffin joint), thin sole and shallow collateral groves. Hooves of this type are usually really wide in circumference and some people may consider this as an advantage. That is, of course, not the case and what they actually need is to become smaller in the circumference and narrower. As they do, the wide shape of the sole becomes smaller and more oblong.
An illustration showing a simple analogy how the collapsing tubules make the hoof get wider and shallower. These horses in most cases stand with raised fetlock or put the overloaded leg in front to ease the ddft pull. They can develop an over at the knee posture in the overloaded limb. Those hooves rarely occur bilaterally - usually they occur as the low foot of the high low horses. It seems that those hooves collapse due to not being able to withstand the amount of load the horse bears on them because of compensating for some problems in the opposite leg. Most of the times they can be improved to some extend but it usually requires at least one new capsule growth.
An example how DCA can change in this type of hoof, which we'll talk about in details in the following articles. TYPE III - CORONARY BAND DROPPED IN FRONT
Hooves with bowed coronary band that drops rapidly at about ½ to ⅓ of the hoof length towards the front are another type of a too wide DCA. (Not to be mistaken with caudally collapsed hooves where the coronary band gets round and drops in the back.) Their biggest problem is usually little concavity and sole depth in the front (due to too short/compressed DHW), however the caudal part often has decent morphology - they can have proper depth, heel height and angle and good digital cushions and frogs. The hoof angle may be okay but the dorsal wall literally is too short. They tend to flare but usually only at the dorsal wall. The QCAs can be from narrow through normal to wide - it seems it doesn’t correlate with the issue.
In the lateral aspect the hoof capsule seems short an tight. They may have problem with getting overal depth (which may or may not improve with shoeing). Again, like in the migrated hooves, you may need to prioritize depth in the dorsal part of the hoof or the hoof angle (if you have any depth to remove at all). The flares in the dorsal part of the hoof wall are common, but they usually don't come back when removed - the solar plane is then wide and short.
When looking from the bottom, often the only obvious problem is little concavity in front of the frog apex. The caudal part of the hoof may be very decent or may be deformed independently to the dorsal part of the hoof capsule. Unless the sole is stretched, the distance from the frog apex to white line at the toe is very short. Some people believe the bowed coronary band shape in such hooves is caused by too high quarters and that relieving them can help. In my opinion it's not the case and it's not the quarters being too high but the dorsal hoof wall being too low (the fact that they improve also in regular flat steel shoes with a flat trim seems to prove that). This type of bow in the coronary band is also not caused by heels running forward, as in many cases they grow at a similar angle as the DHW. Like type II, they usually require new growth to improve the coronary band shape, get proper height of the DHW and gain concavity in front. We see them mostly bilaterally and usually they also improve more or less simultaneously. Like in type I and II, these horses also tend to raise fetlocks when standing (even when the PA is not low) with a hyperextension of the coffin joint and much less of the pastern joint. In my experience they are not as common as types I and II.
An example how DCA can change in this type of hoof, which we'll talk about in details in the following articles. SUMMARY What all 3 types have in common, is the problem with sole depth. Sometimes it may be hard to tell of which type the hoof is, as you may have a combination of all 3 types to various degrees. What is also common for all 3 types and consistent in every case we've examined so far, is that they occur in horses that have a broken back hoof pastern axis - either be it due to too low PA or due to purposely raised pasterns which horses do in order to ease some kind of discomfort in the hoof or higher in the body. In the following articles we will focus on what to do to help them improve, what this process may look like and how much we can achieve. In the next part we are going to talk about the narrow DCA hoof types.
Special thanks to Ada Majocha DVM (Advanced Equine Podiatry - Ada's FB page) for all of her input and time spent on discussing this topic. <3