An important hoof parameter that has probably never been considered before - introduction
WHAT IS DCA
The angle between the dorsal hoof wall and the coronary band in the lateral aspect of the hoof capsule - for convenience we have called it DCA (Dorsal hoof wall - Coronary band Angle).
When evaluating hooves, there are so many parameters to be taken into account. There are normal ranges set for the values of PA, dorsal hoof wall angle, sole depth, heel length/height, coronary band angle, etc. However, there is one really important parameter that we have found not much mention of - the angle between the dorsal hoof wall and the coronary band (in the lateral view) - and it seems some systems assume this angle to be constant in every hoof, thus irrelevant.
HOW DO YOU MEASURE DCA
This angle can only be measured in the lateral 2D view and the photos used for comparison should be taken at a specific and consistent angle and distance from each hoof. (Measuring DCA using photos taken at different angles and distance will likely give different results! - The article on hoof distortions in photography is about to come.) Unlike commonly established, we don't measure the coronary band angle using a straight line from the coronary band at the toe to the coronary band at the heel bulb. We find that it can deform due to various reasons and that the bows, especially the ones in the dorsal part of the hoof capsule, shouldn't be ignored. We use about a ⅓ rd to a half of the coronary band length starting from the front - to more or less the center of rotation of the coffin joint (the caudal part can be bowed and deformed due to some unrelated reasons like eg. caudal failure) - and the dorsal wall angle (the angle of growth in the upper part of the wall - so we do not take flares into account).
WHY SHOULD YOU MEASURE DCA
What is most important is that this angle varies - not only between horses (this could mean that it is dependent on genes) or between individual hooves (could be due to the factors occuring during the growth and development of the bones) but it is not even constant for each specific hoof over a period of time.
We observe that specific ranges of angle values go hand in hand with the characteristic features of the hoof. We have been using this parameter in our practice for some time already - to determine the condition of each individual hoof. We feel it may be telling you more about the ‘real’ hoof (and whole body) situation than any other parameter: both the value of the angle and how fast this angle can change over a period of time. (More about it to be read in the next parts of this article.)
We have examined numerous hooves in our archives and have found that in the best hooves DCA is within the range of 100-108 degrees with the accurate value depending on each individual horse’s conformation. We are still working on establishing this range. So far we have observed that DCA below 95 degrees and above 115 degrees almost always indicates that we are dealing with some kind of hoof pathology.
The differences in the value of the DCA can be really significant – so far we have found it to be up to 43 degrees.
And it can change really quickly – up to around 10-11 degrees in 6 weeks. Photos of the same hoof, 6 weeks apart.
WHY DOES DCA MATTER
Simply because it is not possible to achieve proper hoof proportions when DCA is out of range.
We have picked 3 hooves - one with a really small value of DCA (horse with a ddft contracture), one close to ideal and one with a very wide DCA (horse that has undergone tenotomy) to illustrate the problem. Note that none of those cases has a big problem with underrun heels - they are almost parallel to the DHW.
It's not possible to just trim a proper hoof out of a hoof that has either too small or too high value of the DCA, nor can it be achieved with any shoeing package like wedges etc.
1. too small DCA, too steep DHW angle 2. hoof with good proportions 3. too big DCA, too low DHW angle
To obtain proper (like in the hoof in the middle) DHW angle to the ground, one would have to trim or wedge accordingly.
An attempt to achieve the same DHW length and angle on hooves with different DCAs - note the heel height/length.
With a too narrow DCA one would have to trim into the soft tissue, whereas with a too wide DCA, after wedging, the coronary band would be almost parallel to the ground and the heel length close to DHW length.
An attempt to achieve the same heel height on hooves with different DCAs - note the vast difference in the DHW angle.
An attempt to achieve the same coronary band angle (30°). Not only will it give you massively varying hoof angles, but with many hooves it may not even be possible without actually cutting into live tissue!
The fact that DCA for each specific hoof can change over time indicates that there is not a consistent relationship between the coronary band and the coffin bone. It makes the use the coronary band angle as an indicator of a proper or improper palmar/plantar angle or the use the 30 degree gauge to tell the PA without x-rays questionable, especially when DCA is out of range.
An example how DCA affects the relationship between the coronary band and the PA. The first hoof has DCA of 130 degrees and the PA gauge would give an error of 17 (!) degrees. The second hoof's DCA is within the normal range. Photos from Ada Majocha's archive.
An example of a front (1) and hind (2) hooves with wide DCA values and a template showing a value some systems would assume every front (105°) and hind (95°) hoof has.
Although you can not change DCA with a trim or any shoeing package directly, you can trigger those changes to happen over time. As mentioned above, specific DCA ranges go hand in hand with characteristic hoof features that indicate what we are dealing with, what the hoof needs in order to improve and determine how much we can help ad hoc.
WHAT HAPPENS WHEN DCA IS OUT OF RANGE
We have distinguished 3 types of hooves with too high value of DCA (above 108-110 degrees) and 3 types of hooves with too low value of DCA (below 100 degrees).
Wide DCA hoof types:
Flat and collapsed
Coronary band dropped in front
Narrow DCA hoof types:
After a severe inflammation like abscess, hoof injury or laminitis (sometimes temporary)
We will write about each type, how they can be improved and what may possibly affect the DCA value in the next articles.
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