Founder & Laminitis (Under Construction)
The following diagram comes from the May ‘99 issue of Practical Horseman:
This is a good depiction showing the progression from a healthy foot to a rotated one. However, the heels which give us most of the information about the possibility of rotation, have been obscured.
The important information with respect to rotation, laminitis, and founder can be found in the thickness of the sensitive laminae, as well as the orientation of the coffin bone relative to them.
1. Healthy Foot. The sensitive laminae (pink) are close, tight, and parallel to the insensitive laminae (white line). The actual foot resembles the shape of the healthy, diagrammed one. With its low heel, the coffin bone is parallel to the toe wall which is the surest way to ensure a healthy white line and healthy, tight, laminae that can solidly suspend the coffin bone and prevent founder espisode.
2. Mildly Pathological Foot. The wall of the coffin bone is no longer parallel to the hoof wall which causes the laminae to stretch at the bottom and begin to adopt a ‘wedge-shape’: narrower at the top at wider at the bottom. This puts constant stress on the overstretched laminae towards the bottom.
3. Severe Pathology. Founder – Rotation with Separation. The ‘wedge’ is extreme now, with the laminae much longer at the bottom than the top. The bone is far out of parallel with the hoof wall. The constant downward stress and pull on the lower part of the laminae has caused them to fail, allowing the suspension of the bone to the inside of the hoof wall to be lost and the bone to rotate.
February 23, 2007 at 12:38 am
OK, I’m trying to understand this. If the laminae have failed can you see it by looking at the foot from the bottom?
February 23, 2007 at 2:53 am
No, usually you cannot. When you are looking at the white line on the bottom of the sole, you are seeing that narrow grey strip that is below the pink wedge on the diagram. Those are the insensitive laminae. Sometimes the white line does become wider and separated as a result of incorrect hoof form, and that gives you an indication that something is not right, but not necessarily that the laminae have failed, at least not yet. It could also just be a stretched white line from a too-long toe, with no effect on the laminae. The best way to see failing/failed laminae is on an xray, but if the damage is very slight, it can be hard to detect even then. The best defense is to ensure a low enough heel that the bone and the toe wall are parallel.
You can however see the bulge in the sole when the bone has rotated, in some cases. This is what you’re seeing in the third diagram – founder. The bone is very close to the surface because the sole is so thin there and it can look like the sole is convex. The next step after this is actual penetration of the bone through the sole.
I hope that helps clear it up somewhat. Please ask any more questions you might still have.