The following xrays depict radiographically the laminar wedge as well as the rotation characteristic of founder. They correspond to the photographs of the laminar wedge in the previous post.
The horse was diagnosed with rotation of 12 degrees. The space between the laminae at the top of the hoof (L1) is smaller than the space at the bottom (L2). These two measurements should be the same, or stated another way the wall of the Coffin Bone (red line) should be parallel to the hoof wall (metal marker seen in gray). When the space at the bottom is greater this indicates the laminae have given way and the bone has begun to rotate, or founder. The wide space at the bottom, L2, is now full of torn and dead laminae, inflammation and blood, and this is what becomes the laminar wedge.
The importance of correct laminar spacing (he calls it the Horn-Laminar zone) is discussed by Ric Redden here
Here is an umarked Xray of the same foot:
Click on thumbnail for larger image.
The Laminar Wedge
is the space in the front of the hoof at the toe, where stretched and torn laminae have caused the coffin bone to rotate away from the hoof wall. The space between coffin bone and hoof wall has widened at the bottom, relative to the top, and has filled with wound secretion, blood and torn and dead laminae.
From the Front
The ‘dead’ laminae are black.
From the Top
From the side. The tip of the toe no longer contacts the ground.
(the photos are of both front feet, both of which foundered).
The horse has relatively flat soles, so the buildup of excess sole was especially harmful and painful.
Right Front Foot
Bruises were revealed underneath the excess sole immediately after it was trimmed away.
Left Front Foot
(click on thumbnail for larger image)
This foot had already developed abscesses underneath the excess sole, corresponding exactly to the outline of the sole ‘lumps’, visible in the small thumbnail to the left.
Here is an example of a horse with sidebone on both front feet. The lateral cartilages have ossified into what looks literally like a bone on the sides. The parts that appear ‘broken’ are most likely not fully ossified yet.
The plainly prominent and deep collateral grooves can prevent flexing of the foot which further prevents shock absorption, which can contribute to the formation of sidebone.
This is a Left Front foot with the inside wall curving to the inside, in a bell-shaped fashion (red dotted line Fig. 2). This is being caused in part by the sole at the inside toe which is too high (Fig. 1) as well as the toe too long.
This young mustang, never shod, has very thick and extremely hard walls which do not break off with wear but continue growing in a distorted way, and altering the horse’s stance.
Fig. 1 Fig. 2
The trimming treats this condition similarly to a flare but also lowers the toe on the inside (sole is removed). So, there are cases when sole forward of the frog does need to be rasped. The trimming is complicated by the inside-growing direction the walls have adopted. Now that the inside wall is growing more correctly, the outside wall needs to begin to start growing in a more outwardly direction (more visible in Fig 3 due to the angle of the photograph). Advanced trimming techniques such as floating the heel and the diagonal toe will allow this to occur.
Fig. 3 Fig. 4
A photo from an early trim shows how all the pressure was put on the inside wall by the long toe, with all the compression rings on the inside only.
Here is an example of overgrown bar that has migrated forward onto the sole creating the appearance of a ‘false’ or ‘double’ sole. The material is not merged with the sole and is distinctly different in appearance and texture.
After 5 months of trimming:
The bars are brought back to their correct position ending alongside the collateral grooves and approximately to the midpoint of the frog. Also note the expansion of the contracted heels.
These pictures are courtesy of a barefoot trimmer in the Midwest.
The horse in question is a 30+ (?) yo neglected (starvation) rescue case.
Overgrown bars can lead to a variety of problems, such as exerting pressure on the hoof wall which causes it to crack.
The Right Hind hoof has a crack starting at the lateral toe quarter which began with an abscess. (As seen here).
Before trim After trim
Both bars are too long, grown above the height of the frog preventing it from being weightbearing. The lateral bar has extended almost to the frog’s apex and overlaid onto the sole. At the green arrow it is raised above the sole by at least 1/4″. The furthest point of the bar (where the blue arrow starts), exerts pressure on the wall when the foot is weightbearing, in the direction of that arrow and splits the wall apart. The underrun heels also contribute to the problem. To correct the problem, the bars have been shortened and brought back approximately to the frog’s midpoint, the heels have been lowered and brought back to the widest point of the frog, and the toe has been backed up. These changes will allow proper forces to be exerted on the hoof capsule allowing the crack to grow out.
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.
Below is an Xray of a Right Front hoof. The right side is the medial side, the left is the lateral one. (The view is from the front).
The two views are the same, one shown un-marked up for clarity.
The tops of the collateral grooves are indicated with red marks. The depth of the collateral groove is determined by the height (or length) of the bar, which is not visible on xray. The collateral groove on the medial side is very deep, much more so than the lateral side. It appears to be projecting up into the bottom of the coffin bone which is probably very painful, since this area is full of sensitive tissue. The bar and collateral groove has pushed up the inside side of the foot, displacing the balance of the foot. The inside wall is much higher and longer than the outside. The hairline and top of the wall/coronary band are indicated with the red arrows. The two points should be straight across, parallel with the ground. Another detrimental effect of this deep collateral groove is the displacement of the P3/P2 joint. The joint space is narrower on the outside, wider on the inside. This can lead to ossifications and arthritic problems such as sidebone and ringbone.
Lowering the bar on the inside to the same length as the outside will correct these balance problems.