Page 55 - November 2017

Laminae
Damaged Laminae
Sole Coffin Bone
Keeping ice on a horse with laminitis can be very
beneficial, especially prior to the onset of signs,
as body tissue remains vital much longer when Damage and overload to the laminae manifests itself as laminitis. Coffin bone rotation, when the front tips kept cold. down through the sole (pictured), is an indication of what is going on.
horses. The paragraph started with, ‘First, do no harm,’ and I feel this means not pounding nails into that foot. Screws are usually painless. But when I first talked about putting screws in a horse’s foot, a lot of people resisted the idea. There are many farriers who still will not put screws in a foot.
“The 1887 encyclopedia of the horse featured a drawing of a shoe that was designed almost the same as the clog, but made of metal, and it had to be nailed on. The added concussion of nailing a shoe onto an already damaged, painful foot can be horrific in some cases. Imagine your child in a bike accident, hitting his head on the concrete resulting in severe brain concussion. If a doctor restrained the child and began hitting him on the head with a hammer, you’d be protesting. Yet, we do similar things to our horses.”
Another treatment that has been found to be very beneficial in cases of laminitis is the use of ice, especially prior to the onset of signs. Traditionally, studies have found that keeping the feet cold can be one of the best therapies.
“People need to realize that laminitis is an ongoing process—like a fire that just keeps spreading,” Steward said. “It doesn’t just stop. It would be helpful if someone would manufac- ture a turbulating ice boot that a horse could wear while lying down, without wetting the stall. The colder you get the legs/feet, the better they do, and the quicker they heal.”
As a comparison, he uses the example of an individual drowning in a lake. That person would have more chance of survival (without brain damage) if they were immersed in a cold lake rather than in a warm one, since body
tissues remain vital a lot longer when cold. “This is why we want ice around the foot,”
he says. “People talk about benefits of oxygen and blood flow, but glucose probably has more benefit than oxygen. The foot can live without oxygen for quite a while because there are still some processes that continue. In the face of high oxygen levels, damaged tissue actually deteriorates pretty fast. This is called oxidation and that’s why we take antioxidants.
“We’d like to have the affected horse be able to lie down and get the weight off his feet. The damaged laminae can’t handle a lot of weight. What we are seeing with laminitis are the overload manifestations of the damage to the laminae. The rotation of the coffin bone (the front tipping down through the sole) is a manifestation of what is going on.”
Another comparison would be the roof of
a house in which termites had eaten the rafters caving in due to heavy snow. “The rafters being weakened is the problem, analogous to the damaged lamellar apparatus, and now the roof is caving in, and that’s the overload injury manifestation—analogous to coffin bone rota- tion,” he says. “A horse’s foot can handle 1,200 pounds of pressure/weight on the laminae. But if that horse had a problem that damaged the laminae (such as colic surgery, grain overload, severe illness, endotoxemia, uterine infection, snakebite poisons damaging the blood supply to the foot, etc.), this changes.
“Inside the hoof, venules (very small blood vessels in the microcirculation that allow blood to return from the capillary beds to drain into the larger blood vessels) are unique in that they have huge muscles around them. Consequently,
these venules are sensitive to a variety of chemi- cals and conditions such as injury due to run- ning down a gravel road too hard, too fast, too long, or enteritis or a chemical coming through the bloodstream. These tiny vessels react by going into venospasm (a spasmodic constric- tion of a vein and increased basal resting tone). These little blood vessels clamp shut (creating a serious problem and interfering with shunting blood around the foot).
“Dr. Christopher Pollitt in Australia dis- covered that there are shunts in the foot. The blood can go down to the foot and turn around and come back without going into the foot. When it does that, there are cellular functions going on that produce lymph (liquid found within the lymphatic vessels and collected
from tissues in all parts of the body), with is analogous to grey water in a sewage recycling system. The blood vessels pump blood and some of the fluid component leaks out into the lymph system, but most of it comes right back (recycled) into the blood vessels. Any fluid that doesn’t go back into the veins accumulates into the lymphatic system.”
Steward says the reason we need a horse
to continue to move around, to not stand still all the time and to keep the foot moving, is
to put alternating pressure and to create a pumping action on the lymphatic system. This allows expansion and contraction of the hoof structures so the lymph is not accumulating in the tissues.
“The old timers used to say the horse has two hearts; the ‘pump’ in the feet helps push the blood back up the leg,” he says. “That’s the theory behind my wooden shoe (Steward Clog)
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EQUINE HEALTH