NEW METHODS FOR THE TREATMENT OF NAVICULAR DISEASE

More than 15 years of research and experience with the treatment of navicular disease have revealed that pressure on the navicular region, as a result of excessively long bars and heels, leads to a painful inflammation of the corium adjacent to the navicular bone and, therefore, clinical lameness. The enlarged cavities in the navicular bone, demonstrable by X-ray diagnosis, are not painful and therefore are not related to clinical lameness. They are the result of congestion of the digital arteries caused by an unphysiological position of the navicular bone as a result of high heels and bars.

In the last 3 years, the course and healing of navicular syndrome was documented on 53 horses of various breeds.

The shoes were removed, the living conditions of the horse changed to more closely approximate the natural amount of movement of a horse each day, and the shape of the hoof capsule was, over the course of months, returned (close) to its natural form through proper trimming. Depending on the length of time the problem had been in existence, and how far living conditions could be optimized, the return to full use of a horse diagnosed with "podotrochlosis" can take a few weeks to nine months.

In the course of several decades of observations, it was found that, through the pressure of blood vessels congested by the contraction of the hoof through shoeing, bone mass is reduced. This means that the passageways of blood vessels in the navicular bone and coffin bone, in a shod horse or one with contracted heels (no circulatory pump in the hoof capsule), are significantly enlarged when compared to a horse with a sound foot and proper movement.

When a horse goes lame, more and more often X-rays are taken to aid in diagnosis. When enlarged foraminae nutritiae are detected in the navicular bone, navicular syndrome is usually the diagnosis.

The size and shape of these cavities varies in all horses. These variations are attributed to a number of causes, from age to immunological deficiencies. However, more recent studies have proven that there exists no direct relationship between the shape of the cavities and clinical lameness.

However, what is proven 100% of the time is that "navicular" horses ALL have long, underslung heels and bars which contact the ground (or shoe) even when non-weighbearing. This causes a lever action into the sole and results in bruising and tearing in the area of the bars under the navicular bone. To escape the pain, the horse tries to put less pressure on the heel and therefore more on the toe; the angle between the coffin bone and middle phalanx decreases, causing the navicular bone to close off the Aa. digitales. This results in congestion above this point and enlargement of arteries.

Lameness disappears after elimination of this hoof form and restoration of the natural, flat shape. No relapse has ever been noted.

This leads to the conclusion that the so-called "navicular syndrome" has its cause in an unnatural hoof form, more specifically in excessively long heels and bars, which put pressure into the navicular region and cause inflammation (pain) of the corium in this area. Since, below the region of congestion, blood flow and therefore nerve action is reduced, at first there is little or no pain with this situation. Only after increased inflammation, which returns blood to the affected area, is lameness noted.

The belief that steep hooves are proper (perhaps caused by the mistaken idea that they relieve the flexor tendons) therefore causes many cases of navicular. It is not navicular syndrome which is hereditary, but ignorance of the proper hoof shape.

LAMINITIS

The same steep hoof form is also responsible for a deficiency of blood flow and chronic overload of the dorsal part of the laminae, which sets the stage for acute laminitis.

A 12-year study of more than 200 coffin bones from slaughtered horses shows that rarely does one find a coffin bone not deformed and damaged by improper hoof shape. The palmar processes of a healthy coffin bone form an opening parabolic shape, while in contracted hooves it shows an elliptic arch The length of a healthy coffin bone equals its width; the commonly deformed coffin bone is narrower than it is long.

The horse's weight, with each step, is equally distributed onto the laminae. (In a calculation, this results in about 8kg per sq cm of laminae, at a canter.) Horses live with this for 30-40 years even in rocky areas.

Studies of wild horses show the coffin bone of a natural foot parallel to the ground and the frog/ bulbs actually touching the ground.

Domestic horses, however, are largely forced to live with high heels, and no frog contact. A change in the distribution of pressure results; the steeper the coffin bone, the more weight moves to the tip of the coffin bone and the more the laminae there are overloaded. Soft ground is less harmful under these conditions than hard ground.

The overloading of the laminae can be borne for some time if there is optimal circulation and good horn quality (unshod hoof). If anything like a metabolic disorder occurs, such as an excess in protein, the overloaded area becomes inflamed. Horses show pain and shift their weight rearward, onto parts of the hoof where the laminae is still intact.

With wild horses, acute laminitis heals quickly, since the animal has to migrate with the herd, and circulation resolves the laminitis within a few days. The rearward shift also shortens the overlong heels.

Veterinary treatment, however, focuses mainly on the inflammation, or the already occurred rotation of the coffin bone. However, seen from a pathophysiological point of view, inflammation is a functional measure for repair: through increased bloodflow, metabolism (the exchange of waste products for nutrients and oxygen) is intensified. Basically, an inflammation is a natural repair mechanism; it causes pain, but has a function, and suppressing it (as with anti-inflammatories) prevents this natural healing mechanism from working.

This suppression of inflammation is usually done through medication and/or wedge pads. Metabolism diminishes, and healing becomes slow if not impossible, since healing requires increased metabolism.

Also, the use of wedge pads or bar shoes only increases the problem, doubling the pressure put onto the damaged region. Cells in the already damaged area die off, while cells on the edges of the afflicted area remain inflamed, producing wound secretion instead of stabilizing horn. Acute laminitis, therefore, is a long time in the making.

The "sudden" appearance of laminitis is brought on either by additional overload or several possible poisonous ingredients; however, these are not the causes for the laminitis, rather the "straw that broke the camel's back".

Pollitt shows dramatically in his video that a steep hoof is insufficiently supplied with blood; this is especially severe when the horse moves little, because it means long persisting vasoconstriction without the short frequent opening by joint motion.

So far, 50 horses with acute laminitis were healed exclusively by lowering the palmar processes (bringing the hoof, and as such the coffin bone, back into its original position through trimming), and optimizing blood flow through the foot with movement, not medication or shoeing, etc.

Removing the cause (overload of the coffin bone) took 2-8 weeks, depending on the stage of the disease at the beginning. After 3-5 months, as soon as 75% of the coffin bone was tightly connected with the laminae again, the horse was able to move pain-free.

Copyright Dr. vet. med. H. Strasser
Blathofstr. 42/1, 72074 Tuebingen, Germany
Tel/Fax: (011) 497071-87572
Ed. & Canadian contact: Sabine Naujoks Box 44, Qualicum Beach, BC, V9K 1S7

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© 2002 - 2007 by The Naked Hoof Pty. Ltd. All rights reserved. No part of these publications may be reproduced by any means whatsoever without the written permission of the publisher and/or authors. The information and products contained within these webpages and articles are intended for educational purposes only, and not for diagnosing or medicinally prescribing in any way. Readers are cautioned to seek expert advice from a qualified health professional before pursuing any form of treatment on their animals. Opinions expressed herein are those of the authors and do not necessarily reflect those of the publisher.

Last edited: 30 June, 2007
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